Patent Publication Number: US-11044273-B2

Title: Assurance of security rules in a network

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of, and priority to, U.S. Provisional Patent Application No. 62/690,436, filed on Jun. 27, 2018, entitled “ASSURANCE OF SECURITY RULES IN A NETWORK”, the content of which is hereby expressly incorporated by reference in its entirety. 
     This application is related to U.S. Non-Provisional patent application Ser. No. 16/217,559, filed Dec. 12, 2018, entitled “ASSURANCE OF SECURITY RULES IN A NETWORK”, and U.S. Non-Provisional patent application Ser. No. 16/217,607, filed Dec. 12, 2018, entitled “ASSURANCE OF SECURITY RULES IN A NETWORK”, both of which are hereby expressly incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present technology pertains to assurance of security rules in a network. 
     BACKGROUND 
     Computer networks are becoming increasingly complex, often involving low level and high level configurations at various layers of the network. For example, computer networks generally include numerous security, routing, and service policies, which together define the behavior and operation of the network. Network operators have a wide array of configuration options for tailoring the network to the needs of users. While the different configuration options provide network operators significant flexibility and control over the network, they also add complexity to the network. In addition, network operators often add, delete, and edit policies throughout the life of the network. Given the high complexity of networks and the vast number of policies and policy changes typically implemented in a network, it can be extremely difficult to keep track of the policies in the network, avoid conflicts between policies in the network, and ensure that the policies in the network comply with the intended behavior and operation of the network. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe the manner in which the above-recited and other advantages and features of the disclosure can be obtained, a more particular description of the principles described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only example embodiments of the disclosure and are not to be considered to limit its scope, the principles herein are described and explained with additional specificity and detail through the use of the drawings in which: 
         FIGS. 1A and 1B  illustrate example network environments; 
         FIG. 2A  illustrates an example object model of an example network; 
         FIG. 2B  illustrates an example object model for a tenant object in the example object model from  FIG. 2A ; 
         FIG. 2C  illustrates an example association of various objects in the example object model from  FIG. 2A ; 
         FIG. 2D  illustrates a schematic diagram of example models implemented based on the example object model from  FIG. 2A ; 
         FIG. 3A  illustrates an example assurance appliance system; 
         FIG. 3B  illustrates an example system diagram for network assurance; 
         FIG. 4  illustrates an example diagram for constructing device-specific logical models based on a logical model of a network; 
         FIG. 5A  illustrates a schematic diagram of example inputs and outputs of an example policy analyzer; 
         FIG. 5B  illustrates an equivalency diagram for determining equivalence between different network models; 
         FIG. 5C  illustrates an example architecture for performing equivalence checks and identifying conflict rules; 
         FIGS. 6A through 6C  illustrate example Reduced Ordered Binary Decision Diagrams; 
         FIG. 7  illustrates an example method for network assurance; 
         FIG. 8  illustrates an example user interface for accessing assurance compliance menus of an assurance compliance tool; 
         FIG. 9  illustrates an example compliance requirement management interface which allows a user to manage compliance requirements; 
         FIG. 10  illustrates an example compliance requirement interface for creating a new compliance requirement; 
         FIG. 11  illustrates an example EPG (Endpoint Group) selector interface for selecting an EPG selector for a security compliance requirement; 
         FIG. 12  illustrates an example configuration of a compliance requirement interface after a user selects and chooses an EPG selector from an EPG selector interface; 
         FIG. 13  illustrates an example configuration of a compliance requirement interface for enabling a user to select a communication operator for a security compliance requirement; 
         FIG. 14  illustrates an example configuration of a compliance requirement interface for selecting an EPG selector and associated attributes for a particular EPG selector in a compliance requirement definitions view; 
         FIG. 15  illustrates an example EPG selector interface for selecting an EPG selector for a security compliance requirement; 
         FIG. 16  illustrates a compliance requirement interface depicting an example configuration of a security compliance requirement created through the compliance requirement interface; 
         FIGS. 17A through 17C  illustrate example configurations of a compliance requirement interface for creating a compliance requirement; 
         FIGS. 18A through 18E  illustrate example configurations of a traffic selector interface for creating a traffic selector for a security compliance requirement; 
         FIG. 19  illustrates an example EPG selector interface for creating an EPG selector for a security compliance requirement; 
         FIGS. 20A through 20D  illustrate example configurations of a compliance requirement sets interface; 
         FIG. 21  illustrates an example compliance requirements interface identifying compliance requirements associated with a compliance requirement set; 
         FIG. 22  illustrates a diagram of an example definitions scheme for configuring compliance requirements; 
         FIGS. 23A and 23B  illustrate example configurations of a compliance score interface; 
         FIGS. 24A and 24B  illustrate example views of a compliance analysis interface; 
         FIG. 25  illustrates an example interface for searching compliance events; 
         FIG. 26  illustrates an example method for creating and verifying security compliance requirements; 
         FIG. 27  illustrates an example method for creating a security compliance requirement and checking a compliance of policies associated with objects on a same network context; 
         FIG. 28  illustrates an example method for creating a security compliance requirement and checking a compliance of policies associated with objects on different network contexts; 
         FIG. 29  illustrates an example network device; and 
         FIG. 30  illustrates an example computing system architecture. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments of the disclosure are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations may be used without parting from the spirit and scope of the disclosure. Thus, the following description and drawings are illustrative and are not to be construed as limiting. Numerous specific details are described to provide a thorough understanding of the disclosure. However, in certain instances, well-known or conventional details are not described in order to avoid obscuring the description. References to one or an embodiment in the present disclosure can be references to the same embodiment or any embodiment; and, such references mean at least one of the embodiments. 
     Reference to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. 
     The terms used in this specification generally have their ordinary meanings in the art, within the context of the disclosure, and in the specific context where each term is used. Alternative language and synonyms may be used for any one or more of the terms discussed herein, and no special significance should be placed upon whether or not a term is elaborated or discussed herein. In some cases, synonyms for certain terms are provided. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any terms discussed herein is illustrative only, and is not intended to further limit the scope and meaning of the disclosure or of any example term. Likewise, the disclosure is not limited to various embodiments given in this specification. 
     Without intent to limit the scope of the disclosure, examples of instruments, apparatus, methods and their related results according to the embodiments of the present disclosure are given below. Note that titles or subtitles may be used in the examples for convenience of a reader, which in no way should limit the scope of the disclosure. Unless otherwise defined, technical and scientific terms used herein have the meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In the case of conflict, the present document, including definitions will control. 
     Additional features and advantages of the disclosure will be set forth in the description which follows, and in part will be obvious from the description, or can be learned by practice of the herein disclosed principles. The features and advantages of the disclosure can be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the disclosure will become more fully apparent from the following description and appended claims, or can be learned by the practice of the principles set forth herein. 
     OVERVIEW 
     Software-defined networks (SDNs) and data centers, such as application-centric infrastructure (ACI) networks, can be managed from one or more centralized elements, such as application policy infrastructure controllers (APICs) in an ACI network or network managers in other SDN networks. A network operator can define various configurations, objects, rules, etc., for the network, which can be implemented by the one or more centralized elements. The configurations provided by the network operator can reflect the network operator&#39;s intent for the network, meaning, how the network operator intends for the network and its components to operate. Such user intents can be programmatically encapsulated in network models stored at the centralized elements. The models can represent the user intents and reflect the configuration of the network. For example, the models can represent the object and policy universe (e.g., endpoints, tenants, endpoint groups, contexts, application profiles, policies, etc.) as defined for the particular network by the user intents and/or centralized elements. 
     In many cases, various nodes and/or controllers in a network may contain respective information or representations of the network and network state. For example, different controllers may store different logical models of the network and each node in a fabric of the network may contain its own model for the network. The approaches set forth herein provide assurance of contracts or policies in the network. A network operator can specify a compliance requirement and check that it is accurately enforced across the network and does not conflict with other rules in the network. For example, a network operator can specify a security rule that indicates which endpoint groups (EPGs) a particular EPG should or should not be able to communicate with, and how such communications can be conducted (if allowed). A network assurance appliance can retrieve and analyze one or more logical, concrete, and/or hardware models of the network to determine whether the specified security rule(s) are violated, satisfied, applied, etc. The network assurance appliance can generate events indicating whether the specified security rule(s) are violated, satisfied, applied, etc., and how the security rule(s) are violated or unenforced if such is the case. 
     Disclosed herein are systems, methods, and computer-readable media for configuring compliance requirements via a graphical user interface for compliance management, and performing assurance of rules and policies in a network based on the configured compliance requirements. In some examples, a system or method can receive, via a user interface, EPG inclusion rules defining which EPGs on a network should be included in each of a plurality of EPG selectors representing respective sets of EPGs that satisfy the EPG inclusion rules. The system or method can then select the respective sets of EPGs that satisfy the EPG inclusion rules for inclusion in the plurality of EPG selectors. Each respective set of EPGs can be selected based on a respective portion of the EPG inclusion rules that is associated with the respective set of EPGs. 
     The system or method can create the plurality of EPG selectors based on the respective sets of EPGs. Each of the plurality of EPG selectors can include one of the respective sets of EPGs. The system or method can create a traffic selector including traffic parameters received via the user interface, which identify traffic corresponding to the traffic selector. The system or method can create a security compliance requirement for the network based on configuration data received via the user interface, including a first EPG selector and a second EPG selector from the plurality of EPG selectors, the traffic selector, and a communication operator defining a communication condition for traffic associated with the first EPG selector, the second EPG selector, and the traffic selector. The system or method can determine whether security policies on the network comply with the security compliance requirement, and generate one or more compliance assurance events indicating whether the security policies configured on the network comply (e.g., satisfy, violate, apply or enforce, etc.) with the security compliance requirement. 
     Based on the one or more compliance assurance events, the system or method can present, via the user interface, a compliance result indicating whether the security compliance requirement is satisfied, violated, or not applied by any of the security policies. In some cases, the compliance result can include an indication of a cause for the security compliance requirement being satisfied, violated, or not applied. The cause can include a set of policy objects and/or one or more security policies. The set of policy objects can include a consumer EPG, a provider EPG, a contract, a filter, a tenant, a virtual routing and forwarding (VRF) object, an application profile, etc. In some cases, the compliance result can identify a compliance event severity, a number of security compliance issues, a compliance score, a count of security compliance issues by category, a compliance score by category, etc. The category can include a type of security compliance requirement, a type of resource affected, a policy object affected, etc. 
     In some examples, the user interface can include an EPG selector interface for creating and configuring EPG selectors, a traffic selector interface for creating and configuring traffic selectors, a compliance requirement interface for creating and configuring compliance requirements based on the EPG selectors and the traffic selectors, and a compliance requirement set interface for creating sets of compliance requirements. 
     EXAMPLE EMBODIMENTS 
     The present technology involves system, methods, and computer-readable media for configuring compliance requirements via a graphical user interface for compliance management, and performing assurance of rules and policies in a network based on the configured compliance requirements. The present technology will be described in the following disclosure as follows. The discussion begins with a discussion of network and compliance assurance, and a description of example computing environments, as shown in  FIGS. 1A and 1B . A discussion of network models for network assurance, as shown in  FIGS. 2A through 2D , and network modeling and assurance systems, as shown in  FIGS. 3A-B ,  4 ,  5 A-C,  6 A-C, and  7  will then follow. The discussion proceeds with a description of example security compliance requirements as well as methods and techniques for creating and checking security compliance requirements, as shown in  FIGS. 8 through 28 . The discussion concludes with a description of example network and computing devices, as shown in  FIGS. 29 and 30 , including example hardware components suitable for hosting software and performing computing operations. The disclosure now turns to a discussion of network and compliance assurance. 
     Network assurance is the guarantee or determination that the network is behaving as intended by the network operator and has been configured properly (e.g., the network is doing what it is intended to do). Intent can encompass various network operations, such as bridging, routing, security, service chaining, endpoints, compliance, QoS (Quality of Service), audits, etc. Intent can be embodied in one or more policies, configurations, etc., defined for the network and individual network elements (e.g., switches, routers, applications, resources, etc.). In some cases, the configurations, policies, etc., defined by a network operator may not be accurately reflected in the actual behavior of the network. For example, a network operator specifies configuration A for a type of traffic but later finds that the network is actually applying configuration B to that traffic or otherwise processing that traffic in a manner that is inconsistent with configuration A. This can be a result of many different causes, such as hardware errors, software bugs, varying priorities, configuration conflicts, misconfigured settings, improper rule rendering by devices, upgrades, configuration changes, failures, etc. As another example, a network operator defines configuration C for the network, but one or more configurations in the network cause the network to behave in a manner that is inconsistent with the intent reflected by configuration C. 
     The approaches herein can provide network compliance assurance by modeling various aspects of the network, performing consistency, compliance, and/or other network assurance checks. The network assurance approaches herein can be implemented in various types of networks, including private networks, such as local area networks (LANs); enterprise networks; standalone or traditional networks, such as data center networks; networks including a physical or underlay layer and a logical or overlay layer, such as a VXLAN or SDN network (e.g., Application Centric Infrastructure (ACI) or VMware NSX networks); etc. 
     Network models can be constructed for a network and implemented for network assurance. A network model can provide a representation of one or more aspects of a network, including, without limitation the network&#39;s policies, configurations, requirements, security, routing, topology, applications, hardware, filters, contracts, access control lists, infrastructure, etc. For example, a network model can provide a mathematical representation of configurations in the network. As will be further explained below, different types of models can be generated for a network. 
     Such models can be implemented to ensure that the behavior of the network will be consistent (or is consistent) with the intended behavior reflected through specific configurations (e.g., policies, settings, definitions, etc.) implemented by the network operator. Unlike traditional network monitoring, which involves sending and analyzing data packets and observing network behavior, network assurance can be performed through modeling without necessarily ingesting packet data or monitoring traffic or network behavior. This can result in foresight, insight, and hindsight: problems can be prevented before they occur, identified when they occur, and fixed immediately after they occur. 
     Thus, network assurance can involve modeling properties of the network to deterministically predict the behavior of the network. The network can be determined to be healthy if the model(s) indicate proper behavior (e.g., no inconsistencies, conflicts, errors, etc.). The network can be determined to be functional, but not fully healthy, if the modeling indicates proper behavior but some inconsistencies. The network can be determined to be non-functional and not healthy if the modeling indicates improper behavior and errors. If inconsistencies or errors are detected by the modeling, a detailed analysis of the corresponding model(s) can allow one or more underlying or root problems to be identified with great accuracy. 
     The approaches herein also enable a network administrator or operator to specify a compliance requirement(s) and check that the specified compliance requirement(s) is being enforced across the network and is not otherwise being violated or contradicted by other rules or policies in the network. For example, a network administrator can specify a security rule that indicates which EPGs a specific EPG should or should not be able or allowed to communicate with, and how the specific EPG should communicate with those EPGs it should be able or allowed to communicate with. A network assurance appliance can retrieve and analyze a logical, concrete, and/or hardware models of the network to determine whether or not the specified security rule(s) are being violated, satisfied, applied, etc., based on a comparison of the specified security rule(s) and the network model(s) (e.g., the logical, concrete, and/or hardware models). The network assurance appliance can generate events indicating whether or not the specified security rule(s) complies with the network models and is being violated, satisfied, applied, etc., in the network. The network administrator or operator can specify (e.g., via a user interface) one or more security or policy requirements (e.g., rules, conditions, nodes, etc.) that should or should not be satisfied, applied, violated, etc., in the network, and quickly receive compliance results indicating whether such security or policy requirements are being applied, violated, satisfied, etc. 
     Defining a Security Requirement 
     A network administrator can define a security requirement that includes, for example, a requirement name, a requirement description, a requirement type, a first EPG set, a communication operator, a second EPG set, and a traffic selector or communication filter. The compliance assurance system can then check or verify whether the security requirement and associated parameters are being violated, enforced, applied, satisfied, etc., in the network. 
     To define an EPG set, the network administrator can specify one or more EPGs, tenants, domain names, VRFs (virtual routing and forwarding instances), application profiles, bridge domains, EPG tags/categories, or other container/grouping of EPGs or other parameters. The network administrator can explicitly include or exclude certain EPGs. Because the EPGs in certain groupings (e.g., Application Profiles, VRFs, etc.) may be dynamic and change from epoch to epoch, the assurance appliance may identify the EPGs in the EPG set in each epoch being assured. 
     The communication operator can include, for example, conditions such as must not talk to, must talk to, may talk to, etc. A must talk to condition can mean that one must be able to talk to on all specified ports, while may talk to condition can mean that one may be able to talk on one or more of the specified ports. 
     The traffic selector or communication filter can include, for example, an Ethernet protocol or EtherType for communication (e.g., IPv6, IPv4, MPLS Unicast, ARP, MAC security, etc.); an IP protocol (e.g., ICMP, IGMP, IGP, TCP, UDP, etc.); a TCP session state; one or more ports for communication; a number of steps/hops within the network for indirect communications (e.g., less that 5 hops, more than 1 hop, etc.), which may be used to check that communications are routed through a middle box such as a firewall; hops from one EPG to another EPG; etc. 
     For example, a network administrator can create a security requirement named “Security Requirement 1”, and define it as “EPG Set 1 must talk to EPG Set 2 on TCP ports 80-100.” Here, the security requirement includes a name, an indication of which EPG sets are associated with the security requirement, a condition or communication operator indicating that one EPG set must talk to another EPG set, and the specific protocol and ports for such communications. 
     Once the assurance appliance receives the security rule, the assurance appliance can retrieve the configuration data from the network (e.g., via a network controller such as an APIC). The configuration data may include, for example, contracts, settings, hardware (e.g., ternary content-addressable memory) rules, etc. In some cases, the configuration data may also include forwarding plane configuration data such as, for example, FIB (forwarding information base) entries on one or more network devices (e.g., one or more leaf switches), subnet configurations for one or more bridge domains (BDs) and/or EPGs on a network controller such as an APIC, etc. The assurance appliance may check that the configuration data complies with the security rule. Based on the check, the assurance appliance may generate events that specify whether the configurations in the network violate, satisfy, apply, etc., the security rule. In some cases, the events may be generated on a per-EPG basis. For example, for the “Security Requirement 1” example above, if EPG Set 1 contained 3 EPGs and EPG Set 2 contained 5 EPGs, the assurance appliance may generate 15 events specifying whether the communications from each EPG in EPG Set 1 to each EPG in EPG Set 2 satisfy or violate the Security Requirement 1. 
     In order to check compliance with the security rule, the assurance appliance may retrieve (e.g., via a network controller such as an APIC) one or more network models for the network, such as a logical, concrete, and/or hardware model, as further explained below, to check if the security rule complies with the rules or policies in the one or more network models. In some implementations, hardware rules, such as TCAM rules, in fabric nodes such as leaf nodes can also be checked for compliance with the security rule. Depending on which policy definition or implementation level (e.g., the logical model, the concrete model, the TCAM/hardware model, etc.) is checked, different events and/or types of events may be generated. 
     In some examples, a network administrator may also specify a requirement set that includes one or more security requirements. For example, Requirement Set 1 may include security requirements Security Requirement 1, Security Requirement 5, and Security Requirement 7. The network administrator may also specify which network fabrics the requirement set should be applied to. For example, the network administrator may specify that the Requirement Set 1 should be applied to Fabric 1 and Fabric 3. 
     Checking Compliance with the Security Requirement 
     The process for checking compliance with one or more security requirements can include obtaining a network model, such as a logical model identifying contracts, VRFs, EPGs, etc., specified in the network. The process can involve checking EPG-EPG pairs in EPG sets. A modeling library can be implemented to perform the actual checks. Each contract, taboo, VRF mode, EPG mode, etc., can be inspected and used to construct a BDD (Binary Decision Diagram) or ROBDD (Reduced Ordered Binary Decision Diagram), which is used to check compliance with the security requirement, as further described herein. The various contracts in the network model(s) can be converted into a flat list of rules. BDDs or ROBDDs can be used to represent each rule/action in a contract as a Boolean function, which can then be used to perform compliance checks between the rules/actions. 
     Below are example compliance cases: 
     Example 1—EPG1 and EPG2 are in the Same VRF 
     The system constructs two ROBDDs for that VRF, including an ROBDD representing traffic that is permitted in the VRF (VRF_permit_ROBDD) and an ROBDD representing traffic that is denied in the VRF (VRF_deny_ROBDD), and an ROBDD for the security requirement (Sec_ROBDD). The system then checks whether the Sec_ROBDD is contained in the VRF_deny_ROBDD or the VRF_permit_ROBDD. For example, in some cases, if the security requirement specifies a deny requirement, the system can check whether the Sec_ROBDD is contained in the VRF_deny_ROBDD, and if the security requirement specifies a permit requirement, the system can check whether the Sec_ROBDD is contained in the VRF_permit_ROBDD. 
     Based on this containment check, the system can determine whether the security requirement is satisfied and which contracts satisfy or do not satisfy the security requirement. To illustrate, assume a security requirement specifies that “EPG1 must not talk to EPG2”. The system can check whether the Sec_ROBDD for the security requirement specifying that “EPG1 must not talk to EPG2” is contained in the VRF_deny_ROBDD associated with the VRF to determine if the security requirement is satisfied or violated. Assume instead that the security requirement specifies that “EPG1 must talk to EPG2”. Here, the system can check whether the Sec_ROBDD for the security requirement specifying that “EPG1 must talk to EPG2” is contained in the VRF_permit_ROBDD associated with the VRF to determine if the security requirement is satisfied or violated. 
     This example case can have several sub-use cases, such as (1) Enforced VRF mode or Unenforced VRF mode; (2) Enforced EPG mode or Unenforced EPG mode; Taboo contract versus Permit contract; etc. 
     Example 2—EPG1 and EPG2 are in Separate VRFs 
     The system determines that EPG1 and EPG2 are in different VRFs. The system then determines which VRF contains the rules for traffic between EPG1 and EPG2. 
     Suppose that EPG1 is a consumer EPG in VRF1, EPG2 is a provider EPG in VRF2, and the system determines that the rules for traffic between EPG1 and EPG2 are in VRF1. Here, the system constructs an ROBDD for VRF1 (VRF1_ROBDD) and an ROBDD for the Security Requirement (Sec_ROBDD). The system then checks that Sec_ROBDD is contained in VRF1_ROBDD. Based on this containment check, the system can determine whether the security requirement is satisfied and which contracts satisfy or violate the security requirement. 
     Reporting Compliance 
     Based on the compliance check, the assurance appliance may generate an interface that shows the EPG pairs for a security rule and whether each EPG pair is in compliance or non-compliance with the security rule. This compliance check and reporting system provides significant advantages. 
     When designing a network fabric, a network administrator may know or understand how communications in the network fabric should be configured, how or which communications should be restricted, how the network should behave, etc. However, during operation of the network, this information may become unclear, forgotten, obsolete, incorrect, or improper, particularly as the complexity of the network grows, the network changes or evolves, and network policies are added or removed. It can be indeed very difficult to keep track of the rules, behavior, state, and requirements of the network. As a result, it can be very difficult to ensure that network configurations are respected (e.g., are enforced, satisfied, not violated, etc.) and there are few safeguards that protect the configurations or restrictions in the network. 
     The subject technology allows for the configuration of the network to be specified as invariants for the network. These invariants may be specified in one or more security rules/requirements, for example. The subject technology allows for such invariants to be tested or checked to determine whether such invariants are being enforced, satisfied, violated, etc., in view of the current state of the network (e.g., the current network configuration and policies). Thus, the network administrator or operator can simply define a specific rule or requirement that should be enforced or satisfied in the network and run a check to determine whether such rule or requirement is indeed being enforced or satisfied by the network. This allows the network administrator or operator to ensure that the network continues to behave as it should and identify any conflicting, obsolete, or improper rules or policies that may be causing the network to behave otherwise, even as the complexity of the network grows, old policies are removed or forgotten, new policies are implemented, or other changes take place in the network over time. 
     Having described various aspects of network and compliance assurance, the disclosure now turns to a discussion of example network environments for network and compliance assurance. 
       FIG. 1A  illustrates a diagram of an example Network Environment  100 , such as a data center. The Network Environment  100  can include a Fabric  120  which can represent the physical layer or infrastructure (e.g., underlay) of the Network Environment  100 . Fabric  120  can include Spines  102  (e.g., spine routers or switches) and Leafs  104  (e.g., leaf routers or switches) which can be interconnected for routing or switching traffic in the Fabric  120 . Spines  102  can interconnect Leafs  104  in the Fabric  120 , and Leafs  104  can connect the Fabric  120  to an overlay or logical portion of the Network Environment  100 , which can include application services, servers, virtual machines, containers, endpoints, etc. Thus, network connectivity in the Fabric  120  can flow from Spines  102  to Leafs  104 , and vice versa. The interconnections between Leafs  104  and Spines  102  can be redundant (e.g., multiple interconnections) to avoid a failure in routing. In some examples, Leafs  104  and Spines  102  can be fully connected, such that any given Leaf is connected to each of the Spines  102 , and any given Spine is connected to each of the Leafs  104 . Leafs  104  can be, for example, top-of-rack (“ToR”) switches, aggregation switches, gateways, ingress and/or egress switches, provider edge devices, and/or any other type of routing or switching device. 
     Leafs  104  can be responsible for routing and/or bridging tenant or customer packets and applying network policies or rules. Network policies and rules can be driven by one or more Controllers  116 , and/or implemented or enforced by one or more devices, such as Leafs  104 . Leafs  104  can connect other elements to the Fabric  120 . For example, Leafs  104  can connect Servers  106 , Hypervisors  108 , Virtual Machines (VMs)  110 , Applications  112 , Network Device  114 , etc., with Fabric  120 . Such elements can reside in one or more logical or virtual layers or networks, such as an overlay network. In some cases, Leafs  104  can encapsulate and decapsulate packets to and from such elements (e.g., Servers  106 ) in order to enable communications throughout Network Environment  100  and Fabric  120 . Leafs  104  can also provide any other devices, services, tenants, or workloads with access to Fabric  120 . In some cases, Servers  106  connected to Leafs  104  can similarly encapsulate and decapsulate packets to and from Leafs  104 . For example, Servers  106  can include one or more virtual switches or routers or tunnel endpoints for tunneling packets between an overlay or logical layer hosted by, or connected to, Servers  106  and an underlay layer represented by Fabric  120  and accessed via Leafs  104 . 
     Applications  112  can include software applications, services, containers, appliances, functions, service chains, etc. For example, Applications  112  can include a firewall, a database, a CDN server, an IDS/IPS, a deep packet inspection service, a message router, a virtual switch, etc. An application from Applications  112  can be distributed, chained, or hosted by multiple endpoints (e.g., Servers  106 , VMs  110 , etc.), or may run or execute entirely from a single endpoint. 
     VMs  110  can be virtual machines hosted by Hypervisors  108  or virtual machine managers running on Servers  106 . VMs  110  can include workloads running on a guest operating system on a respective server. Hypervisors  108  can provide a layer of software, firmware, and/or hardware that creates, manages, and/or runs the VMs  110 . Hypervisors  108  can allow VMs  110  to share hardware resources on Servers  106 , and the hardware resources on Servers  106  to appear as multiple, separate hardware platforms. Moreover, Hypervisors  108  on Servers  106  can host one or more VMs  110 . 
     In some cases, VMs  110  and/or Hypervisors  108  can be migrated to other Servers  106 . Servers  106  can similarly be migrated to other locations in Network Environment  100 . For example, a server connected to a leaf can be changed to connect to a different or additional leaf. Such configuration or deployment changes can involve modifications to settings, configurations and policies that are applied to the resources being migrated as well as other network components. 
     In some cases, one or more Servers  106 , Hypervisors  108 , and/or VMs  110  can represent or reside in a tenant space. Tenant space can include workloads, services, applications, devices, networks, and/or resources associated with one or more clients or subscribers. Accordingly, traffic in Network Environment  100  can be routed based on specific tenant policies, agreements, configurations, etc. Moreover, addressing can vary between tenants. In some configurations, tenant spaces can be divided into logical segments and/or networks and separated from logical segments and/or networks associated with other tenants. Addressing, policy, security and configuration information between tenants can be managed by Controllers  116 , Servers  106 , Leafs  104 , etc. 
     Configurations in Network Environment  100  can be implemented at a logical level, a hardware level (e.g., physical), and/or both. For example, configurations can be implemented at a logical and/or hardware level based on endpoint or resource attributes, such as endpoint types and/or application groups or profiles, through a software-defined network (SDN) framework (e.g., Application-Centric Infrastructure (ACI) or VMWARE NSX). To illustrate, one or more administrators can define configurations at a logical level (e.g., application or software level) through Controllers  116 , which can implement or propagate such configurations through Network Environment  100 . In some examples, Controllers  116  can be Application Policy Infrastructure Controllers (APICs) in an ACI framework. In other examples, Controllers  116  can be one or more management components for associated with other SDN solutions, such as NSX Managers. 
     Such configurations can define rules, policies, priorities, protocols, attributes, objects, etc., for routing and/or classifying traffic in Network Environment  100 . For example, such configurations can define attributes and objects for classifying and processing traffic based on Endpoint Groups (EPGs), Security Groups (SGs), VM types, bridge domains (BDs), virtual routing and forwarding instances (VRFs), tenants, priorities, firewall rules, etc. Other example network objects and configurations are further described below. Traffic policies and rules can be enforced based on tags, attributes, or other characteristics of the traffic, such as protocols associated with the traffic, EPGs associated with the traffic, SGs associated with the traffic, network address information associated with the traffic, etc. Such policies and rules can be enforced by one or more elements in Network Environment  100 , such as Leafs  104 , Servers  106 , Hypervisors  108 , Controllers  116 , etc. As previously explained, Network Environment  100  can be configured according to one or more particular software-defined network (SDN) solutions, such as CISCO ACI or VMWARE NSX. These example SDN solutions are briefly described below. 
     ACI can provide an application-centric or policy-based solution through scalable distributed enforcement. ACI supports integration of physical and virtual environments under a declarative configuration model for networks, servers, services, security, requirements, etc. For example, the ACI framework implements EPGs, which can include a collection of endpoints or applications that share common configuration requirements, such as security, QoS, services, etc. Endpoints can be virtual/logical or physical devices, such as VMs, containers, hosts, or physical servers that are connected to Network Environment  100 . Endpoints can have one or more attributes such as a VM name, guest OS name, a security tag, application profile, etc. Application configurations can be applied between EPGs, instead of endpoints directly, in the form of contracts. Leafs  104  can classify incoming traffic into different EPGs. The classification can be based on, for example, a network segment identifier such as a VLAN ID, VXLAN Network Identifier (VNID), NVGRE Virtual Subnet Identifier (VSID), MAC address, IP address, etc. 
     In some cases, classification in the ACI infrastructure can be implemented by Application Virtual Switches (AVS), which can run on a host, such as a server or switch. For example, an AVS can classify traffic based on specified attributes, and tag packets of different attribute EPGs with different identifiers, such as network segment identifiers (e.g., VLAN ID). Finally, Leafs  104  can tie packets with their attribute EPGs based on their identifiers and enforce policies, which can be implemented and/or managed by one or more Controllers  116 . Leaf  104  can classify to which EPG the traffic from a host belongs and enforce policies accordingly. 
     Another example SDN solution is based on VMWARE NSX. With VMWARE NSX, hosts can run a distributed firewall (DFW) which can classify and process traffic. Consider a case where three types of VMs, namely, application, database and web VMs, are put into a single layer-2 network segment. Traffic protection can be provided within the network segment based on the VM type. For example, HTTP traffic can be allowed among web VMs, and disallowed between a web VM and an application or database VM. To classify traffic and implement policies, VMWARE NSX can implement security groups, which can be used to group the specific VMs (e.g., web VMs, application VMs, database VMs). DFW rules can be configured to implement policies for the specific security groups. To illustrate, in the context of the previous example, DFW rules can be configured to block HTTP traffic between web, application, and database security groups. 
     Returning to  FIG. 1A , Network Environment  100  can deploy different hosts via Leafs  104 , Servers  106 , Hypervisors  108 , VMs  110 , Applications  112 , and Controllers  116 , such as VMWARE ESXi hosts, WINDOWS HYPER-V hosts, bare metal physical hosts, etc. Network Environment  100  may interoperate with a variety of Hypervisors  108 , Servers  106  (e.g., physical and/or virtual servers), orchestration platforms, etc. Network Environment  100  may implement a declarative model to allow its integration with application design and holistic network policy. 
     Controllers  116  can provide centralized access to fabric information, application configuration, resource configuration, application-level configuration modeling for a software-defined network (SDN) infrastructure, integration with management systems or servers, etc. Controllers  116  can form a control plane that interfaces with an application plane via northbound APIs and a data plane via southbound APIs. 
     As previously noted, Controllers  116  can define and manage application-level model(s) for configurations in Network Environment  100 . In some cases, application or device configurations can also be managed and/or defined by other components. For example, a hypervisor or virtual appliance, such as a VM or container, can run a server or management tool to manage software and services in Network Environment  100 , including configurations and settings for virtual appliances. 
     As illustrated above, Network Environment  100  can include one or more different types of SDN solutions, hosts, etc. For the sake of clarity and explanation purposes, various examples in the disclosure will be described with reference to an ACI framework, and Controllers  116  may be interchangeably referenced as controllers, APICs, or APIC controllers. However, it should be noted that the technologies and concepts herein are not limited to ACI solutions and may be implemented in other architectures and scenarios, including other SDN solutions as well as other types of networks which may not deploy an SDN solution. 
     Further, as referenced herein, the term “hosts” can refer to Servers  106  (e.g., physical or logical), Hypervisors  108 , VMs  110 , containers (e.g., Applications  112 ), etc., and can run or include any type of server or application solution. Non-limiting examples of “hosts” can include virtual switches or routers, such as distributed virtual switches (DVS), application virtual switches (AVS), vector packet processing (VPP) switches; VCENTER and NSX MANAGERS; bare metal physical hosts; HYPER-V hosts; VMs; DOCKER Containers; etc. 
       FIG. 1B  illustrates another example of Network Environment  100 . In this example, Network Environment  100  includes Endpoints  122  connected to Leafs  104  in Fabric  120 . Endpoints  122  can be physical and/or logical or virtual entities, such as servers, clients, VMs, hypervisors, software containers, applications, resources, network devices, workloads, etc. For example, an Endpoint  122  can be an object that represents a physical device (e.g., server, client, switch, etc.), an application (e.g., web application, database application, etc.), a logical or virtual resource (e.g., a virtual switch, a virtual service appliance, a virtualized network function (VNF), a VM, a service chain, etc.), a container running a software resource (e.g., an application, an appliance, a VNF, a service chain, etc.), storage, a workload or workload engine, etc. Endpoints  122  can have an address (e.g., an identity), a location (e.g., host, network segment, virtual routing and forwarding (VRF) instance, domain, etc.), one or more attributes (e.g., name, type, version, patch level, OS name, OS type, etc.), a tag (e.g., security tag), a profile, etc. 
     Endpoints  122  can be associated with respective Logical Groups  118 . Logical Groups  118  can be logical entities containing endpoints (physical and/or virtual) grouped together according to one or more attributes, such as endpoint type (e.g., VM type, workload type, application type, etc.), one or more requirements (e.g., policy requirements, security requirements, QoS requirements, customer requirements, resource requirements, etc.), a resource name (e.g., VM name, application name, etc.), a profile, platform or operating system (OS) characteristics (e.g., OS type or name including guest and/or host OS, etc.), an associated network or tenant, one or more policies, a tag, etc. For example, a logical group can be an object representing a collection of endpoints grouped together. To illustrate, Logical Group 1 can contain client endpoints, Logical Group 2 can contain web server endpoints, Logical Group 3 can contain application server endpoints, Logical Group N can contain database server endpoints, etc. In some examples, Logical Groups  118  are EPGs in an ACI environment and/or other logical groups (e.g., SGs) in another SDN environment. 
     Traffic to and/or from Endpoints  122  can be classified, processed, managed, etc., based Logical Groups  118 . For example, Logical Groups  118  can be used to classify traffic to or from Endpoints  122 , apply policies to traffic to or from Endpoints  122 , define relationships between Endpoints  122 , define roles of Endpoints  122  (e.g., whether an endpoint consumes or provides a service, etc.), apply rules to traffic to or from Endpoints  122 , apply filters or access control lists (ACLs) to traffic to or from Endpoints  122 , define communication paths for traffic to or from Endpoints  122 , enforce requirements associated with Endpoints  122 , implement security and other configurations associated with Endpoints  122 , etc. 
     In an ACI environment, Logical Groups  118  can be EPGs used to define contracts in the ACI. Contracts can include rules specifying what and how communications between EPGs take place. For example, a contract can define what provides a service, what consumes a service, and what policy objects are related to that consumption relationship. A contract can include a policy that defines the communication path and all related elements of a communication or relationship between endpoints or EPGs. For example, a Web EPG can provide a service that a Client EPG consumes, and that consumption can be subject to a filter (ACL) and a service graph that includes one or more services, such as firewall inspection services and server load balancing. 
       FIG. 2A  illustrates a diagram of an example schema of an SDN network, such as Network Environment  100 . The schema can define objects, properties, and relationships associated with the SDN network. In this example, the schema is a Management Information Model  200  as further described below. However, in other configurations and implementations, the schema can be a different model or specification associated with a different type of network. 
     The following discussion of Management Information Model  200  references various terms which shall also be used throughout the disclosure. Accordingly, for clarity, the disclosure shall first provide below a list of terminology, which will be followed by a more detailed discussion of Management Information Model  200 . 
     As used herein, an “Alias” can refer to a changeable name for a given object. Even if the name of an object, once created, cannot be changed, the Alias can be a field that can be changed. The term “Aliasing” can refer to a rule (e.g., contracts, policies, configurations, etc.) that overlaps other rules. For example, Contract 1 defined in a logical model of a network can be said to be aliasing Contract 2 defined in the logical model of the network if Contract 1 completely overlaps Contract 2. In this example, by aliasing Contract 2, Contract 1 renders Contract 2 redundant or inoperable. For example, if Contract 1 has a higher priority than Contract 2, such aliasing can render Contract 2 redundant based on Contract 1&#39;s overlapping and higher priority characteristics. 
     As used herein, the term “APIC” can refer to one or more controllers (e.g., Controllers  116 ) in an ACI framework. The APIC can provide a unified point of automation and management, policy programming, application deployment, health monitoring for an ACI multitenant fabric. The APIC can be implemented as a single controller, a distributed controller, or a replicated, synchronized, and/or clustered controller. 
     As used herein, the term “BDD” can refer to a binary decision diagram and the term “ROBDD” can refer to a reduced ordered binary decision diagram. A binary decision diagram or reduced ordered binary decision diagram can be a data structure representing variables and/or functions, such as Boolean functions. 
     As used herein, the term “BD” can refer to a bridge domain A bridge domain can be a set of logical ports that share the same flooding or broadcast characteristics. Like a virtual LAN (VLAN), bridge domains can span multiple devices. A bridge domain can be a Layer 2 construct. 
     As used herein, a “Consumer” can refer to an endpoint, resource, and/or EPG that consumes a service. 
     As used herein, a “Context” can refer to an address or network domain, such as a Layer 3 (L3) address domain. In some cases, a context can allow multiple instances of a routing table to exist and work simultaneously. This increases functionality by allowing network paths to be segmented without using multiple devices. Non-limiting examples of a context can include a Virtual Routing and Forwarding (VRF) instance, a private network, and so forth. 
     As used herein, the term “Contract” can refer to rules or configurations that specify what and how communications in a network are conducted (e.g., allowed, denied, filtered, processed, etc.). In an ACI network, contracts can specify how communications between endpoints and/or EPGs take place. In some examples, a contract can provide rules akin to an access control list. 
     As used herein, the term “Distinguished Name” (DN) can refer to a unique name that describes an object, such as an MO, and locates its place in Management Information Model  200 . In some cases, the DN can be (or equate to) a Fully Qualified Domain Name (FQDN). 
     As used herein, the term “Endpoint Group” (EPG) can refer to a logical entity or object associated with a collection or group of endoints as previously described with reference to  FIG. 1B . 
     As used herein, the term “Filter” can refer to a parameter or configuration for allowing communications. For example, in a whitelist model where communications are blocked by default, a communication must be given explicit permission to prevent such communication from being blocked. A filter can define permission(s) for one or more communications or packets. A filter can thus function similar to an ACL or Firewall rule. In some examples, a filter can be implemented in a packet (e.g., TCP/IP) header field, such as L3 protocol type, L4 (Layer 4) ports, and so on, which is used to allow inbound or outbound communications between endpoints or EPGs, for example. 
     As used herein, the term “L2 Out” can refer to a bridged connection. A bridged connection can connect two or more segments of the same network so that they can communicate. In an ACI framework, an L2 out can be a bridged (Layer 2) connection between an ACI fabric (e.g., Fabric  120 ) and an outside Layer 2 network, such as a switch. 
     As used herein, the term “L3 Out” can refer to a routed connection. A routed Layer 3 connection uses a set of protocols that determine the path that data follows in order to travel across networks from its source to its destination. Routed connections can perform forwarding (e.g., IP forwarding) according to a protocol selected, such as BGP (border gateway protocol), OSPF (Open Shortest Path First), EIGRP (Enhanced Interior Gateway Routing Protocol), etc. 
     As used herein, the term “Managed Object” (MO) can refer to an abstract representation of objects managed in a network (e.g., Network Environment  100 ). The objects can be concrete objects (e.g., a switch, server, adapter, etc.), or logical objects (e.g., an application profile, an EPG, a fault, etc.). 
     As used herein, the term “Management Information Tree” (MIT) can refer to a hierarchical management information tree containing the MOs of a system. For example, in ACI, the MIT contains the MOs of the ACI fabric (e.g., Fabric  120 ). The MIT can also be referred to as a Management Information Model (MIM), such as Management Information Model  200 . 
     As used herein, the term “Policy” can refer to one or more specifications for controlling some aspect of system or network behavior. For example, a policy can include a named entity that contains specifications for controlling some aspect of system behavior. To illustrate, a Layer 3 Outside Network Policy can contain the BGP protocol to enable BGP routing functions when connecting Fabric  120  to an outside Layer 3 network. 
     As used herein, the term “Profile” can refer to the configuration details associated with a policy. For example, a profile can include a named entity that contains the configuration details for implementing one or more instances of a policy. To illustrate, a switch node profile for a routing policy can contain the switch-specific configuration details to implement the BGP routing protocol. 
     As used herein, the term “Provider” refers to an object or entity providing a service. For example, a provider can be an EPG that provides a service. 
     As used herein, the term “Subject” refers to one or more parameters in a contract for defining communications. For example, in ACI, subjects in a contract can specify what information can be communicated and how. Subjects can function similar to ACLs. 
     As used herein, the term “Tenant” refers to a unit of isolation in a network. For example, a tenant can be a secure and exclusive computing environment. A tenant can be a unit of isolation from a policy perspective, but does not necessarily represent a private network. Indeed, ACI tenants can contain multiple private networks (e.g., VRFs). Tenants can represent a customer in a service provider setting, an organization or domain in an enterprise setting, or just a grouping of policies. 
     As used herein, the term “VRF” refers to a virtual routing and forwarding instance. The VRF can define a Layer 3 address domain that allows multiple instances of a routing table to exist and work simultaneously. This increases functionality by allowing network paths to be segmented without using multiple devices. Also known as a context or private network. 
     Having described various terms used herein, the disclosure now returns to a discussion of Management Information Model (MIM)  200  in  FIG. 2A . As previously noted, MIM  200  can be a hierarchical management information tree or MIT. Moreover, MIM  200  can be managed and processed by Controllers  116 , such as APICs in an ACI. Controllers  116  can enable the control of managed resources by presenting their manageable characteristics as object properties that can be inherited according to the location of the object within the hierarchical structure of the model. 
     The hierarchical structure of MIM  200  starts with Policy Universe  202  at the top (Root) and contains parent and child nodes  116 ,  204 ,  206 ,  208 ,  210 ,  212 . Nodes  116 ,  202 ,  204 ,  206 ,  208 ,  210 ,  212  in the tree represent the managed objects (MOs) or groups of objects. Each object in the fabric (e.g., Fabric  120 ) has a unique distinguished name (DN) that describes the object and locates its place in the tree. The Nodes  116 ,  202 ,  204 ,  206 ,  208 ,  210 ,  212  can include the various MOs, as described below, which contain policies that govern the operation of the system. 
     Controllers  116  (e.g., APIC controllers) can provide management, policy programming, application deployment, and health monitoring for Fabric  120 . 
     Node  204  includes a tenant container for policies that enable an administrator to exercise domain-based access control. Non-limiting examples of tenants can include:
         User tenants defined by the administrator according to the needs of users. They contain policies that govern the operation of resources such as applications, databases, web servers, network-attached storage, virtual machines, and so on.   A common tenant provided by the system but can be configured by the administrator. It contains policies that govern the operation of resources accessible to all tenants, such as firewalls, load balancers, Layer 4 to Layer 7 services, intrusion detection appliances, and so on.   An infrastructure tenant which can be provided by the system but can be configured by the administrator. It contains policies that govern the operation of infrastructure resources such as the fabric overlay (e.g., VXLAN). It also enables a fabric provider to selectively deploy resources to one or more user tenants. Infrastructure tenant polices can be configurable by the administrator.   A management tenant which can be provided by the system but can be configured by the administrator. It contains policies that govern the operation of fabric management functions used for in-band and out-of-band configuration of fabric nodes. The management tenant contains a private out-of-bound address space for the Controller/Fabric internal communications that is outside the fabric data path that provides access through the management port of the switches. The management tenant enables discovery and automation of communications with VM controllers.       

