Patent Description:
In a network environment, sensors can be placed at various devices or elements in the network to collect flow data and network statistics from different locations. The collected data from the sensors can be analyzed to monitor and troubleshoot the network. The data collected from the sensors can provide valuable details about the status, security, or performance of the network, as well as any network elements. Information about the sensors can also help interpret the data from the sensors, in order to infer or ascertain additional details from the collected data. For example, understanding the placement of a sensor relative to other sensors in the network can provide a context to the data reported by the sensors, which can further help identify specific patterns or conditions in the network. Network tools can be used to generate data related to flow data and network statistics. Such network tools are typically updated to create newer versions of the tools. Updated network tools are typically backwards compatible. More specifically, a new version of a network tool can usually read data generated or gathered by older versions of the network tool. However, network tools are typically not forward compatible. More specifically, an older version of a network tool typically is unable to read data generated or gathered by newer versions of the network tool. Accordingly, the older version of a network tool will fail to function as designed as they are unable to read data generated or gathered by a newer version of the network tool. This problem is further exacerbated by the fact that often users roll back versions of network tools.

An application distribution service providing access to application binaries that represent different versions of applications that are compatible with various device types is described in <CIT>. A particular application binary can be chosen for a device based on device compatibility data.

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.

The disclosed technology addresses the need in the art for providing network assurance. The present technology involves system, methods, and computer-readable media for versioning data generated by a network tool to provide compatibility across different versions of the network tool. The present technology will be described in the following disclosure as follows.

The discussion begins with an introductory discussion of network assurance and a description of example computing environments, as illustrated in <FIG> and <FIG>. A discussion of network models for network assurance, as shown in <FIG>, and network assurance systems and methods, as shown in <FIG> and <FIG> will then follow. The discussion continues with a description and examples of versioning assurance data, as shown in <FIG> and <FIG>. The discussion concludes with a description of an example network device, as illustrated in <FIG>, and an example computing device, as illustrated in <FIG>, including example hardware components suitable for hosting software applications and performing computing operations. The disclosure now turns to an introductory discussion of network 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 network and individual network elements (e.g., switches, routers, applications, resources, etc.). However, often times, the configurations, policies, etc., defined by a network operator are incorrect or not accurately reflected in the actual behavior of the network. For example, a network operator specifies a configuration A for one or more types of traffic but later finds out 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, misconfiguration of one or more settings, improper rule rendering by devices, unexpected errors or events, software upgrades, configuration changes, failures, etc. As another example, a network operator implements configuration C but one or more other configurations result in the network behaving in a manner that is inconsistent with the intent reflected by the implementation of configuration C. For example, such a situation can result when configuration C conflicts with other configurations in the network.

The approaches herein can provide network assurance by modeling various aspects of the network and/or performing consistency checks as well as other network assurance checks. The network assurance approaches herein can be implemented in various types of networks, including a private network, such as a local area network (LAN); an enterprise network; a standalone or traditional network, such as a data center network; a network including a physical or underlay layer and a logical or overlay layer, such as a VXLAN or software-defined network (SDN) (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's policies, configurations, requirements, security, routing, topology, applications, hardware, filters, contracts, access control lists, infrastructure, etc. 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 modeling can consume numerous types of smart events which model a large amount of behavioral aspects of the network. Smart events can impact various aspects of the network, such as underlay services, overlay services, tenant connectivity, tenant security, tenant endpoint (EP) mobility, tenant policy, tenant routing, resources, etc..

Having described various aspects of network assurance, the disclosure now turns to a discussion of example network environments for network assurance.

<FIG> illustrates a diagram of an example Network Environment <NUM>, such as a data center. The Network Environment <NUM> can include a Fabric <NUM> which can represent the physical layer or infrastructure (e.g., underlay) of the Network Environment <NUM>. Fabric <NUM> can include Spines <NUM> (e.g., spine routers or switches) and Leafs <NUM> (e.g., leaf routers or switches) which can be interconnected for routing or switching traffic in the Fabric <NUM>. Spines <NUM> can interconnect Leafs <NUM> in the Fabric <NUM>, and Leafs <NUM> can connect the Fabric <NUM> to an overlay or logical portion of the Network Environment <NUM>, which can include application services, servers, virtual machines, containers, endpoints, etc. Thus, network connectivity in the Fabric <NUM> can flow from Spines <NUM> to Leafs <NUM>, and vice versa. The interconnections between Leafs <NUM> and Spines <NUM> can be redundant (e.g., multiple interconnections) to avoid a failure in routing. In some embodiments, Leafs <NUM> and Spines <NUM> can be fully connected, such that any given Leaf is connected to each of the Spines <NUM>, and any given Spine is connected to each of the Leafs <NUM>. Leafs <NUM> 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 <NUM> 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 <NUM>, and/or implemented or enforced by one or more devices, such as Leafs <NUM>. Leafs <NUM> can connect other elements to the Fabric <NUM>. For example, Leafs <NUM> can connect Servers <NUM>, Hypervisors <NUM>, Virtual Machines (VMs) <NUM>, Applications <NUM>, Network Device <NUM>, etc., with Fabric <NUM>. Such elements can reside in one or more logical or virtual layers or networks, such as an overlay network. In some cases, Leafs <NUM> can encapsulate and decapsulate packets to and from such elements (e.g., Servers <NUM>) in order to enable communications throughout Network Environment <NUM> and Fabric <NUM>. Leafs <NUM> can also provide any other devices, services, tenants, or workloads with access to Fabric <NUM>. In some cases, Servers <NUM> connected to Leafs <NUM> can similarly encapsulate and decapsulate packets to and from Leafs <NUM>. For example, Servers <NUM> 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 <NUM> and an underlay layer represented by Fabric <NUM> and accessed via Leafs <NUM>.

Applications <NUM> can include software applications, services, containers, appliances, functions, service chains, etc. For example, Applications <NUM> 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 <NUM> can be distributed, chained, or hosted by multiple endpoints (e.g., Servers <NUM>, VMs <NUM>, etc.), or may run or execute entirely from a single endpoint.

VMs <NUM> can be virtual machines hosted by Hypervisors <NUM> or virtual machine managers running on Servers <NUM>. VMs <NUM> can include workloads running on a guest operating system on a respective server. Hypervisors <NUM> can provide a layer of software, firmware, and/or hardware that creates, manages, and/or runs the VMs <NUM>. Hypervisors <NUM> can allow VMs <NUM> to share hardware resources on Servers <NUM>, and the hardware resources on Servers <NUM> to appear as multiple, separate hardware platforms. Moreover, Hypervisors <NUM> on Servers <NUM> can host one or more VMs <NUM>.

In some cases, VMs <NUM> and/or Hypervisors <NUM> can be migrated to other Servers <NUM>. Servers <NUM> can similarly be migrated to other locations in Network Environment <NUM>. For example, a server connected to a specific 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 <NUM>, Hypervisors <NUM>, and/or VMs <NUM> can represent or reside in a tenant or customer space. Tenant space can include workloads, services, applications, devices, networks, and/or resources that are associated with one or more clients or subscribers. Accordingly, traffic in Network Environment <NUM> can be routed based on specific tenant policies, spaces, agreements, configurations, etc. Moreover, addressing can vary between one or more 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 <NUM>, Servers <NUM>, Leafs <NUM>, etc..

