Patent Publication Number: US-2021176268-A1

Title: Mechanism for identifying differences between network snapshots

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a Continuation of U.S. application Ser. No. 15/992,071, filed on May 29, 2018, which in turn, claims priority to U.S. Provisional Application 62/622,019, filed on Jan. 25, 2018, entitled “FRAMEWORK FOR IMPLEMENTING NETWORK POLICY ENFORCEMENT,” the content of which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The subject matter of this disclosure relates in general to the field of computer networks, and more specifically to efficiently transferring large amounts of data generated by systems managing a network. 
     BACKGROUND 
     An enterprise application is a set of workloads (e.g., computing, networking, and storage) that are generally distributed across various nodes (or endpoints) of a network and the relationships (e.g., connectivity, dependencies, network and security policies, etc.) between the workloads. A typical application may include a presentation tier, an application tier, and a data tier. The presentation tier may depend on the application tier and authentication services, and the application tier may depend on the web tier and external network services (e.g., a travel reservation system, an ordering tool, a billing tool, etc.). These tiers may further depend on firewall, load balancing, wide area network (WAN) acceleration, and other network services. An enterprise can include hundreds or thousands of applications of similar and different architectures. 
     An expansive or thorough understanding of a data center and applications running in the data center can be critical for network management tasks such as anomaly detection (e.g., network attacks and misconfiguration), asset management (e.g., monitoring, capacity planning, consolidation, migration, and continuity planning), and compliance (e.g. conformance with governmental regulations, industry standards, and corporate policies). Despite the complexities of the interrelationships among workloads discussed above, the many approaches for developing insight into an enterprise&#39;s workloads require comprehensive knowledge on the part of human operators and processes that are manual and largely customized for a particular enterprise. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       In order to describe the manner in which the above-recited and other advantages and features of the disclosure can be obtained, a more particular description of the principles briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only embodiments of the disclosure and are not therefore to be considered to be limiting of its scope, the principles herein are described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1  illustrates an example of a network traffic monitoring system, in accordance with an embodiment; 
         FIG. 2  illustrates an example of a network environment, in accordance with an embodiment; 
         FIG. 3  illustrates an example of a data pipeline for generating network insights based on collected network information, in accordance with an embodiment; 
         FIG. 4  illustrates an example of a network traffic monitoring system providing network snapshots to subscribers, in accordance with an embodiment; 
         FIG. 5  illustrates an example of a process for compiling a network snapshot, in accordance with an embodiment; 
         FIG. 6  illustrates an example of a process for identifying a difference between network snapshots, in accordance with an embodiment; and 
         FIGS. 7A and 7B  illustrate examples of systems in accordance with some embodiments. 
     
    
    
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     The detailed description set forth below is intended as a description of various configurations of embodiments and is not intended to represent the only configurations in which the subject matter of this disclosure can be practiced. The appended drawings are incorporated herein and constitute a part of the detailed description. The detailed description includes specific details for the purpose of providing a more thorough understanding of the subject matter of this disclosure. However, it will be clear and apparent that the subject matter of this disclosure is not limited to the specific details set forth herein and may be practiced without these details. In some instances, structures and components are shown in block diagram form in order to avoid obscuring the concepts of the subject matter of this disclosure. 
     Overview 
     Aspects of the subject technology relate to a network traffic monitoring system configured to receive network data and process data generated by sensors deployed across nodes of a network and generate a network snapshot based on the network data and the process data. The system may partition the network snapshot into a set of network snapshot segments and provide the set of network snapshot segments to a stream processing system, wherein the set of network snapshot segments are configured to be transmitted via a snapshot stream managed by the stream processing system to a subscriber system. 
     Aspects of the subject technology relate to a subscriber system configured to receive a set of network snapshot segments from an output stream of a stream processing service, compile the set of network snapshot segments from the set of messages into a first network snapshot and a second network snapshot, and compare the first network snapshot and the second network snapshot to identify a difference between the first network snapshot and the second network snapshot. 
     DESCRIPTION 
     Various embodiments of the disclosure are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the relevant art will recognize that other components and configurations may be used without departing from the spirit and scope of the disclosure. 
     Sensors deployed in a network can be used to gather network information related to network traffic of nodes operating in the network and process information for nodes and applications running in the network. Gathered network information can be analyzed to provide insights into the operation of the nodes in the network, otherwise referred to as analytics. In particular, discovered application or inventories, application dependencies, policies, efficiencies, resource and bandwidth usage, and network flows can be determined for the network using the network traffic data. For example, an analytics engine can be configured to automate discovery of applications running in the network, map the applications&#39; interdependencies, or generate a set of proposed network policies for implementation. 
     The analytics engine can monitor network information, process information, and other relevant information of traffic passing through the network using a sensor network that provides multiple perspectives for the traffic. The sensor network can include sensors for networking devices (e.g., routers, switches, network appliances), physical servers, hypervisors or shared kernels, and virtual partitions (e.g., VMs or containers), and other network elements. The analytics engine can analyze the network information, process information, and other pertinent information to determine various network insights. 
     The analytics engine may continuously track this information over time and generate state information associated with a particular moment in time. The state information may be considered a “snapshot.” The analytics engine can periodically take snapshots of the states of applications, servers, network devices, and/or other elements of the network. In other embodiments, the analytics engine can capture the snapshots when events of interest occur, such as a change to a network policy; an application experiencing latency that exceeds an application latency threshold; the network experiencing latency that exceeds a network latency threshold; failure of server, network device, or other network element; and similar circumstances. Snapshots can include a variety of telemetry associated with network elements. 