     Node  206  can contain access policies that govern the operation of switch access ports that provide connectivity to resources such as storage, compute, Layer 2 and Layer 3 (bridged and routed) connectivity, virtual machine hypervisors, Layer 4 to Layer 7 devices, and so on. If a tenant requires interface configurations other than those provided in the default link, Cisco Discovery Protocol (CDP), Link Layer Discovery Protocol (LLDP), Link Aggregation Control Protocol (LACP), or Spanning Tree Protocol (STP), an administrator can configure access policies to enable such configurations on the access ports of Leafs  104 . 
     Node  206  can contain fabric policies that govern the operation of the switch fabric ports, including such functions as Network Time Protocol (NTP) server synchronization, Intermediate System-to-Intermediate System Protocol (IS-IS), Border Gateway Protocol (BGP) route reflectors, Domain Name System (DNS) and so on. The fabric MO contains objects such as power supplies, fans, chassis, and so on. 
     Node  208  can contain VM domains that group VM controllers with similar networking policy requirements. VM controllers can share virtual space (e.g., VLAN or VXLAN space) and application EPGs. Controllers  116  communicate with the VM controller to publish network configurations such as port groups that are then applied to the virtual workloads. 
     Node  210  can contain Layer 4 to Layer 7 service integration life cycle automation framework that enables the system to dynamically respond when a service comes online or goes offline. Policies can provide service device package and inventory management functions. 
     Node  212  can contain access, authentication, and accounting (AAA) policies that govern user privileges, roles, and security domains of Fabric  120 . 
     The hierarchical policy model can fit well with an API, such as a REST API interface. When invoked, the API can read from or write to objects in the MIT. URLs can map directly into distinguished names that identify objects in the MIT. Data in the MIT can be described as a self-contained structured tree text document encoded in XML or JSON, for example. 
       FIG. 2B  illustrates an example object model  220  for a tenant portion of MIM  200 . As previously noted, a tenant is a logical container for application policies that enable an administrator to exercise domain-based access control. A tenant thus represents a unit of isolation from a policy perspective, but does not necessarily represent a private network. Tenants can represent a customer in a service provider setting, an organization or domain in an enterprise setting, or just a convenient grouping of policies. Moreover, tenants can be isolated from one another or can share resources. 
     Tenant portion  204 A of MIM  200  can include various entities, and the entities in Tenant Portion  204 A can inherit policies from parent entities. Non-limiting examples of entities in Tenant Portion  204 A can include Filters  240 , Contracts  236 , Outside Networks  222 , Bridge Domains  230 , VRF Instances  234 , and Application Profiles  224 . 
     Bridge Domains  230  can include Subnets  232 . Contracts  236  can include Subjects  238 . Application Profiles  224  can contain one or more EPGs  226 . Some applications can contain multiple components. For example, an e-commerce application could require a web server, a database server, data located in a storage area network, and access to outside resources that enable financial transactions. Application Profile  224  contains as many (or as few) EPGs as necessary that are logically related to providing the capabilities of an application. 
     EPG  226  can be organized in various ways, such as based on the application they provide, the function they provide (such as infrastructure), where they are in the data center (such as DMZ), or whatever organizing principle that a fabric or tenant administrator chooses to use. 
     EPGs in the fabric can contain various types of EPGs, such as application EPGs, Layer 2 external outside network instance EPGs, Layer 3 external outside network instance EPGs, management EPGs for out-of-band or in-band access, etc. EPGs  226  can also contain Attributes  228 , such as encapsulation-based EPGs, IP-based EPGs, or MAC-based EPGs. 
     As previously mentioned, EPGs can contain endpoints (e.g., EPs  122 ) that have common characteristics or attributes, such as common policy requirements (e.g., security, virtual machine mobility (VMM), QoS, or Layer 4 to Layer 7 services). Rather than configure and manage endpoints individually, they can be placed in an EPG and managed as a group. 
     Policies apply to EPGs, including the endpoints they contain. An EPG can be statically configured by an administrator in Controllers  116 , or dynamically configured by an automated system such as VCENTER or OPENSTACK. 
     To activate tenant policies in Tenant Portion  204 A, fabric access policies should be configured and associated with tenant policies. Access policies enable an administrator to configure other network configurations, such as port channels and virtual port channels, protocols such as LLDP, CDP, or LACP, and features such as monitoring or diagnostics. 
       FIG. 2C  illustrates an example Association  260  of tenant entities and access entities in MIM  200 . Policy Universe  202  contains Tenant Portion  204 A and Access Portion  206 A. Thus, Tenant Portion  204 A and Access Portion  206 A are associated through Policy Universe  202 . 
     Access Portion  206 A can contain fabric and infrastructure access policies. Typically, in a policy model, EPGs are coupled with VLANs. For traffic to flow, an EPG is deployed on a leaf port with a VLAN in a physical, VMM, L2 out, L3 out, or Fiber Channel domain, for example. 
     Access Portion  206 A thus contains Domain Profile  236  which can define a physical, VMM, L2 out, L3 out, or Fiber Channel domain, for example, to be associated to the EPGs. Domain Profile  236  contains VLAN Instance Profile  238  (e.g., VLAN pool) and Attacheable Access Entity Profile (AEP)  240 , which are associated directly with application EPGs. The AEP  240  deploys the associated application EPGs to the ports to which it is attached, and automates the task of assigning VLANs. While a large data center can have thousands of active VMs provisioned on hundreds of VLANs, Fabric  120  can automatically assign VLAN IDs from VLAN pools. This saves time compared with trunking down VLANs in a traditional data center. 
       FIG. 2D  illustrates a schematic diagram of example models for a network, such as Network Environment  100 . The models can be generated based on specific configurations and/or network state parameters associated with various objects, policies, properties, and elements defined in MIM  200 . The models can be implemented for network analysis and assurance, and may provide a depiction of the network at various stages of implementation and levels of the network. 
     As illustrated, the models can include L_Model  270 A (Logical Model), LR_Model  270 B (Logical Rendered Model or Logical Runtime Model), Li_Model  272  (Logical Model for i), Ci_Model  274  (Concrete model for i), and/or Hi_Model  276  (Hardware Model for i). 
     L_Model  270 A is the logical representation of various elements in MIM  200  as configured in a network (e.g., Network Environment  100 ), such as objects, object properties, object relationships, and other elements in MIM  200  as configured in a network. L_Model  270 A can be generated by Controllers  116  based on configurations entered in Controllers  116  for the network, and thus represents the logical configuration of the network at Controllers  116 . This is the declaration of the “end-state” expression that is desired when the elements of the network entities (e.g., applications, tenants, etc.) are connected and Fabric  120  is provisioned by Controllers  116 . Because L_Model  270 A represents the configurations entered in Controllers  116 , including the objects and relationships in MIM  200 , it can also reflect the “intent” of the administrator: how the administrator wants the network and network elements to behave. 
     L_Model  270 A can be a fabric or network-wide logical model. For example, L_Model  270 A can account configurations and objects from each of Controllers  116 . As previously explained, Network Environment  100  can include multiple Controllers  116 . In some cases, two or more Controllers  116  may include different configurations or logical models for the network. In such cases, L_Model  270 A can obtain any of the configurations or logical models from Controllers  116  and generate a fabric or network wide logical model based on the configurations and logical models from all Controllers  116 . L_Model  270 A can thus incorporate configurations or logical models between Controllers  116  to provide a comprehensive logical model. L_Model  270 A can also address or account for any dependencies, redundancies, conflicts, etc., that may result from the configurations or logical models at the different Controllers  116 . 
     LR_Model  270 B is the abstract model expression that Controllers  116  (e.g., APICs in ACI) resolve from L_Model  270 A. LR_Model  270 B can provide the configuration components that would be delivered to the physical infrastructure (e.g., Fabric  120 ) to execute one or more policies. For example, LR_Model  270 B can be delivered to Leafs  104  in Fabric  120  to configure Leafs  104  for communication with attached Endpoints  122 . LR_Model  270 B can also incorporate state information to capture a runtime state of the network (e.g., Fabric  120 ). 
     In some cases, LR_Model  270 B can provide a representation of L_Model  270 A that is normalized according to a specific format or expression that can be propagated to, and/or understood by, the physical infrastructure of Fabric  120  (e.g., Leafs  104 , Spines  102 , etc.). For example, LR_Model  270 B can associate the elements in L_Model  270 A with specific identifiers or tags that can be interpreted and/or compiled by the switches in Fabric  120 , such as hardware plane identifiers used as classifiers. 
     Li_Model  272  is a switch-level or switch-specific model obtained from L_Model  270 A and/or LR_Model  270 B. Li_Model  272  can project L_Model  270 A and/or LR_Model  270 B on a specific switch or device i, and thus can convey how L_Model  270 A and/or LR_Model  270 B should appear or be implemented at the specific switch or device i. 
     For example, Li_Model  272  can project L_Model  270 A and/or LR_Model  270 B pertaining to a switch i to capture a switch-level representation of L_Model  270 A and/or LR_Model  270 B at switch i. To illustrate, Li_Model  272  L 1  can represent L_Model  270 A and/or LR_Model  270 B projected to, or implemented at, Leaf 1 ( 104 ). Thus, Li_Model  272  can be generated from L_Model  270 A and/or LR_Model  270 B for individual devices (e.g., Leafs  104 ) on Fabric  120 . 
     In some cases, Li_Model  272  can be represented using JSON (JavaScript Object Notation). For example, Li_Model  272  can include JSON objects, such as Rules, Filters, Entries, and Scopes. 
     Ci_Model  274  is the actual in-state configuration at the individual fabric member i (e.g., switch i). In other words, Ci_Model  274  is a switch-level or switch-specific model that is based on Li_Model  272 . For example, Controllers  116  can deliver Li_Model  272  to Leaf 1 ( 104 ). Leaf 1 ( 104 ) can take Li_Model  272 , which can be specific to Leaf 1 ( 104 ), and render the policies in Li_Model  272  into a concrete model, Ci_Model  274 , that runs on Leaf 1 ( 104 ). Leaf 1 ( 104 ) can render Li_Model  272  via the OS on Leaf 1 ( 104 ), for example. Thus, Ci_Model  274  can be analogous to compiled software, as it is the form of Li_Model  272  that the switch OS at Leaf 1 ( 104 ) can execute. 
     In some cases, Li_Model  272  and Ci_Model  274  can have a same or similar format. For example, Li_Model  272  and Ci_Model  274  can be based on JSON objects. Having the same or similar format can facilitate objects in Li_Model  272  and Ci_Model  274  to be compared for equivalence or congruence. Such equivalence or congruence checks can be used for network analysis and assurance, as further described herein. 
     Hi_Model  276  is also a switch-level or switch-specific model for switch i, but is based on Ci_Model  274  for switch i. Hi_Model  276  is the actual configuration (e.g., rules) stored or rendered on the hardware or memory (e.g., TCAM memory) at the individual fabric member i (e.g., switch i). For example, Hi_Model  276  can represent the configurations (e.g., rules) which Leaf 1 ( 104 ) stores or renders on the hardware (e.g., TCAM memory) of Leaf 1 ( 104 ) based on Ci_Model  274  at Leaf 1 ( 104 ). The switch OS at Leaf 1 ( 104 ) can render or execute Ci_Model  274 , and Leaf 1 ( 104 ) can store or render the configurations from Ci_Model  274  in storage, such as the TCAM at Leaf 1 ( 104 ). The configurations from Hi_Model  276  stored or rendered by Leaf 1 ( 104 ) represent the configurations that will be implemented by Leaf 1 ( 104 ) when processing traffic. 
     While Models  272 ,  274 ,  276  are shown as device-specific models, similar models can be generated or aggregated for a collection of fabric members (e.g., Leafs  104  and/or Spines  102 ) in Fabric  120 . When combined, device-specific models, such as Model  272 , Model  274 , and/or Model  276 , can provide a representation of Fabric  120  that extends beyond a particular device. For example, in some cases, Li_Model  272 , Ci_Model  274 , and/or Hi_Model  276  associated with some or all individual fabric members (e.g., Leafs  104  and Spines  102 ) can be combined or aggregated to generate one or more aggregated models based on the individual fabric members. 
     As referenced herein, the terms H Model, T Model, and TCAM Model can be used interchangeably to refer to a hardware model, such as Hi_Model  276 . For example, Ti Model, Hi Model and TCAMi Model may be used interchangeably to refer to Hi_Model  276 . 
     Models  270 A,  270 B,  272 ,  274 ,  276  can provide representations of various aspects of the network or various configuration stages for MIM  200 . For example, one or more of Models  270 A,  270 B,  272 ,  274 ,  276  can be used to generate Underlay Model  278  representing one or more aspects of Fabric  120  (e.g., underlay topology, routing, etc.), Overlay Model  280  representing one or more aspects of the overlay or logical segment(s) of Network Environment  100  (e.g., COOP, MPBGP, tenants, VRFs, VLANs, VXLANs, virtual applications, VMs, hypervisors, virtual switching, etc.), Tenant Model  282  representing one or more aspects of Tenant portion  204 A in MIM  200  (e.g., security, forwarding, service chaining, QoS, VRFs, BDs, Contracts, Filters, EPGs, subnets, etc.), Resources Model  284  representing one or more resources in Network Environment  100  (e.g., storage, computing, VMs, port channels, physical elements, etc.), etc. 
     In general, L_Model  270 A can be the high-level expression of what exists in the LR_Model  270 B, which should be present on the concrete devices as Ci_Model  274  and Hi_Model  276  expression. If there is a gap between models, there may be inconsistent configurations or problems. 
       FIG. 3A  illustrates a diagram of an example Assurance Appliance System  300  for network assurance. In this example, Assurance Appliance System  300  can include k Resources  110  (e.g., VMs) operating in cluster mode. Resources  110  can refer to VMs, software containers, bare metal devices, Endpoints  122 , or any other physical or logical systems or components. It should be noted that, while  FIG. 3A  illustrates a cluster mode configuration, other configurations are also contemplated herein, such as a single mode configuration (e.g., single VM, container, or server) or a service chain for example. 
     Assurance Appliance System  300  can run on one or more Servers  106 , Resources  110 , Hypervisors  108 , EPs  122 , Leafs  104 , Controllers  116 , or any other system or resource. For example, Assurance Appliance System  300  can be a logical service or application running on one or more Resources  110  in Network Environment  100 . 
     The Assurance Appliance System  300  can include Data Framework  308  (e.g., APACHE APEX, HADOOP, HDFS, ZOOKEEPER, etc.). In some cases, assurance checks can be written as, or provided by, individual operators that reside in Data Framework  308 . This enables a natively horizontal scale-out architecture that can scale to arbitrary number of switches in Fabric  120  (e.g., ACI fabric). 
     Assurance Appliance System  300  can poll Fabric  120  at a configurable periodicity (e.g., an epoch). In some examples, the analysis workflow can be setup as a DAG (Directed Acyclic Graph) of Operators  310 , where data flows from one operator to another and eventually results are generated and persisted to Database  302  for each interval (e.g., each epoch). 
     The north-tier implements API Server (e.g., APACHE TOMCAT, SPRING framework, etc.)  304  and Web Server  306 . A graphical user interface (GUI) interacts via the APIs exposed to the customer. These APIs can also be used by the customer to collect data from Assurance Appliance System  300  for further integration into other tools. 
     Operators  310  in Data Framework  308  can together support assurance operations. Below are non-limiting examples of assurance operations that can be performed by Assurance Appliance System  300  via Operators  310 . 
     Security Policy Adherence 
     Assurance Appliance System  300  can check to make sure the configurations or specification from L_Model  270 A, which may reflect the user&#39;s intent for the network, including for example the security policies and contracts, are correctly implemented and/or rendered in Li_Model  272 , Ci_Model  274 , and Hi_Model  276 , and thus properly implemented and rendered by the fabric members (e.g., Leafs  104 ), and report any errors, contract violations, or irregularities found. 
     Static Policy Analysis 
     Assurance Appliance System  300  can check for issues in the specification of the user&#39;s intent or intents (e.g., identify contradictory or conflicting policies in L_Model  270 A). Assurance Appliance System  300  can identify lint events based on the intent specification of a network. The lint and policy analysis can include semantic and/or syntactic checks of the intent specification(s) of a network. 
     TCAM Utilization 
     TCAM is a scarce resource in the fabric (e.g., Fabric  120 ). However, Assurance Appliance System  300  can analyze the TCAM utilization by the network data (e.g., Longest Prefix Match (LPM) tables, routing tables, VLAN tables, BGP updates, etc.), Contracts, Logical Groups  118  (e.g., EPGs), Tenants, Spines  102 , Leafs  104 , and other dimensions in Network Environment  100  and/or objects in MIM  200 , to provide a network operator or user visibility into the utilization of this scarce resource. This can greatly help for planning and other optimization purposes. 
     Endpoint Checks 
     Assurance Appliance System  300  can validate that the fabric (e.g. fabric  120 ) has no inconsistencies in the Endpoint information registered (e.g., two leafs announcing the same endpoint, duplicate subnets, etc.), among other such checks. 
     Tenant Routing Checks 
     Assurance Appliance System  300  can validate that BDs, VRFs, subnets (both internal and external), VLANs, contracts, filters, applications, EPGs, etc., are correctly programmed 
     Infrastructure Routing 
     Assurance Appliance System  300  can validate that infrastructure routing (e.g., IS-IS protocol) has no convergence issues leading to black holes, loops, flaps, and other problems. 
     MP-BGP Route Reflection Checks 
     The network fabric (e.g., Fabric  120 ) can interface with other external networks and provide connectivity to them via one or more protocols, such as Border Gateway Protocol (BGP), Open Shortest Path First (OSPF), etc. The learned routes are advertised within the network fabric via, for example, MP-BGP. These checks can ensure that a route reflection service via, for example, MP-BGP (e.g., from Border Leaf) does not have health issues. 
     Logical Lint and Real-Time Change Analysis 
     Assurance Appliance System  300  can validate rules in the specification of the network (e.g., L_Model  270 A) are complete and do not have inconsistencies or other problems. MOs in the MIM  200  can be checked by Assurance Appliance System  300  through syntactic and semantic checks performed on L_Model  270 A and/or the associated configurations of the MOs in MIM  200 . Assurance Appliance System  300  can also verify that unnecessary, stale, unused or redundant configurations, such as contracts, are removed. 
       FIG. 3B  illustrates an architectural diagram of an example system  350  for network assurance, such as Assurance Appliance System  300 . In some cases, system  350  can correspond to the DAG of Operators  310  previously discussed with respect to  FIG. 3A   
     In this example, Topology Explorer  312  communicates with Controllers  116  (e.g., APIC controllers) in order to discover or otherwise construct a comprehensive topological view of Fabric  120  (e.g., Spines  102 , Leafs  104 , Controllers  116 , Endpoints  122 , and any other components as well as their interconnections). While various architectural components are represented in a singular, boxed fashion, it is understood that a given architectural component, such as Topology Explorer  312 , can correspond to one or more individual Operators  310  and may include one or more nodes or endpoints, such as one or more servers, VMs, containers, applications, service functions (e.g., functions in a service chain or virtualized network function), etc. 
     Topology Explorer  312  is configured to discover nodes in Fabric  120 , such as Controllers  116 , Leafs  104 , Spines  102 , etc. Topology Explorer  312  can additionally detect a majority election performed amongst Controllers  116 , and determine whether a quorum exists amongst Controllers  116 . If no quorum or majority exists, Topology Explorer  312  can trigger an event and alert a user that a configuration or other error exists amongst Controllers  116  that is preventing a quorum or majority from being reached. Topology Explorer  312  can detect Leafs  104  and Spines  102  that are part of Fabric  120  and publish their corresponding out-of-band management network addresses (e.g., IP addresses) to downstream services. This can be part of the topological view that is published to the downstream services at the conclusion of Topology Explorer&#39;s  312  discovery epoch (e.g., 5 minutes, or some other specified interval). 
     In some examples, Topology Explorer  312  can receive as input a list of Controllers  116  (e.g., APIC controllers) that are associated with the network/fabric (e.g., Fabric  120 ). Topology Explorer  312  can also receive corresponding credentials to login to each controller. Topology Explorer  312  can retrieve information from each controller using, for example, REST calls. Topology Explorer  312  can obtain from each controller a list of nodes (e.g., Leafs  104  and Spines  102 ), and their associated properties, that the controller is aware of. Topology Explorer  312  can obtain node information from Controllers  116  including, without limitation, an IP address, a node identifier, a node name, a node domain, a node URI, a node_dm, a node role, a node version, etc. 
     Topology Explorer  312  can also determine if Controllers  116  are in quorum, or are sufficiently communicatively coupled amongst themselves. For example, if there are n controllers, a quorum condition might be met when (n/2+1) controllers are aware of each other and/or are communicatively coupled. Topology Explorer  312  can make the determination of a quorum (or identify any failed nodes or controllers) by parsing the data returned from the controllers, and identifying communicative couplings between their constituent nodes. Topology Explorer  312  can identify the type of each node in the network, e.g. spine, leaf, APIC, etc., and include this information in the topology information generated (e.g., topology map or model). 
     If no quorum is present, Topology Explorer  312  can trigger an event and alert a user that reconfiguration or suitable attention is required. If a quorum is present, Topology Explorer  312  can compile the network topology information into a JSON object and pass it downstream to other operators or services, such as Unified Collector  314 . 
     Unified Collector  314  can receive the topological view or model from Topology Explorer  312  and use the topology information to collect information for network assurance from Fabric  120 . Unified Collector  314  can poll nodes (e.g., Controllers  116 , Leafs  104 , Spines  102 , etc.) in Fabric  120  to collect information from the nodes. 
     Unified Collector  314  can include one or more collectors (e.g., collector devices, operators, applications, VMs, etc.) configured to collect information from Topology Explorer  312  and/or nodes in Fabric  120 . For example, Unified Collector  314  can include a cluster of collectors, and each of the collectors can be assigned to a subset of nodes within the topological model and/or Fabric  120  in order to collect information from their assigned subset of nodes. For performance, Unified Collector  314  can run in a parallel, multi-threaded fashion. 
     Unified Collector  314  can perform load balancing across collectors in order to streamline the efficiency of the overall collection process. Load balancing can be optimized by managing the distribution of subsets of nodes to collectors, for example by randomly hashing nodes to collectors. 
     In some cases, Assurance Appliance System  300  can run multiple instances of Unified Collector  314 . This can also allow Assurance Appliance System  300  to distribute the task of collecting data for each node in the topology (e.g., Fabric  120  including Spines  102 , Leafs  104 , Controllers  116 , etc.) via sharding and/or load balancing, and map collection tasks and/or nodes to a particular instance of Unified Collector  314  with data collection across nodes being performed in parallel by various instances of Unified Collector  314 . Within a given node, commands and data collection can be executed serially. Assurance Appliance System  300  can control the number of threads used by each instance of Unified Collector  314  to poll data from Fabric  120 . 
     Unified Collector  314  can collect models (e.g., L_Model  270 A and/or LR_Model  270 B) from Controllers  116 , switch software configurations and models (e.g., Ci_Model  274 ) from nodes (e.g., Leafs  104  and/or Spines  102 ) in Fabric  120 , hardware configurations and models (e.g., Hi_Model  276 ) from nodes (e.g., Leafs  104  and/or Spines  102 ) in Fabric  120 , etc. Unified Collector  314  can collect Ci_Model  274  and Hi_Model  276  from individual nodes or fabric members, such as Leafs  104  and Spines  102 , and L_Model  270 A and/or LR_Model  270 B from one or more controllers (e.g., Controllers  116 ) in Network Environment  100 . 
     Unified Collector  314  can poll devices that Topology Explorer  312  discovers to collect data from Fabric  120  (e.g., from the constituent members of the fabric). Unified Collector  314  can collect the data using interfaces exposed by Controllers  116  and/or switch software (e.g., switch OS), including, for example, a Representation State Transfer Interface and a Secure Shell Interface. 
     In some cases, Unified Collector  314  collects L_Model  270 A, LR_Model  270 B, and/or Ci_Model  274  via a REST API, and the hardware information (e.g., configurations, tables, fabric card information, rules, routes, etc.) via SSH using utilities provided by the switch software, such as virtual shell (VSH or VSHELL) for accessing the switch command-line interface (CLI) or VSH_LC shell for accessing runtime state of the line card. 
     Unified Collector  314  can poll other information from Controllers  116 , including, without limitation: topology information, tenant forwarding/routing information, tenant security policies, contracts, interface policies, physical domain or VMM domain information, OOB (out-of-band) management IP&#39;s of nodes in the fabric, etc. 
     Unified Collector  314  can poll information from nodes (e.g., Leafs  104  and Spines  102 ) in Fabric  120 , including without limitation: Ci_Models  274  for VLANs, BDs, and security policies; Link Layer Discovery Protocol (LLDP) information of nodes (e.g., Leafs  104  and/or Spines  102 ); endpoint information from EPM/COOP; fabric card information from Spines  102 ; routing information base (RIB) tables from nodes in Fabric  120 ; security group hardware tables (e.g., TCAM tables) from nodes in Fabric  120 ; etc. 
     In some cases, Unified Collector  314  can obtain runtime state from the network and incorporate runtime state information into L_Model  270 A and/or LR_Model  270 B. Unified Collector  314  can also obtain multiple logical models from Controllers  116  and generate a comprehensive or network-wide logical model (e.g., L_Model  270 A and/or LR_Model  270 B) based on the logical models. Unified Collector  314  can compare logical models from Controllers  116 , resolve dependencies, remove redundancies, etc., and generate a single L_Model  270 A and/or LR_Model  270 B for the entire network or fabric. 
     Unified Collector  314  can collect the entire network state across Controllers  116  and fabric nodes or members (e.g., Leafs  104  and/or Spines  102 ). For example, Unified Collector  314  can use a REST interface and an SSH interface to collect the network state. This information collected by Unified Collector  314  can include data relating to the link layer, VLANs, BDs, VRFs, security policies, etc. The state information can be represented in LR_Model  270 B, as previously mentioned. Unified Collector  314  can then publish the collected information and models to any downstream operators that are interested in or require such information. Unified Collector  314  can publish information as it is received, such that data is streamed to the downstream operators. 
     Data collected by Unified Collector  314  can be compressed and sent to downstream services. In some examples, Unified Collector  314  can collect data in an online or real-time fashion, and send the data downstream as it is collected for further analysis. In some examples, Unified Collector  314  can collect data in an offline fashion, and compile the data for later analysis or transmission. 
     Assurance Appliance System  300  can contact Controllers  116 , Spines  102 , Leafs  104 , and other nodes to collect various types of data. In some scenarios, Assurance Appliance System  300  may experience a failure (e.g., connectivity problem, hardware or software error, etc.) that prevents it from being able to collect data for a period of time. Assurance Appliance System  300  can handle such failures seamlessly, and generate events based on such failures. 
     Switch Logical Policy Generator  316  can receive L_Model  270 A and/or LR_Model  270 B from Unified Collector  314  and calculate Li_Model  272  for each network device i (e.g., switch i) in Fabric  120 . For example, Switch Logical Policy Generator  316  can receive L_Model  270 A and/or LR_Model  270 B and generate Li_Model  272  by projecting a logical model for each individual node i (e.g., Spines  102  and/or Leafs  104 ) in Fabric  120 . Switch Logical Policy Generator  316  can generate Li_Model  272  for each switch in Fabric  120 , thus creating a switch logical model based on L_Model  270 A and/or LR_Model  270 B for each switch. 
     Each Li_Model  272  can represent L_Model  270 A and/or LR_Model  270 B as projected or applied at a network device i (e.g., switch i) in Fabric  120 . In some cases, Li_Model  272  can be normalized or formatted in a manner that is compatible with the network device. For example, Li_Model  272  can be formatted in a manner that can be read or executed by the network device. To illustrate, Li_Model  272  can included specific identifiers (e.g., hardware plane identifiers used by Controllers  116  as classifiers, etc.) or tags (e.g., policy group tags) that can be interpreted by the respective network device. In some cases, Li_Model  272  can include JSON objects. For example, Li_Model  272  can include JSON objects to represent rules, filters, entries, scopes, etc. 
     The format used for Li_Model  272  can be the same as, or consistent with, the format of Ci_Model  274 . For example, both Li_Model  272  and Ci_Model  274  may be based on JSON objects. Similar or matching formats can enable Li_Model  272  and Ci_Model  274  to be compared for equivalence or congruence. Such equivalency checks can aid in network analysis and assurance as further explained herein. 