Configurations in Network Environment <NUM> 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 <NUM>, which can implement or propagate such configurations through Network Environment <NUM>. In some examples, Controllers <NUM> can be Application Policy Infrastructure Controllers (APICs) in an ACI framework. In other examples, Controllers <NUM> 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 <NUM>. 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 <NUM>, such as Leafs <NUM>, Servers <NUM>, Hypervisors <NUM>, Controllers <NUM>, etc. As previously explained, Network Environment <NUM> 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 <NUM>. 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 <NUM> 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 fabric 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 <NUM> 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 <NUM>. Leaf <NUM> 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-<NUM> 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 now to <FIG>, Network Environment <NUM> can deploy different hosts via Leafs <NUM>, Servers <NUM>, Hypervisors <NUM>, VMs <NUM>, Applications <NUM>, and Controllers <NUM>, such as VMWARE ESXi hosts, WINDOWS HYPER-V hosts, bare metal physical hosts, etc. Network Environment <NUM> may interoperate with a variety of Hypervisors <NUM>, Servers <NUM> (e.g., physical and/or virtual servers), SDN orchestration platforms, etc. Network Environment <NUM> may implement a declarative model to allow its integration with application design and holistic network policy.

Controllers <NUM> 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 <NUM> 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 <NUM> can define and manage application-level model(s) for configurations in Network Environment <NUM>. In some cases, application or device configurations can also be managed and/or defined by other components in the network. 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 <NUM>, including configurations and settings for virtual appliances.

As illustrated above, Network Environment <NUM> 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 <NUM> 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 <NUM> (e.g., physical or logical), Hypervisors <NUM>, VMs <NUM>, containers (e.g., Applications <NUM>), 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> illustrates another example of Network Environment <NUM>. In this example, Network Environment <NUM> includes Endpoints <NUM> connected to Leafs <NUM> in Fabric <NUM>. Endpoints <NUM> 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 <NUM> 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 <NUM> 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 <NUM> can be associated with respective Logical Groups <NUM>. Logical Groups <NUM> can be logical entities containing endpoints (physical and/or logical 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 <NUM> can contain client endpoints, Logical Group <NUM> can contain web server endpoints, Logical Group <NUM> can contain application server endpoints, Logical Group N can contain database server endpoints, etc. In some examples, Logical Groups <NUM> are EPGs in an ACI environment and/or other logical groups (e.g., SGs) in another SDN environment.

Traffic to and/or from Endpoints <NUM> can be classified, processed, managed, etc., based Logical Groups <NUM>. For example, Logical Groups <NUM> can be used to classify traffic to or from Endpoints <NUM>, apply policies to traffic to or from Endpoints <NUM>, define relationships between Endpoints <NUM>, define roles of Endpoints <NUM> (e.g., whether an endpoint consumes or provides a service, etc.), apply rules to traffic to or from Endpoints <NUM>, apply filters or access control lists (ACLs) to traffic to or from Endpoints <NUM>, define communication paths for traffic to or from Endpoints <NUM>, enforce requirements associated with Endpoints <NUM>, implement security and other configurations associated with Endpoints <NUM>, etc..

In an ACI environment, Logical Groups <NUM> 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> illustrates a diagram of an example Management Information Model <NUM> for an SDN network, such as Network Environment <NUM>. The following discussion of Management Information Model <NUM> 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 <NUM>.

As used herein, an "Alias" can refer to a changeable name for a given object. Thus, even if the name of an object, once created, cannot be changed, the Alias can be a field that can be changed.

As used herein, the term "Aliasing" can refer to a rule (e.g., contracts, policies, configurations, etc.) that overlaps one or more other rules. For example, Contract <NUM> defined in a logical model of a network can be said to be aliasing Contract <NUM> defined in the logical model of the network if Contract <NUM> overlaps Contract <NUM>. In this example, by aliasing Contract <NUM>, Contract <NUM> may render Contract <NUM> redundant or inoperable. For example, if Contract <NUM> has a higher priority than Contract <NUM>, such aliasing can render Contract <NUM> redundant based on Contract <NUM>'s overlapping and higher priority characteristics.

As used herein, the term "APIC" can refer to one or more controllers (e.g., Controllers <NUM>) 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 tree. A binary decision tree can be a data structure representing 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 L2 (Layer <NUM>) 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 L3 (Layer <NUM>) 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. Non-limiting examples of a context or L3 address domain 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 and configurations akin to an Access Control List (ACL).

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 <NUM>. 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 endpoints as previously described with reference to <FIG>.

As used herein, the term "Filter" can refer to a parameter or configuration for allowing communications. For example, in a whitelist model where all 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 <NUM>) 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 <NUM>) connection between an ACI fabric (e.g., Fabric <NUM>) and an outside Layer <NUM> network, such as a switch.

As used herein, the term "L3 Out" can refer to a routed connection. A routed Layer <NUM> 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 that are managed in a network (e.g., Network Environment <NUM>). 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.). The MOs can be network resources or elements that are managed in the network. For example, in an ACI environment, an MO can include an abstraction of an ACI fabric (e.g., Fabric <NUM>) resource.

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 <NUM>). The MIT can also be referred to as a Management Information Model (MIM), such as Management Information Model <NUM>.

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 <NUM> Outside Network Policy can contain the BGP protocol to enable BGP routing functions when connecting Fabric <NUM> to an outside Layer <NUM> 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 virtual computing environment. In ACI, 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 <NUM> 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) <NUM> in <FIG>. As previously noted, MIM <NUM> can be a hierarchical management information tree or MIT. Moreover, MIM <NUM> can be managed and processed by Controllers <NUM>, such as APICs in an ACI. Controllers <NUM> 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 <NUM> starts with Policy Universe <NUM> at the top (Root) and contains parent and child nodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. Nodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> in the tree represent the managed objects (MOs) or groups of objects. Each object in the fabric (e.g., Fabric <NUM>) has a unique distinguished name (DN) that describes the object and locates its place in the tree. The Nodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> can include the various MOs, as described below, which contain policies that govern the operation of the system.

Controllers <NUM> (e.g., APIC controllers) can provide management, policy programming, application deployment, and health monitoring for Fabric <NUM>.

Node <NUM> 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.

The common tenant is 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 <NUM> to Layer <NUM> services, intrusion detection appliances, and so on.

The infrastructure tenant is 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.

The management tenant is 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 virtual machine controllers.

Node <NUM> can contain access policies that govern the operation of switch access ports that provide connectivity to resources such as storage, compute, Layer <NUM> and Layer <NUM> (bridged and routed) connectivity, virtual machine hypervisors, Layer <NUM> to Layer <NUM> 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 <NUM>.

Node <NUM> 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 <NUM> 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 <NUM> communicate with the VM controller to publish network configurations such as port groups that are then applied to the virtual workloads.

Node <NUM> can contain Layer <NUM> to Layer <NUM> 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 <NUM> can contain access, authentication, and accounting (AAA) policies that govern user privileges, roles, and security domains of Fabric <NUM>.

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> illustrates an example object model <NUM> for a tenant portion of MIM <NUM>. 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 it 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 204A of MIM <NUM> can include various entities, and the entities in Tenant Portion 204A can inherit policies from parent entities. Non-limiting examples of entities in Tenant Portion 204A can include Filters <NUM>, Contracts <NUM>, Outside Networks <NUM>, Bridge Domains <NUM>, VRF Instances <NUM>, and Application Profiles <NUM>.

Bridge Domains <NUM> can include Subnets <NUM>. Contracts <NUM> can include Subjects <NUM>. Application Profiles <NUM> can contain one or more EPGs <NUM>. 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 <NUM> contains as many (or as few) EPGs as necessary that are logically related to providing the capabilities of an application.

EPG <NUM> 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 structure of 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 <NUM> external outside network instance EPGs, Layer <NUM> external outside network instance EPGs, management EPGs for out-of-band or in-band access, etc. EPGs <NUM> can also contain Attributes <NUM>, such as encapsulation-based EPGs, IP-based EPGs, or MAC-based EPGs.

As previously mentioned, EPGs can contain endpoints (e.g., EPs <NUM>) that have common characteristics or attributes, such as common policy requirements (e.g., security, virtual machine mobility (VMM), QoS, or Layer <NUM> to Layer <NUM> 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 <NUM>, or dynamically configured by an automated system such as VCENTER or OPENSTACK.