     Several end users may be interested in this information. However, each snapshot for an entire network or network cluster, may be quite large in size. Furthermore, the network state may be updated often, causing several snapshots to be created and created often. There are many technical limitations to transmitting and receiving that amount of data often enough for end users to stay in sync, especially when multiple snapshots are generated in relatively quick succession. 
     Aspects of the subject technology address these technical problems by fragmenting each snapshot into smaller chunks or segments. A first segment may be tagged with a “start” label and a last segment may be tagged with an “end” label. Each segment of a snapshot may also be numbered (e.g., from 0 to n, where n is assigned to the last segment). 
     The segments of the snapshot are then provided to a stream processing service for distribution in an output stream. The stream processing service allows for several end users to subscribe to the output stream containing the snapshot segments (and snapshot fragments for subsequent snapshots). 
     A client application may subscribe to the output stream and begin receiving stream messages. Each stream message may include a snapshot segment. In order to compile a snapshot, however, all of the segments for the snapshot must be received. The client application may use the tag (e.g., start/end tags) and/or the enumeration of a received segment to determine which segment has been transmitted, and which segments should be requested from the stream processing service. For example, if the first segment received by a client application is segment 5, the client application may request segments 0-4 from the stream processing service or request transmission of the stream starting from 5 segments back (e.g., rewinding the stream). Once a segment tagged with the “end” label is received, the client application may compile the segments into a snapshot. In some cases, the snapshot may be converted into a generic format that may be consumed by multiple diverse parties. 
     After a first network snapshot is received, the client application may continue to receive messages from the output stream and compile subsequent network snapshots. The client application may compare a first network snapshot and a second network snapshot to compute a delta or a difference between the network snapshots. This delta or difference may represent a change in a network policy or other data associated with the network. The delta or difference may then be provided to an end user for consumption. For example, the end user may use the delta to update their snapshot stored by the end user so that their snapshot may be in sync with the most recent snapshot provided by the output stream without having to re-implement the entire snapshot. 
     The client application may interface with an end user (e.g., an end user device) and provide additional features to the end user. For example, the end user may provide one or more lists of IP addresses, subnets, or ranges of IP addresses that the end user has an interest in. The client application may filter out the data in the snapshots based on the list of IP addresses and provide the desired data to the end user. Alternatively, the client application may compute the delta or difference in snapshots associated with the list of IP address pool of interest. The reduced set of data may be stored by the end user. 
     In some situations, network snapshots may be generated and provided to the stream processing service at a fast pace. For example, if network snapshots are generated based on network events or policy updates and the network events or policy updates occur in rapid succession, multiple network snapshots may be provided to the stream processing service before a client application can finish receiving and compiling a first network snapshot. In order to keep the client application up to date, the client application can skip intervening network snapshots and begin receiving the most recent network snapshot. 
     Referring now to the drawings,  FIG. 1  is an illustration of a network traffic monitoring system  100  in accordance with an embodiment. The network traffic monitoring system  100  can include a configuration manager  102 , sensors  104 , a collector module  106 , a data mover module  108 , an analytics engine  110 , and a presentation module  112 . In  FIG. 1 , the analytics engine  110  is also shown in communication with out-of-band data sources  114 , third party data sources  116 , and a network controller  118 . 
     The configuration manager  102  can be used to provision and maintain the sensors  104 , including installing sensor software or firmware in various nodes of a network, configuring the sensors  104 , updating the sensor software or firmware, among other sensor management tasks. For example, the sensors  104  can be implemented as virtual partition images (e.g., virtual machine (VM) images or container images), and the configuration manager  102  can distribute the images to host machines. In general, a virtual partition may be an instance of a VM, container, sandbox, or other isolated software environment. The software environment may include an operating system and application software. For software running within a virtual partition, the virtual partition may appear to be, for example, one of many servers or one of many operating systems executed on a single physical server. The configuration manager  102  can instantiate a new virtual partition or migrate an existing partition to a different physical server. The configuration manager  102  can also be used to configure the new or migrated sensor. 
     The configuration manager  102  can monitor the health of the sensors  104 . For example, the configuration manager  102  may request for status updates and/or receive heartbeat messages, initiate performance tests, generate health checks, and perform other health monitoring tasks. In some embodiments, the configuration manager  102  can also authenticate the sensors  104 . For instance, the sensors  104  can be assigned a unique identifier, such as by using a one-way hash function of a sensor&#39;s basic input/out system (BIOS) universally unique identifier (UUID) and a secret key stored by the configuration image manager  102 . The UUID can be a large number that may be difficult for a malicious sensor or other device or component to guess. In some embodiments, the configuration manager  102  can keep the sensors  104  up to date by installing the latest versions of sensor software and/or applying patches. The configuration manager  102  can obtain these updates automatically from a local source or the Internet. 
     The sensors  104  can reside on various nodes of a network, such as a virtual partition (e.g., VM or container)  120 ; a hypervisor or shared kernel managing one or more virtual partitions and/or physical servers  122 , an application-specific integrated circuit (ASIC)  124  of a switch, router, gateway, or other networking device, or a packet capture (pcap)  126  appliance (e.g., a standalone packet monitor, a device connected to a network devices monitoring port, a device connected in series along a main trunk of a datacenter, or similar device), or other element of a network. The sensors  104  can monitor network traffic between nodes, and send network traffic data and corresponding data (e.g., host data, process data, user data, etc.) to the collectors  106  for storage. For example, the sensors  104  can sniff packets being sent over its hosts&#39; physical or virtual network interface card (NIC), or individual processes can be configured to report network traffic and corresponding data to the sensors  104 . Incorporating the sensors  104  on multiple nodes and within multiple partitions of some nodes of the network can provide for robust capture of network traffic and corresponding data from each hop of data transmission. In some embodiments, each node of the network (e.g., VM, container, or other virtual partition  120 , hypervisor, shared kernel, or physical server  122 , ASIC  124 , pcap  126 , etc.) includes a respective sensor  104 . However, it should be understood that various software and hardware configurations can be used to implement the sensor network  104 . 