     Switch Logical Configuration Generator  316  can also perform change analysis and generate lint events or records for problems discovered in L_Model  270 A and/or LR_Model  270 B. The lint events or records can be used to generate alerts for a user or network operator. 
     Policy Operator  318  can receive Ci_Model  274  and Hi_Model  276  for each switch from Unified Collector  314 , and Li_Model  272  for each switch from Switch Logical Policy Generator  316 , and perform assurance checks and analysis (e.g., security adherence checks, TCAM utilization analysis, etc.) based on Ci_Model  274 , Hi_Model  276 , and Li_Model  272 . Policy Operator  318  can perform assurance checks on a switch-by-switch basis by comparing one or more models. 
     Returning to Unified Collector  314 , Unified Collector  314  can also send L_Model  270 A and/or LR_Model  270 B to Routing Policy Parser  320 , and Ci_Model  274  and Hi_Model  276  to Routing Parser  326 . 
     Routing Policy Parser  320  can receive L_Model  270 A and/or LR_Model  270 B and parse the model(s) for information that may be relevant to downstream operators, such as Endpoint Checker  322  and Tenant Routing Checker  324 . Similarly, Routing Parser  326  can receive Ci_Model  274  and Hi_Model  276  and parse each model for information for downstream operators, Endpoint Checker  322  and Tenant Routing Checker  324 . 
     After Ci_Model  274 , Hi_Model  276 , L_Model  270 A and/or LR_Model  270 B are parsed, Routing Policy Parser  320  and/or Routing Parser  326  can send cleaned-up protocol buffers (Proto Buffs) to the downstream operators, Endpoint Checker  322  and Tenant Routing Checker  324 . Endpoint Checker  322  can then generate events related to Endpoint violations, such as duplicate IPs, APIPA, etc., and Tenant Routing Checker  324  can generate events related to the deployment of BDs, VRFs, subnets, routing table prefixes, etc. 
       FIG. 4  illustrates an example diagram  400  for constructing node-specific logical networks (e.g., Li_Models  272 ) based on a Logical Model  270  of a network, such as Network Environment  100 . Logical Model  270  can include L_Model  270 A and/or LR_Model  270 B, as shown in  FIG. 2D . Logical Model  270  can include objects and configurations of the network to be pushed to the devices in Fabric  120 , such as Leafs  104 . Logical Model  270  can provide a network-wide representation of the network. Thus, Logical Model  270  can be used to construct a Node-Specific Logical Model (e.g., Li_Model  272 ) for nodes in Fabric  120  (e.g., Leafs  104 ). 
     Logical Model  270  can be adapted for each of the nodes (e.g., Leafs  104 ) in order to generate a respective logical model for each node, which represents, and/or corresponds to, the portion(s) and/or information from Logical Model  270  that is pertinent to the node, and/or the portion(s) and/or information from Logical Model  270  that should be, and/or is, pushed, stored, and/or rendered at the node. Each of the Node-Specific Logical Models, Li_Model  272 , can contain those objects, properties, configurations, data, etc., from Logical Model  270  that pertain to the specific node, including any portion(s) from Logical Model  270  projected or rendered on the specific node when the network-wide intent specified by Logical Model  270  is propagated or projected to the individual node. In other words, to carry out the intent specified in Logical Model  270 , the individual nodes (e.g., Leafs  104 ) can implement respective portions of Logical Model  270  such that together, the individual nodes can carry out the intent specified in Logical Model  270 . 
       FIG. 5A  illustrates a schematic diagram of an example system for policy analysis in a network (e.g., Network Environment  100 ). Policy Analyzer  504  can perform assurance checks to detect configuration violations, logical lint events, contradictory or conflicting policies, unused contracts, incomplete configurations, routing checks, rendering errors, incorrect rules, etc. Policy Analyzer  504  can check the specification of the user&#39;s intent or intents in L_Model  270 A (or Logical Model  270  as shown in  FIG. 4 ) to determine if any configurations in Controllers  116  are inconsistent with the specification of the user&#39;s intent or intents. 
     Policy Analyzer  504  can include one or more of the Operators  310  executed or hosted in Assurance Appliance System  300 . However, in other configurations, Policy Analyzer  504  can run one or more operators or engines that are separate from Operators  310  and/or Assurance Appliance System  300 . For example, Policy Analyzer  504  can be implemented via a VM, a software container, a cluster of VMs or software containers, an endpoint, a collection of endpoints, a service function chain, etc., any of which may be separate from Assurance Appliance System  300 . 
     Policy Analyzer  504  can receive as input Logical Model Collection  502 , which can include Logical Model  270  as shown in  FIG. 4 ; and/or L_Model  270 A, LR_Model  270 B, and/or Li_Model  272  as shown in  FIG. 2D . Policy Analyzer  504  can also receive as input Rules  508 . Rules  508  can be defined, for example, per feature (e.g., per object, per object property, per contract, per rule, etc.) in one or more logical models from the Logical Model Collection  502 . Rules  508  can be based on objects, relationships, definitions, configurations, and any other features in MIM  200 . Rules  508  can specify conditions, relationships, parameters, and/or any other information for identifying configuration violations or issues. 
     Rules  508  can include information for identifying syntactic violations or issues. For example, Rules  508  can include one or more statements and/or conditions for performing syntactic checks. Syntactic checks can verify that the configuration of a logical model and/or the Logical Model Collection  502  is complete, and can help identify configurations or rules from the logical model and/or the Logical Model Collection  502  that are not being used. Syntactic checks can also verify that the configurations in the hierarchical MIM  200  have been properly or completely defined in the Logical Model Collection  502 , and identify any configurations that are defined but not used. To illustrate, Rules  508  can specify that every tenant defined in the Logical Model Collection  502  should have a context configured; every contract in the Logical Model Collection  502  should specify a provider EPG and a consumer EPG; every contract in the Logical Model Collection  502  should specify a subject, filter, and/or port; etc. 
     Rules  508  can also include information for performing semantic checks and identifying semantic violations. Semantic checks can check conflicting rules or configurations. For example, Rule1 and Rule2 can overlap and create aliasing issues, Rule1 can be more specific than Rule2 and result in conflicts, Rule1 can mask Rule2 or inadvertently overrule Rule2 based on respective priorities, etc. Thus, Rules  508  can define conditions which may result in aliased rules, conflicting rules, etc. To illustrate, Rules  508  can indicate that an allow policy for a communication between two objects may conflict with a deny policy for the same communication between two objects if the allow policy has a higher priority than the deny policy. Rules  508  can indicate that a rule for an object renders another rule unnecessary due to aliasing and/or priorities. As another example, Rules  508  can indicate that a QoS policy in a contract conflicts with a QoS rule stored on a node. 
     Policy Analyzer  504  can apply Rules  508  to the Logical Model Collection  502  to check configurations in the Logical Model Collection  502  and output Configuration Violation Events  506  (e.g., alerts, logs, notifications, etc.) based on any issues detected. Configuration Violation Events  506  can include semantic or semantic problems, such as incomplete configurations, conflicting configurations, aliased rules, unused configurations, errors, policy violations, misconfigured objects, incomplete configurations, incorrect contract scopes, improper object relationships, etc. 
     In some cases, Policy Analyzer  504  can iteratively traverse each node in a tree generated based on the Logical Model Collection  502  and/or MIM  200 , and apply Rules  508  at each node in the tree to determine if any nodes yield a violation (e.g., incomplete configuration, improper configuration, unused configuration, etc.). Policy Analyzer  504  can output Configuration Violation Events  506  when it detects any violations. 
       FIG. 5B  illustrates an example equivalency diagram  510  of network models. In this example, the Logical Model  270  can be compared with the Hi_Model  276  obtained from one or more Leafs  104  in the Fabric  120 . This comparison can provide an equivalency check in order to determine whether the logical configuration of the Network Environment  100  at the Controller(s)  116  is consistent with, or conflicts with, the rules rendered on the one or more Leafs  104  (e.g., rules and/or configurations in storage, such as TCAM). For explanation purposes, Logical Model  270  and Hi_Model  276  are illustrated as the models compared in the equivalency check example in  FIG. 5B . However, it should be noted that, in other examples, other models can be checked to perform an equivalency check for those models. For example, an equivalency check can compare Logical Model  270  with Ci_Model  274  and/or Hi_Model  276 , Li_Model  272  with Ci_Model  274  and/or Hi_Model  276 , Ci_Model  274  with Hi_Model  276 , etc. 
     Equivalency checks can identify whether the network operator&#39;s configured intent is consistent with the network&#39;s actual behavior, and whether information propagated between models and/or devices in the network is consistent, conflicts, contains errors, etc. For example, a network operator can define objects and configurations for Network Environment  100  from Controller(s)  116 . Controller(s)  116  can store the definitions and configurations from the network operator and construct a logical model (e.g., L_Model  270 A) of Network Environment  100 . Controller(s)  116  can push the definitions and configurations provided by the network operator and reflected in the logical model to each of the nodes (e.g., Leafs  104 ) in Fabric  120 . In some cases, the Controller(s)  116  may push a node-specific version of the logical model (e.g., Li_Model  272 ) that reflects the information in the logical model of the network (e.g., L_Model  270 A) pertaining to that node. 
     The nodes in the Fabric  120  can receive such information and render or compile rules on the node&#39;s software (e.g., Operating System). The rules/configurations rendered or compiled on the node&#39;s software can be constructed into a Construct Model (e.g., Ci_Model  274 ). The rules from the Construct Model can then be pushed from the node&#39;s software to the node&#39;s hardware (e.g., TCAM) and stored or rendered as rules on the node&#39;s hardware. The rules stored or rendered on the node&#39;s hardware can be constructed into a Hardware Model (e.g., Hi_Model  276 ) for the node. 
     The various models (e.g., Logical Model  270  and Hi_Model  276 ) can thus represent the rules and configurations at each stage (e.g., intent specification at Controller(s)  116 , rendering or compiling on the node&#39;s software, rendering or storing on the node&#39;s hardware, etc.) as the definitions and configurations entered by the network operator are pushed through each stage. Accordingly, an equivalency check of various models, such as Logical Model  270  and Hi_Model  276 , Li_Model  272  and Ci_Model  274  or Hi_Model  276 , Ci_Model  274  and Hi_Model  276 , etc., can be used to determine whether the definitions and configurations have been properly pushed, rendered, and/or stored at any stage associated with the various models. 
     If the models pass the equivalency check, then the definitions and configurations at checked stage (e.g., Controller(s)  116 , software on the node, hardware on the node, etc.) can be verified as accurate and consistent. By contrast, if there is an error in the equivalency check, then a misconfiguration can be detected at one or more specific stages. The equivalency check between various models can also be used to determine where (e.g., at which stage) the problem or misconfiguration has occurred. For example, the stage where the problem or misconfiguration occurred can be ascertained based on which model(s) fail the equivalency check. 
     The Logical Model  270  and Hi_Model  276  can store or render the rules, configurations, properties, definitions, etc., in a respective structure  512 A,  512 B. For example, Logical Model  270  can store or render rules, configurations, objects, properties, etc., in a data structure  512 A, such as a file or object (e.g., JSON, XML, etc.), and Hi_Model  276  can store or render rules, configurations, etc., in a storage  512 B, such as TCAM memory. The structure  512 A,  512 B associated with Logical Model  270  and Hi_Model  276  can influence the format, organization, type, etc., of the data (e.g., rules, configurations, properties, definitions, etc.) stored or rendered. 
     For example, Logical Model  270  can store the data as objects and object properties  514 A, such as EPGs, contracts, filters, tenants, contexts, BDs, network wide parameters, etc. The Hi_Model  276  can store the data as values and tables  514 B, such as value/mask pairs, range expressions, auxiliary tables, etc. As a result, the data in Logical Model  270  and Hi_Model  276  can be normalized, canonized, diagramed, modeled, re-formatted, flattened, etc., to perform an equivalency between Logical Model  270  and Hi_Model  276 . For example, the data can be converted using bit vectors, Boolean functions, ROBDDs, etc., to perform a mathematical check of equivalency between Logical Model  270  and Hi_Model  276 . 
       FIG. 5C  illustrates example Architecture  520  for performing equivalence checks of models. Rather than employing brute force to determine the equivalence of input models, the network models can instead be represented as specific data structures, such as Reduced Ordered Binary Decision Diagrams (ROBDDs) and/or bit vectors. In this example, input models are represented as ROBDDs, where each ROBDD is canonical (unique) to the input rules and their priority ordering. 
     Each network model is first converted to a flat list of priority ordered rules. In some examples, contracts can be specific to EPGs and thus define communications between EPGs, and rules can be the specific node-to-node implementation of such contracts. Architecture  520  includes a Formal Analysis Engine  522 . In some cases, Formal Analysis Engine  522  can be part of Policy Analyzer  504  and/or Assurance Appliance System  300 . For example, Formal Analysis Engine  522  can be hosted within, or executed by, Policy Analyzer  504  and/or Assurance Appliance System  300 . To illustrate, Formal Analysis Engine  522  can be implemented via one or more operators, VMs, containers, servers, applications, service functions, etc., on Policy Analyzer  504  and/or Assurance Appliance System  300 . In other cases, Formal Analysis Engine  522  can be separate from Policy Analyzer  504  and/or Assurance Appliance System  300 . For example, Formal Analysis Engine  522  can be a standalone engine, a cluster of engines hosted on multiple systems or networks, a service function chain hosted on one or more systems or networks, a VM, a software container, a cluster of VMs or software containers, a cloud-based service, etc. 
     Formal Analysis Engine  522  includes an ROBDD Generator  526 . ROBDD Generator  526  receives Input  524  including flat lists of priority ordered rules for Models  272 ,  274 ,  276  as shown in  FIG. 2D . These rules can be represented as Boolean functions, where each rule consists of an action (e.g. Permit, Permit_Log, Deny, Deny_Log) and a set of conditions that will trigger that action (e.g. one or more configurations of traffic, such as a packet source, destination, port, header, QoS policy, priority marking, etc.). For example, a rule might be designed as Permit all traffic on port 80. In some examples, each rule might be an n-bit string with m-fields of key-value pairs. For example, each rule might be a 147 bit string with 13 fields of key-value pairs. 
     As a simplified example, consider a flat list of the priority ordered rules L1, L2, L3, and L4 in Li_Model  272 , where L1 is the highest priority rule and L4 is the lowest priority rule. A given packet is first checked against rule L1. If L1 is triggered, then the packet is handled according to the action contained in rule L1. Otherwise, the packet is then checked against rule L2. If L2 is triggered, then the packet is handled according to the action contained in rule L2. Otherwise, the packet is then checked against rule L3, and so on, until the packet either triggers a rule or reaches the end of the listing of rules. 
     The ROBDD Generator  526  can calculate one or more ROBDDs or BDDs (binary decision diagrams) for the constituent rules L1-L4 of one or more models. An ROBDD can be generated for each action encoded by the rules L1-L4, or each action that may be encoded by the rules L1-L4, such that there is a one-to-one correspondence between the number of actions and the number of ROBDDs or BDDs generated. For example, the rules L1-L4 might be used to generate BDDs  540 , including L_Permit BDD , L_Permit_Log BDD , L_Deny BDD , and L_Deny_Log BDD . 
     Generally, ROBDD Generator  526  begins its calculation with the highest priority rule of Input  524  in the listing of rules received. Continuing the example of rules L1-L4 in Li_Model  272 , ROBDD Generator  526  begins with rule L1. Based on the action specified by rule L1 (e.g. Permit, Permit_Log, Deny, Deny_Log), rule L1 is added to the corresponding ROBDD for that action. Next, rule L2 will be added to the corresponding ROBDD for the action that it specifies. In some examples, a reduced form of L2 can be used, given by L1′L2, with L1′ denoting the inverse of L1. This process is then repeated for rules L3 and L4, which have reduced forms given by (L1+L2)′L3 and (L1+L2+L3)′L4, respectively. 
     Notably, L_Permit BDD  and each of the other action-specific ROBDDs encode the portion of each constituent rule L1, L2, L3, L4 that is not already captured by higher priority rules. That is, L1′L2 represents the portion of rule L2 that does not overlap with rule L1, (L1+L2)′L3 represents the portion of rule L3 that does not overlap with either rules L1 or L2, and (L1+L2+L3)′L4 represents the portion of rule L4 that does not overlap with either rules L1 or L2 or L3. This reduced form can be independent of the action specified by an overlapping or higher priority rule and can be calculated based on the conditions that will cause the higher priority rules to trigger. 
     ROBDD Generator  526  likewise can generate an ROBDD for each associated action of the remaining models associated with Input  524 , such as Ci_Model  274  and Hi_Model  276  in this example, or any other models received by ROBDD Generator  526 . From the ROBDDs generated, the formal equivalence of any two or more ROBDDs of models can be checked via Equivalence Checker  528 , which builds a conflict ROBDD encoding areas of conflict between input ROBDDs. 
     In some examples, the ROBDDs being compared will be associated with the same action. For example, Equivalence Checker  528  can check the formal equivalence of L_Permit BDD  against H_Permit BDD  by calculating the exclusive disjunction between L_Permit BDD  and H_Permit BDD . More particularly, L_Permit BDD ⊕H_Permit BDD  (i.e. L_Permit BDD  XOR H_Permit BDD ) is calculated, although it is understood that the description below is also applicable to other network models (e.g., Logical Model  270 , L_Model  270 A, LR_Model  270 B, Li_Model  272 , Ci_Model  274 , Hi_Model  276 , etc.) and associated actions (Permit, Permit_Log, Deny, Deny_Log, etc.). 
     An example calculation is illustrated in  FIG. 6A , which depicts a simplified representation of a Permit conflict ROBDD  600 A calculated for L_Permit BDD  and H_Permit BDD . As illustrated, L_Permit BDD  includes a unique portion  602  (shaded) and an overlap  604  (unshaded) Similarly, H_Permit BDD  includes a unique portion  606  (shaded) and the same overlap  604 . 
     The Permit conflict ROBDD  600 A includes unique portion  602 , which represents the set of packet configurations and network actions that are encompassed within L_Permit BDD  but not H_Permit BDD  (i.e. calculated as L_Permit BDD *H_Permit BDD ′), and unique portion  606 , which represents the set of packet configurations and network actions that are encompassed within H_Permit BDD  but not L_Permit BDD  (i.e. calculated as L_Permit BDD ′*H_Permit BDD ). Note that the unshaded overlap  604  is not part of Permit conflict ROBDD  600 A. 
     Conceptually, the full circle illustrating L_Permit BDD  (e.g. unique portion  602  and overlap  604 ) represents the fully enumerated set of packet configurations that are encompassed within, or trigger, the Permit rules encoded by input model Li_Model  272 . For example, assume Li_Model  272  contains the rules: 
     L1: port=[1-3] Permit 
     L2: port=4 Permit 
     L3: port=[6-8] Permit 
     L4: port=9 Deny 
     where ‘port’ represents the port number of a received packet, then the circle illustrating L_Permit BDD  contains the set of all packets with port=[1-3], 4, [6-8] that are permitted. Everything outside of this full circle represents the space of packet conditions and/or actions that are different from those specified by the Permit rules contained in Li_Model  272 . For example, rule L4 encodes port=9 Deny and would fall outside of the region carved out by L_Permit BDD . 
     Similarly, the full circle illustrating H_Permit BDD  (e.g., unique portion  606  and overlap  604 ) represents the fully enumerated set of packet configurations and network actions encompassed within, or trigger, the Permit rules encoded by the input model Hi_Model  276 , which contains the rules and/or configurations rendered in hardware. Assume that Hi_Model  276  contains the rules: 
     H1: port=[1-3] Permit 
     H2: port=5 Permit 
     H3: port=[6-8] Deny 
     H4: port=10 Deny_Log 
     In the comparison between L_Permit BDD  and H_Permit BDD , only rules L1 and H1 are equivalent, because they match on both packet condition and action. L2 and H2 are not equivalent because even though they specify the same action (Permit), this action is triggered on a different port number (4 vs. 5). L3 and H3 are not equivalent because even though they trigger on the same port number (6-8), they trigger different actions (Permit vs. Deny). L4 and H4 are not equivalent because they trigger on a different port number (9 vs. 10) and also trigger different actions (Deny vs. Deny_Log). As such, overlap  604  contains only the set of packets that are captured by Permit rules L1 and H1, i.e., the packets with port=[1-3] that are permitted. Unique portion  602  contains only the set of packets that are captured by the Permit rules L2 and L3, while unique portion  606  contains only the set of packets that are captured by Permit rule H2. These two unique portions encode conflicts between the packet conditions upon which Li_Model  272  will trigger a Permit, and the packet conditions upon which the hardware rendered Hi_Model  276  will trigger a Permit. Consequently, it is these two unique portions  602  and  606  that make up Permit conflict ROBDD  600 A. The remaining rules L4, H3, and H4 are not Permit rules and consequently are not represented in L_Permit BDD , H_Permit BDD , or Permit conflict ROBDD  600 A. 
     In general, the action-specific overlaps between any two models contain the set of packets that will trigger the same action no matter whether the rules of the first model or the rules of the second model are applied, while the action-specific conflict ROBDDs between these same two models contains the set of packets that result in conflicts by way of triggering on a different condition, triggering a different action, or both. 
     It should be noted that in the example described with respect to  FIG. 6A , Li_Model  272  and Hi_Model  276  are used as example input models for illustration purposes, but other models may be similarly used. For example, in some cases, a conflict ROBDD can be calculated based on Logical Model  270 , shown in  FIG. 4 , and/or any of the models  270 A,  270 B,  272 ,  274 ,  276  in  FIG. 2D . 
     Moreover, for purposes of clarity in the discussion above, Permit conflict ROBDD  600 A portrays L_Permit BDD  and H_Permit BDD  as singular entities rather than illustrating the effect of each individual rule. Accordingly,  FIGS. 6B and 6C  present Permit conflict ROBDDs with individual rules depicted.  FIG. 6B  presents a Permit conflict ROBDD  600 B taken between the listing of rules L1, L2, H1, and H2.  FIG. 6C  presents a Permit conflict ROBDD  600 C that adds rule H3 to Permit conflict ROBDD  600 B. Both Figures maintain the same shading convention introduced in  FIG. 6A , wherein a given conflict ROBDD comprises only the shaded regions that are shown. 
     Turning to  FIG. 6B , illustrated is a Permit conflict ROBDD  600 B that is calculated across a second L_Permit BDD  consisting of rules L1 and L2, and a second H_Permit BDD  consisting of rules H1 and H2. As illustrated, rules L1 and H1 are identical, and entirely overlap with one another both rules consists of the overlap  612  and overlap  613 . Overlap  612  is common between rules L1 and H1, while overlap  613  is common between rules L1, H1, and L2. For purposes of subsequent explanation, assume that rules L1 and H1 are both defined by port=[1-13] Permit. 
     Rules L2 and H2 are not identical. Rule L2 consists of overlap  613 , unique portion  614 , and overlap  616 . Rule H2 consists only of overlap  616 , as it is contained entirely within the region encompassed by rule L2. For example, rule L2 might be port=[10-20] Permit, whereas rule H2 might be port=[15-17] Permit. Conceptually, this is an example of an error that might be encountered by a network assurance check, wherein an Li_Model  272  rule (e.g., L2) specified by a user intent was incorrectly rendered into a node&#39;s memory (e.g., switch TCAM) as an Hi_Model  276  rule (e.g., H2). In particular, the scope of the rendered Hi_Model  276  rule H2 is smaller than the intended scope specified by the user intent contained in L2. For example, such a scenario could arise if a switch TCAM runs out of space, and does not have enough free entries to accommodate a full representation of an Li_Model  272  rule. 
     Regardless of the cause, this error is detected by the construction of the Permit conflict ROBDD  600 B as L_Permit BDD ⊕H_Permit BDD , where the results of this calculation are indicated by the shaded unique portion  614 . This unique portion  614  represents the set of packet configurations and network actions that are contained within L_Permit BDD  but not H_Permit BDD . In particular, unique portion  614  is contained within the region encompassed by rule L2 but is not contained within either of the regions encompassed by rules H1 and H2, and specifically comprises the set defined by port=[14,18-20] Permit. 
     To understand how this is determined, recall that rule L2 is represented by port=[10-20] Permit. Rule H1 carves out the portion of L2 defined by port=[10-13] Permit, which is represented as overlap  613 . Rule H2 carves out the portion of L2 defined by port=[15-17] Permit, which is represented as overlap  616 . This leaves port=[14,18-20] Permit as the non-overlap portion of the region encompassed by L2, and thus unique portion  614  comprises Permit conflict ROBDD  600 B. 
       FIG. 6C  illustrates Permit conflict ROBDD  600 C which is identical to Permit conflict ROBDD  600 B with the exception of a newly-added third rule, H3: port=[19-25] Permit. Rule H3 includes an overlap portion  628 , which represents the set of conditions and actions contained in both rules H3 and L2, and further consists of a unique portion  626 , which represents the set of conditions and actions that are contained only in rule H3. Conceptually, this could represent an error wherein an Li_Model  272  rule (e.g., L2) specified by a user intent was incorrectly rendered into node memory as two Hi_Model  276  rules (e.g., H2 and H3). There is no inherent fault with a single Li_Model  272  rule being represented as multiple Hi_Model  276  rules. Rather, the fault herein lies in the fact that the two corresponding Hi_Model  276  rules do not adequately capture the full extent of the set of packet configurations encompassed by Permit rule L2. Rule H2 is too narrow in comparison to rule L2, as discussed above with respect to  FIG. 6B , and rule H3 is both too narrow and improperly extended beyond the boundary of the region encompasses by rule L2. 
     As was the case before, this error is detected by the construction of the conflict ROBDD  600 C, as L_Permit BDD ⊕H_Permit BDD , where the results of this calculation are indicated by the shaded unique portion  624 , representing the set of packet configurations and network actions that are contained within L_Permit BDD  but not H_Permit BDD , and the shaded unique portion  626 , representing the set of packet configurations and network actions that are contained within H_Permit BDD  but not L_Permit BDD . In particular, unique portion  624  is contained only within rule L2, and comprises the set defined by port=[14, 18] Permit, while unique portion  626  is contained only within rule H3, and comprises the set defined by port=[21-25] Permit. Thus, Permit conflict ROBDD  600 C comprises the set defined by port=[14, 18, 21-25] Permit. 
     Reference is made above only to Permit conflict ROBDDs, although it is understood that conflict ROBDDs are generated for each action associated with a given model. For example, a complete analysis of the Li_Model  272  and Hi_Model  276  mentioned above might entail using ROBDD Generator  526  to generate the eight ROBDDs L_Permit BDD , L_Permit_Log BDD , L_Deny- BDD , and L_Deny_Log BDD , H_Permit BDD , H_Permit_Log BDD , H_Deny BDD , and H_Deny_Log BDD , and then using Equivalence Checker  528  to generate a Permit conflict ROBDD, Permit_Log conflict ROBDD, Deny conflict ROBDD, and Deny_Log conflict ROBDD. 
     In general, Equivalence Checker  528  generates action-specific conflict ROBDDs based on input network models, or input ROBDDs from ROBDD Generator  526 . As illustrated in  FIG. 5C , Equivalence Checker  528  receives the input pairs (L BDD , H BDD ), (L BDD , C BDD ), (C BDD , H BDD ), although it is understood that these representations are for clarity purposes, and may be replaced with any of the action-specific ROBDDs discussed above. From these action-specific conflict ROBDDs, Equivalence Checker  528  may determine that there is no conflict between the inputs—that is, a given action-specific conflict ROBDD is empty. In the context of the examples of  FIGS. 6A-6C , an empty conflict ROBDD would correspond to no shaded portions being present. In the case where this determination is made for the given action-specific conflict ROBDD, Equivalence Checker  528  might generate a corresponding action-specific “PASS” indication  530  that can be transmitted externally from formal analysis engine  522 . 
     However, if Equivalence Checker  528  determines that there is a conflict between the inputs, and that a given action-specific conflict ROBDD is not empty, then Equivalence Checker  528  will not generate PASS indication  530 , and can instead transmit the given action-specific conflict ROBDD  532  to a Conflict Rules Identifier  534 , which identifies the specific conflict rules that are present. In some examples, an action-specific “PASS” indication  530  can be generated for every action-specific conflict ROBDD that is determined to be empty. In some examples, the “PASS” indication  530  might only be generated and/or transmitted once every action-specific conflict ROBDD has been determined to be empty. 
     If one or more action-specific conflict ROBDDs are received, Conflict Rules Identifier  534  may receive as input the flat listing of priority ordered rules that are represented in each of the conflict ROBDDs  532 . For example, if Conflict Rules Identifier  534  receives the Permit conflict ROBDD corresponding to L_Permit BDD ⊕H_Permit BDD , the flat listings of priority ordered rules Li, Hi used to generate L_Permit BDD  and H_Permit BDD  are also received as input. 
     The Conflict Rules Identifier  534  then identifies specific conflict rules from each listing of priority ordered rules and builds a listing of conflict rules  536 . In order to do so, Conflict Rules Identifier  534  iterates through the rules contained within a given listing and calculates the intersection between the set of packet configurations and network actions that is encompassed by each given rule, and the set that is encompassed by the action-specific conflict ROBDD. For example, assume that a list of j rules was used to generate L_Permit BDD . For each rule j, Conflict Rules Identifier  534  computes:
 