To activate tenant policies in Tenant Portion 204A, 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> illustrates an example Association <NUM> of tenant entities and access entities in MIM <NUM>. Policy Universe <NUM> contains Tenant Portion 204A and Access Portion 206A. Thus, Tenant Portion 204A and Access Portion 206A are associated through Policy Universe <NUM>.

Access Portion 206A 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 206A thus contains Domain Profile <NUM> which can define a physical, VMM, L2 out, L3 out, or Fiber Channel domain, for example, to be associated to the EPGs. Domain Profile <NUM> contains VLAN Instance Profile <NUM> (e.g., VLAN pool) and Attacheable Access Entity Profile (AEP) <NUM>, which are associated directly with application EPGs. The AEP <NUM> 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 <NUM> can automatically assign VLAN IDs from VLAN pools. This saves time compared with trunking down VLANs in a traditional data center.

<FIG> illustrates a schematic diagram of example models for implementing MIM <NUM>. The network assurance models can include L_Model 270A (Logical Model), LR_Model 270B (Logical Rendered Model or Logical Runtime Model), Li_Model <NUM> (Logical Model for i), Ci_Model <NUM> (Concrete model for i), and Hi_Model <NUM> (Hardware model or TCAM Model for i).

L_Model 270A is the logical representation of the objects and their relationships in MIM <NUM>. L_Model 270A can be generated by Controllers <NUM> based on configurations entered in Controllers <NUM> for the network, and thus represents the configurations of the network at Controllers <NUM>. This is the declaration of the "end-state" expression that is desired when the elements of the network entities (e.g., applications) are connected and Fabric <NUM> is provisioned by Controllers <NUM>. In other words, because L_Model 270A represents the configurations entered in Controllers <NUM>, including the objects and relationships in MIM <NUM>, it can also reflect the "intent" of the administrator: how the administrator wants the network and network elements to behave.

LR_Model 270B is the abstract model expression that Controllers <NUM> (e.g., APICs in ACI) resolve from L_Model 270A. LR_Model 270B can thus provide the elemental configuration components that would be delivered to the physical infrastructure (e.g., Fabric <NUM>) to execute one or more policies. For example, LR_Model 270B can be delivered to Leafs <NUM> in Fabric <NUM> to configure Leafs <NUM> for communication with attached Endpoints <NUM>.

Li_Model <NUM> is a switch-level or switch-specific model obtained from Logical Model 270A and/or Resolved Model 270B. For example, Li_Model <NUM> can represent the portion of L_Model 270A and/or LR_Model 270B pertaining to a specific switch or router i. To illustrate, Li_Model <NUM><NUM> can represent the portion of L_Model 270A and/or LR_Model 270B pertaining to Leaf <NUM> (<NUM>). Thus, Li_Model <NUM> can be generated from L_Model 270A and/or LR_Model 270B for one or more switch or routers (e.g., Leafs <NUM> and/or Spines <NUM>) on Fabric <NUM>.

Ci_Model <NUM> is the actual in-state configuration at the individual fabric member i (e.g., switch i). In other words, Ci_Model <NUM> is a switch-level or switch-specific model that is based on Li_Model <NUM>. For example, Controllers <NUM> can deliver Li_Model <NUM> to Leaf <NUM> (<NUM>). Leaf <NUM> (<NUM>) can take Li_Model <NUM>, which can be specific to Leaf <NUM> (<NUM>), and render the policies in Li_Model <NUM> into a concrete model, Ci_Model <NUM>, that runs on Leaf <NUM> (<NUM>). Leaf <NUM> (<NUM>) can render Li_Model <NUM> via the OS on Leaf <NUM> (<NUM>), for example. Thus, Ci_Model <NUM> can be analogous to compiled software, as it is the form of Li_Model <NUM> that the switch OS at Leaf <NUM> (<NUM>) can execute.

Hi_Model <NUM> is also a switch-level or switch-specific model for switch i, but is based on Ci_Model <NUM> for switch i. Hi_Model <NUM> 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 <NUM> can represent the configurations (e.g., rules) which Leaf <NUM> (<NUM>) stores or renders on the hardware (e.g., TCAM memory) of Leaf <NUM> (<NUM>) based on Ci_Model <NUM> at Leaf <NUM> (<NUM>). The switch OS at Leaf <NUM> (<NUM>) can render or execute Ci_Model <NUM>, and Leaf <NUM> (<NUM>) can store or render the configurations from Ci Model in storage, such as the memory or TCAM at Leaf <NUM> (<NUM>). The configurations from Hi_Model <NUM> stored or rendered by Leaf <NUM> (<NUM>) represent the configurations that will be implemented by Leaf <NUM> (<NUM>) when processing traffic.

While Models <NUM>, <NUM>, <NUM> are shown as device-specific models, similar models can be generated or aggregated for a collection of fabric members (e.g., Leafs <NUM> and/or Spines <NUM>) in Fabric <NUM>. When combined, device-specific models, such as Model <NUM>, Model <NUM>, and/or Model <NUM>, can provide a representation of Fabric <NUM> that extends beyond a particular device. For example, in some cases, Li_Model <NUM>, Ci Model <NUM>, and/or Hi Model <NUM> associated with some or all individual fabric members (e.g., Leafs <NUM> and Spines <NUM>) 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 <NUM>. For example, Ti Model, Hi Model and TCAMi Model may be used interchangeably to refer to Hi_Model <NUM>.

Models 270A, 270B, <NUM>, <NUM>, <NUM> can provide representations of various aspects of the network or various configuration stages for MIM <NUM>. For example, one or more of Models 270A, 270B, <NUM>, <NUM>, <NUM> can be used to generate Underlay Model <NUM> representing one or more aspects of Fabric <NUM> (e.g., underlay topology, routing, etc.), Overlay Model <NUM> representing one or more aspects of the overlay or logical segment(s) of Network Environment <NUM> (e.g., COOP, MPBGP, tenants, VRFs, VLANs, VXLANs, virtual applications, VMs, hypervisors, virtual switching, etc.), Tenant Model <NUM> representing one or more aspects of Tenant portion 204A in MIM <NUM> (e.g., security, forwarding, service chaining, QoS, VRFs, BDs, Contracts, Filters, EPGs, subnets, etc.), Resources Model <NUM> representing one or more resources in Network Environment <NUM> (e.g., storage, computing, VMs, port channels, physical elements, etc.), etc..

In general, L_Model 270A can be the high-level expression of what exists in the LR_Model 270B, which should be present on the concrete devices as Ci_Model <NUM> and Hi_Model <NUM> expression. If there is any gap between the models, there may be inconsistent configurations or problems.

<FIG> illustrates a diagram of an example Assurance Appliance <NUM> for network assurance. In this example, Assurance Appliance <NUM> can include k VMs <NUM> operating in cluster mode. VMs are used in this example for explanation purposes. However, it should be understood that other configurations are also contemplated herein, such as use of containers, bare metal devices, Endpoints <NUM>, or any other physical or logical systems. Moreover, while <FIG> 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 <NUM> can run on one or more Servers <NUM>, VMs <NUM>, Hypervisors <NUM>, EPs <NUM>, Leafs <NUM>, Controllers <NUM>, or any other system or resource. For example, Assurance Appliance <NUM> can be a logical service or application running on one or more VMs <NUM> in Network Environment <NUM>.

The Assurance Appliance <NUM> can include Data Framework <NUM>, which can be based on, for example, APACHE APEX and HADOOP. In some cases, assurance checks can be written as individual operators that reside in Data Framework <NUM>. This enables a natively horizontal scale-out architecture that can scale to arbitrary number of switches in Fabric <NUM> (e.g., ACI fabric).