     As the sensors  104  capture communications and corresponding data, they may continuously send network traffic data to the collectors  106 . The network traffic data can include metadata relating to a packet, a collection of packets, a flow, a bidirectional flow, a group of flows, a session, or a network communication of another granularity. That is, the network traffic data can generally include any information describing communication on all layers of the Open Systems Interconnection (OSI) model. For example, the network traffic data can include source/destination MAC address, source/destination IP address, protocol, port number, etc. In some embodiments, the network traffic data can also include summaries of network activity or other network statistics such as number of packets, number of bytes, number of flows, bandwidth usage, response time, latency, packet loss, jitter, and other network statistics. 
     The sensors  104  can also determine additional data for each session, bidirectional flow, flow, packet, or other more granular or less granular network communication. The additional data can include host and/or endpoint information, virtual partition information, sensor information, process information, user information, tenant information, application information, network topology, application dependency mapping, cluster information, or other information corresponding to each flow. 
     In some embodiments, the sensors  104  can perform some preprocessing of the network traffic and corresponding data before sending the data to the collectors  106 . For example, the sensors  104  can remove extraneous or duplicative data or they can create summaries of the data (e.g., latency, number of packets per flow, number of bytes per flow, number of flows, etc.). In some embodiments, the sensors  104  can be configured to only capture certain types of network information and disregard the rest. In some embodiments, the sensors  104  can be configured to capture only a representative sample of packets (e.g., every 1,000th packet or other suitable sample rate) and corresponding data. 
     Since the sensors  104  may be located throughout the network, network traffic and corresponding data can be collected from multiple vantage points or multiple perspectives in the network to provide a more comprehensive view of network behavior. The capture of network traffic and corresponding data from multiple perspectives rather than just at a single sensor located in the data path or in communication with a component in the data path, allows the data to be correlated from the various data sources, which may be used as additional data points by the analytics engine  110 . Further, collecting network traffic and corresponding data from multiple points of view ensures more accurate data is captured. For example, other types of sensor networks may be limited to sensors running on external-facing network devices (e.g., routers, switches, network appliances, etc.) such that east-west traffic, including VM-to-VM or container-to-container traffic on a same host, may not be monitored. In addition, packets that are dropped before traversing a network device or packets containing errors may not be accurately monitored by other types of sensor networks. The sensor network  104  of various embodiments substantially mitigates or eliminates these issues altogether by locating sensors at multiple points of potential failure. Moreover, the network traffic monitoring system  100  can verify multiple instances of data for a flow (e.g., source endpoint flow data, network device flow data, and endpoint flow data) against one another. 
     In some embodiments, the network traffic monitoring system  100  can assess a degree of accuracy of flow data sets from multiple sensors and utilize a flow data set from a single sensor determined to be the most accurate and/or complete. The degree of accuracy can be based on factors such as network topology (e.g., a sensor closer to the source may be more likely to be more accurate than a sensor closer to the destination), a state of a sensor or a node hosting the sensor (e.g., a compromised sensor/node may have less accurate flow data than an uncompromised sensor/node), or flow data volume (e.g., a sensor capturing a greater number of packets for a flow may be more accurate than a sensor capturing a smaller number of packets). 
     In some embodiments, the network traffic monitoring system  100  can assemble the most accurate flow data set and corresponding data from multiple sensors. For instance, a first sensor along a data path may capture data for a first packet of a flow but may be missing data for a second packet of the flow while the situation is reversed for a second sensor along the data path. The network traffic monitoring system  100  can assemble data for the flow from the first packet captured by the first sensor and the second packet captured by the second sensor. 
     As discussed, the sensors  104  can send network traffic and corresponding data to the collectors  106 . In some embodiments, each sensor can be assigned to a primary collector and a secondary collector as part of a high availability scheme. If the primary collector fails or communications between the sensor and the primary collector are not otherwise possible, a sensor can send its network traffic and corresponding data to the secondary collector. In other embodiments, the sensors  104  are not assigned specific collectors but the network traffic monitoring system  100  can determine an optimal collector for receiving the network traffic and corresponding data through a discovery process. In such embodiments, a sensor can change where it sends it network traffic and corresponding data if its environments changes, such as if a default collector fails or if the sensor is migrated to a new location and it would be optimal for the sensor to send its data to a different collector. For example, it may be preferable for the sensor to send its network traffic and corresponding data on a particular path and/or to a particular collector based on latency, shortest path, monetary cost (e.g., using private resources versus a public resources provided by a public cloud provider), error rate, or some combination of these factors. In other embodiments, a sensor can send different types of network traffic and corresponding data to different collectors. For example, the sensor can send first network traffic and corresponding data related to one type of process to one collector and second network traffic and corresponding data related to another type of process to another collector. 