( L _Permit BDD   ⊕H _Permit BDD )* L   j  
 
If this calculation equals zero, the rule L j  is not part of the conflict ROBDD and therefore is not a conflict rule. If this calculation does not equal zero, then the given rule L j  is part of the Permit conflict ROBDD and therefore is a conflict rule that is added to the listing of conflict rules  536 .
 
     For example, in  FIG. 6C , Permit conflict ROBDD  600 C includes the shaded portions  624  and  626 . Starting with the two rules L1, L2 used to generate L_Permit BDD , it can be calculated that:
 
( L _Permit BDD   ⊕H _Permit BDD )* L 1=0
 
Thus, rule L1 does not overlap with Permit conflict ROBDD  600 C and therefore is not a conflict rule. However, it can be calculated that:
 
( L _Permit BDD   ⊕H _Permit BDD )* L 21≠0
 
Meaning that rule L2 does overlap with Permit conflict ROBDD  600 C at overlap portion  624  and therefore is a conflict rule and is added to the listing of conflict rules  536 .
 
     The same form of computation can also be applied to the list of rules H1, H2, H3, used to generate H_Permit BDD . It can be calculated that:
 
( L _Permit BDD   ⊕H _Permit BDD )* H 1=0
 
Thus, rule H1 does not overlap with Permit conflict ROBDD  600 C and therefore is not a conflict rule. It can also be calculated that:
 
( L _Permit BDD   ⊕H _Permit BDD )* H 2=0
 
Thus, rule H2 does not overlap with Permit conflict ROBDD  600 C and therefore is not a conflict rule. Finally, it can be calculated that:
 
( L _Permit BDD   ⊕H _Permit BDD )* H 3≠0
 
Meaning that rule H2 does overlap with Permit conflict ROBDD  600 C at overlap portion  626  and therefore is a conflict rule and can be added to the listing of conflict rules  552 . In the context of the present example, the complete listing of conflict rules  536  derived from Permit conflict ROBDD  600 C is {L2, H3}, as one or both of these rules have been configured or rendered incorrectly.
 
     In some examples, one of the models associated with Input  524  may be treated as a reference or standard, meaning that rules contained within that model are assumed to be correct. As such, Conflict Rules Identifier  536  only needs to compute the intersection of a given action-specific conflict ROBDD and the set of associated action-specific rules from the non-reference model. For example, the Li_Model  272  can be treated as a reference or standard, because it is directly derived from user inputs used to define L_Model  270 A,  270 B. The Hi_Model  276 , on the other hand, passes through several transformations before being rendered into a node&#39;s hardware, and is more likely to be subject to error. Accordingly, Conflict Rules Identifier  534  would only compute
 
( L _Permit BDD   ⊕H _Permit BDD )* H   j  
 
for each of the rules (or each of the Permit rules) j in the Hi_Model  276 , which can cut the required computation time significantly.
 
     Additionally, Conflict Rules Identifier  534  need not calculate the intersection of the action-specific conflict ROBDD and the entirety of each rule, but instead, can use a priority-reduced form of each rule. In other words, this is the form in which the rule is represented within the ROBDD. For example, the priority reduced form of rule H2 is H1′H2, or the contribution of rule H2 minus the portion that is already captured by rule H1. The priority reduced form of rule H3 is (H1+H2)′H3, or the contribution of rule H3 minus the portion that is already captured by rules H1 or H2. The priority reduced form of rule H4 is (H1+H2+H3)′H4, or the contribution of rule H4 minus the portion that is already captured by rules H1 and H2 and H3. 
     As such, the calculation instead reduces to:
 
( L _Permit BDD   ⊕H _Permit BDD )*( H 1+ . . . + H   j-1 )′ H   j  
 
for each rule (or each Permit rule) j that is contained in the Hi_Model  276 . While there are additional terms introduced in the equation above as compared to simply calculating
 
( L _Permit BDD   ⊕H _Permit BDD )* H   j ,
 
the priority-reduced form is in fact computationally more efficient. For each rule j, the priority-reduced form (H1+ . . . +H j-1 )′H j  encompasses a smaller set of packet configurations and network actions, or encompasses an equally sized set, as compared to the non-reduced form H j . The smaller the set for which the intersection calculation is performed against the conflict ROBDD, the more efficient the computation.
 