Assurance Appliance <NUM> can poll Fabric <NUM> at a configurable periodicity (e.g., an epoch). The analysis workflow can be setup as a DAG (Directed Acyclic Graph) of Operators <NUM>, where data flows from one operator to another and eventually results are generated and persisted to Database <NUM> for each interval (e.g., each epoch).

The north-tier implements API Server (e.g., APACHE Tomcat and Spring framework) <NUM> and Web Server <NUM>. 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 <NUM> for further integration into other tools.

Operators <NUM> in Data Framework <NUM> (e.g., APEX/Hadoop) can together support assurance operations. Below are non-limiting examples of assurance operations that can be performed by Assurance Appliance <NUM> via Operators <NUM>.

Assurance Appliance <NUM> can check to make sure the configurations or specification from L_Model 270A, which may reflect the user's intent for the network, including for example the security policies and customer-configured contracts, are correctly implemented and/or rendered in Li_Model <NUM>, Ci_Model <NUM>, and Hi_Model <NUM>, and thus properly implemented and rendered by the fabric members (e.g., Leafs <NUM>), and report any errors, contract violations, or irregularities found.

Assurance Appliance <NUM> can check for issues in the specification of the user's intent or intents (e.g., identify contradictory or conflicting policies in L_Model 270A).

TCAM is a scarce resource in the fabric (e.g., Fabric <NUM>). However, Assurance Appliance <NUM> 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 <NUM> (e.g., EPGs), Tenants, Spines <NUM>, Leafs <NUM>, and other dimensions in Network Environment <NUM> and/or objects in MIM <NUM>, 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.

Assurance Appliance <NUM> can validate that the fabric (e.g. fabric <NUM>) has no inconsistencies in the Endpoint information registered (e.g., two leafs announcing the same endpoint, duplicate subnets, etc.), among other such checks.

Assurance Appliance <NUM> can validate that BDs, VRFs, subnets (both internal and external), VLANs, contracts, filters, applications, EPGs, etc., are correctly programmed.

Assurance Appliance <NUM> can validate that infrastructure routing (e.g., IS-IS protocol) has no convergence issues leading to black holes, loops, flaps, and other problems.

The network fabric (e.g., Fabric <NUM>) 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.

Assurance Appliance <NUM> can validate rules in the specification of the network (e.g., L_Model 270A) are complete and do not have inconsistencies or other problems. MOs in the MIM <NUM> can be checked by Assurance Appliance <NUM> through syntactic and semantic checks performed on L_Model 270A and/or the associated configurations of the MOs in MIM <NUM>. Assurance Appliance <NUM> can also verify that unnecessary, stale, unused or redundant configurations, such as contracts, are removed.

<FIG> illustrates an architectural diagram of an example system <NUM> for network assurance. In some cases, system <NUM> can correspond to the DAG of Operators <NUM> previously discussed with respect to <FIG> In this example, Topology Explorer <NUM> communicates with Controllers <NUM> (e.g., APIC controllers) in order to discover or otherwise construct a comprehensive topological view of Fabric <NUM> (e.g., Spines <NUM>, Leafs <NUM>, Controllers <NUM>, Endpoints <NUM>, 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 <NUM>, can correspond to one or more individual Operators <NUM> 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 <NUM> is configured to discover nodes in Fabric <NUM>, such as Controllers <NUM>, Leafs <NUM>, Spines <NUM>, etc. Topology Explorer <NUM> can additionally detect a majority election performed amongst Controllers <NUM>, and determine whether a quorum exists amongst Controllers <NUM>. If no quorum or majority exists, Topology Explorer <NUM> can trigger an event and alert a user that a configuration or other error exists amongst Controllers <NUM> that is preventing a quorum or majority from being reached. Topology Explorer <NUM> can detect Leafs <NUM> and Spines <NUM> that are part of Fabric <NUM> 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's <NUM> discovery epoch (e.g., <NUM> minutes, or some other specified interval).

Unified Collector <NUM> can receive the topological view from Topology Explorer <NUM> and use the topology information to collect information for network assurance from Fabric <NUM>. Such information can include L_Model 270A and/or LR_Model 270B from Controllers <NUM>, switch software configurations (e.g., Ci_Model <NUM>) from Leafs <NUM> and/or Spines <NUM>, hardware configurations (e.g., Hi_Model <NUM>) from Leafs <NUM> and/or Spines <NUM>, etc. Unified Collector <NUM> can collect Ci_Model <NUM> and Hi_Model <NUM> from individual fabric members (e.g., Leafs <NUM> and Spines <NUM>).

Unified Collector <NUM> can poll the devices that Topology Explorer <NUM> discovers in order to collect data from Fabric <NUM> (e.g., from the constituent members of the fabric). Unified Collector <NUM> can collect the data using interfaces exposed by Controller <NUM> and/or switch software (e.g., switch OS), including, for example, a Representation State Transfer (REST) Interface and a Secure Shell (SSH) Interface.

In some cases, Unified Collector <NUM> collects L_Model 270A, LR_Model 270B, and/or Ci_Model <NUM> 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 <NUM> can poll other information from Controllers <NUM>, including: topology information, tenant forwarding/routing information, tenant security policies, contracts, interface policies, physical domain or VMM domain information, OOB (out-of-band) management IP's of nodes in the fabric, etc..

Unified Collector <NUM> can also poll other information from Leafs <NUM> and Spines <NUM>, such as: Ci Models <NUM> for VLANs, BDs, security policies, Link Layer Discovery Protocol (LLDP) connectivity information of Leafs <NUM> and/or Spines <NUM>, endpoint information from EPM/COOP, fabric card information from Spines <NUM>, routing information base (RIB) tables, forwarding information base (FIB) tables from Leafs <NUM> and/or Spines <NUM>, security group hardware tables (e.g., TCAM tables) from switches, etc..

Assurance Appliance <NUM> can run one or more instances of Unified Collector <NUM>. For example, Assurance Appliance <NUM> can run one, two, three, or more instances of Unified Collector <NUM>. The task of data collecting for each node in the topology (e.g., Fabric <NUM> including Spines <NUM>, Leafs <NUM>, Controllers <NUM>, etc.) can be sharded or load balanced, to a unique instance of Unified Collector <NUM>. Data collection across the nodes can thus be performed in parallel by one or more instances of Unified Collector <NUM>. Within a given node, commands and data collection can be executed serially. Assurance Appliance <NUM> can control the number of threads used by each instance of Unified Collector <NUM> to poll data from Fabric <NUM>.

Data collected by Unified Collector <NUM> can be compressed and sent to downstream services. In some examples, Unified Collector <NUM> can collect data in an online fashion or real-time fashion, and send the data downstream, as it is collected, for further analysis. In some examples, Unified Collector <NUM> can collect data in an offline fashion, and compile the data for later analysis or transmission.

Assurance Appliance <NUM> can contact Controllers <NUM>, Spines <NUM>, Leafs <NUM>, and other nodes to collect various types of data. In some scenarios, Assurance Appliance <NUM> 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 <NUM> can handle such failures seamlessly, and generate events based on such failures.

Switch Logical Policy Generator <NUM> can receive L_Model 270A and/or LR_Model 270B from Unified Collector <NUM> and calculate Li_Model <NUM> for each network device i (e.g., switch i) in Fabric <NUM>. For example, Switch Logical Policy Generator <NUM> can receive L_Model 270A and/or LR_Model 270B and generate Li_Model <NUM> by projecting a logical model for each individual node i (e.g., Spines <NUM> and/or Leafs <NUM>) in Fabric <NUM>. Switch Logical Policy Generator <NUM> can generate Li_Model <NUM> for each switch in Fabric <NUM>, thus creating a switch logical model based on L_Model 270A for each switch.