     The collectors  106  can be any type of storage medium that can serve as a repository for the network traffic and corresponding data captured by the sensors  104 . In some embodiments, data storage for the collectors  106  is located in an in-memory database, such as dashDB from IBM®, although it should be appreciated that the data storage for the collectors  106  can be any software and/or hardware capable of providing rapid random access speeds typically used for analytics software. In various embodiments, the collectors  106  can utilize solid state drives, disk drives, magnetic tape drives, or a combination of the foregoing according to cost, responsiveness, and size requirements. Further, the collectors  106  can utilize various database structures such as a normalized relational database or a NoSQL database, among others. 
     In some embodiments, the collectors  106  may only serve as network storage for the network traffic monitoring system  100 . In such embodiments, the network traffic monitoring system  100  can include a data mover module  108  for retrieving data from the collectors  106  and making the data available to network clients, such as the components of the analytics engine  110 . In effect, the data mover module  108  can serve as a gateway for presenting network-attached storage to the network clients. In other embodiments, the collectors  106  can perform additional functions, such as organizing, summarizing, and preprocessing data. For example, the collectors  106  can tabulate how often packets of certain sizes or types are transmitted from different nodes of the network. The collectors  106  can also characterize the traffic flows going to and from various nodes. In some embodiments, the collectors  106  can match packets based on sequence numbers, thus identifying traffic flows and connection links. As it may be inefficient to retain all data indefinitely in certain circumstances, in some embodiments, the collectors  106  can periodically replace detailed network traffic data with consolidated summaries. In this manner, the collectors  106  can retain a complete dataset describing one period (e.g., the past minute or other suitable period of time), with a smaller dataset of another period (e.g., the previous 2-10 minutes or other suitable period of time), and progressively consolidate network traffic and corresponding data of other periods of time (e.g., day, week, month, year, etc.). In some embodiments, network traffic and corresponding data for a set of flows identified as normal or routine can be winnowed at an earlier period of time while a more complete data set may be retained for a lengthier period of time for another set of flows identified as anomalous or as an attack. 
     Computer networks may be exposed to a variety of different attacks that expose vulnerabilities of computer systems in order to compromise their security. Some network traffic may be associated with malicious programs or devices. The analytics engine  110  may be provided with examples of network states corresponding to an attack and network states corresponding to normal operation. The analytics engine  110  can then analyze network traffic and corresponding data to recognize when the network is under attack. In some embodiments, the network may operate within a trusted environment for a period of time so that the analytics engine  110  can establish a baseline of normal operation. Since malware is constantly evolving and changing, machine learning may be used to dynamically update models for identifying malicious traffic patterns. 
     In some embodiments, the analytics engine  110  may be used to identify observations which differ from other examples in a dataset. For example, if a training set of example data with known outlier labels exists, supervised anomaly detection techniques may be used. Supervised anomaly detection techniques utilize data sets that have been labeled as normal and abnormal and train a classifier. In a case in which it is unknown whether examples in the training data are outliers, unsupervised anomaly techniques may be used. Unsupervised anomaly detection techniques may be used to detect anomalies in an unlabeled test data set under the assumption that the majority of instances in the data set are normal by looking for instances that seem to fit to the remainder of the data set. 
     The analytics engine  110  can include a data lake  130 , an application dependency mapping (ADM) module  140 , and elastic processing engines  150 . The data lake  130  is a large-scale storage repository that provides massive storage for various types of data, enormous processing power, and the ability to handle nearly limitless concurrent tasks or jobs. In some embodiments, the data lake  130  is implemented using the Hadoop® Distributed File System (HDFS™) from Apache® Software Foundation of Forest Hill, Md. HDFS™ is a highly scalable and distributed file system that can scale to thousands of cluster nodes, millions of files, and petabytes of data. HDFS™ is optimized for batch processing where data locations are exposed to allow computations to take place where the data resides. HDFS™ provides a single namespace for an entire cluster to allow for data coherency in a write-once, read-many access model. That is, clients can only append to existing files in the node. In HDFS™, files are separated into blocks, which are typically 64 MB in size and are replicated in multiple data nodes. Clients access data directly from data nodes. 
     In some embodiments, the data mover  108  receives raw network traffic and corresponding data from the collectors  106  and distributes or pushes the data to the data lake  130 . The data lake  130  can also receive and store out-of-band data  114 , such as statuses on power levels, network availability, server performance, temperature conditions, cage door positions, and other data from internal sources, and third party data  116 , such as security reports (e.g., provided by Cisco® Systems, Inc. of San Jose, Calif., Arbor Networks® of Burlington, Mass., Symantec® Corp. of Sunnyvale, Calif., Sophos® Group plc of Abingdon, England, Microsoft® Corp. of Seattle, Wash., Verizon® Communications, Inc. of New York, N.Y., among others), geolocation data, IP watch lists, Whois data, configuration management database (CMDB) or configuration management system (CMS) as a service, and other data from external sources. In other embodiments, the data lake  130  may instead fetch or pull raw traffic and corresponding data from the collectors  106  and relevant data from the out-of-band data sources  114  and the third party data sources  116 . In yet other embodiments, the functionality of the collectors  106 , the data mover  108 , the out-of-band data sources  114 , the third party data sources  116 , and the data lake  130  can be combined. Various combinations and configurations are possible as would be known to one of ordinary skill in the art. 
     Each component of the data lake  130  can perform certain processing of the raw network traffic data and/or other data (e.g., host data, process data, user data, out-of-band data or third party data) to transform the raw data to a form useable by the elastic processing engines  150 . In some embodiments, the data lake  130  can include repositories for flow attributes  132 , host and/or endpoint attributes  134 , process attributes  136 , and policy attributes  138 . In some embodiments, the data lake  130  can also include repositories for VM or container attributes, application attributes, tenant attributes, network topology, application dependency maps, cluster attributes, etc. 