     In some cases, the Conflict Rules Identifier  534  can output a listing of conflict rules  536  (whether generated from both input models, or generated only a single, non-reference input model) to a destination external to Formal Analysis Engine  522 . For example, the conflict rules  536  can be output to a user or network operator in order to better understand the specific reason that a conflict occurred between models. 
     In some examples, a Back Annotator  538  can be disposed between Conflict Rules Identifier  534  and the external output. Back Annotator  538  can associate each given rule from the conflict rules listing  536  with the specific parent contract or other high-level intent that led to the given rule being generated. In this manner, not only is a formal equivalence failure explained to a user in terms of the specific rules that are in conflict, the equivalence failure is also explained to the user in terms of the high-level user action, configuration, or intent that was entered into the network and ultimately created the conflict rule. In this manner, a user can more effectively address conflict rules, by adjusting or otherwise targeting them at their source or parent. 
     In some examples, the listing of conflict rules  536  may be maintained and/or transmitted internally to Formal Analysis Engine  522 , to enable further network assurance analyses and operations such as event generation, counter-example generation, QoS assurance, etc. 
     The disclosure now turns to  FIG. 7 , which illustrate an example method for general network assurance. The method is provided by way of example, as there are a variety of ways to carry out the method. Additionally, while the example method is illustrated with a particular order of blocks or steps, those of ordinary skill in the art will appreciate that  FIG. 7 , and the blocks shown therein, can be executed in any order and can include fewer or more blocks than illustrated. 
     Each block shown in  FIG. 7  represents one or more steps, processes, methods or routines in the method. For the sake of clarity and explanation purposes, the blocks in  FIG. 7  are described with reference to Network Environment  100 , Assurance Appliance System  300 , and Network Models  270 ,  270 A-B,  272 ,  274 ,  276 , Policy Analyzer  504 , and Formal Equivalence Engine  522 , as shown in  FIGS. 1A-B ,  2 D,  3 A,  5 A, and  5 C. 
     With reference to  FIG. 7 , at step  700 , Assurance Appliance System  300  can collect data and obtain models associated with Network Environment  100 . The models can include Logical Model  270 , as shown in  FIG. 4 , and/or any of Models  270 A-B,  272 ,  274 ,  276 , as shown in  FIG. 2D . The data can include fabric data (e.g., topology, switch, interface policies, application policies, etc.), network configurations (e.g., BDs, VRFs, L2 Outs, L3 Outs, protocol configurations, etc.), QoS policies (e.g., DSCP, priorities, bandwidth, queuing, transfer rates, SLA rules, performance settings, etc.), security configurations (e.g., contracts, filters, etc.), application policies (e.g., EPG contracts, application profile settings, application priority, etc.), service chaining configurations, routing configurations, etc. Other non-limiting examples of information collected or obtained can include network data (e.g., RIB/FIB, VLAN, MAC, ISIS, DB, BGP, OSPF, ARP, VPC, LLDP, MTU, network or flow state, logs, node information, routes, etc.), rules and tables (e.g., TCAM rules, ECMP tables, routing tables, etc.), endpoint dynamics (e.g., EPM, COOP EP DB, etc.), statistics (e.g., TCAM rule hits, interface counters, bandwidth, packets, application usage, resource usage patterns, error rates, latency, dropped packets, etc.). 
     At step  702 , Assurance Appliance System  300  can analyze and model the received data and models. For example, Assurance Appliance System  300  can perform formal modeling and analysis, which can involve determining equivalency between models, including configurations, policies, etc. Assurance Appliance System  300  can analyze and/or model some or all portions of the data and models. For example, in some cases, Assurance Appliance System  300  may analyze and model contracts, policies, rules, and state data, but exclude other portions of information. 
     At step  704 , Assurance Appliance System  300  can generate one or more smart events. Assurance Appliance System  300  can generate smart events using deep object hierarchy for detailed analysis, such as tenants, switches, VRFs, filters, prefixes, ports, contracts, subjects, etc. At step  706 , Assurance Appliance System  300  can visualize the smart events, analysis and/or models. Assurance Appliance System  300  can display problems and alerts for analysis and debugging, in a user-friendly GUI. 
       FIG. 8  illustrates an example User Interface  800  for accessing Assurance Compliance Menus  802 - 812  of an assurance compliance tool. In this example, the Assurance Compliance Menus  802 - 812  include a Dashboard Menu  802  which can be selected to access a dashboard page, interface, tool, sub-menu, etc.; a Change Management Menu  804  which can be selected to access a change management page, interface, tool, sub-menu, etc.; a Verify and Diagnose Menu  806  which can be selected to access a page, interface, tool, sub-menu, etc., for verification and diagnosis functions and information; an Optimization Menu  808  which can be selected to access a page, interface, tool, sub-menu, etc., for viewing and/or implementing assurance and/or network optimizations; a Compliance and Audit Menu  810  for accessing compliance and audit features such as pages, interfaces, tools, sub-menus, functions, etc., and a Smart Events Menu  812  for accessing smart events and/or smart event pages, interfaces, tools, sub-menus, etc. 
     The Compliance and Audit Menu  810  can include a Compliance Analysis Menu  814 A and an Audit and Assurance Menu  814 B. The Compliance Analysis Menu  814 A includes Menu Sub-items  816 A-B, which include a Compliance Analysis Menu Sub-item  816 A for accessing a compliance analysis feature and a Manage Compliance Requirements Menu Sub-item  816 B for managing compliance requirements. The Audit and Assurance Menu  814 B includes Menu Sub-items  818 A-B, which include a Download Assurance Data Menu Sub-item  818 A for downloading assurance data and a Reports Menu Sub-item  818 B for generating assurance reports. 
       FIG. 9  illustrates a Compliance Requirement Management Interface  900  which allows a user to manage compliance requirements. The Compliance Requirement Management Interface  900  can be accessed through the Manage Compliance Requirements Menu Sub-item  816 B from Compliance Analysis Menu  814 A in Compliance and Audit Menu  810  of User Interface  800  shown in  FIG. 8 . The Compliance Requirement Management Interface  900  includes various Tabs  902 - 908  for managing compliance requirements. The Tabs  902 - 908  can be menus, navigation links, navigation pages or tools, selectable interface elements, etc. The Tabs  902 - 908  can include a Compliance Requirement Sets Tab  902 , a Compliance Requirements Tab  904 , an EPG Selector Tab  906 , and a Traffic Selector Tab  908 . 
     The Compliance Requirement Sets Tab  902  can be used to access, modify, and/or create sets or groups of compliance requirements. In some cases, the Compliance Requirement Sets Tab  902  allows a user to view any compliance requirement sets that have been configured, including their respective names, descriptions, status (e.g., active, inactive, etc.), settings (e.g., compliance requirements, compliance requirement details and policies, etc.), and so forth. Compliance requirement sets can be created using compliance requirements configured in the system (e.g., via Compliance Requirements Tab  904 ). 
     The Compliance Requirements Tab  904  allows a user to access, modify, and/or create compliance requirements; the EPG Selector Tab  906  allows a user to access, modify, and/or create EPG selectors which define rules and/or attributes for determining which EPGs to include or exclude in specific sets of EPGs associated with the EPG selectors; and the Traffic Selector Tab  908  allows a user to access, modify, and/or create traffic selectors which provide traffic filters and/or parameters such as traffic protocols, ports, etc. A more detailed description of the Tabs  902 - 908  in the Compliance Requirement Management Interface  900  will be further described below. 
       FIG. 10  illustrates a Compliance Requirement Interface  1000  for creating a compliance requirement. The Compliance Requirement Interface  1000  can be accessed from Compliance Requirements Tab  904  in Compliance Requirement Management Interface  900 . The Compliance Requirement Interface  1000  includes a New Compliance Requirement Section  1002  for providing compliance requirement definitions or settings to create a new compliance requirement. 
     The New Compliance Requirement Section  1002  includes a Compliance Requirement Name Field  1004 , where the user can provide a name for the new compliance requirement being created, and a Compliance Requirement Description Field  1006 , where the user can provide a description of the new compliance requirement. The New Compliance Requirement Section  1002  can also include a Compliance Type Field  1008  where a user can define the type of compliance requirement being created, such as a traffic segmentation requirement, a traffic restriction requirement, a resource attribute requirement, a naming convention requirement, etc. In this example, the Compliance Type Field  1008  indicates that the compliance type selected for the new compliance requirement is Segmentation  1008 A. 
     The New Compliance Requirement Section  1002  also includes a Compliance Requirement Definitions View  1010  depicting Nodes  1012 - 1016  representing Compliance Definitions  1018 A-C associated with the new compliance requirement. For example, Node  1012  represents an EPG Selector Definition  1018 A for EPG Selector A, that is selected or is to be selected for the new compliance requirement. Node  1016  represents an EPG Selector Definition  1018 C for EPG Selector B, which is another EPG selector selected or to be selected for the new compliance requirement. Node  1014  represents a Communication Operator Definition  1018 B for defining a communication operator for traffic associated with the EPG selectors in Nodes  1012  and  1016 . 
     In some cases, the Nodes  1012 - 1016  in the Compliance Requirement Definitions View  1010  can be depicted with interconnections and/or according to an order or flow of configuration tasks or definitions for creating the compliance requirement. For example, Node  1012  can be a first node which represents the first definition or configuration task for creating the compliance requirement (e.g., selecting an EPG selector for EPG Selector A), Node  1014  can be the subsequent node which represents the next definition or configuration task (e.g., selecting a communications operator), and Node  1016  can be the last node representing the last definition or configuration task for creating the compliance requirement (e.g., selecting an EPG selector for EPG Selector B). In some cases, the Compliance Definitions  1018 A-C can be displayed or populated for the Nodes  1012 - 1016  as (or after) they are defined. In some cases, each of the Nodes  1012 - 1016  can depict (e.g., via text or labels, check marks or other visual indicators displayed in or with the Nodes  1012 - 1016 , etc.) which compliance definition has been selected (if any) for that node and/or whether the compliance definition selection or configuration process for that node has completed or not. 
     The New Compliance Requirement Section  1002  includes an EPG Selector Section  1020  for selecting an EPG selector and associated attributes for EPG Selector A (i.e., Node  1012 ). The EPG Selector Section  1020  includes an EPG Selector Option  1022  for selecting an EPG selector. The EPG Selector Option  1022  can be, for example and without limitation, a drop-down menu where a user can select an EPG selector, a link to a pop-up window or interface where a user can select an EPG selector, an EPG selector browse function, etc. 
     The EPG Selector Section  1020  can also include a Consumer/Provider Label Field  1024  which allows a user to select a consumer or provider label for the EPG selector selected in the EPG Selector Option  1022 . The consumer and provider labels allow EPGs or EPG selectors to be classified as consumers or providers, which define the relationship between an EPG or EPG selector and a compliance requirement. Thus, the EPG Selector Option  1022  allows a user to select an EPG selector for EPG Selector A (i.e., Node  1012 ) and the Consumer/Provider Label Field  1024  allows the user to apply a consumer or provider label to the selected EPG selector for EPG Selector A. Note, however, that in some cases the Consumer/Provider Label Field  1024  may be optional and the user may complete configuring the EPG Selector A (i.e., Node  1012 ) without applying or selecting a consumer or provider label. 
       FIG. 11  illustrates an EPG Selector Interface  1110  for selecting an EPG selector. The EPG Selector Interface  1110  can be accessed through the EPG Selector Option  1022  in the Compliance Requirement Interface  1000 , and allows a user to select an EPG selector for EPG Selector A (i.e., Node  1012 ). The EPG Selector Interface  1110  includes an EPG Column  1112  which lists EPG Selectors  1116  that the user can select from, and a Description Column  1114  which includes optional Descriptions  1118  for the EPG Selectors  1116  listed in the EPG Column  1112 . The Description Column  1114  may or may not include a description ( 1118 ) for each of the EPG Selectors  1116  listed in the EPG Column  1112 . 
     In this example, the EPG Selector Interface  1110  illustrates a Selection  1120  from the EPG Selectors  1116 , which in this case is EPG Selector San Jose. This indicates that the user has selected EPG Selector San Jose as the EPG selector for EPG Selector A (i.e., Node  1012 ). The EPG Selector Interface  1110  can include a Choose Option  1122  where the user can choose the EPG Selector San Jose based on the Selection  1120  and proceed with EPG Selector San Jose as the EPG selector for EPG Selector A (i.e., Node  1012 ). 
       FIG. 12  illustrates a Configuration  1200  of the Compliance Requirement Interface  1000  after the user selects and chooses an EPG selector for EPG Selector A (i.e., Node  1012 ) from the EPG Selector Interface  1110 . As illustrated in the Configuration  1200  of the Compliance Requirement Interface  1000 , the Compliance Requirement Definitions View  1010  in the New Compliance Requirement Section  1002  has been updated to identify the Chosen EPG Selector  1202  for EPG Selector A (i.e., Node  1012 ), which in this example is EPG Selector San Jose. Thus, the Configuration  1200  of the Compliance Requirement Interface  1000  shows that the EPG Selector San Jose has been chosen at Node  1012  corresponding to the EPG Selector A. 
     Once an EPG selector has been chosen for EPG Selector A (i.e., Node  1012 ), the user can select a communication operator (i.e., Node  1014 ) for the new compliance requirement.  FIG. 13  illustrates a Configuration  1300  of the Compliance Requirement Interface  1000  for enabling the user to select a communication operator for the new compliance requirement. Here, the Configuration  1300  of the Compliance Requirement Interface  1000  includes a Communication Operator Section  1302  with Communication Operator Options  1304 - 1308  that the user can select for the new compliance requirement. The Communication Operator Options  1304 - 1308  in this non-limiting example include a Must Not Talk To option ( 1304 ), a May Only Talk To option ( 1306 ), and a Must Talk To option ( 1308 ). It should be noted that other communication operator options than those depicted in  FIG. 13  can also be included, and some implementations may include other type(s) and/or a different number (more or less) of communication operator options. 
     In the Configuration  1300 , the Compliance Requirement Definitions View  1010  shows a Must Not Talk To operator  1308  selected as the communication operator (i.e., Node  1014 ) for the new compliance requirement. The Must Not Talk To operator  1308  can be selected via the Communication Operator Option  1304  in the Communication Operator Section  1302 , as previously described. The Configuration  1300  also shows the Chosen EPG Selector  1202  for EPG Selector A (i.e., Node  1012 ), EPG Selector San Jose, has been assigned a consumer label, indicating that the EPG Selector San Jose is a consumer EPG Selector. The user can assign the consumer label via the Consumer/Provider Label Field  1024  in the EPG Selector Section  1020  of the Compliance Requirement Interface  1000 , as shown in  FIGS. 10 and 12 . 
       FIG. 14  illustrates a Configuration  1400  of the Compliance Requirement Interface  1000  for selecting an EPG selector and associated attributes for EPG Selector B (i.e., Node  1016 ) shown in the Compliance Requirement Definitions View  1010 . The Configuration  1400  includes an EPG Selector Section  1402  for selecting the EPG selector and associated attributes for EPG Selector B (i.e., Node  1016 ). The EPG Selector Section  1402  includes an EPG Selector Option  1404  for selecting an EPG selector. The EPG Selector Option  1404  can be, for example and without limitation, a drop-down menu where a user can select an EPG selector, a link to a pop-up window or interface where a user can select an EPG selector, an EPG selector browse function, etc. 
     The EPG Selector Section  1402  can also include a Consumer/Provider Label Field  1406  for selecting a consumer or provider label for the EPG selector selected in the EPG Selector Option  1404 . In this example, the Consumer/Provider Label Field  1406  shows Provider Label  1408  selected for the EPG Selector B (i.e., Node  1016 ). Thus, the EPG Selector chosen by the user via the EPG Selector Option  1404  will receive the Provider Label  1408  classifying it as a provider. 
       FIG. 15  illustrates an EPG Selector Interface  1500  for selecting an EPG selector for EPG Selector B (i.e., Node  1016 ). The EPG Selector Interface  1500  can be generated or presented in response to a selection of the EPG Selector Option  1404  in the EPG Selector Section  1402  as shown in the Configuration  1400  of the Compliance Requirement Interface  1000 . The EPG Selector Interface  1500  includes an EPG Column  1502  which lists EPG Selectors  1506  that the user can select from, and a Description Column  1504  which includes optional Descriptions  1508  corresponding to the EPG Selectors  1506  listed in the EPG Column  1502 . 
     In this example, the EPG Selector Interface  1500  illustrates a Selection  1510  for EPG Selector B (i.e., Node  1016 ) from the EPG Selectors  1506 , which in this case is EPG Selector Palo Alto. This indicates that the user has selected EPG Selector Palo Alto as the EPG selector for EPG Selector B (i.e., Node  1016 ). The EPG Selector Interface  1500  can include a Choose Option  1512  where the user can choose the Selection  1120  (EPG Selector Palo Alto) and proceed with EPG Selector Palo Alto as the EPG selector for EPG Selector B (i.e., Node  1016 ). 
     Once the user has selected the EPG Selector Palo Alto for EPG Selector B (i.e., Node  1016 ) via the Choose Option  1512 , the user is returned to the Compliance Requirement Interface  1000  which is updated to reflect that the EPG Selector Palo Alto has been selected for EPG Selector B (i.e., Node  1016 ). With reference to  FIG. 16 , the Compliance Requirement Definitions View  1010  of the Compliance Requirement Interface  1000  identifies EPG Selector Palo Alto as the Chosen EPG Selector  1602  for EPG Selector B (i.e., Node  1016 ), and indicates that the EPG Selector Palo Alto has been selected as a provider. The Compliance Requirement Definitions View  1010  also reflects that the Compliance Definitions  1018 A-C for Nodes  1012 - 1016  have been selected or configured. At this point, the user has completed creating the new compliance requirement. 
       FIG. 17A  illustrates a Configuration  1700  of the Compliance Requirement Interface  1000  depicting various features for creating a different compliance requirement. In this example, the compliance requirement is an SLA (service level agreement) requirement, as reflected by the SLA Selection  1702  in the Compliance Type Field  1008 . 
     The Compliance Requirement Definitions View  1010  includes Compliance Definitions  1018 A-C for selecting an EPG Selector A ( 1018 A), selecting a communication operator ( 1018 B), and selecting an EPG Selector B ( 1018 C). The Compliance Requirement Definitions View  1010  also includes an additional compliance definition, namely Compliance Definition  1704  for selecting a traffic selector. In addition, the Compliance Requirement Definitions View  1010  includes Nodes  1012 - 1016 , respectively corresponding to Compliance Definitions  1018 A-C, as well as Node  1706  corresponding to Compliance Definition  1704  for selecting a traffic selector. 
     The Compliance Requirement Definitions View  1010  includes an indication that a Must Talk To Operator  1708  has been selected or configured as the communication operator in the Compliance Definition  1018 B associated with Node  1014 . The Must Talk To Operator  1708  for the Compliance Definition  1018 B can be selected or configured as previously described in  FIG. 13 . In  FIG. 17A , the Compliance Definitions  1018 A,  1018 C and  1704  corresponding to Nodes  1012 ,  1016 , and  1706  have not been selected or configured. Accordingly, the Compliance Definitions  1018 A,  1018 C and  1704  can be selected or configured to complete the compliance requirement. 
     The Compliance Requirement Interface  1000  in Configuration  1700  includes EPG Selector Section  1020  for selecting an EPG selector and associated attributes for EPG Selector A (i.e., Node  1012 ). The EPG Selector Section  1020  includes EPG Selector Option  1022  for selecting the EPG selector, and Consumer/Provider Label Field  1024  for selecting a consumer or provider label for the EPG selector. Through the EPG Selector Section  1020 , the user can select or configure an EPG selector for Compliance Definition  1018 A. The user can also select an EPG selector and any associated attributes for the Compliance Definition  1018 C, as previously described. 
       FIG. 17B  illustrates a Configuration  1750  of the Compliance Requirement Interface  1000  for selecting a traffic selector for Compliance Definition  1704  associated with Node  1706 . Here, a Traffic Selector Section  1756  includes Traffic Selection Options  1758 A-C for selecting a Traffic Selector Type  1758 . The Traffic Selection Options  1758 A-C in this non-limiting example include an option for selecting all traffic ( 1758 A), an option for selecting any traffic ( 1758 B), and an option for choosing a specific traffic selector ( 1758 C). 
     In  FIG. 17B , the user has selected the all traffic option ( 1758 A) in the Traffic Selection Options  1758 A-C. Accordingly, the Compliance Definition  1704  for the traffic selector corresponding to Node  1706  reflects that the Chosen Traffic Selector  1754  is all traffic. The Chosen Traffic Selector  1754  provides that the Compliance Definitions  1018 A-C should apply to all traffic associated with the EPG selectors configured for the Compliance Definitions  1018 A and  1018 C, which define the EPG Selector A and EPG Selector B for the compliance requirement. In this example, the Compliance Definitions  1018 A-C and  1704  provide that Consumer EPG Selector San Jose ( 1202 ) must talk to ( 1708 ) Provider EPG Selector New York ( 1752 ) on all traffic ( 1754 ). 
     The option for choosing a specific traffic selector ( 1758 C) can allow a user to select from traffic selectors that have been configured in the system and/or are available for selection. In some cases, the option for choosing a specific traffic selector can allow a user to select a traffic selector with more granular specifications, different filters (e.g., protocol filters, IP filters, name filters, attribute filters, port filters, etc.), etc., than the all or any traffic selector options. 
       FIG. 17C  illustrates an example of a different traffic selector chosen for the Compliance Definition  1704  and a different Compliance Type  1008  selected for the new compliance requirement. Here, the Compliance Type  1008  has been changed to Traffic Restriction  1762  (as opposed to SLA  1702  in the previous example) and a different traffic selector, Traffic Selector  1760 , has been selected through the Choose Traffic Selector Option  1758 C. In this example, Traffic Selector  1760  is configured to only apply to specific traffic, as opposed to all or any traffic as provided in Traffic Selector Options  1758 A and  1758 B. For example, the Traffic Selector  1760  may apply only to traffic on a specific protocol, port, EtherType, etc. Having chosen Traffic Selector  1760  through the Choose Traffic Selector Option  1758 C, the Compliance Requirement Definitions View  1010  now reflects the chosen Traffic Selector  1760  as the traffic selector configured for the Compliance Definition  1704  associated with Node  1706 . 
     The previous examples illustrate aspects for creating new compliance requirements. However, before creating a compliance requirement, one or more traffic selectors and EPG selectors can be configured for creating the compliance requirement.  FIGS. 18A-E  illustrate aspects for creating traffic selectors and  FIG. 19  illustrates aspects for creating an EPG selector. 
     With reference to  FIG. 18A , a New Traffic Selector Interface  1800  can be accessed from the Traffic Selector Tab  908 . The New Traffic Selector Interface  1800  can include a Create New Traffic Selector Section  1802 , which can include a Traffic Selector Name Field  1804 , a Traffic Selector Description Field  1806 , and a Traffic Selector Configuration Section  1808 . 
     The Traffic Selector Configuration Section  1808  can allow a user to configure rules and/or filters for traffic associated with the traffic selector being created. For example, the Traffic Selector Configuration Section  1808  can allow a user to define attributes of the traffic associated with the traffic selector, such as a protocol, a port, an EtherType, etc. In this example, the Traffic Selector Configuration Section  1808  includes Traffic Attribute Fields  1812  and  1814 , which allow the user to define an EtherType (e.g., IPv4, ARP, IPv6, LACP, MPLS, SRP, etc.) for the traffic (e.g., via Traffic Attribute Field  1812 ) and an IP protocol (e.g., TCP, UDP, OSPF, etc.) for the traffic (e.g., via Traffic Attribute Field  1814 ). The Traffic Selector Configuration Section  1808  can also include an Operator  1810  which identifies a communication action (e.g., talk or communicate on) that applies to the traffic having the attributes defined in the Traffic Attribute Fields  1812  and  1814 . 
     The Traffic Selector Configuration Section  1808  can include an Add Talk On Link  1816  which a user can select to add additional traffic rules or filters for the traffic selector.  FIG. 18B  illustrates the New Traffic Selector Interface  1800  after a user has configured the Traffic Attribute Fields  1812  and  1814  and added Traffic Configuration Set  1822  via Add Talk On Link  1816 . 
     Traffic Configuration Set  1822  includes Operator  1824  and Traffic Attribute Fields  1826  and  1828 . Operator  1824  and Traffic Attribute Fields  1826  and  1828  provide additional criteria or filters (i.e., in addition to the criteria or filters defined via Operator  1810  and Traffic Attribute Fields  1812  and  1814 ) for the traffic selector. In this example, Traffic Attribute Fields  1826  and  1828  allow a user to define another EtherType ( 1826 ) and IP protocol ( 1828 ) for the traffic, and Operator  1824  is an And operator indicating that Traffic Configuration Set  1822  should also apply to traffic having the attributes defined in Traffic Attribute Fields  1826  and  1828 . 
     Moreover, the Traffic Attribute Fields  1812  and  1814  in  FIG. 18B  have been configured to include IPv4  1818  as the EtherType in Traffic Attribute Field  1812  and OSPF (Open Shortest Path First)  1820  as the IP protocol in Traffic Attribute Field  1814 . Thus, together the Operator  1810  and Traffic Attribute Fields  1812  and  1814  indicate that the traffic selector also corresponds to traffic communicating on IPv4 ( 1818 ) and OSPF ( 1820 ). 
       FIG. 18C  illustrates a Direction-Based Traffic Configuration Section  1830  in New Traffic Selector Interface  1800  for providing additional configuration options for the Traffic Configuration Set  1822 . The additional configuration options in the Direction-Based Traffic Configuration Section  1830  allow a user to provide additional conditions or configurations for each direction of traffic (e.g., from EPG Selector A to EPG Selector B and vice versa). 
     The Direction-Based Traffic Configuration Section  1830  can include Configuration Fields  1838 - 1842  for each Traffic Direction  1834  and  1836 . For example, the Direction-Based Traffic Configuration Section  1830  can include a source port field ( 1838 ) for specifying a traffic source port, a destination port field ( 1840 ) for specifying a traffic destination port, and a log flag setting field ( 1842 ) for confirming that a log flag is set. The Direction-Based Traffic Configuration Section  1830  can include the source port field ( 1838 ), the destination port field ( 1840 ) and the log flag setting field ( 1842 ) for each Traffic Direction  1834  and  1836 , which in this example includes traffic from EPG Selector A to EPG Selector B (Traffic Direction  1834 ) and traffic from EPG Selector B to EPG Selector A (Traffic Direction  1836 ). Thus, through the Configuration Fields  1838 - 1842  in the Direction-Based Traffic Configuration Section  1830 , the user can configure attributes or conditions for each specific Traffic Direction  1834  and  1836  (e.g., from EPG Selector A to EPG Selector B, and from EPG Selector B to EPG Selector A). 
     The Direction-Based Traffic Configuration Section  1830  can also include a Reverse Ports Option  1832 , which the user can select, activate, enable, etc., to reverse the ports (e.g., source and destination ports) or port values in the source port field ( 1838 ) and the destination port field ( 1840 ) of the two Traffic Directions  1834  and  1836 . 
       FIG. 18C  also illustrates example EtherType and IP Protocol selections ( 1844  and  1846 ) for the Traffic Attribute Fields  1826  and  1828 . In  FIG. 18C , the Traffic Attribute Field  1826  for EtherType is set to IPv4 ( 1844 ) and the Traffic Attribute Field  1828  for IP Protocol is set to User Datagram Protocol ( 1846 ) or UDP. Together, the selections ( 1818 ,  1820 ,  1844 ,  1846 ) in the Traffic Attribute Fields  1812 - 1814  and  1826 - 1828  of the Traffic Selector Configuration Section  1808 , including the Traffic Configuration Set  1822 , provide that the traffic selector being created applies to traffic having an IPv4 ( 1818 ) EtherType ( 1812 ) and OSPF ( 1820 ) IP Protocol ( 1814 ) and traffic having an IPv4 ( 1844 ) EtherType ( 1826 ) and UDP ( 1846 ) IP Protocol ( 1828 ). 
     With reference to  FIG. 18D , a user can add a Traffic Selector Configuration Section  1850  (e.g., via Add Links  1816 ) to provide additional configurations, conditions, filters, etc., for the new traffic selector being created. The Traffic Selector Configuration Section  1850  can be additional to, and/or separate from, the Traffic Selector Configuration Section  1808 , and can allow the user to configure additional and/or alternative conditions, filters, settings, etc. 
     In adding the Traffic Selector Configuration Section  1850 , the user can select an Operator  1844 , which can serve as a logical or Boolean operator (e.g., AND, OR, etc.), to specify whether the configurations or attributes in the Traffic Selector Configuration Section  1850  should apply in addition to (e.g., AND) or alternatively to (e.g., OR) the configurations or attributes in the Traffic Selector Configuration Section  1808 . In the example of  FIG. 18D , the Operator  1844  is an OR operator. Therefore, the Operator  1844  provides that the new traffic selector being created in  FIG. 18D  should apply to traffic having the characteristics or conditions specified in the Traffic Selector Configuration Section  1808  or traffic having the characteristics or conditions specified in the Traffic Selector Configuration Section  1850 . 
     The Traffic Selector Configuration Section  1850  can include Traffic Attribute Fields  1846  and  1848 , which allow a user to define traffic attributes in the Traffic Selector Configuration Section  1850  for the new traffic selector. In this example, Traffic Attribute Fields  1846  and  1848  allow a user to define an EtherType ( 1846 ) and an IP protocol ( 1848 ) for the traffic.  FIG. 18D  shows example Selections  1818  and  1852  for the Traffic Attribute Fields  1846  and  1848 , including IPv4 ( 1818 ) for the EtherType field ( 1846 ) and TCP ( 1852 ) for the IP protocol field ( 1848 ). 
     The Traffic Selector Configuration Section  1850  can also include a Direction-Based Traffic Configuration Section  1854  for providing additional configuration options for each direction of traffic (e.g., from EPG Selector A to EPG Selector B, and from EPG Selector B to EPG Selector A). The Direction-Based Traffic Configuration Section  1854  can include Configuration Fields  1838 - 1842  for each Traffic Direction  1834  and  1836 . For example, the Direction-Based Traffic Configuration Section  1854  can include a source port field ( 1838 ) for specifying a traffic source port, a destination port field ( 1840 ) for specifying a traffic destination port, and a log flag setting field ( 1842 ) for confirming that a log flag is set. The Direction-Based Traffic Configuration Section  1854  can include the source port field ( 1838 ), the destination port field ( 1840 ) and the log flag setting field ( 1842 ) for each Traffic Direction  1834  and  1836 , which in this example includes traffic from EPG Selector A to EPG Selector B (Traffic Direction  1834 ) and traffic from EPG Selector B to EPG Selector A (Traffic Direction  1836 ). 