Switch Logical Configuration Generator <NUM> can also perform change analysis and generate lint events or records for problems discovered in L_Model 270A and/or LR_Model 270B. The lint events or records can be used to generate alerts for a user or network operator.

Policy Operator <NUM> can receive Ci_Model <NUM> and Hi_Model <NUM> for each switch from Unified Collector <NUM>, and Li_Model <NUM> for each switch from Switch Logical Policy Generator <NUM>, and perform assurance checks and analysis (e.g., security adherence checks, TCAM utilization analysis, etc.) based on Ci_Model <NUM>, Hi_Model <NUM>, and Li_Model <NUM>. Policy Operator <NUM> can perform assurance checks on a switch-by-switch basis by comparing one or more of the models.

Returning to Unified Collector <NUM>, Unified Collector <NUM> can also send L_Model 270A and/or LR_Model 270B to Routing Policy Parser <NUM>, and Ci_Model <NUM> and Hi_Model <NUM> to Routing Parser <NUM>.

Routing Policy Parser <NUM> can receive L_Model 270A and/or LR_Model 270B and parse the model(s) for information that may be relevant to downstream operators, such as Endpoint Checker <NUM> and Tenant Routing Checker <NUM>. Similarly, Routing Parser <NUM> can receive Ci_Model <NUM> and Hi_Model <NUM> and parse each model for information for downstream operators, Endpoint Checker <NUM> and Tenant Routing Checker <NUM>.

After Ci_Model <NUM>, Hi_Model <NUM>, L_Model 270A and/or LR_Model 270B are parsed, Routing Policy Parser <NUM> and/or Routing Parser <NUM> can send cleaned-up protocol buffers (Proto Buffs) to the downstream operators, Endpoint Checker <NUM> and Tenant Routing Checker <NUM>. Endpoint Checker <NUM> can then generate events related to Endpoint violations, such as duplicate IPs, APIPA, etc., and Tenant Routing Checker <NUM> can generate events related to the deployment of BDs, VRFs, subnets, routing table prefixes, etc..

<FIG> illustrates a schematic diagram of an example system for static policy analysis in a network (e.g., Network Environment <NUM>). Static Policy Analyzer <NUM> can perform assurance checks to detect configuration violations, logical lint events, contradictory or conflicting policies, unused contracts, incomplete configurations, etc. Static Policy Analyzer <NUM> can check the specification of the user's intent or intents in L_Model 270A to determine if any configurations in Controllers <NUM> are inconsistent with the specification of the user's intent or intents.

Static Policy Analyzer <NUM> can include one or more of the Operators <NUM> executed or hosted in Assurance Appliance <NUM>. However, in other configurations, Static Policy Analyzer <NUM> can run one or more operators or engines that are separate from Operators <NUM> and/or Assurance Appliance <NUM>. For example, Static Policy Analyzer <NUM> can be a VM, a cluster of VMs, or a collection of endpoints in a service function chain.

Static Policy Analyzer <NUM> can receive as input L_Model 270A from Logical Model Collection Process <NUM> and Rules <NUM> defined for each feature (e.g., object) in L_Model 270A. Rules <NUM> can be based on objects, relationships, definitions, configurations, and any other features in MIM <NUM>. Rules <NUM> can specify conditions, relationships, parameters, and/or any other information for identifying configuration violations or issues.

Moreover, Rules <NUM> can include information for identifying syntactic violations or issues. For example, Rules <NUM> can include one or more rules for performing syntactic checks. Syntactic checks can verify that the configuration of L_Model 270A is complete, and can help identify configurations or rules that are not being used. Syntactic checks can also verify that the configurations in the hierarchical MIM <NUM> are complete (have been defined) and identify any configurations that are defined but not used. To illustrate, Rules <NUM> can specify that every tenant in L_Model 270A should have a context configured; every contract in L_Model 270A should specify a provider EPG and a consumer EPG; every contract in L_Model 270A should specify a subject, filter, and/or port; etc..

Rules <NUM> can also include rules for performing semantic checks and identifying semantic violations or issues. Semantic checks can check conflicting rules or configurations. For example, Rule1 and Rule2 can have aliasing issues, Rule1 can be more specific than Rule2 and thereby create conflicts/issues, etc. Rules <NUM> can define conditions which may result in aliased rules, conflicting rules, etc. To illustrate, Rules <NUM> can specify that an allow policy for a specific communication between two objects can conflict with a deny policy for the same communication between two objects if they allow policy has a higher priority than the deny policy, or a rule for an object renders another rule unnecessary.

Static Policy Analyzer <NUM> can apply Rules <NUM> to L_Model 270A to check configurations in L_Model 270A and output Configuration Violation Events <NUM> (e.g., alerts, logs, notifications, etc.) based on any issues detected. Configuration Violation Events <NUM> 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, Static Policy Analyzer <NUM> can iteratively traverse each node in a tree generated based on L_Model 270A and/or MIM <NUM>, and apply Rules <NUM> at each node in the tree to determine if any nodes yield a violation (e.g., incomplete configuration, improper configuration, unused configuration, etc.). Static Policy Analyzer <NUM> can output Configuration Violation Events <NUM> when it detects any violations.

<FIG> illustrates a flowchart for an example network assurance method. The method shown in <FIG> 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, those of ordinary skill in the art will appreciate that <FIG> 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> represents one or more steps, processes, methods or routines in the method. For the sake of clarity and explanation purposes, the blocks in <FIG> are described with reference to Assurance Appliance <NUM>, Models 270A-B, <NUM>, <NUM>, <NUM>, and Network Environment <NUM>, as shown in <FIG>, <FIG>, and <FIG>.

At step <NUM>, Assurance Appliance <NUM> can collect data and obtain models associated with Network Environment <NUM>. The models can include Models 270A-B, <NUM>, <NUM>, <NUM>. The data can include fabric data (e.g., topology, switch, interface policies, application policies, EPGs, etc.), network configurations (e.g., BDs, VRFs, L2 Outs, L3 Outs, protocol configurations, etc.), security configurations (e.g., contracts, filters, etc.), service chaining configurations, routing configurations, and so forth. Other information collected or obtained can include, for example, network data (e.g., RIB/FIB, VLAN, MAC, ISIS, DB, BGP, OSPF, ARP, VPC, LLDP, MTU, QoS, etc.), rules and tables (e.g., TCAM rules, ECMP tables, etc.), endpoint dynamics (e.g., EPM, COOP EP DB, etc.), statistics (e.g., TCAM rule hits, interface counters, bandwidth, etc.).

At step <NUM>, Assurance Appliance <NUM> can analyze and model the received data and models. For example, Assurance Appliance <NUM> can perform formal modeling and analysis, which can involve determining equivalency between models, including configurations, policies, etc..

At step <NUM>, Assurance Appliance <NUM> can generate one or more smart events. Assurance Appliance <NUM> can generate smart events using deep object hierarchy for detailed analysis, such as Tenants, switches, VRFs, rules, filters, routes, prefixes, ports, contracts, subjects, etc..

At step <NUM>, Assurance Appliance <NUM> can visualize the smart events, analysis and/or models. Assurance Appliance <NUM> can display problems and alerts for analysis and debugging, in a user-friendly GUI.

Network tools can be used to generate data related to flow data and network statistics. Such network tools are typically updated to create newer versions of the tools. Updated network tools are typically backwards compatible. More specifically, a new version of a network tool can usually read data generated or gathered by older versions of the network tool. However, network tools are typically not forward compatible. More specifically, an older version of a network tool typically is unable to read data generated or gathered by newer versions of the network tool. Accordingly, the older version of a network tool will fail to function as designed as they are unable to read/parse data generated or gathered by a newer version of the network tool. This problem is further exacerbated by the fact that users roll back versions of network tools, when the upgrade does not perform as expected. Such a rollback can be performed at any time including, but not limited to, times when the newer version of the tool has already generated data. Under these circumstances, the database can contain a mix of data generated by the different versions of the software. Furthermore, when such a rollback is performed, a typical requirement is that there is no data loss before and after the upgrade/rollback. As a result, earlier versions of the network tools are unable to read assurance data created or gathered by later versions of the network tools, thereby leading to failures in the earlier versions of the network tools.