     The flow attributes  132  relate to information about flows traversing the network. A flow is generally one or more packets sharing certain attributes that are sent within a network within a specified period of time. The flow attributes  132  can include packet header fields such as a source address (e.g., Internet Protocol (IP) address, Media Access Control (MAC) address, Domain Name System (DNS) name, or other network address), source port, destination address, destination port, protocol type, class of service, among other fields. The source address may correspond to a first endpoint (e.g., network device, physical server, virtual partition, etc.) of the network, and the destination address may correspond to a second endpoint, a multicast group, or a broadcast domain. The flow attributes  132  can also include aggregate packet data such as flow start time, flow end time, number of packets for a flow, number of bytes for a flow, the union of TCP flags for a flow, among other flow data. 
     The host and/or endpoint attributes  134  describe host and/or endpoint data for each flow, and can include host and/or endpoint name, network address, operating system, CPU usage, network usage, disk space, ports, logged users, scheduled jobs, open files, and information regarding files and/or directories stored on a host and/or endpoint (e.g., presence, absence, or modifications of log files, configuration files, device special files, or protected electronic information). As discussed, in some embodiments, the host and/or endpoints attributes  134  can also include the out-of-band data  114  regarding hosts such as power level, temperature, and physical location (e.g., room, row, rack, cage door position, etc.) or the third party data  116  such as whether a host and/or endpoint is on an IP watch list or otherwise associated with a security threat, Whois data, or geocoordinates. In some embodiments, the out-of-band data  114  and the third party data  116  may be associated by process, user, flow, or other more granular or less granular network element or network communication. 
     The process attributes  136  relate to process data corresponding to each flow, and can include process name (e.g., bash, httpd, netstat, etc.), ID, parent process ID, path (e.g., /usr2/username/bin/, /usr/local/bin, /usr/bin, etc.), CPU utilization, memory utilization, memory address, scheduling information, nice value, flags, priority, status, start time, terminal type, CPU time taken by the process, the command that started the process, and information regarding a process owner (e.g., user name, ID, user&#39;s real name, e-mail address, user&#39;s groups, terminal information, login time, expiration date of login, idle time, and information regarding files and/or directories of the user). 
     The policy attributes  138  contain information relating to network policies. Policies establish whether a particular flow is allowed or denied by the network as well as a specific route by which a packet traverses the network. Policies can also be used to mark packets so that certain kinds of traffic receive differentiated service when used in combination with queuing techniques such as those based on priority, fairness, weighted fairness, token bucket, random early detection, round robin, among others. The policy attributes  138  can include policy statistics such as a number of times a policy was enforced or a number of times a policy was not enforced. The policy attributes  138  can also include associations with network traffic data. For example, flows found to be non-conformant can be linked or tagged with corresponding policies to assist in the investigation of non-conformance. 
     The analytics engine  110  may include any number of engines  150 , including for example, a flow engine  152  for identifying flows (e.g., flow engine  152 ) or an attacks engine  154  for identify attacks to the network. In some embodiments, the analytics engine can include a separate distributed denial of service (DDoS) attack engine  155  for specifically detecting DDoS attacks. In other embodiments, a DDoS attack engine may be a component or a sub-engine of a general attacks engine. In some embodiments, the attacks engine  154  and/or the DDoS engine  155  can use machine learning techniques to identify security threats to a network. For example, the attacks engine  154  and/or the DDoS engine  155  can be provided with examples of network states corresponding to an attack and network states corresponding to normal operation. The attacks engine  154  and/or the DDoS engine  155  can then analyze network traffic data to recognize when the network is under attack. In some embodiments, the network can operate within a trusted environment for a time to establish a baseline for normal network operation for the attacks engine  154  and/or the DDoS. 
     The analytics engine  110  may further include a search engine  156 . The search engine  156  may be configured, for example to perform a structured search, an NLP (Natural Language Processing) search, or a visual search. Data may be provided to the engines from one or more processing components. 
     The analytics engine  110  can also include a policy engine  158  that manages network policy, including creating and/or importing policies, monitoring policy conformance and non-conformance, enforcing policy, simulating changes to policy or network elements affecting policy, among other policy-related tasks. 
     The ADM module  140  can determine dependencies of applications of the network. That is, particular patterns of traffic may correspond to an application, and the interconnectivity or dependencies of the application can be mapped to generate a graph for the application (i.e., an application dependency mapping). In this context, an application refers to a set of networking components that provides connectivity for a given set of workloads. For example, in a three-tier architecture for a web application, first endpoints of the web tier, second endpoints of the application tier, and third endpoints of the data tier make up the web application. The ADM module  140  can receive input data from various repositories of the data lake  130  (e.g., the flow attributes  132 , the host and/or endpoint attributes  134 , the process attributes  136 , etc.). The ADM module  140  may analyze the input data to determine that there is first traffic flowing between external endpoints on port  80  of the first endpoints corresponding to Hypertext Transfer Protocol (HTTP) requests and responses. The input data may also indicate second traffic between first ports of the first endpoints and second ports of the second endpoints corresponding to application server requests and responses and third traffic flowing between third ports of the second endpoints and fourth ports of the third endpoints corresponding to database requests and responses. The ADM module  140  may define an ADM for the web application as a three-tier application including a first EPG comprising the first endpoints, a second EPG comprising the second endpoints, and a third EPG comprising the third endpoints. 