     The Direction-Based Traffic Configuration Section  1854  can also include a Reverse Ports Option  1832 , as previously explained. The Direction-Based Traffic Configuration Section  1854  can also include a Check TCP Flags Option  1856  for each Traffic Direction  1834  and  1836  (e.g., from EPG Selector A to EPG Selector B, and from EPG Selector B to EPG Selector A). The Check TCP Flags Option  1856  is a TCP-specific configuration option which can be provided because, for example, the user has selected TCP ( 1852 ) as the IP protocol in the Traffic Attribute Field  1848 . Thus, the options, settings, attributes, conditions, fields, etc., available in a traffic configuration section (e.g.,  1808 ,  1850 ) can vary based on what is selected in the traffic attribute fields (e.g.,  1812 - 1814 ,  1826 - 1828 ,  1846 - 1848 ), to include options, settings, attributes, conditions, fields, etc., that may be specific to a selected attribute such as an EtherType or an IP protocol. In this example, the user has selected TCP ( 1852 ) in the Traffic Attribute Field  1848  and the Check TCP Flags Option  1856  is an option specific to TCP provided because TCP has been selected as the IP protocol in Traffic Attribute Field  1848 . 
     In  FIG. 18D , the Check TCP Flags Option  1856  for Traffic Direction  1834  (from EPG Selector A to EPG Selector B) has not been selected or enabled, while the Check TCP Flags Option  1856  for Traffic Direction  1836  (from EPG Selector B to EPG Selector A) has been selected or enabled. Because the Check TCP Flags Option  1856  for Traffic Direction  1836  has been selected or enabled, the Direction-Based Traffic Configuration Section  1854  can provide additional configuration options pertaining to the Check TCP Flags Option  1856  selected or enabled. For example, when the Check TCP Flags Option  1856  is selected or enabled, the Direction-Based Traffic Configuration Section  1854  can provide a TCP Flag Set Field  1858 A, where a user can specify which set TCP flags (e.g., ACK flag, SYN flag, FIN flag, URG flag, PSH flag, RST flag, ECE flag, CWR flag, etc.) should be checked, and a TCP Flag Not Set Field  1858 B, where a user can specify which TCP flags that are not set should be checked. 
       FIG. 18E  illustrates another example configuration of the New Traffic Selector Interface  1800  and the Create New Traffic Selector Section  1802  for creating a new traffic selector. The Create New Traffic Selector Section  1802  includes Traffic Selector Name Field  1804  and Traffic Selector Description Field  1806 . In addition, the Create New Traffic Selector Section  1802  includes an EtherType Field  1860  where the user can specify or select an EtherType. In this example, the EtherType Value  1862  in the EtherType Field  1860  has been set to “Any”, meaning that any EtherType can satisfy the EtherType condition or definition in the EtherType Field  1860 . 
     The Create New Traffic Selector Section  1802  can include an Exception Option  1864 , which when selected or enabled allows the user to provide or define exceptions through a Traffic Selector Exceptions Section  1870 . Thus, the Exception Option  1864  allows the user to define exceptions for scenarios that otherwise satisfy the EtherType condition or definition (e.g.,  1862 ) specified in the EtherType Field  1860  of the Create New Traffic Selector Section  1802 . 
     In  FIG. 18E , the Exception Option  1864  has been selected or enabled. Moreover, Traffic Selector Exceptions Section  1870  has been provided to allow the user to define specific configurations or attributes corresponding to the exception(s). Here, the Traffic Selector Exceptions Section  1870  includes Attribute Fields  1866 - 1868 , which in this example include an EtherType field ( 1866 ) and a protocol field ( 1868 ). The Attribute Field Selections  1872 - 1874  specified for the Attribute Fields  1866 - 1868  are IP ( 1872 ) for EtherType (Attribute Field  1866 ) and TCP ( 1874 ) for the protocol field (Attribute Field  1868 ). 
     Traffic Selector Exceptions Section  1870  includes a Reverse Ports Option  1832  selected for traffic in both Traffic Directions  1834  and  1836  (e.g., from EPG Selector A to EPG Selector B and vice versa). Traffic Selector Exceptions Section  1870  can also include a Flag Settings Section  1876 , a Source Port Field  1838 , a Destination Port Field  1840 , and a Log Option  1890  (e.g., for logging statistics, events, etc.) for each of the Traffic Directions  1834  and  1836 , to allow the user to provide specific configurations or attributes for each direction of traffic. 
     The Flag Settings Section  1876  pertains to TCP flag settings, which in some implementations is provided as an option in response to the user selecting TCP ( 1874 ) in the protocol field (e.g., Attribute Field  1868 ). The Flag Settings Section  1876  can include an Established Option  1878 , which applies to cases where a TCP session or flag (e.g., ACK, RST, etc.) has been established, and a Not Established Option  1880 , which applies to cases where a TCP session or flag has not been established. Under the Not Established Option  1880 , the Flag Settings Section  1876  can include Flag Options  1882 - 1888 , which allow a user to select or specify specific TCP flags (e.g., SYN, ACK, RST, FIN, etc.) corresponding to the Not Established Option  1880  (e.g., having a not established state or status). 
       FIG. 19  illustrates a New EPG Selector Interface  1900  for creating an EPG selector. As previously explained, to create compliance requirements a user may first create EPG selector(s) and traffic selector(s) that can be used to configure the compliance requirements. The New EPG Selector Interface  1900  provides an interface where the user can create a new EPG selector and define specific configurations or attributes for that EPG selector. 
     The New EPG Selector Interface  1900  includes a Create New EPG Selector Section  1902  where the user can input specific attributes, values, conditions, settings, etc., for the EPG selector being created. The Create New EPG Selector Section  1902  can include an EPG Selector Name Field  1904  where the user can provide a name for the EPG selector being created, and an EPG Selector Description Field  1906  where the user can input a description for the EPG selector. 
     The Create New EPG Selector Section  1902  can include Included EPGs Link  1908 A for accessing included EPGs and/or Included EPGs Section  1910 , and Excluded EPGs Link  1908 B for accessing excluded EPGs and/or Excluded EPGs Section  1940 . The Included EPGs Section  1910  allows a user to define attributes or criteria for determining which EPGs should be included in the EPG selector, and the Excluded EPGs Section  1940  allows a user to define attributes or criteria for determining which (if any) EPGs should be excluded from the EPG selector. 
     Included EPGs Section  1910  can include one or more Inclusion Criteria Sets  1912 ,  1920  for specifying the parameters, attributes and/or criteria to be used in determining which EPGs should be included in the EPG selector. For example, the Inclusion Criteria Set  1912  can include Inclusion Parameters  1914  that should be met by an EPG to be included in the EPG selector. The Inclusion Parameters  1914  can include Object Definitions  1916 A-C and Expressions  1918 A-C defining properties or attributes associated with the Object Definitions  1916 A-C. The Object Definitions  1916 A-C can specify or define specific objects, such as EPGs, tenants, distinguished names (DNs), application profiles (APs), VRFs, EPG tags, etc., and the Expressions  1918 A-C can define specific properties or attributes associated with the objects defined in the Object Definitions  1916 A-C. The Object Definitions  1916 A-C and Expressions  1918 A-C can provide the criteria or parameters used to determine which EPGs should be included in the EPG selector. 
     For example, the Object Definitions  1916 A include EPG, DN, and tenant objects, and the Expression  1918 A includes the value or expression “secure”. Here, the Object Definitions  1916 A and Expression  1918 A together provide that an EPG with DN/tn- (e.g., tenant name) “secure” should be included in the EPG selector. Moreover, the Object Definition  1916 B includes AP (Application Profile) and the Expression  1918 B includes the value or expression “Any”, meaning that any application profile should be included in the EPG selector. The Object Definition  1916 C corresponds to an EPG name and the Expression  1918 C includes the value or expression “PCI”, meaning that an EPG with the name “PCI” should be included in the EPG selector. Thus, based on the Object Definitions  1916 A-C and Expressions  1918 A-C, the Inclusion Parameters  1914  provide that an EPG would match the conditions or parameters in the Object Definitions  1916 A-C and Expressions  1918 A-C and would be included in the EPG selector if it has the DN/tn-secure, is associated with any application profile, and has the name “PCI”. 
     The Included EPGs Section  1910  can include additional inclusion criteria sets (e.g.,  1920 ). In  FIG. 19 , the Included EPGs Section  1910  also includes Inclusion Criteria Set  1920 , which is another inclusion criteria set. The Inclusion Criteria Set  1920  in this example includes Inclusion Parameters  1922 ,  1924 , and  1926 . Inclusion Parameters  1924  and  1926  are nested or “AND” parameters, meaning that the Inclusion Parameters  1924  and  1926  should be met in addition to Inclusion Parameters  1922  as opposed to alternatively or in lieu of. Thus, to be included in the EPG selector based on the Inclusion Parameters  1922 ,  1924 ,  1926 , an EPG should satisfy or meet all of the Inclusion Parameters  1922 ,  1924 ,  1926 . 
     In this example, Inclusion Parameters  1922  includes Object Definitions  1928  and Expression  1930 . Object Definitions  1928  include tenant, DN, and tn- or tenant name, and Expression  1930  includes the value “secure”. Thus, Object Definitions  1928  and Expression  1930  provide that an EPG should be included in the EPG selector if the EPG is included in a tenant with DN/tn-secure (e.g., EPG in tenant with DN and tenant name “secure”). 
     Inclusion Parameters  1924  include Object Definitions  1932 A (VRF, DN, tn-) and Expression  1934 A (“common”), and Object Definition  1932 B (context) and Expression  1934 B (“default”). According to Inclusion Parameters  1924 , to be included in the EPG selector, in addition to satisfying Inclusion Parameters  1914 , an EPG should also be in a VRF with DN/tn-common and the context “default” (ctx-default). Inclusion Parameters  1926  include Object Definition  1936  (EPG-Tag) and Expression  1938  (“Any”). Thus, based on Inclusion Parameters  1926 , to be included in the EPG selector, in addition to satisfying the Inclusion Parameters  1914  and  1924 , an EPG should also have an EPG tag “Any” (e.g., any EPG tag). 
     The Included EPGs Section  1910  can also include Remove Elements  1946  which can be selected or used to remove one or more parameters. For example, the Inclusion Parameters  1924  and  1926  in the Inclusion Criteria Set  1920  can include Remove Elements  1946  that a user can use to remove any or all parameters provided in the Inclusion Parameters  1924  and  1926 . To illustrate, if the user determines that the Inclusion Parameters  1926  are unnecessary or should be removed, the user can select the Remove Element  1946  corresponding to the Inclusion Parameters  1926  (e.g., the Remove Element  1946  next to or closest to the Inclusion Parameters  1926 , a remove element that is associated with the Inclusion Parameters  1926 , and/or a remove element that is configured to allow the user specify what the user wants to remove). The Included EPGs Section  1910  can also include Add Elements  1948  that enable a user to add inclusion or exclusion parameters and/or criteria sets. 
     Excluded EPGs Section  1940  allows a user to provide Exclusion Criteria Sets  1944 . Each exclusion criteria set can include exclusion parameters with object definitions and expressions similar to the Included EPGs Section  1910 , as well as any other criteria or type of criteria. 
       FIG. 20A  illustrates an example Configuration  2020  of a Compliance Requirement Sets Interface  2000 . The Compliance Requirement Sets Interface  2000  can be accessed from the Compliance Requirement Sets Tab  902 . The Compliance Requirement Sets Interface  2000  can display a Table  2010  identifying Compliance Requirement Sets  2012  configured in the system, and may be used to access, modify, add, or remove information associated with the Compliance Requirement Sets  2012  on the system. The Table  2010  can include a Name Column  2002 , a Status Column  2004  which indicates whether a compliance requirement set is active or inactive, an Association Column  2006  which indicates whether a compliance requirement set is associated with an assurance group (e.g., a group of compliance requirement sets) or is not associated with an assurance group, and an Action Column  2008 . 
     The Compliance Requirement Sets  2012  in Configuration  2020  are thus displayed in the Table  2010  by name, status (e.g., active, inactive), association (e.g., is associated with an assurance group, is not associated with an assurance group or a group of compliance requirement sets), and action. For example, Row 1 ( 2016 ) of the Table  2010  includes a compliance requirement set with the name “Requirement Set 1”, an active status, and an association with an assurance group. 
     The Table  2010  in the Compliance Requirement Sets Interface  2000  can also include Filter Fields  2014 A-C where a user can input or select filtering criteria or values for filtering Compliance Requirement Sets  2012  displayed in the Table  2010 . For example, the Compliance Requirement Sets Interface  2000  can include a Name Filter Field  2014 A where a user can filter compliance requirement sets by name, a Status Filter Field  2014 B where a user can filter compliance requirement sets by status, and an Association Filter Field  2014 C where a user can filter compliance requirement sets by association (or lack thereof). 
     The Compliance Requirement Sets Interface  2000  can include a Settings Function  2018  which allows a user to modify columns and/or information presented in the Table  2010  and/or the Compliance Requirement Sets Interface  2000 . For example, the Table  2010  in the example Configuration  2020  of the Compliance Requirement Sets Interface  2000  includes a Name Column  2002 , a Status Column  2004 , an Association Column  2006 , and an Action Column  2008 , as previously explained. The Settings Function  2018  allows the columns in Table  2010  to be modified to include more or less columns or information, including one or more different or same columns 
     For example, with reference to  FIG. 20B , when a user selects or activates the Settings Function  2018 , the Compliance Requirement Sets Interface  2000  can present an Interface Element  2022  such as a window, screen, frame, graphic, box, prompt, pop-up, etc., which presents Columns  2024  that may be added to, or removed from, the Table  2010 . Non-limiting examples of columns ( 2024 ) that can be added to the Table  2010  from the Interface Element  2022  include a compliance requirement set description column, a compliance requirements column identifying the compliance requirements configured for each compliance requirement set presented in the Table  2010 , an associated assurance groups column identifying the assurance groups that the compliance requirement sets ( 2012 ) displayed in the Table  2010  are associated with (if any), a column indicating a time since each compliance requirement set had a hit for an associated assurance group, a column indicating the last epoch where a compliance requirement set had a hit, a column indicating whether a compliance requirement set is used in the current epoch, one or more columns indicating a time or event that last activated a compliance requirement set, one or more columns indicating a time or event that last changed a compliance requirement set, etc. 
       FIG. 20C  illustrates the Compliance Requirement Sets Interface  2000  and Table  2010  after columns in the Table  2010  have been added and removed via the Interface Element  2022  accessed from through Settings Function  2018 . In this example, a Compliance Requirement Set Description Column  2030  and a Compliance Requirements Column  2032  have been added to the Table  2010 , and the Action Column  2008  has been removed from the Table  2010 . 
     Compliance Requirement Set Description Column  2030  includes a description of Compliance Requirement Sets  2012  displayed in Table  2010 , and Compliance Requirements Column  2032  includes a link or list for viewing the compliance requirements configured for Compliance Requirement Sets  2012  in Table  2010 . The Compliance Requirement Set Description Column  2030  and the Compliance Requirements Column  2032  can include Filters  2014 D-E for filtering compliance requirement sets based on a compliance requirement set description (e.g., Filter  2014 D) and/or one or more configured compliance requirements (e.g., Filter  2014 E). 
       FIG. 20D  illustrates a view of Compliance Requirement Sets Interface  2000  depicting a Table  2040  of attributes and/or statistics associated with a compliance requirement set selected from Compliance Requirement Sets  2012  in Table  2010  shown in  FIGS. 20A-C . The Table  2040  includes an Assurance Group Column  2042  identifying associated assurance groups, a Column  2044  identifying a time since the compliance requirement set had a hit for the current assurance group, a Column  2046  identifying a last epoch where the compliance requirement set had a hit, and a Column  2048  identifying whether the compliance requirement set is used in the current epoch. 
     The Table  2040  can include Rows  2050  of information for Columns  2042 - 2048 . Moreover, the Columns  2042 - 2048  can include Filters  2052 A-D for filtering information in the Table  2040 . For example, Column  2042  can include Filter  2052 A for filtering information from Column  2042 , Column  2044  can include Filter  2052 B for filtering information from Column  2044 , Column  2046  can include Filter  2052 C for filtering information from Column  2046 , and Column  2048  can include Filter  2052 D for filtering information from Column  2048 . 
     Turning back to  FIG. 20C , when a user selects from the Compliance Requirements Column  2032  to view the compliance requirements associated with a compliance requirement set in Table  2010  of the Compliance Requirement Sets Interface  2000 , the system can present an interface or view (e.g., a screen, a frame, a window, a tab, etc.) displaying the selected compliance requirements. For example, if a user selects View List Link  2034  from the Compliance Requirements Column  2032  in Table  2010 , the system will display the compliance requirements associated with the compliance requirement set corresponding to the View List Link  2034 . 
     To illustrate, with reference to  FIG. 21 , when a user selects View List Link  2034 , the system can present a Compliance Requirements Interface  2100  identifying the compliance requirements (and associated information) associated with the compliance requirement set associated with the View List Link  2034 . The Compliance Requirements Interface  2100  includes a Table  2120  of Compliance Requirements  2118 . The Table  2120  includes various Columns  2102 - 2114  of information associated with the Compliance Requirements  2118 , and the Columns  2102 - 2114  can include Filters  2136 A-G for filtering the compliance requirement information in Table  2120 . 
     In this example, the Table  2120  includes a Compliance Requirement Name Column  2102  which includes the names of the Compliance Requirements  2118 , a Compliance Requirement Description Column  2104  which includes descriptions of the Compliance Requirements  2118 , a Compliance Requirement Type Column  2106  which identifies the types of compliance requirements (e.g., segmentation requirement, traffic restriction requirement, naming convention requirement, resource or object attribute requirement, SLA requirement, etc.) of the Compliance Requirements  2118 , an EPG Selector A Column  2108  which identifies the EPGs selected as the EPG selector A (e.g., the source or destination EPG) for the Compliance Requirements  2118 , a Communication Operator Column  2110  which identifies the communication operators (e.g., may talk, must talk, must not talk, etc.) configured for the Compliance Requirements  2118 , an EPG Selector B Column  2112  which identifies the EPGs selected as the EPG selector B (e.g., the source or destination EPG) for the Compliance Requirements  2118 , and a Traffic Selector Column  2114  which identifies the specific traffic selectors configured for the Compliance Requirements  2118 . 
     The various Columns  2102 - 2114  in Table  2120  include respective information pertaining to the Compliance Requirements  2118  included in the Table  2120 . To illustrate, in Row 1 ( 2138 ) of Table  2120 , the Name Entry  2122  in the Compliance Requirement Name Column  2102  indicates the name of the compliance requirement associated with Row 1 ( 2138 ) is “Requirement 21”, the Description Entry  2124  in the Compliance Requirement Description Column  2104  includes the description “Description  21 ” for the compliance requirement associated with Row 1 ( 2138 ), the Type Entry  2126  in the Compliance Requirement Type Column  2106  indicates that the type of the compliance requirement associated with Row 1 ( 2138 ) is “Segmentation”, EPG Entry  2128  in the EPG Selector A Column  2108  indicates that the EPG selected as the EPG Selector A for the compliance requirement associated with Row 1 ( 2138 ) is “EPG-21”, the Operator Entry  2130  in the Communication Operator Column  2110  indicates that the communications operator for the compliance requirement associated with Row 1 ( 2138 ) is “May Talk”, the EPG Entry  2132  in the EPG Selector B Column  2112  indicates that the EPG selected as the EPG Selector B for the compliance requirement associated with Row 1 ( 2138 ) is “EPG −1”, and the Traffic Selector Entry  2134  in the Traffic Selector Column  2114  indicates that the traffic selector configured for the compliance requirement associated with Row 1 ( 2138 ) is “Traffic Selector F1”. 
       FIG. 22  illustrates a diagram of an example Definitions Scheme  2200  for configuring compliance requirements. Definitions Scheme  2200  first includes an EPG Selector Object  2202  representing an EPG Selector A for a compliance requirement. The user here can provide definitions for EPG Selector Object  2202  to configure the EPG selector A for the compliance requirement. The Definition Sets  2212  provide an example of Definitions  2214 - 2226  set for the EPG Selector Object  2202 . The Definitions  2214 - 2226  provide the definitions (e.g., attributes, conditions, expressions, filters, criteria, parameters, etc.) for determining which EPG(s) should be in the EPG selector Object  2202  (e.g., the EPG(s) to be included in the EPG Selector A for the compliance requirement). The Definitions  2214 - 2226  can include definitions for including and/or excluding EPG(s) in the EPG Selector Object  2202 . The example definitions ( 2214 - 2226 ) in the Definition Sets  2212  include criteria for selecting or including an EPG based on a tenant associated with the EPG, a VRF associated with the EPG, an EPG tag associated with the EPG, a bridge domain (BD) associated with the EPG, etc. 
     The Definitions Scheme  2200  further includes a Communication Operator Object  2204  representing the communication operator for the compliance requirement. The Communication Operator Object  2204  can include a communication operator definition (e.g., may talk to, must talk to, must not talk to, etc.) for the Communication Operator Object  2204 . The Definitions Scheme  2200  includes EPG Selector Object  2206  representing the EPG Selector B for the compliance requirement. The EPG Selector Object  2206  can include a definitions set with definitions for determining which EPG(s) to include in the EPG Selector B, such as the Definitions  2214 - 2226  in Definitions Sets  2212  associated with EPG Selector Object  2202  associated with EPG Selector A. 
     The Definitions Scheme  2200  includes Traffic Selector Scope Object  2208  and Traffic Selector Object  2210 . Traffic Selector Object  2210  represents the traffic selector for the compliance requirement, and can include definitions for identifying the traffic selector(s) for the compliance requirement. Traffic Selector Scope Object  2208  can include definitions specifying the scope or rules for determining which traffic selectors configured for Traffic Selector Object  2210  can or must satisfy or comply with the compliance requirement. For example, the Traffic Selector Scope Object  2208  can include definition(s) specifying which traffic selectors (e.g.,  2210 ) should satisfy or comply with the requirements defined for the Communication Operator Object  2204  and the EPG Selector Objects  2202  and  2206  (e.g., EPG Selector A may talk to EPG Selector B, EPG Selector A must talk to EPG Selector B, EPG Selector A must not talk to EPG Selector B, etc.). 
     To illustrate, the Traffic Selector Scope Object  2208  can specify that communications matching the requirements defined for the Communication Operator Object  2204  and the EPG Selector Objects  2202  and  2206  must be allowed/denied on all or any traffic selectors associated with the Traffic Selector Object  2210 . For example, the Traffic Selector Scope Object  2208  can specify that EPG Selector A (e.g.,  2202 ) may, must, or must not talk to EPG Selector B on all traffic selectors (e.g.,  2210 ). As another example, the Traffic Selector Scope Object  2208  can specify that EPG Selector A (e.g.,  2202 ) may, must, or must not talk to EPG Selector B on any traffic selectors (e.g.,  2210 ). Thus, the Traffic Selector Scope Object  2208  can define which traffic selectors must apply/comply with the compliance requirement, including for example whether all traffic selectors must apply/comply, whether only a subset or any (e.g., at least one) of the traffic selectors must apply/comply, etc. 
       FIG. 23A  illustrates an example Configuration  2300  of a Compliance Score Interface  2302 . The Compliance Score Interface  2302  can display compliance scores and statistics. The compliance scores or statistics presented in the Compliance Score Interface  2302  can be derived by using any compliance requirements defined as previously described to perform assurance operations for determining whether the compliance requirements are satisfied (fully or partially), applied or enforced, violated (fully or partially), etc., based on the policies and/or configurations implemented in the network, such as ACI policies programmed in a network controller (e.g., an APIC controller), hardware (e.g., TCAM) rules programmed on devices in the network, etc. 
     In some implementations, the compliance scores and statistics can be displayed for specific types or categories of compliance requirements. For example, Compliance Score Interface  2302  can include an Overall Menu  2304  for accessing overall compliance scores (e.g., compliance scores for all types of compliance requirements, a Segmentation Menu  2306  for accessing or viewing compliance scores for segmentation requirements, an SLA Requirements Menu  2308  for accessing or viewing compliance scores for SLA requirements, an SLA With Traffic Restriction Requirements Menu  2310  for accessing or viewing compliance scores for SLA with traffic restriction requirements, a Naming Convention Requirements Menu  2312  for accessing or viewing compliance scores for naming convention requirements, or a Configuration Requirements Menu  2314  for accessing or viewing compliance scores for a specific configuration requirement. 
     In the example Configuration  2300  in  FIG. 23A , the Compliance Score Interface  2302  displays compliance score information under the Overall Menu  2304 . Here, the Compliance Score Interface  2302  includes a Compliance Score Graphic  2320 A displaying a Compliance Score  2318 A indicating a compliance by Policy  2316 A and a Compliance Score Graphic  2320 B displaying a Compliance Score  2318 B indicating a compliance by State  2316 B. 
     The Compliance Score Graphics  2320 A-B in this example are pie charts divided into Slices  2322 - 2326  representing or illustrating the numerical proportion of compliance requirements partially or fully violated (Slice  2322 ), not applied (Slice  2324 ), and fully satisfied (Slice  2326 ). Thus, the Compliance Score Graphics  2320 A-B can provide a total compliance score (e.g.,  2318 A and  2318 B) and an indication of the number or proportion of compliance requirements violated (partially or fully), not applied, or satisfied. This information can indicate the degree to which the configuration and/or behavior of the network complies or satisfies the compliance requirements. 
       FIG. 23B  illustrates another Configuration  2350  of the Compliance Score Interface  2302  where the slices (e.g.,  2322 - 2326 ) of Compliance Score Graphic  2320 A are subdivided by requirement types or categories. For example, the Slice  2322  representing compliance requirements that are violated (partially or fully) is subdivided into Slices  2322 A-F, where each slice ( 2322 A-F) corresponds to a particular compliance requirement type or category, such as a segmentation requirement, an SLA requirement, an SLA with traffic restriction requirement, a naming convention requirement, a resource attribute requirement, a specific configuration requirement, etc. Moreover, the Slice  2324  representing compliance requirements that are not applied is subdivided into Slices  2324 A-F, where each slice ( 2324 A-F) corresponds to a particular compliance requirement type or category. Further, the Slice  2326  representing compliance requirements that are fully satisfied is subdivided into Slices  2326 A-F, where each slice ( 2326 A-F) corresponds to a particular compliance requirement type or category. 
     In some cases, the Compliance Score Graphics  2320 A-B and/or the Slices ( 2322 ,  2324 ,  2326 ,  2322 A-F,  2324 A-F,  2326 A-F) in  FIGS. 23A and 23B  can be dynamic, and can be selected to drill down (e.g., access more specific details) on the associated information. For example, a user can select Slice  2322 A representing the compliance requirements violated (partially or fully) for a specific compliance requirement type or category (e.g., a segmentation requirement, an SLA requirement, etc.) to access additional information or statistics associated with that slice (i.e., Slice  2322 A), such as a timestamp or epoch of each violation, the specific compliance requirement(s) that were violated, the specific network policies or conditions that caused the compliance requirement violations, any patterns associated with the compliance requirement violations, items associated with the compliance requirement violations (e.g., objects, network segments, network devices, network configurations or policies, packets or flows, etc.), information about the compliance requirement violations (e.g., descriptions, notifications, statistics, compliance or configuration suggestions, violation culprits, requirements information, network conditions during the compliance requirement violations, information about objects associated with the compliance violations such as VRFs or EPGs, etc.), and/or any other relevant information. 
     While the Compliance Score Graphics  2320 A-B in  FIGS. 23A-B  are shown as pie charts, it should be noted that such configuration or implementation is provided as a non-limiting example for explanation purposes, and other types or configurations of the Compliance Score Graphics  2320 A-B and/or other ways for presenting the compliance score information are also contemplated herein. For example, in some implementations, the compliance score information can be presented in a list, report, bar graph, table, log, heat map, and/or in any other scheme or configuration either in addition to or in lieu of the pie charts depicted by the Compliance Score Graphics  2320 A-B. 
       FIG. 24A  illustrates an example View  2400  of a Compliance Analysis Interface  2402 . The compliance and analysis information presented in the Compliance Analysis Interface  2402  can be derived by using any compliance requirements defined as previously described, to perform assurance operations for determining whether the compliance requirements are satisfied (fully or partially), applied or enforced, violated (fully or partially), etc., based on the policies and/or configurations implemented in the network. 
     In View  2400 , the Compliance Analysis Interface  2402  includes a Section  2404  identifying compliance events by severity, including Critical Violations  2406 A, Major Violations  2406 B, Minor Violations  2406 C, Warnings  20406 D, Enforcements  2406 E, and Total  2406 F. The Compliance Analysis Interface  2402  can also include a Section  2408  identifying compliance violations by compliance type, including violations for Communication Requirements  2410 A, Resource Attribute Requirements  2410 B, and Naming Convention Requirements  2410 C. 
     The Compliance Analysis Interface  2402  can further include a Section  2412  identifying unhealthy resources, including tenants ( 2414 A), application profiles ( 2414 B) and EPGs ( 2414 C), by communication compliance issues. Moreover, the Compliance Analysis Interface  2402  can include a Section  2416  identifying unhealthy resources, including tenants ( 2414 A), VRFs ( 2414 D), EPGs ( 2414 C), BDs ( 2414 D), and subnets ( 2414 E), by resource attribute compliance issues. The Compliance Analysis Interface  2402  can also include a Section  2420  identifying unhealthy resources, including tenants ( 2414 A), VRFs ( 2414 D), EPGs ( 2414 C), BDs ( 2414 D), and subnets ( 2414 E), by naming convention compliance issues. In this example, the Sections  2412 ,  2416 , and  2420  can provide resource or object specific violations or issues for each of the compliance types in Section  2408 . Thus, the Sections  2412 ,  2416 , and  2420  can provide a different or more granular view of the violations or issues identified for each compliance type in Section  2408 . 
       FIG. 24B  illustrates another View  2430  of the Compliance Analysis Interface  2402  including various Tables  2432 - 2442  of compliance information and statistics. In this example, the Compliance Analysis Interface  2402  includes a Table  2432  presenting the top tenants by EPG count violations, a Table  2434  presenting the top tenants by communication compliance issues, a Table  2436  presenting the top tenants by resource attribute issues, a Table  2438  presenting the top tenants by naming convention issues, a Table  2440  presenting the top tenants by resource attribute issue type, and a Table  2442  presenting compliance violations and enforcements by compliance requirement sets and compliance requirements. 