In order to address these challenges, assurance data created by a network tool can be versioned. More specifically, assurance data created by a network tool can be versioned according to a version state of an instance of the network tool used to create the assurance data. Subsequently, access to assurance data can be controlled according to version states of instances of a network tool used to create the assurance data and version states of instances of the network tool requesting access to the assurance data. More specifically, an instance of a network tool can be allowed access to assurance data if it has the same version state or a greater version state than an instance of the network tool that created the assurance data. This ensures that an instance of a network tool is only allowed to access assurance data that the instance of the network tool is capable of reading, thereby reducing or eliminating changes that instances of a network tool will crash or fail as a result of accessing assurance data incompatible with the instances of the network tool.

<FIG> illustrates an environment <NUM> for versioning assurance data generated or gathered by a network tool for a network environment. More specifically, the environment <NUM> associates assurance data with a specific version state of an instance of a network tool used to gather and/or generate the data. Subsequently, the environment <NUM> controls access the assurance data, e.g. by instances of the network tool, based on version states of the instances of the network tool and a version state of the instance of the network tool used to gather and/or generate the data.

The environment shown in <FIG> includes an assurance data versioning system <NUM>, a first network tool instance <NUM>-<NUM>, a second network tool instance <NUM>-<NUM>, and a third network tool instance <NUM>-<NUM> (herein referred to as "network tool instances <NUM>"), and an assurance data store <NUM>. The network tool instances <NUM> function to monitor a network environment. The network tool instances <NUM> can be instances of an applicable network tool for monitoring a network. More specifically, the network tool instances <NUM> can be instances of a network tool configured to provide assurance in a network environment, such as the assurance appliance <NUM>.

In functioning as network tools for providing assurance in a network environment, the network tool instances <NUM> can generate, gather, and read assurance data. Assurance data includes applicable data used in providing assurance for a network environment. More specifically, assurance data can be generated from or otherwise include network events generated in a network environment. Network events can include events related to operation of a network environment, such as the events described herein. For example, a network event can include an event occurring within a specific logical tenant space on a specific router indicating the router has failed a policy test.

Network events can be associated with an event state. An event state can indicate a grade or subject associated with a network event. For example, an event state of a network event can indicate whether the network event is a passing event, a failing event, an informational event, or an error event.

Network events can be generated by and received from a controller, application, or appliance, e.g. assurance appliance <NUM>. More specifically, network events can be generated in response to checks or queries performed in a network environment, e.g. at a configurable periodicity. For example, a network event can be generated at a controller in response to performing a policy check on an EPG in a network environment. Additionally, network events can be generated based on operation of a network environment. For example, a network event can indicate an error occurred during operation of a network environment within a specific logical location in a tenant space in the network environment. A network event can include can include one or a combination of values of parameters defining the network event, an event state associated with the network event, a generated error or warning, a log, and stimuli and circumstances that led to creation of the network event.

Network events and corresponding event states can be associated with or otherwise classified by event categories. Event categories can be defined according to characteristics of a network environment in operation causing creation of corresponding network events. Examples of event categories include policy events, tenant routing events, configuration violation events, logical lint events, and forwarding events. For example, if a failure event is created in response to a bridge domain failing to adhere to a policy during a policy check, then the event can be classified as a failed policy event. In another example, if a network device in a tenant logical space passes a forwarding or routing check, then the event can be characterized as a passing forwarding event.

The network tool instances <NUM> are different executions of one or more network tools. The network tool instances <NUM> can be defined and/or separated according to time. For example, the first network tool instance <NUM>-<NUM> can be a session in the morning when an assurance appliance is executed to provide assurance in a network environment and the second network tool instance <NUM> can be another session in the afternoon when the assurance appliance is executed to further provide assurance in the network environment. Additionally, the network tool instances <NUM> can be defined and/or separated by actual executions of one or more network tools. For example, the first network tool instance <NUM>-<NUM> can occur as a network tool is operated and end when the network tool is shut down. Further in the example, the second network tool instance <NUM>-<NUM> can occur when the network tool is executed again after being shut down and last until the network tool is shut down again.

Additionally, the network tool instances <NUM> can correspond to specific version states of a network tool. A version state of a network tool is a unique state of a network tool corresponding to a specific version of the network tool. For example, a version state of a network tool can uniquely correspond to a first release of the network tool. In another example, a version state of a network tool can uniquely correspond to an updated release of the network tool. More specifically, if an initial release of a network tool is updated to include additional features as part of a later release from the initial release, then a first version state can uniquely correspond to the initial release of the network tool and a second version state can uniquely correspond to the later release of the network tool including the updated network tool with the additional features.

Version states can be ranked with respect to each other. For example, a first version state can be ranked higher than a second version state and vice versa the second version state can be ranked lower than the first version state. In particular, version states can be ranked with respect to each other according to specific versions of a network tool corresponding to the version states. Version states can be ranked with respect to each other based on one or a combination of release dates of versions of a network tool corresponding to the version states, differences in features between the versions of the network tool corresponding to the version states, and commonalities in features shared by the versions of the network tool corresponding to the version states. For example, a second network tool version released after a first network tool version can correspond to a second version state that is higher than a first version state corresponding to the first network tool version. In another example, a second network tool version including additional features absent from a first network tool version can correspond to a second version state that is higher than a first version state corresponding to the first network tool version.

Additionally, version states can uniquely correspond to version identifiers. More specifically, a first version state can uniquely correspond with a first version identifier while a second version state can uniquely correspond with a second version identifier, e.g. as part of a monotonically increasing version identifiers. Accordingly, version identifiers can be used to identify version states that uniquely correspond with the version identifiers. Version identifiers can be assigned to version states using an applicable versioning scheme. More specifically, version identifiers can be assigned to version states using a sequence-based versioning scheme. For example, a first version of an initial release of a network tool can be assigned "<NUM>" while a second version of the initial release of the network tool can be assigned "<NUM>.

The network tool instances <NUM> can have one or a combination of different version states, e.g. higher and lower version states, and the same version state. For example, the first network tool instance <NUM>-<NUM> can be a newer version/higher version state of a network tool, while the second network tool instance <NUM>-<NUM> can be an older version/lower version state of the network tool when compared to the first network tool instance <NUM>-<NUM>. Further in the example, a user can roll the network tool back from the first network tool instance <NUM>-<NUM> at the newer version of the network tool to the second network tool instance <NUM>-<NUM> at the older version of the network tool. This is common in practice, as often times a user does not want to pay for a license for a new version of a network tool, e.g. after testing out the newer version of the network tool, and subsequently rolls back to the older version of the network tool.

In another example of version states of the network tool instances <NUM>, the third network tool instance <NUM>-<NUM> and the first network tool instance <NUM>-<NUM> can be newer version(s)/higher version state(s) of a network tool, while the second network tool instance <NUM>-<NUM> can be an older version/lower version state of the network tool when compared to the first network tool instance <NUM>-<NUM> and the third network tool interface <NUM>-<NUM>. Further in the example, the third network tool instance <NUM>-<NUM> can have the same or a higher version state as the first network tool instance <NUM>-<NUM>. Still further in the example, a user can roll the network tool back from the first network tool instance <NUM>-<NUM> at the newer version of the network tool to the second network tool instance <NUM>-<NUM> at the older version of the network tool. Subsequently the user can roll the network tool forward from the older version at the second network tool instance <NUM>-<NUM> to a newer version of the network tool at the third network tool instance <NUM>-<NUM>. This is common in practice, as often times a user switches between different licenses and different versions of a network tool utilized by the user.