     The presentation module  112  can include an application programming interface (API) or command line interface (CLI)  160 , a security information and event management (STEM) interface  162 , and a web front-end  164 . As the analytics engine  110  processes network traffic and corresponding data and generates analytics data, the analytics data may not be in a human-readable form or it may be too voluminous for a user to navigate. The presentation module  112  can take the analytics data generated by analytics engine  110  and further summarize, filter, and organize the analytics data as well as create intuitive presentations for the analytics data. 
     In some embodiments, the API or CLI  160  can be implemented using Hadoop® Hive from Apache® for the back end, and Java® Database Connectivity (JDBC) from Oracle® Corporation of Redwood Shores, Calif., as an API layer. Hive is a data warehouse infrastructure that provides data summarization and ad hoc querying. Hive provides a mechanism to query data using a variation of structured query language (SQL) that is called HiveQL. JDBC is an application programming interface (API) for the programming language Java®, which defines how a client may access a database. 
     In some embodiments, the SIEM interface  162  can be implemented using Kafka for the back end, and software provided by Splunk®, Inc. of San Francisco, Calif. as the SIEM platform. Kafka is a distributed messaging system that is partitioned and replicated. Kafka uses the concept of topics. Topics are feeds of messages in specific categories. In some embodiments, Kafka can take raw packet captures and telemetry information from the data mover  108  as input, and output messages to a STEM platform, such as Splunk®. The Splunk® platform is utilized for searching, monitoring, and analyzing machine-generated data. 
     In some embodiments, the web front-end  164  can be implemented using software provided by MongoDB®, Inc. of New York, N.Y. and Hadoop® ElasticSearch from Apache® for the back-end, and Ruby on Rails™ as the web application framework. MongoDB® is a document-oriented NoSQL database based on documents in the form of JavaScript® Object Notation (JSON) with dynamic schemas. ElasticSearch is a scalable and real-time search and analytics engine that provides domain-specific language (DSL) full querying based on JSON. Ruby on Rails™ is model-view-controller (MVC) framework that provides default structures for a database, a web service, and web pages. Ruby on Rails™ relies on web standards such as JSON or extensible markup language (XML) for data transfer, and hypertext markup language (HTML), cascading style sheets, (CS S), and JavaScript® for display and user interfacing. 
     Although  FIG. 1  illustrates an example configuration of the various components of a network traffic monitoring system, those of skill in the art will understand that the components of the network traffic monitoring system  100  or any system described herein can be configured in a number of different ways and can include any other type and number of components. For example, the sensors  104 , the collectors  106 , the data mover  108 , and the data lake  130  can belong to one hardware and/or software module or multiple separate modules. Other modules can also be combined into fewer components and/or further divided into more components. 
       FIG. 2  illustrates an example of a network environment  200  in accordance with an embodiment. In some embodiments, a network traffic monitoring system, such as the network traffic monitoring system  100  of  FIG. 1 , can be implemented in the network environment  200 . It should be understood that, for the network environment  200  and any environment discussed herein, there can be additional or fewer nodes, devices, links, networks, or components in similar or alternative configurations. Embodiments with different numbers and/or types of clients, networks, nodes, cloud components, servers, software components, devices, virtual or physical resources, configurations, topologies, services, appliances, deployments, or network devices are also contemplated herein. Further, the network environment  200  can include any number or type of resources, which can be accessed and utilized by clients or tenants. The illustrations and examples provided herein are for clarity and simplicity. 
     The network environment  200  can include a network fabric  202 , a Layer 2 (L2) network  204 , a Layer 3 (L3) network  206 , and servers  208   a ,  208   b ,  208   c ,  208   d , and  208   e  (collectively,  208 ). The network fabric  202  can include spine switches  210   a ,  210   b ,  210   c , and  210   d  (collectively, “ 210 ”) and leaf switches  212   a ,  212   b ,  212   c ,  212   d , and  212   e  (collectively, “ 212 ”). The spine switches  210  can connect to the leaf switches  212  in the network fabric  202 . The leaf switches  212  can include access ports (or non-fabric ports) and fabric ports. The fabric ports can provide uplinks to the spine switches  210 , while the access ports can provide connectivity to endpoints (e.g., the servers  208 ), internal networks (e.g., the L2 network  204 ), or external networks (e.g., the L3 network  206 ). 
     The leaf switches  212  can reside at the edge of the network fabric  202 , and can thus represent the physical network edge. For instance, in some embodiments, the leaf switches  212   d  and  212   e  operate as border leaf switches in communication with edge devices  214  located in the external network  206 . The border leaf switches  212   d  and  212   e  may be used to connect any type of external network device, service (e.g., firewall, deep packet inspector, traffic monitor, load balancer, etc.), or network (e.g., the L3 network  206 ) to the fabric  202 . 
     Although the network fabric  202  is illustrated and described herein as an example leaf-spine architecture, one of ordinary skill in the art will readily recognize that various embodiments can be implemented based on any network topology, including any data center or cloud network fabric. Indeed, other architectures, designs, infrastructures, and variations are contemplated herein. For example, the principles disclosed herein are applicable to topologies including three-tier (including core, aggregation, and access levels), fat tree, mesh, bus, hub and spoke, etc. Thus, in some embodiments, the leaf switches  212  can be top-of-rack switches configured according to a top-of-rack architecture. In other embodiments, the leaf switches  212  can be aggregation switches in any particular topology, such as end-of-row or middle-of-row topologies. In some embodiments, the leaf switches  212  can also be implemented using aggregation switches. 