     The Table  2432  presenting the top tenants by EPG count violations can include a Tenant Column  2444  identifying tenants for each row of statistics or information, a Communication Requirement Count Column  2446  including the number of communication compliance requirement violations for each tenant in Tenant Column  2444 , a Resource Attribute Count Column  2448  including the number of resource attribute compliance requirement violations for each tenant in Tenant Column  2444 , and a Naming Convention Count Column  2450  including the number of naming convention compliance requirement violations for each tenant in Tenant Column  2444 . 
     The Table  2434  presenting the top tenants by communication compliance issues can include Tenant Column  2444 , and Columns  2452 - 2456  including the number of communication compliance issues (e.g., traffic selector issues, traffic compliance issues, etc.) for various types of events, such as critical events ( 2452 ), major events ( 2454 ), and minor events ( 2456 ). For example, Column  2452  can display the number of critical events (e.g., communication compliance critical events) for each tenant in Tenant Column  2444 , Column  2454  can display the number of major events (e.g., communication compliance major events) for each tenant in Tenant Column  2444 , and Column  2456  can display the number of minor events (e.g., communication compliance minor events) for each tenant in Tenant Column  2444 . 
     The Table  2436  presenting the top tenants by resource attribute compliance issues can include Tenant Column  2444 , and Columns  2452 - 2456  including the number of resource attribute compliance issues for various types of events, such as critical events ( 2452 ), major events ( 2454 ), and minor events ( 2456 ). For example, Column  2452  can display the number of critical events (e.g., resource attribute compliance critical events) for each tenant in Tenant Column  2444 , Column  2454  can display the number of major events (e.g., resource attribute compliance major events) for each tenant in Tenant Column  2444 , and Column  2456  can display the number of minor events (e.g., resource attribute compliance minor events) for each tenant in Tenant Column  2444 . 
     The Table  2438  presenting the top tenants by naming convention issues can include Tenant Column  2444 , and Columns  2452 - 2456  including the number of naming convention compliance issues for various types of events, such as critical events ( 2452 ), major events ( 2454 ), and minor events ( 2456 ). For example, Column  2452  can display the number of critical events (e g, naming convention compliance critical events) for each tenant in Tenant Column  2444 , Column  2454  can display the number of major events (e g, naming convention compliance major events) for each tenant in Tenant Column  2444 , and Column  2456  can display the number of minor events (e.g., naming convention compliance minor events) for each tenant in Tenant Column  2444 . 
     The Table  2440  presenting the top tenants by resource attribute issue type can include Tenant Column  2444 , and Columns  2458 - 2468  including the number of compliance issues for various resource attribute issue types, such as flood properties (Column  2458 ), endpoint learning properties (Column  2460 ), DHCP relay properties (Column  2462 ), gateway properties (Column  2464 ), privacy properties (Column  2466 ), and VRF properties (Column  2468 ). 
     The Table  2442  presenting compliance violations and enforcements by compliance requirement sets and compliance requirements can include a Compliance Requirement Set Column  2470 , identifying specific compliance requirement sets in the Table  2442 , a Compliance Requirement Column  2472 , identifying specific compliance requirements in the compliance requirement sets listed in Table  2442 , a Compliance Requirement Type Column  2474 , identifying specific compliance requirement types in the Table  2442 , a Violation and Enforcement Column  2476 , identifying whether the specific compliance requirement sets in the Table  2442  are violated or enforced, and a Not Applied Column  2478 , identifying whether the specific compliance requirement sets in the Table  2442  have been applied. 
       FIG. 25  illustrates an example Compliance Events Search Interface  2500 . The Compliance Events Search Interface  2500  allows users to search for specific compliance events generated or calculated based on compliance requirements or compliance requirement sets defined as previously described. The Compliance Events Search Interface  2500  can include a Search Interface  2502  where the user can input search criteria and execute a search based on the search criteria. The Search Interface  2502  includes Search Input Area  2504  where the user can input or select filters (e.g., search criteria) and a Search Filters Area  2506  that includes or identifies each search filter that has been added or configured for a search. Non-limiting examples of search filters can include an event severity filter (e.g., critical, major, minor, warning, etc.), an event type filter (e.g., type of compliance requirement event or issue), an event description filter, an event name filter, an object filter (e.g., EPG, VRF, tenant, BD, application profile, EPG tag, etc.), and so forth. 
     The Compliance Events Search Interface  2500  can include a Search Results Section  2510  which presents Results  2522  of the search performed based on the filters (e.g.,  2506 ) provided in the Search Input Area  2504 . The Results  2522  can include the events that match the filters implemented in the search as well as information associated with the events, such as a severity, a description, an event name, an event type, an event count, an EPG compliance requirement set associated with the event, etc. 
     The Search Results Section  2510  can include an Aggregated Events Option  2508 A for displaying aggregated events and an Individual Events Option  2508 B for displaying individual events. In this example, the Results  2522  include aggregated events based on the Aggregated Events Option  2508 A. 
     The Search Results Section  2510  can include various Columns  2512 - 2520  of information presented as part of the Results  2522 . For example, the Search Results Section  2510  can include a Severity Column  2512  indicating the severity (e.g., critical, major, minor, warning, etc.) of each event in the Results  2522 , an Event Name Column  2514  identifying the name of each event, an Event Subcategory Column  2516  indicating an associated event subcategory, a Count Column  2518  indicating a count for each event, and an Event Description Column  2520  including any description available (if any) for each event. The Search Results Section  2510  can also include Filters  2524 A-C for applying specific filters to the Results  2522 . 
     Having disclosed example system components and concepts, the disclosure now turns to the example methods for creating and verifying security compliance requirements, shown in  FIGS. 26-28 . The steps outlined herein are examples and can be implemented in any combination, including combinations that exclude, add, or modify certain steps. 
     With reference to  FIG. 26 , at step  2602 , a method for creating security compliance requirements and verifying the security compliance requirements in a network can include receiving, via a user interface, EPG inclusion rules (e.g.,  1914 ,  1922 ,  1924 ,  1926 ,  1944 ) defining which EPGs on a network (e.g., Network Environment  100 ) should be included in each of a plurality of EPG selectors (e.g., EPG Selectors  1116 , EPG Selectors  1506 ). The plurality of EPG selectors can represent respective sets of EPGs that satisfy the EPG inclusion rules. 
     The EPG inclusion rules can be received via, for example, a portion, section, or interface of the user interface, which allows a user to create and/or configure EPG selectors, such as New EPG Selector Interface  1900 . Moreover, the EPG inclusion rules can include rules, criteria, parameters, conditions, etc., for including EPGs in the EPG selectors as well as excluding EPGs from the EPG selectors (e.g.,  1914 ,  1916 A-C,  1918 A-C,  1922 ,  1924 ,  1926 ,  1928 ,  1930 ,  1932 A-B,  1934 A-B,  1936 ,  1938 ,  1944 ). For example, the EPG inclusion rules can include filters for selecting EPGs in the network for inclusion in an EPG selectors based on a VRF associated with the EPGs, a tenant associated with the EPGs, an application profile associated with the EPGs, a name (or portion of a name) associated with the EPGs, a tag (e.g., EPG tag) associated with the EPGs, a label associated with the EPGs, and/or any other criteria or attributes associated with the EPGs. 
     At step  2604 , the method can include selecting the respective sets of EPGs that satisfy the EPG inclusion rules for inclusion in the plurality of EPG selectors. In some examples, each respective set of EPGs can be selected based on a portion of the EPG inclusion rules that is associated with, or applies to, the respective set of EPGs. For example, each respective set of EPGs can be selected based on EPG inclusion rules that apply to the respective set of EPGs and/or define criteria (e.g., parameters, filters, conditions, attributes, etc.) that match the respective set of EPGs. 
     At step  2606 , the method can involve creating the plurality of EPG selectors based on the respective sets of EPGs. Each of the respective sets of EPGs can include one or more EPGs, and each of the plurality of EPG selectors can include one or more of the respective sets of EPGs. 
     At step  2608 , the method can include creating a traffic selector including traffic parameters (e.g.,  1818 ,  1820 ,  1832 ,  1834 ,  1842 ,  1844 ,  1846 ,  1852 ,  1856 ,  1858 A,  1858 B,  1862 ,  1864 ,  1872 ,  1874 ,  1876 ,  1890 ) received via the user interface. The traffic selector can be created as shown in  FIGS. 18A-E  via a traffic selector interface (e.g., New Traffic Selector Interface  1800 ) associated with the user interface. The traffic selector can represent or include, for example, specific traffic, including a specific type(s) of traffic, a specific category (or categories) of traffic, a specific class (or classes) of traffic, traffic having specific attributes, etc. 
     The traffic represented by the traffic selector can be defined by the traffic parameters. For example, the traffic parameters can be used to identify, classify, select, filter, etc., specific traffic to be included in, added to, associated with, mapped to, applied to, etc., the traffic selector. The traffic parameters can include, for example, traffic attributes, criteria, categories, filters, etc., for traffic associated with the traffic selector. Non-limiting examples of traffic parameters include traffic protocols (e.g., OSPF, EGP, IGP, TCP, UDP, ICMP, IGMP, EIGRP, PIM, any, etc.), EtherTypes (e.g., IPv6, IPv4, MPLS, Trill, ARP, FCOE, MAC security, unspecified, etc.), ports (e.g., source ports, destination ports), exceptions, flags, traffic direction-based traffic settings, addresses, state (e.g., session state, protocol state, etc.), port ranges, traffic priority values, etc., any of which can be used to identify, select, classify, associate, include, etc., traffic by matching or comparing the traffic with the traffic parameters. Traffic matching the traffic parameters for a traffic selector can be associated with, added to, or assigned to the traffic selector. 
     At step  2610 , the method can include creating a security compliance requirement for the network based on a first EPG selector (e.g., the Chosen EPG Selector  1202  for EPG Selector A as shown in  FIG. 17C ) from the plurality of EPG selectors, a second EPG selector (e.g., the Chosen EPG Selector  1752  for EPG Selector B as shown in  FIG. 17C ) from the plurality of EPG selectors, the traffic selector, and a communication operator (e.g., Communication Operator Definition  1018 B) defining a communication condition (e.g.,  1708 ) for traffic associated with the first EPG selector, the second EPG selector, and the traffic selector. The security compliance requirement can be created and configured using the user interface. 
     To illustrate, as shown in  FIGS. 17A-C , a user can access Compliance Requirement Interface  1000  to create the security compliance requirement. Using Compliance Requirement Interface  1000 , the user can configure the security compliance requirement by, for example and without limitation, selecting EPG selectors (e.g., EPG selector A and EPG selector B) for the security compliance requirement, specifying a communication operator (e.g., Communication Operator  1708  associated with Communication Operator Definition  1018 B) for the security compliance requirement, and selecting a traffic selector (e.g., Chosen Traffic Selector  1754  associated with associated with Compliance Definition  1704 , Chosen Traffic Selector  1760  associated with Compliance Definition  1704 ) for the security compliance requirement. 
     The communication operator a communication condition or requirement for traffic between EPGs in the EPG selectors associated with the security compliance requirement (e.g., the first and second EPG selectors). Non-limiting examples of communication operators include a “may talk to” condition, a “may only talk to” condition, a “must be able to talk to” condition, and a “must not talk to” condition. For example, the communication operator configured for the security compliance requirement can specify that the first EPG selector may talk to the second EPG selector on the traffic selector, the first EPG selector may only talk to the second EPG selector on the traffic selector, the first EPG selector must be able to talk to the second EPG selector on the traffic selector, or the first EPG selector must not talk to the second EPG selector on the traffic selector. 
     The security compliance requirement can define a security requirement that should be enforced, applied, satisfied, etc., in the network for traffic between the EPGs in the EPG selectors of the security compliance requirement, which matches the attributes, criteria, etc., specified by the security compliance requirement, such as the conditions provided by the communication operator(s) and the traffic selector(s) defined for the security compliance requirement. The security compliance requirement can be used to perform a compliance or assurance verification (e.g., via an assurance, compliance, or containment check as further described herein) in the network. The compliance or assurance verification can determine whether the policies, state, and/or configuration of the network comply (e.g., apply, satisfy, etc.) the security compliance requirement or otherwise violate (fully or partially) or fail to apply/enforce the security compliance requirement. 
     At step  2612 , the method can include determining whether security policies (e.g., rules, contracts, policy settings, filters, access control list entries, etc.) on the network (e.g., security policies configured on Controller  116 , Leafs  104 , etc.) comply (e.g., satisfy, violate, apply, enforce, etc.) with the security compliance requirement. In some cases, this determination can involve comparing security policies on the network with the security compliance requirement to determine whether the security compliance requirement is satisfied (fully or partially), violated (fully or partially), applied, or enforced by the security policies. 
     In some implementations, a compliance system (e.g., Assurance Appliance System  300 , Policy Analyzer  504 , Formal Analysis Engine  522 ) can obtain the security compliance requirement and perform a check (e.g., an equivalence, assurance, or compliance check) by comparing the security compliance requirement (or a representation thereof) with security policies on the network (or a representation thereof) to determine whether the security policies comply with the security compliance requirement. For example, the compliance system can perform a check between the security policies and the security compliance requirement as described in  FIGS. 5A-C  and  6 A-C. 
     In some examples, a compliance system (e.g., Assurance Appliance System  300 ) can use a model of the network (e.g., Logical Model  270 , Hardware Model  276 , etc.) to determine whether policies on the network (e.g., policies represented in the model) comply with the security compliance requirement. For example, the compliance system can generate a data structure, such as a BDD (e.g.,  540 ), an ROBDD (e.g.,  600 A,  600 B,  600 C), an n-bit vector or string, a flat list of rules, etc., representing Logical Model  270  (and/or policies and configurations therein) as well as a data structure for each pair of EPGs from the first and second EPG selectors (e.g., each pair of EPGs including one EPG from the first EPG selector and one EPG from the second EPG selector) representing the pair of EPGs, the communication operator, and the traffic selector. 
     The compliance system can then perform a containment check for the data structure of each pair of EPGs to determine if the data structure of each pair of EPGs is contained in the data structure representing Logical Model  270 . If the data structures of each pair of EPGs are contained in the data structure representing Logical Model  270 , the compliance system can determine that the policies in the network satisfy the security compliance requirement. If the data structure of one or more pairs of EPGs is not contained (fully and/or partially) in the data structure representing Logical Model  270 , the compliance system can determine that the policies in the network violate or do not apply the security compliance requirement. 
     For example, assume the first EPG selector includes EPG1 and EPG2, and the second EPG selector of the security compliance requirement includes EPG3 and EPG4. Further assume that the communication operator includes the conditions “must talk to”, and the traffic selector includes the traffic parameters TCP protocol and Ethertype IPv6. Based on the first and second EPG selectors, the communication operator, and the traffic selector, the security compliance requirement in this example provides that EPG1 and EPG 2 (i.e., the first EPG selector) must talk to EPG 3 and EPG 4 (i.e., the second EPG selector) using TCP protocol and IPv6. 
     To determine whether policies in the network comply with this example compliance requirement, the compliance system can create a BDD representing EPG1, EPG3, the communication operator, and the traffic selector; a BDD representing EPG1, EPG4, the communication operator, and the traffic selector; a BDD representing EPG2, EPG3, the communication operator, and the traffic selector; and a BDD representing EPG2, EPG4, the communication operator, and the traffic selector. The system has created a BDD for each pair of EPGs in the first and second EPG selectors, representing the compliance requirement as it pertains to each pair of EPGs. The compliance system can perform a containment check for each BDD by determining whether each BDD is contained in a BDD created for Logical Model  270 . The BDD created for Logical Model  270  can represent policies and configurations of the network. 
     If the BDDs for all the pairs of EPGs are contained in the BDD created for Logical Model  270 , the compliance system can determine that the policies in the network comply with the security compliance requirement. On the other hand, if one or more BDDs corresponding to one or more of the pairs of EPGs are not fully contained in the BDD created for Logical Model  270 , the compliance system can determine that the security compliance requirement is at least partially violated or not fully applied by the policies in the network. 
     To illustrate, assume Logical Model  270  contains the following policies for traffic between EPG1 and EPG2: 
     R1: Source=EPG1; Destination=EPG2; Protocol=TCP; Type=IPv4; Port=80; Action=Allow 
     R2: Source=EPG1; Destination=EPG2; Protocol=*; Type=*; Port=*; Action=Deny 
     In addition, assume a security compliance requirement has been created with the following security requirements for traffic between EPG1 and EPG2: 
     S1: EPG1 may talk to EPG2 only on Protocol TCP, EtherType IPv4, and Port 80; 
     where EPG1 is an EPG from EPG Selector A, EPG2 is an EPG from EPG Selector B, “must talk to” represents the communication operator associated with the security compliance requirement, and the traffic parameters “only on Protocol TCP, EtherType IPv4, and Port 80” represent the traffic selector associated with the security compliance requirement. 
     To perform a containment check between rules S1 and R1 and R2, the method can can create respective data structures, such as BDDs, for S1, R1, and R2, and determine whether the BDD for S1 is contained within the BDD for R1 and R2. In this example, R1 provides that traffic between EPG1 and EPG2 transmitted over TCP, IPv4, and port 80 is allowed; while R2 provides that all traffic between EPG1 and EPG2 is denied. Since R1 has a higher priority than R2, the result is that traffic between EPG1 and EPG2 transmitted over TCP, IPv4, and port 80 is allowed and all other traffic between EPG1 and EPG2 is denied. These requirements in R1 and R2 are consistent with the requirements in S1. Therefore, the containment check will result in an equivalency between the respective data structures for S1, R1, and R2, indicating that the security compliance requirement as it pertains to EPG1 and EPG2 is satisfied by the policies in Logical Model  270  for traffic between EPG1 and EPG2 (i.e., R1 and R2). 
     At step  2614 , the method can include generating compliance assurance events indicating whether the security policies configured on the network comply with the security compliance requirement. For example, after determining whether the policies in the network comply with the security compliance requirement, the compliance system can generate compliance assurance events based on the results of the check from step  2612 . The compliance system can raise or generate an event for each compliance result or determination, or raise or generate events only for certain types of compliance results or determinations, such as when the security compliance requirement is violated (fully and/or partially), satisfied (fully and/or partially), not applied or enforced, etc. 
     In some cases, the method can include presenting the compliance assurance events on a display or interface (e.g.,  2302 ,  2402 ,  2500 ). The compliance assurance events presented can include compliance results. The compliance results can indicate whether the security compliance requirement was violated (partially or fully), satisfied (partially or fully), applied or enforced, etc. The compliance results can be specific to an epoch or a period when the compliance check was performed. However, in some cases, the compliance results can include results from other compliance checks and/or periods or epochs, for example. 
     The compliance assurance events and/or compliance results presented in the graphical user interface can include compliance scores, event counts (e.g., violations, compliance warnings, passed compliance checks, enforcement events, etc.), information about the security compliance requirement(s) checked, information about resources or objects (e.g., EPGs, VRFs, tenants, bridge domains, subnets, application profiles, contracts, filters, workloads, devices, etc.) associated with one or more security compliance requirements checks, an indication of the policies or objects implicated by an event (e.g., policies or objects that caused the event to be raised), etc. 
     In some cases, the information presented for the compliance assurance events and/or compliance results can be grouped into one or more categories and presented by category or categories. For example, compliance assurance events and/or compliance results can be presented by type of security compliance requirement, type of result (e.g., violation, enforcement, requirement pass, warning, etc.), type of object or resource (e.g., by tenant, EPG, VRF, tenant, subnet, server, resource or security group, etc.), severity of event (e.g., critical, major, minor, warning, etc.), type of issue, event count, resource attributes (e.g., flood properties, VRF properties, privacy properties, endpoint properties, etc.), specific policies or requirements, etc. 
     Moreover, the information can be presented in different ways based on one or more factors such as user preferences. For example, compliance assurance events and related information can be presented based on a specific organization or sorting of the compliance assurance events and related information. To illustrate, compliance assurance events can be sorted and presented by event counts, epochs (or any interval or schedule), priorities, severity, event or resource rankings, compliance scores, compliance requirement types, compliance issues, resource or event attributes, specific policies, specific compliance requirements, compliance requirement sets, etc. 
     In some cases, compliance assurance events can be presented along with an indication of a cause for the events being raised. For example, compliance assurance events can be presented along with an indication of a cause for the security compliance requirement being satisfied, violated, or not applied. When presenting the cause, the specific objects and/or policies involved in the cause and/or included in the security compliance requirement can also be identified. For example, assume a compliance assurance event is generated for a security compliance requirement that is violated. The compliance assurance event identifying the violation can be presented along with an indication of the policies, requirements, or objects that caused the violation and/or a list of policy constructs (e.g., EPGs, VRF, application profile, bridge domain, tenant, filter, contract, etc.) associated with the security compliance requirement, the policy or policies that caused the violation, and/or the resources or objects involved in the violation or the compliance check. For example, the violation can be presented along with an indication that the violation was caused by a specific contract or rule between a specific consumer EPG and a specific provider EPG. 
     In some cases, the method can include grouping security compliance requirements into sets including multiple security compliance requirements. Moreover, a specific security compliance requirement or security compliance requirement set can be associated with a particular fabric or segment of the network and applied specifically to that particular fabric or segment of the network. For example, if the network includes multiple fabrics, a security compliance requirement or security compliance requirements set can be associated with one or more fabrics, and used to check if the one or more fabrics (or the policies associated with the one or more fabrics) comply with such security compliance requirement or security compliance requirements set. Thus, step  2612  for determining compliance can be performed based on the security policies in the one or more fabrics and the security compliance requirement or security compliance requirements set. 
     In some cases, the method can include determining whether a state of the network complies with the security compliance requirement. For example, the method can include comparing the security compliance requirement to rules programmed on the network devices (e.g., switches, routers, etc.) in the network, such as ACLs and/or rules programmed on the hardware memory (e.g., TCAM) of network nodes (e.g., Leafs  104 ). To illustrate, the method can include comparing (e.g., by performing a containment or assurance check) one or more first data structures (e.g., BDDs, ROBDDs, vectors, flat rules, etc.) representing the security compliance requirement with one or more second data structures (e.g., BDDs, ROBDDs, vectors, flat rules, etc.) representing hardware policy entries (e.g., TCAM entries) configured on network devices in the network, and based on the comparison, determining whether the hardware policy entries configured on the network devices satisfy, violate, or apply the security compliance requirement. 
     In some implementations, the one or more second data structures representing hardware policy entries configured on the network devices can be created based on one or more hardware models (e.g., Hardware Model  276 ) created for the network. For example, a hardware model associated with a switch in the network can be used to construct one or more BDDs, which can represent a portion of the state of the network reflected in the switch (e.g., the rules programmed on the switch for implementing or enforcing security policies in the network), and the one or more BDDs can be used to determine if the portion of the state of the network complies with the security compliance requirement. Similar containment checks can be performed using hardware models associated with other switches in the network, and the aggregated results can indicate whether the state of the network complies with the security compliance requirement. In some cases, this can involve performing a containment check by checking if one or more BDDs created for, and representing, the security compliance requirement are contained in the one or more BDDs constructed from the hardware model(s) representing the state of the network. 
       FIG. 27  illustrates an example method for creating a security compliance requirement and determining compliance of policies involving objects on a same network context. The objects can include, for example, EPGs, application profiles, contracts, network domains, filters, tenants, policies, policy constructs, etc. Moreover, the network context can include, for example, a private network, a network domain, a VRF, a subnet, a bridge domain, etc. In this example method, the objects are EPGs and the network context is a VRF. However, in other examples, the objects and/or network context can include other types of objects, policy constructs, and/or network contexts, such as security groups, subnets, bridge domains, network contexts, group policy objects, etc. 
     At step  2702 , the method can include creating a security compliance requirement (e.g., via Compliance Requirement Interface  1000 ) for a network (e.g., Network Environment  100 ), the security compliance requirement including a first EPG selector (e.g., the Chosen EPG Selector  1202  for EPG Selector A as shown in  FIG. 17C ) and a second EPG selector (e.g., the Chosen EPG Selector  1752  for EPG Selector B as shown in  FIG. 17C ) representing respective sets of EPGs, a traffic selector, and a communication operator (e.g., Communication Operator Definition  1018 B). 
     The respective sets of EPGs associated with the first and second EPG selectors can be selected or determined based on EPG inclusion rules (e.g.,  1914 ,  1922 ,  1924 ,  1926 ,  1944 ) as previously explained. The traffic selector can include traffic parameters (e.g.,  1818 ,  1820 ,  1832 ,  1834 ,  1842 ,  1844 ,  1846 ,  1852 ,  1856 ,  1858 A,  1858 B,  1862 ,  1864 ,  1872 ,  1874 ,  1876 ,  1890 ) identifying traffic associated with the traffic selector. The traffic parameters can be used to match traffic to the traffic selector and/or identify what traffic corresponds to the traffic selector. The communication operator can define a communication condition (e.g.,  1708 ) for traffic associated with the first and second EPG selectors and the traffic selector, such as a “may talk to” condition, a “must talk to” condition, a “must not talk to” condition, a “may only talk to” condition, etc. 
     At step  2704 , the method can involve creating, for each distinct pair of EPGs from the respective sets of EPGs, a first respective data structure representing the distinct pair of EPGs, the communication operator, and the traffic selector. The distinct pair of EPGs can include a respective EPG from each of the first EPG selector and the second EPG selector (e.g., each pair of EPGs can include one EPG from the first EPG selector and one EPG from the second EPG selector). The first respective data structure can be, for example, a BDD (e.g.,  540 ), an ROBDD (e.g.,  600 A,  600 B,  600 C), an n-bit vector or string, a flat list of rules, etc., representing the distinct pair of EPGs, the communication operator, and the traffic selector. For example, the first respective data structure can be a BDD representing one or more variables, rules, values, Boolean functions, etc., associated with the distinct pair of EPGs, the communication operator, and the traffic selector.  FIGS. 5A-C  and  6 A-C and their accompanying description provide example data structures, such as ROBDDs, generated for example objects and/or rules and used to perform assurance or containment checks. 
     At step  2706 , the method can include creating a second respective data structure representing a model of the network (e.g., Logical Model  270 ). The second respective data structure can be, for example, a BDD (e.g.,  540 ), an ROBDD (e.g.,  600 A,  600 B,  600 C), an n-bit vector or string, a flat list of rules, etc., representing the model (e.g., Logical Model  270 ) of the network and/or policies and configurations therein. 
     At step  2708 , the method can include determining whether the first respective data structure is contained in the second respective data structure to yield a containment check. For example, a compliance system, such as Assurance Appliance System  300 , can perform a containment check for each first respective data structure (e.g., the data structure created for each distinct pair of EPGs) to determine if each first respective data structure is contained in the second respective data structure representing the model of the network. 
     At step  2710 , the method can include determining whether security policies configured on the network comply with (e.g., satisfy, violate, or apply) the security compliance requirement based on the containment check. For example, if the first respective data structure of each distinct pair of EPGs is contained in the second respective data structure representing the model of the network (e.g., Logical Model  270 ), a compliance system (e.g., Assurance Appliance System  300 ) can determine that the policies in the network satisfy the security compliance requirement. If the first respective data structure of each distinct pair of EPGs is not contained (fully and/or partially) in the second respective data structure representing the model of the network, the compliance system can determine that the policies in the network violate or do not apply the security compliance requirement. If only some of the first respective data structures are not contained (fully and/or partially) in the second respective data structure, the compliance system can determine that only some policies in the network violate or do not apply the security compliance requirement. 
     In some cases, the compliance system can determine which policies in the network and/or which policy constructs or policies represented by the first respective data structures violate or do not apply the security compliance requirement based on the containment check. For example, the compliance system can identify which of the first respective data structures are not contained in the second respective data structure and based on this determine which policies and/or policy constructs are associated with the failed containment check. 