The assurance data versioning system <NUM> can version assurance data and control access to the assurance data based on version states of a network tool. More specifically, the assurance data versioning system <NUM> can version received assurance data and control access to the assurance data based on version states of a network tool in order to provide compatibility across different versions of the network tool. For example, the version assurance data versioning system <NUM> can ensure that an instance of a network tool at a specific version state is capable of reading assurance data based on the specific version state. Subsequently, the assurance data versioning system <NUM> can allows the instance of the network tool to access the assurance data if it determines the instance of the network tool is capable of reading the assurance data at the specific version state of the instance of the network tool.

The assurance data versioning system <NUM> can receive assurance data from an applicable source, e.g. one or a combination of the network tool instances <NUM>. For example, the assurance data versioning system <NUM> can receive assurance data including network events generated by an assurance appliance in a network environment from the first network tool instance <NUM>-<NUM>. Subsequently, the assurance data versioning system <NUM> can store the assurance data received from the first network tool instance <NUM>-<NUM> in the assurance data store <NUM>.

Further, the assurance data versioning system <NUM> versions received assurance data. More specifically, the assurance data versioning system <NUM> associates received assurance data with a version state of an instance of a network tool that assurance data is received from and/or a network tool that created the assurance data. For example, the assurance data versioning system <NUM> can associate assurance data received from the first network tool instance <NUM>-<NUM> with a version state of the first network tool instance <NUM>-<NUM>.

In associating received assurance data with a version state of a network tool instance, the assurance data versioning system <NUM> appends a version identifier uniquely corresponding to the version state to the assurance data. For example, if the first network tool instance <NUM>-<NUM> is a second version of a network tool, then the assurance data versioning system <NUM> can append an identifier indicating the second version of the network tool to assurance data received from the first network tool instance <NUM>-<NUM>. More specifically, in appending a version identifier uniquely corresponding to a version state to received assurance data, the assurance data versioning system <NUM> can add the version identifier to one or more headers of data included as part of the received assurance data. Subsequently, the assurance data versioning system <NUM> can store assurance data with appended version identifiers in the assurance data store <NUM>.

The assurance data versioning system <NUM> can control access by the network tool instances <NUM> to received assurance data as part of providing compatibility across different versions of a network tool. More specifically, the assurance data versioning system <NUM> controls access by the network tool instances <NUM> to received assurance data based on version states of the network tool instances <NUM>. For example, the assurance data versioning system <NUM> can deny the second network tool instance <NUM>-<NUM> access to assurance data generated by the first network tool instance <NUM>-<NUM> based on either or both a version state of the second network tool instance <NUM>-<NUM> and a version state of the first network tool instance <NUM>-<NUM>. Further in the example, the assurance data versioning system <NUM> can allow the third network tool instance <NUM>-<NUM> to access the assurance data generated by the first network tool instance <NUM>-<NUM> based on either or both a version state of the third network tool instance <NUM>-<NUM> and the version state of the first network tool instance <NUM>-<NUM>.

Further, the assurance data versioning system <NUM> controls access to received assurance data based on version states of the network tool instances <NUM> according to version constraints. Version constraints are constraints that dictate whether a network tool instance can access assurance data based on version states. More specifically, version constraints can depend on or otherwise incorporate ranking of version states with respect to each other. For example, version constraints can specify preventing network tool instances from accessing assurance data if version states of the instances are ranked less than a version state of a network tool instance that created the assurance data, e.g. previous versions of the network tool. Conversely, version constraints can specify allowing network tool instances access to assurance data if version states of the instances are greater than or equal to a version state of a network tool instance that created the assurance data. For example, version constraints can specify allowing network tool instances to access assurance data if the versions of the instances are the same or updated versions of a network tool compared to a version of an instance of the network tool used to gather the assurance data.

Version constrains for controlling access to assurance data can be specific to the assurance data, an instance of a network tool used to generate the assurance data, and a network tool used to generate the assurance data. For example, a version constraint can be specific to a network tool and specify that only instances of the network tool at version states higher than or equal to a version state of an instance of the network tool that created assurance data can actually access the assurance data. In another example, a version constrain can be unique to specific assurance data and indicate specific version states of instances of a network tool allowed to access the specific assurance data.

The assurance data versioning system <NUM> can receive queries from the network tool instances to access assurance data. Further, the assurance data versioning system <NUM> can determine whether to provide the network tool instances <NUM> with access to assurance data in response to received queries from the network tool instances <NUM>. For example, the assurance data versioning system <NUM> can receive from the second network tool instance <NUM>-<NUM> a query for assurance data generated by the first network tool instance <NUM>-<NUM>. Subsequently, the assurance data versioning system <NUM> can determine whether to allow the second network tool instance <NUM>-<NUM> to access the assurance data in response to the received query. The assurance data versioning system <NUM> can determine whether to allow the network tool instances <NUM> to access assurance data in response to received queries for the assurance data based on version constraints for the assurance data. For example, the assurance data versioning system <NUM> can from the second network tool instance <NUM>-<NUM> receive a query for assurance data generated by the first network tool instance <NUM>-<NUM>. Further in the example, the assurance data versioning system <NUM> can determine whether to provide the second network tool instance <NUM>-<NUM> access to the assurance data in response to the query based on a version constraint for the network tool.

The assurance data versioning system <NUM> can use version identifiers to determine whether to provide the network tool instances <NUM> access to assurance data. More specifically, the assurance data versioning system <NUM> can use version identifiers and version constraints to determine whether to provide the network tool instances access to assurance data. For example, the assurance data versioning system <NUM> can use a version identifier appended to assurance data to determine a version state of an originating network tool instance that generated the assurance data. Further in the example, based on a version state of a network tool instance requesting access to the assurance data and the version state of the originating network tool instance, the assurance data versioning system <NUM> can determine whether the network tool instance requesting access meets the requirements of a version constraint associated with the assurance data. Still further in the example, if the assurance data versioning system <NUM> determines that the network tool instance requesting access does meet the requirements of the version constrain, then the assurance data versioning system <NUM> can provide the network tool instance access to the assurance data.

In controlling access to assurance data based on versions states of the network tool instances <NUM>, the assurance data versioning system <NUM> can reduce a chance that the network tool instances <NUM> fail to function as designed. More specifically, the assurance data versioning system <NUM> can reduce a chance that the network tool instances <NUM> fail to function as designed as a result of the network tool instances <NUM> inability to read assurance data but still being granted access to the assurance data. For example, if a second network tool instance <NUM>-<NUM> is an earlier version of a network tool as compared to the first network tool instance <NUM>-<NUM> and is unable to read assurance data generated by the first network tool instance <NUM>-<NUM>. Further in the example, the assurance data versioning system <NUM> can deny the second network tool instance <NUM>-<NUM> access to the assurance data generated by the first network tool instance <NUM>-<NUM>, thereby eliminating a change that the second network tool instance <NUM>-<NUM> will fail to function as designed as a result of trying to read and being unable to read the assurance data generated by the first network tool instance <NUM>-<NUM>. Accordingly, the assurance data versioning system <NUM> can provide compatibility across different versions of a network tool, e.g. by denying versions of the network tool access to data that will cause the versions of the network tool to fail to function as designed or that the version of the network tool are otherwise unable to read.

<FIG> illustrates a flowchart for an example method of versioning data generate by a network tool to provide compatibility across different versions of the network tool. The method shown in <FIG> 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, those of ordinary skill in the art will appreciate that <FIG> 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> represents one or more steps, processes, methods or routines in the method. For the sake of clarity and explanation purposes, the blocks in <FIG> are described with reference to the environment <NUM>, shown in <FIG>.