     Moreover, the topology illustrated in  FIG. 2  and described herein is readily scalable and may accommodate a large number of components, as well as more complicated arrangements and configurations. For example, the network may include any number of fabrics  202 , which may be geographically dispersed or located in the same geographic area. Thus, network nodes may be used in any suitable network topology, which may include any number of servers, virtual machines or containers, switches, routers, appliances, controllers, gateways, or other nodes interconnected to form a large and complex network. Nodes may be coupled to other nodes or networks through one or more interfaces employing any suitable wired or wireless connection, which provides a viable pathway for electronic communications. 
     Network communications in the network fabric  202  can flow through the leaf switches  212 . In some embodiments, the leaf switches  212  can provide endpoints (e.g., the servers  208 ), internal networks (e.g., the L2 network  204 ), or external networks (e.g., the L3 network  206 ) access to the network fabric  202 , and can connect the leaf switches  212  to each other. In some embodiments, the leaf switches  212  can connect endpoint groups (EPGs) to the network fabric  202 , internal networks (e.g., the L2 network  204 ), and/or any external networks (e.g., the L3 network  206 ). EPGs are groupings of applications, or application components, and tiers for implementing forwarding and policy logic. EPGs can allow for separation of network policy, security, and forwarding from addressing by using logical application boundaries. EPGs can be used in the network environment  200  for mapping applications in the network. For example, EPGs can comprise a grouping of endpoints in the network indicating connectivity and policy for applications. 
     As discussed, the servers  208  can connect to the network fabric  202  via the leaf switches  212 . For example, the servers  208   a  and  208   b  can connect directly to the leaf switches  212   a  and  212   b , which can connect the servers  208   a  and  208   b  to the network fabric  202  and/or any of the other leaf switches. The servers  208   c  and  208   d  can connect to the leaf switches  212   b  and  212   c  via the L2 network  204 . The servers  208   c  and  208   d  and the L2 network  204  make up a local area network (LAN). LANs can connect nodes over dedicated private communications links located in the same general physical location, such as a building or campus. 
     The WAN  206  can connect to the leaf switches  212   d  or  212   e  via the L3 network  206 . WANs can connect geographically dispersed nodes over long-distance communications links, such as common carrier telephone lines, optical light paths, synchronous optical networks (SONET), or synchronous digital hierarchy (SDH) links. LANs and WANs can include L2 and/or L3 networks and endpoints. 
     The Internet is an example of a WAN that connects disparate networks throughout the world, providing global communication between nodes on various networks. The nodes typically communicate over the network by exchanging discrete frames or packets of data according to predefined protocols, such as the Transmission Control Protocol/Internet Protocol (TCP/IP). In this context, a protocol can refer to a set of rules defining how the nodes interact with each other. Computer networks may be further interconnected by an intermediate network node, such as a router, to extend the effective size of each network. The endpoints  208  can include any communication device or component, such as a computer, server, blade, hypervisor, virtual machine, container, process (e.g., running on a virtual machine), switch, router, gateway, host, device, external network, etc. 
     In some embodiments, the network environment  200  also includes a network controller running on the host  208   a . The network controller is implemented using the Application Policy Infrastructure Controller (APIC™) from Cisco®. The APIC™ provides a centralized point of automation and management, policy programming, application deployment, and health monitoring for the fabric  202 . In some embodiments, the APIC™ is operated as a replicated synchronized clustered controller. In other embodiments, other configurations or software-defined networking (SDN) platforms can be utilized for managing the fabric  202 . 
     In some embodiments, a physical server  208  may have instantiated thereon a hypervisor  216  for creating and running one or more virtual switches (not shown) and one or more virtual machines  218 , as shown for the host  208   b . In other embodiments, physical servers may run a shared kernel for hosting containers. In yet other embodiments, the physical server  208  can run other software for supporting other virtual partitioning approaches. Networks in accordance with various embodiments may include any number of physical servers hosting any number of virtual machines, containers, or other virtual partitions. Hosts may also comprise blade/physical servers without virtual machines, containers, or other virtual partitions, such as the servers  208   a ,  208   c ,  208   d , and  208   e.    
     The network environment  200  can also integrate a network traffic monitoring system, such as the network traffic monitoring system  100  shown in  FIG. 1 . For example, the network traffic monitoring system of  FIG. 2  includes sensors  220   a ,  220   b ,  220   c , and  220   d  (collectively, “220”), collectors  222 , and an analytics engine, such as the analytics engine  110  of  FIG. 1 , executing on the server  208   e . The analytics engine  208   e  can receive and process network traffic data collected by the collectors  222  and detected by the sensors  220  placed on nodes located throughout the network environment  200 . Although the analytics engine  208   e  is shown to be a standalone network appliance in  FIG. 2 , it will be appreciated that the analytics engine  208   e  can also be implemented as a virtual partition (e.g., VM or container) that can be distributed onto a host or cluster of hosts, software as a service (SaaS), or other suitable method of distribution. In some embodiments, the sensors  220  run on the leaf switches  212  (e.g., the sensor  220   a ), the hosts  208  (e.g., the sensor  220   b ), the hypervisor  216  (e.g., the sensor  220   c ), and the VMs  218  (e.g., the sensor  220   d ). In other embodiments, the sensors  220  can also run on the spine switches  210 , virtual switches, service appliances (e.g., firewall, deep packet inspector, traffic monitor, load balancer, etc.) and in between network elements. In some embodiments, sensors  220  can be located at each (or nearly every) network component to capture granular packet statistics and data at each hop of data transmission. In other embodiments, the sensors  220  may not be installed in all components or portions of the network (e.g., shared hosting environment in which customers have exclusive control of some virtual machines). 