     In some cases, the method can include determining that each EPG in at least one distinct pair of EPGs from the sets of EPGs is associated with the same network context (e.g., the same VRF). For example, in some cases, the process for performing containment checks can vary depending on whether the EPGs in a pair of EPGs represented by the first respective data structure are in the same or different network context (e.g., same VRF). To illustrate, when the EPGs are in the same network context (e.g., same VRF), step  2710  can involve determining whether the policies associated with the network context (e.g., the VRF) satisfy, violate, or apply the security compliance requirement, as described herein. 
     On the other hand, if the EPGs in a pair of EPGs are in different network contexts, the containment check process can involve determining where the policies associated with the pair of EPGs may be located (e.g., which network context), as described below with respect to  FIG. 28 . For example, in some cases, the policies associated with a pair of EPGs in different network contexts can be set or located in only one of the network contexts, both network contexts, or none of the network contexts. Accordingly, to perform a compliance check, the method may involve determining where (e.g., which network context or contexts) to look in or check for policies. To illustrate, in some cases, policies associated with a consumer EPG and a provider EPG can be located or set in the network context associated with the consumer EPG. Thus, the policies may not be located or set in the network context associated with the provider EPG. Therefore, to perform the containment check for the policies associated with the consumer and provider EPGs, the method can involve locating the policies in the network context associated with the consumer EPG. Additional details and a description of an example method for performing containment checks involving EPGs in different network contexts are provided below with reference to  FIG. 28 . 
     Referring to  FIG. 27 , in this example method the EPGs are in the same VRF. As previously explained, in some examples, the policies associated with EPGs in a same network context, such as a VRF, can be contained in the network context. Accordingly, in this example, the second respective data structure can be created based at least partly on the policies in the model that are associated with the VRF of the EPGs. The second respective data structure can thus represent policies associated with the VRF. The containment check can therefore involve checking if each first respective data structure is contained in the second respective data structure representing the policies associated with the VRF. 
     In other examples, despite the EPGs being in the same network context, the second respective data structure can be created based all the policies in the model (e.g., Logical Model  270 ) or policies associated with any other portion of the model. The containment check can thus involve checking if each first respective data structure is contained in a second respective data structure that represents all of the policies in the model or policies associated with any other portion of the model. 
     In some cases, the method can include generating one or more compliance assurance events indicating whether the security policies comply with the security compliance requirement. The one or more compliance assurance events can be based on the compliance result in step  2710 . For example, after determining whether the policies in the network comply with the security compliance requirement, a compliance system can generate compliance assurance events based on the results of the check from step  2710 . The compliance system can raise or generate an event for each compliance result or determination, or raise or generate events only for certain types of compliance results or determinations, such as when the security compliance requirement is violated (fully and/or partially), satisfied (fully and/or partially), not applied or enforced, etc. 
     In some cases, the method can include presenting the one or more compliance assurance events on a display or interface (e.g.,  2302 ,  2402 ,  2500 ). The compliance assurance events presented can include the compliance results. The compliance results can indicate whether the security compliance requirement was violated (partially or fully), satisfied (partially or fully), applied or enforced, etc. The compliance results can be specific to an epoch or a current period when the compliance check was performed. However, in some cases, the compliance results can include results from other compliance checks, such as compliance checks performed at various periods of time or epochs, for example. 
     When presenting the compliance assurance events and/or compliance results, the presented information can include compliance scores, event counts, information about the security compliance requirement(s) checked, information about resources or objects associated with one or more security compliance requirements checks, an indication of the policies or objects implicated by an event, etc. In some cases, the information presented for the compliance assurance events and/or compliance results can be grouped into one or more categories and presented by category or categories. For example, compliance assurance events and/or results can be presented by type of security compliance requirement, type of result, type of object or resource, severity of event, type of issue, event count, resource attributes, specific policies or requirements, etc. 
     Moreover, the information can be presented in different ways and configurations based on one or more factors such as user preferences. For example, compliance assurance events and related information can be presented based on a specific organization or sorting of the compliance assurance events and related information. In some cases, compliance assurance events can be presented along with an indication of a cause for the security compliance requirement being raised, as previously described with reference to  FIG. 26 . 
     In some cases, the method can include grouping security compliance requirements into sets including multiple security compliance requirements. Moreover, the method can include associating one or more specific security compliance requirements or security compliance requirement sets with a particular fabric or segment of the network and applying the one or more specific security compliance requirements or security compliance requirement sets specifically to that associated fabric or segment of the network. For example, if the network (e.g., Network Environment  100 ) includes multiple fabrics, a security compliance requirements set can be associated with one or more fabrics, and used to check if the one or more fabrics (or the associated policies) comply with the security compliance requirement set. 
     In some cases, the method can include determining whether a state of the network complies with the security compliance requirement. For example, the method can include comparing the security compliance requirement to rules programmed on the network devices (e.g., switches, routers, etc.) in the network, such as ACLs and/or rules programmed on the hardware memory (e.g., TCAM) of network devices (e.g., Leafs  104 ) in the network. To illustrate, the method can include comparing (e.g., by performing a containment or assurance check) one or more first data structures representing the security compliance requirement with one or more second data structures representing hardware policy entries (e.g., TCAM entries) configured on network devices in the network, and based on the comparison, determining whether the hardware policy entries configured on the network devices satisfy, violate, or apply the security compliance requirement. 
     In some implementations, the one or more second data structures representing hardware policy entries configured on the network devices can be created based on one or more hardware models (e.g., Hardware Model  276 ) created for the network and/or network devices. For example, the hardware model of a switch can be used to construct one or more BDDs, which can represent the state of the network as it pertains to that network device (e.g., the rules programmed on the network device that implement or enforce security policies in the network), and the one or more BDDs can be used in the containment check. 
       FIG. 28  illustrates an example method for creating a security compliance requirement involving objects on different network contexts and determining a compliance of policies associated with the objects on the different network contexts. The objects can include, for example, EPGs, application profiles, contracts, network domains or constructs, filters, tenants, policies, policy constructs, etc. Moreover, the network contexts can include, for example, private networks, network domains, VRFs, subnets, bridge domains, etc. In this example, the objects are EPGs and the private networks are VRFs. 
     At step  2802 , the method can include creating, for a network (e.g.,  100 ), a security compliance requirement (e.g., via Compliance Requirement Interface  1000  as shown in  FIGS. 17A-C ) including EPG selectors (e.g., the Chosen EPG Selector  1202  for EPG Selector A and the Chosen EPG Selector  1752  for EPG Selector B) representing respective sets of EPGs, a traffic selector, and a communication operator (e.g., Communication Operator Definition  1018 B). 
     The respective sets of EPGs associated with the EPG selectors can be selected or determined based on EPG inclusion rules (e.g.,  1914 ,  1922 ,  1924 ,  1926 ,  1944 ) configured as previously explained. The traffic selector can include traffic parameters (e.g.,  1818 ,  1820 ,  1832 ,  1834 ,  1842 ,  1844 ,  1846 ,  1852 ,  1856 ,  1858 A,  1858 B,  1862 ,  1864 ,  1872 ,  1874 ,  1876 ,  1890 ) identifying traffic associated with the traffic selector. The communication operator can define a communication condition (e.g.,  1708 ) for traffic associated with the EPG selectors and the traffic selector, such as a “may talk to” condition, a “must talk to” condition, a “must not talk to” condition, a “may only talk to” condition, etc. 
     At step  2804 , the method can include determining, based on a plurality of distinct pairs of EPGs from the respective sets of EPGs, that respective EPGs in one or more distinct pairs of EPGs are associated with different network contexts in the network. For example, the method can include determining that the EPGs in a pair of EPGs are in a different VRF. Each of the plurality of distinct pairs of EPGs can include a respective EPG from the EPG selectors. For example, a distinct pair of EPGs can include an EPG from a first EPG selector and an EPG from a second EPG selector. 
     At step  2806 , the method can involve determining, for each of the one or more distinct pairs of EPGs, which of the different network context(s) contains security policies for traffic between the respective EPGs in the one or more distinct pairs of EPGs. As previously mentioned, when EPGs in a pair are in different network contexts, policies associated with the pair of EPGs can be located or set in one of the different network contexts, both network contexts, or neither network context. Accordingly, to perform a containment check for a pair of EPGs in different network contexts, the method can include finding where (e.g., which network context(s)) the policies associated with the pair of EPGs are located or set, in order to use those policies for the containment check. 
     In some cases, policies for a pair of EPGs including a consumer and provider can be located on the network context associated with the consumer. Thus, step  2806  can include identifying the consumer EPG, checking the network context associated with the consumer EPG and determining whether the policies are in the network context associated with the consumer EPG. For example, in some cases, rules for traffic in the network between a consumer and provider EPG are created in the network context associated with the consumer EPG. Thus, if a contract between EPG1 and EPG2 specifies that EPG1 is the consumer and EPG2 is the provider, and EPG1 and EPG2 are in different network contexts, the rules for the traffic between EPG1 and EPG2 may be created in the network context of the consumer (i.e., EPG1). Therefore, the compliance check for policies associated with traffic between EPG1 and EPG2 can be done in the network context of the consumer (e.g., EPG1). 
     In some implementations, to determine at step  2806  which network context contains the security policies for traffic between the respective EPGs in a pair of EPGs, the method can involve checking a tag of each EPG in the pair of EPGs. The tag can identify the EPG associated with it. The tags can be, for example, classIDs (class identifiers), pcTags (policy construct tags), or any other tags. In some examples, the tag of an EPG may be used to determine if the EPG is a consumer EPG, if the network context associated with the EPG is a consumer network context, and/or if the network context associated with the EPG contains the policies associated with that EPG. 
     For example, in some cases, the tags can include global and local tags. Global tags can be globally unique across a fabric and local tags may only be unique within a context, such as a VRF. The global and local tags can have respective numbers designated for the tags. The numbers associated with global and local tags can fall within a different number range. For example, global tags can have a number within a global range, such as 1 to 16,385, and local tags can have a number within a local range, such as 16,386 to 65,535. Therefore, the number of a tag can indicate whether the tag is a global tag or a local tag depending on the range it falls in. Moreover, in some cases, consumer EPGs are assigned global tags while provider EPGs are generally assigned local tags. Thus, in some cases, the number of an EPG&#39;s tag can be used to determine or infer whether the EPG is a consumer EPG. Therefore, the tags of a pair of EPGs can be checked to determine which EPG is the consumer and consequently whether the network context associated with that EPG may contain the policies for traffic between the pair of EPGs. 
     Accordingly, to determine at step  2806  which network context contains the security policies for traffic between a pair of EPGs, the method can involve identifying which EPG in the pair of EPGs has a global tag and determining that the EPG with the global tag is the consumer EPG. The method can also involve identifying the network context associated with the consumer EPG and determining that the policies for traffic between the pair of EPGs are in the network context of the EPG identified as the consumer. In some cases, both EPGs in a pair of EPGs may have a global tag. This can be the case if the provider EPG in the pair is a consumer EPG in a different contract and was previously assigned a global tag as the consumer for that contract. If both EPGs in a pair have a global tag, the method at step  2806  can determine that the policies may be created in both of the different network contexts and the containment check (e.g., step  2812  below) should be done on both of the different network contexts. 
     In other cases, both EPGs in a pair of EPGs may have a local tag. Here, the method at step  2806  can determine that a containment check is unnecessary for the pair of EPGs because the pair of EPGs cannot communicate with each other as none of the EPGs in the pair are set as consumer in the contract or policy. Accordingly, the method as it pertains to that pair of EPGs can end without performing steps  2808 ,  2810 ,  2812 , and/or  2814  below. 
     At step  2808 , the method can include creating, for each distinct pair of EPGs from the one or more distinct pairs of EPGs, a first respective data structure representing the distinct pair of EPGs, the communication operator, and the traffic selector. The first respective data structure can be, for example, a BDD (e.g.,  540 ), an ROBDD (e.g.,  600 A,  600 B,  600 C), an n-bit vector or string, a flat list of rules, etc., representing the distinct pair of EPGs, the communication operator, and the traffic selector. The data structure can be created as explained in step  2704  in  FIG. 27 . 
     When only a first one of the different network contexts is determined to contain policies for traffic between the respective EPGs in the one or more distinct pairs of EPGs, at step  2810  the method can include creating a second respective data structure representing a first portion of a model (e.g., Logical Model  270 ) of the network, the first portion of the model containing policies associated with the first one of the different network contexts; and at step  2812  the method can include determining whether the first respective data structure is contained in the second respective data structure to yield a first containment check. The second respective data structure can be, for example, a BDD (e.g.,  540 ), an ROBDD (e.g.,  600 A,  600 B,  600 C), an n-bit vector or string, a flat list of rules, etc., representing the first portion of the model (and/or the configuration data therein) containing the policies associated with the network context(s). Thus, the second respective data structure can encompass the policies in the model corresponding to the network context(s), and consequently the policies associated with the pair of EPGs. The second respective data structure can be created as previously explained with respect to step  2706  in  FIG. 27 . 
     When both of the different network contexts are determined to contain policies for traffic between the respective EPGs in the one or more distinct pairs of EPGs, the method can include, at step  2814 , creating the second respective data structure and a third respective data structure representing a second portion of the logical model (e.g., Logical Model  270 ), the second portion of the logical model containing policies associated with a second one of the different network contexts; and at step  2816  determining whether the first respective data structure is contained in the second and/or third respective data structure to yield a second containment check. 
     The first or second containment checks at steps  2812  or  2816  can be performed for the first respective data structure of each distinct pair of EPGs based on the second and/or third respective data structure, depending on whether policies for traffic between the respective EPGs in the one or more distinct pairs of EPGs are contained in one or both of the different network contexts. An example containment check is described above in step  2708  of  FIG. 27 . 
     At step  2818 , the method can include determining whether security policies for traffic between the respective EPGs in the one or more distinct pairs of EPGs comply (e.g., satisfy, violate, apply) with the security compliance requirement based on the first or second containment check. In some cases, a compliance system such as Assurance Appliance  300  can determine which policies in the network and/or which policy constructs or policies satisfy, violate or do not apply the security compliance requirement based on the first or second containment check. For example, the compliance system can identify which of the first respective data structures are not contained in the second respective data structure and based on this determine which policies and/or policy constructs violate, satisfy, or fail to apply the security compliance requirement. 
     In some cases, the method can include generating one or more compliance assurance events based on the compliance result in step  2814 . The one or more compliance assurance events can be generated and/or displayed as previously described with reference to  FIGS. 26 and 27 . Moreover, the one or more compliance assurance events can present various types of information, such as an indication of the security compliance requirement (and associated configuration settings), an indication of the policies and/or policy constructs that caused an event to be raised, a cause for the compliance result (e.g., a compliance violation, a compliance pass, a failure to apply a security compliance requirement, etc.), a time period or epoch associated with the event, etc. Additional details and examples of compliance assurance events and associated configurations and event presentations are further described above with respect to  FIGS. 26 and 27 . 
     In some cases, the method can include grouping security compliance requirements into security compliance requirement sets including multiple security compliance requirements. Moreover, the method can include associating one or more specific security compliance requirements or security compliance requirement sets with a particular fabric or segment of the network and applying the one or more specific security compliance requirements or security compliance requirement sets to that associated fabric or segment. 
     In some cases, the method can include determining whether a state of the network complies with the security compliance requirement. For example, the method can include comparing the security compliance requirement to rules programmed on network devices (e.g., switches, routers, etc.) in the network, such as ACLs and/or rules programmed on the hardware memory (e.g., TCAM) of network devices (e.g., Leafs  104 ) in the network. To illustrate, the method can include comparing (e.g., by performing a containment or assurance check) one or more first data structures representing the security compliance requirement with one or more second data structures representing hardware policy entries (e.g., TCAM entries) configured on network devices in the network, and based on the comparison, determining whether the hardware policy entries configured on the network devices satisfy, violate, or apply the security compliance requirement. 
     In some implementations, the one or more second data structures representing hardware policy entries configured on the network devices can be created based on one or more hardware models (e.g., Hardware Model  276 ) created for the network and/or network devices. For example, the hardware model of a switch can be used to construct one or more BDDs, which can represent the state of the network as it pertains to that network device (e.g., the rules programmed on the network device that implement or enforce security policies in the network), and the one or more BDDs can be used in the containment check. 
     In some cases, determining whether security policies for traffic between the respective EPGs in distinct pairs of EPGs comply with the security compliance requirement can include performing the method in  FIG. 27  for some pairs of EPGs and the method in  FIG. 28  for other pairs of EPGs. For example, assume some EPG pairs are in a same network context and other EPG pairs are in different network contexts. To determine whether security policies for traffic between the respective EPGs in distinct pairs of EPGs comply with the security compliance requirement, the containment check for the EPG pairs in the same network context can be performed as described in the method of  FIG. 27 , and the containment check for the EPG pairs in different network contexts can be performed as described in the method of  FIG. 28 . The determination can then be performed based on the results of the containment checks for the EPG pairs in the same network context and the EPG pairs in different network contexts. 
     The security compliance requirements in  FIGS. 8-28  have been described with reference to EPGs. However, it should be noted that EPGs are used herein as a non-limiting example for explanation purposes, and other types of objects or constructs are contemplated herein and can be used to create and check security compliance requirements. For example, instead of implementing EPG selectors, in some implementations the security compliance requirements and assurance or compliance checks can implement other object or construct selectors (in addition or in lieu of EPG selectors), such as security groups, application profiles, contracts or rules, network domains, filters, tenants, policy constructs, user groups, policy groups, application groups, service groups, and/or any other group of objects or elements having one or more common attributes (e.g., a common location, a common SLA, a common address domain, a common label, a common configuration, a common security requirement, etc.). 
       FIG. 29  illustrates an example network device  2900  suitable for performing switching, routing, assurance and containment checks, and other networking operations. Network device  2900  includes a central processing unit (CPU)  2904 , interfaces  2902 , and a connection  2910  (e.g., a PCI bus). When acting under the control of software or firmware, the CPU  2904  is responsible for executing packet management, error detection, and/or routing functions. The CPU  2904  preferably accomplishes all these functions under the control of software including an operating system and any appropriate applications software. CPU  2904  may include one or more processors  29029 , such as a processor from the INTEL X296 family of microprocessors. In some cases, processor  29029  can be specially designed hardware for controlling the operations of network device  2900 . In some cases, a memory  2906  (e.g., non-volatile RAM, ROM, TCAM, etc.) also forms part of CPU  2904 . However, there are many different ways in which memory could be coupled to the system. In some cases, the network device  2900  can include a memory and/or storage hardware, such as TCAM, separate from CPU  2904 . Such memory and/or storage hardware can be coupled with the network device  2900  and its components via, for example, connection  2910 . 
     The interfaces  2902  are typically provided as modular interface cards (sometimes referred to as “line cards”). Generally, they control the sending and receiving of data packets over the network and sometimes support other peripherals used with the network device  2900 . Among the interfaces that may be provided are Ethernet interfaces, frame relay interfaces, cable interfaces, DSL interfaces, token ring interfaces, and the like. In addition, various very high-speed interfaces may be provided such as fast token ring interfaces, wireless interfaces, Ethernet interfaces, Gigabit Ethernet interfaces, ATM interfaces, HSSI interfaces, POS interfaces, FDDI interfaces, WIFI interfaces, 3G/4G/5G cellular interfaces, CAN BUS, LoRA, and the like. Generally, these interfaces may include ports appropriate for communication with the appropriate media. In some cases, they may also include an independent processor and, in some instances, volatile RAM. The independent processors may control such communications intensive tasks as packet switching, media control, signal processing, crypto processing, and management. By providing separate processors for the communications intensive tasks, these interfaces allow the master microprocessor  2904  to efficiently perform routing computations, network diagnostics, security functions, etc. 
     Although the system shown in  FIG. 29  is one specific network device of the present disclosure, it is by no means the only network device architecture on which the concepts herein can be implemented. For example, an architecture having a single processor that handles communications as well as routing computations, etc., can be used. Further, other types of interfaces and media could also be used with the network device  2900 . 
     Regardless of the network device&#39;s configuration, it may employ one or more memories (including memory  2906 ) configured to store program instructions for the general-purpose network operations and mechanisms for roaming, route optimization and routing functions described herein. The program instructions may control the operation of an operating system and/or one or more applications, for example The memory or memories may also be configured to store tables such as mobility binding, registration, and association tables, etc. Memory  2906  could also hold various software containers and virtualized execution environments and data. 
     The network device  2900  can also include an application-specific integrated circuit (ASIC), which can be configured to perform routing, switching, and/or other operations. The ASIC can communicate with other components in the network device  2900  via the connection  2910 , to exchange data and signals and coordinate various types of operations by the network device  2900 , such as routing, switching, and/or data storage operations, for example 
       FIG. 30  illustrates an example computing system architecture  3000  including components in electrical communication with each other using a connection  3005 , such as a bus. System architecture  3000  includes a processing unit (CPU or processor)  3010  and a system connection  3005  that couples system components including system memory  3015 , such as read only memory (ROM)  3020  and random access memory (RAM)  3025 , to processor  3010 . The system architecture  3000  can include a cache of high-speed memory connected directly with, in close proximity to, or integrated as part of, processor  3010 . The system architecture  3000  can copy data from memory  3015  and/or storage device  3030  to cache  3012  for quick access by processor  3010 . In this way, the cache can provide a performance boost that avoids processor delays while waiting for data. These and other modules can control processor  3010  to perform various actions. Other memory  3015  may be available for use as well. The memory  3015  can include different types of memory with different performance characteristics. The processor  3010  can include any processor and hardware or software service, such as service 1  3032 , service 2  3034 , and service 3  3036  stored in storage device  3030 , configured to control the processor  3010  as well as a special-purpose processor where software instructions are incorporated into the actual processor design. The processor  3010  may be a completely self-contained computing system, containing multiple cores or processors, a bus, memory controller, cache, etc. A multi-core processor may be symmetric or asymmetric. 
     To enable user interaction with the system architecture  3000 , an input device  3045  can represent any number of input mechanisms, such as a microphone for speech, a touch-sensitive screen for gesture or graphical input, keyboard, mouse, motion input, speech and so forth. An output device  3035  can also be one or more of a number of output mechanisms known to those of skill in the art. In some instances, multimodal systems can enable a user to provide multiple types of input to communicate with the system architecture  3000 . The communications interface  3040  can generally govern and manage the user input and system output. There is no restriction on operating on any particular hardware arrangement and therefore the basic features here may easily be substituted for improved hardware or firmware arrangements as they are developed. 
     Storage device  3030  is a non-volatile memory and can be a hard disk or other types of computer readable media which can store data accessible by a computer, such as magnetic cassettes, flash memory cards, solid state memory devices, digital versatile disks, cartridges, random access memories (RAMs)  3025 , read only memory (ROM)  3020 , and hybrids thereof. 
     The storage device  3030  can include services  3032 ,  3034 ,  3036  for controlling the processor  3010 . Other hardware or software modules are contemplated. The storage device  3030  can be connected to the system connection  3005 . In one aspect, a hardware module that performs a particular function can include the software component stored in a computer-readable medium in connection with the necessary hardware components, such as the processor  3010 , connection  3005 , output device  3035 , and so forth, to carry out the function. 
     For clarity, in some instances the present technology may be presented as including individual functional blocks, including devices, components, steps or routines in a method embodied in software, or combinations of hardware and software. When mentioned, non-transitory computer-readable media expressly exclude energy, electromagnetic waves, and signals per se. 
     Methods according to the above examples can be implemented using instructions in computer readable media. Such instructions can comprise, for example, instructions and data which cause or configure a computer/processing device to perform a certain function(s). Portions of computer resources used can be accessible over a network. The instructions may be, for example, binaries, intermediate format instructions such as assembly language, firmware, or source code. Examples of computer-readable media include magnetic or optical disks, flash memory, USB devices with non-volatile memory, networked storage devices, and so on. 
     Devices implementing methods according to these disclosures can include hardware, firmware and/or software, and can take any of a variety of form factors. Example form factors include laptops, smart phones, small form factor computers, personal digital assistants, rackmount devices, standalone devices, and so on. Functionality described herein also can be embodied in peripherals or add-in cards. Such functionality can also be implemented on a circuit board among different chips or different processes executing in a device. The instructions, media for conveying such instructions, computing resources for executing them, and other structures for supporting such computing resources are means for providing the functions described in these disclosures. 
     Although a variety of examples and information were used to explain aspects within the scope of the claims, no limitation of the claims should be implied based on particular features or arrangements in such examples, as one of ordinary skill would be able to use these examples to derive a variety of implementations. Although some subject matter may have been described in language specific to examples of structural features and/or method steps, it is to be understood that the subject matter defined in the claims is not necessarily limited to these described features or acts. For example, such functionality can be distributed differently or performed in other components. The described features and steps are examples of components within the scope of the claims. 
     Claim language reciting “at least one of” refers to at least one of a set and indicates that one member of the set or multiple members of the set satisfy the claim. For example, claim language reciting “at least one of A and B” means A, B, or A and B.