At step <NUM>, the first instance of the network tool <NUM>-<NUM> at a first specific version state generates network assurance data including network events. The first instance of the network tool <NUM>-<NUM> can provide the generated network assurance data to the assurance data versioning system <NUM>. The first instance of the network tool <NUM>-<NUM> can generate and/or provide the network assurance data at a configurable periodicity. For example, the first instance of the network tool <NUM>-<NUM> can provide the network assurance data at a configurable epoch.

At step <NUM>, the assurance data versioning system <NUM> appends a version identifier uniquely corresponding to the first specific version state of the network tool to the network assurance data generated by the first instance of the network tool <NUM>-<NUM>. More specifically, the assurance data versioning system <NUM> can add a header to the assurance data including an indicator of a version identifier uniquely corresponding to the first specific version state of the first instance of the network tool <NUM>-<NUM>. The assurance data versioning system <NUM> can assign a version identifier to the first specific version state of the network tool corresponding to the first instance of the network tool <NUM>-<NUM> according to an applicable versioning scheme. For example, the assurance data versioning system <NUM> can assign the version identifier to the first specific version sate of the first instance of the network tool <NUM>-<NUM> using a sequence-based versioning scheme.

At step <NUM>, the assurance data versioning system <NUM> receives a query for the network assurance date generated by the first instance of the network tool <NUM>-<NUM> from the second instance of the network tool <NUM>-<NUM>. The second instance of the network tool <NUM>-<NUM> can be at a different version state than the version state of the first instance of the network tool <NUM>-<NUM>. For example, the second instance of the network tool <NUM>-<NUM> can be at a higher version state than the first instance of the network tool <NUM>-<NUM>. In another example, the second instance of the network tool <NUM>-<NUM> can be at the same version state as the first instance of the network tool <NUM>-<NUM>. In yet another example, the second instance of the network tool <NUM>-<NUM> can be at a lower version state than the version state of the first instance of the network tool <NUM>-<NUM>.

At step <NUM>, the assurance data versioning system <NUM> provides the second instance of the network tool <NUM>-<NUM> access to the network assurance data generated by the first instance of the network tool <NUM>-<NUM>. More specifically, the assurance data versioning system <NUM> can provide the second instance of the network tool <NUM>-<NUM> access to the network assurance data according to a version constraint for data generated by the network tool using the version identifier uniquely corresponding to a version state of the first instance of the network tool <NUM>-<NUM> appended to the network assurance data generated by the first instance of the network tool <NUM>-<NUM>. For example, the assurance data versioning system <NUM> can provide the second instance of the network tool <NUM>-<NUM> access to the assurance data if the version state of the second instance of the network tool <NUM>-<NUM> is greater than or equal to the version state of the first instance of the network tool <NUM>-<NUM>.

In summary, systems, methods, and computer-readable media for versioning data generated by a network tool to provide compatibility across different versions of the network tool are described. In some embodiments, a method can include generating network assurance data including network events by a first instance of a network tool at a first specific version state. A version identifier uniquely corresponding to the first specific version state can be appended to the network assurance data. A query for the network assurance data can be received from a second instance of the network tool at a second specific version state. Subsequently, access to the network assurance data can be provided to the second instance of the network tool according to a version constraint for data generated by the network tool using the version identifier uniquely corresponding to the first specific version state and appended to the network assurance data.

The disclosure now turns to <FIG> and <FIG>, which illustrate example network devices and computing devices, such as switches, routers, load balancers, client devices, and so forth.

<FIG> illustrates an example network device <NUM> suitable for performing switching, routing, load balancing, and other networking operations. Network device <NUM> includes a central processing unit (CPU) <NUM>, interfaces <NUM>, and a bus <NUM> (e.g., a PCI bus). When acting under the control of appropriate software or firmware, the CPU <NUM> is responsible for executing packet management, error detection, and/or routing functions. The CPU <NUM> preferably accomplishes all these functions under the control of software including an operating system and any appropriate applications software. CPU <NUM> may include one or more processors <NUM>, such as a processor from the INTEL X86 family of microprocessors. In some cases, processor <NUM> can be specially designed hardware for controlling the operations of network device <NUM>. In some cases, a memory <NUM> (e.g., non-volatile RAM, ROM, etc.) also forms part of CPU <NUM>. However, there are many different ways in which memory could be coupled to the system.

The interfaces <NUM> 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 <NUM>. 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, <NUM>/<NUM>/<NUM> 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 <NUM> to efficiently perform routing computations, network diagnostics, security functions, etc..

Although the system shown in <FIG> is one specific network device of the present invention, it is by no means the only network device architecture on which the present invention can be implemented. For example, an architecture having a single processor that handles communications as well as routing computations, etc., is often used. Further, other types of interfaces and media could also be used with the network device <NUM>.

The network device <NUM> can also include an application-specific integrated circuit (ASIC), which can be configured to perform routing and/or switching operations. The ASIC can communicate with other components in the network device <NUM> via the bus <NUM>, to exchange data and signals and coordinate various types of operations by the network device <NUM>, such as routing, switching, and/or data storage operations, for example.

<FIG> illustrates a computing system architecture <NUM> wherein the components of the system are in electrical communication with each other using a connection <NUM>, such as a bus. Exemplary system <NUM> includes a processing unit (CPU or processor) <NUM> and a system connection <NUM> that couples various system components including the system memory <NUM>, such as read only memory (ROM) <NUM> and random access memory (RAM) <NUM>, to the processor <NUM>. The system <NUM> can include a cache of high-speed memory connected directly with, in close proximity to, or integrated as part of the processor <NUM>. The system <NUM> can copy data from the memory <NUM> and/or the storage device <NUM> to the cache <NUM> for quick access by the processor <NUM>. In this way, the cache can provide a performance boost that avoids processor <NUM> delays while waiting for data. These and other modules can control or be configured to control the processor <NUM> to perform various actions. Other system memory <NUM> may be available for use as well. The memory <NUM> can include multiple different types of memory with different performance characteristics. The processor <NUM> can include any general purpose processor and a hardware or software service, such as service <NUM><NUM>, service <NUM><NUM>, and service <NUM><NUM> stored in storage device <NUM>, configured to control the processor <NUM> as well as a special-purpose processor where software instructions are incorporated into the actual processor design. The processor <NUM> 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 computing device <NUM>, an input device <NUM> 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 <NUM> 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 computing device <NUM>. The communications interface <NUM> 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.

The storage device <NUM> can include services <NUM>, <NUM>, <NUM> for controlling the processor <NUM>. Other hardware or software modules are contemplated. The storage device <NUM> can be connected to the system connection <NUM>. 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 <NUM>, connection <NUM>, output device <NUM>, and so forth, to carry out the function.

Claim 1:
A method performed at an assurance data versioning system (<NUM>), comprising:
receiving network assurance data including network events generated by a first instance (<NUM>-<NUM>) of a network tool having a first specific version state;
appending a version identifier uniquely corresponding to the first specific version state of the network tool to the network assurance data generated by the first instance of the network tool;
receiving a query for the network assurance data generated by the first instance of the network tool from a second instance (<NUM>-<NUM>) of the network tool having a second specific version state; and
providing the second instance of the network tool access to the network assurance data generated by the first instance of the network tool according to a version constraint for data generated by the network tool using the version identifier uniquely corresponding to the first specific version state of the network tool and appended to the network assurance data generated by the first instance of the network tool, wherein the version constraint is a constraint that dictates whether a network tool instance can access assurance data based on network tool instance version states, the providing step comprising:
determining whether the second specific version state of the second instance is greater than or equal to the first specific version state of the first instance of the network tool that generated the network assurance data; and
allowing or preventing access to the network assurance data by the second instance of the network tool in dependence on the determination.