     As shown in  FIG. 2 , a host may include multiple sensors  220  running on the host (e.g., the host sensor  220   b ) and various components of the host (e.g., the hypervisor sensor  220   c  and the VM sensor  220   d ) so that all (or substantially all) packets traversing the network environment  200  may be monitored. For example, if one of the VMs  218  running on the host  208   b  receives a first packet from the WAN  206 , the first packet may pass through the border leaf switch  212   d , the spine switch  210   b , the leaf switch  212   b , the host  208   b , the hypervisor  216 , and the VM. Since all or nearly all of these components contain a respective sensor, the first packet will likely be identified and reported to one of the collectors  222 . As another example, if a second packet is transmitted from one of the VMs  218  running on the host  208   b  to the host  208   d , sensors installed along the data path, such as at the VM  218 , the hypervisor  216 , the host  208   b , the leaf switch  212   b , and the host  208   d  will likely result in capture of metadata from the second packet. 
       FIG. 3  illustrates an example of a data pipeline  300  for generating network insights based on collected network information. The insights generated may include, for example, discovered applications or inventories, application dependencies, policies, efficiencies, resource and bandwidth usage, and network flows can be determined for the network using the network traffic data. In some embodiments, the data pipeline  300  can be directed by a network traffic monitoring system, such as the network traffic monitoring system  100  of  FIG. 1 ; an analytics engine, such as the analytics engine  110  of  FIG. 1 ; or other network service or network appliance. For example, an analytics engine  110  can be configured to discover of applications running in the network, map the applications&#39; interdependencies, generate a set of proposed network policies for implementation, and monitor policy conformance and non-conformance among other network-related tasks. 
     The data pipeline  300  includes a data collection stage  302  in which network traffic data and corresponding data (e.g., host data, process data, user data, etc.) are captured by sensors (e.g., the sensors  104  of  FIG. 1 ) located throughout the network. The data may comprise, for example, raw flow data and raw process data. As discussed, the data can be captured from multiple perspectives to provide a comprehensive view of the network. The data collected may also include other types of information, such as tenant information, virtual partition information, out-of-band information, third party information, and other relevant information. In some embodiments, the flow data and associated data can be aggregated and summarized daily or according to another suitable increment of time, and flow vectors, process vectors, host vectors, and other feature vectors can be calculated during the data collection stage  302 . This can substantially reduce processing. 
     The data pipeline  300  may also include an input data stage  304  in which a network or security administrator or other authorized user may configure insight generation by selecting the date range of the flow data and associated data to analyze, and those nodes for which the administrator wants to analyze. In some embodiments, the administrator can also input side information, such as server load balance, route tags, and previously identified clusters during the input data stage  304 . In other embodiments, the side information can be automatically pulled or another network element can push the side information. 
     The next stage of the data pipeline  300  is pre-processing  306 . During the pre-processing stage  306 , nodes of the network are partitioned into selected node and dependency node subnets. Selected nodes are those nodes for which the user requests application dependency maps and cluster information. Dependency nodes are those nodes that are not explicitly selected by the users for an ADM run but are nodes that communicate with the selected nodes. To obtain the partitioning information, edges of an application dependency map (i.e., flow data) and unprocessed feature vectors can be analyzed. 
     Other tasks can also be performed during the pre-processing stage  306 , including identifying dependencies of the selected nodes and the dependency nodes; replacing the dependency nodes with tags based on the dependency nodes&#39; subnet names; extracting feature vectors for the selected nodes, such as by aggregating daily vectors across multiple days, calculating term frequency-inverse document frequency (tf-idf), and normalizing the vectors (e.g., € 2  normalization); and identifying existing clusters. 
     In some embodiments, the pre-processing stage  306  can include early feature fusion pre-processing. Early fusion is a fusion scheme in which features are combined into a single representation. Features may be derived from various domains (e.g., network, host, virtual partition, process, user, etc.), and a feature vector in an early fusion system may represent the concatenation of disparate feature types or domains. 
     Early fusion may be effective for features that are similar or have a similar structure (e.g., fields of TCP and UDP packets or flows). Such features may be characterized as being a same type or being within a same domain. Early fusion may be less effective for distant features or features of different types or domains (e.g., flow-based features versus process-based features). Thus, in some embodiments, only features in the network domain (i.e., network traffic-based features, such as packet header information, number of packets for a flow, number of bytes for a flow, and similar data) may be analyzed. In other embodiments, analysis may be limited to features in the process domain (i.e., process-based features, such as process name, parent process, process owner, etc.). In yet other embodiments, feature sets in other domains (e.g., the host domain, virtual partition domain, user domain, etc.) may be the. 
     After pre-processing, the data pipeline  300  may proceed to an insight generation stage  308 . During the insight generation stage  308 , the data collected and inputted into the data pipeline  300  may be used to generate various network insights. For example, an analytics engine  110  can be configured to discover of applications running in the network, map the applications&#39; interdependencies, generate a set of proposed network policies for implementation, and monitor policy conformance and non-conformance among other network-related tasks. Various machine learning techniques can be implemented to analyze feature vectors within a single domain or across different domains to generate insights. Machine learning is an area of computer science in which the goal is to develop models using example observations (i.e., training data), that can be used to make predictions on new observations. The models or logic are not based on theory but are empirically based or data-driven. 
     After clusters are identified, the data pipeline  300  can include a post-processing stage  310 . The post-processing stage  310  can include tasks such as filtering insight data, converting the insight data into a consumable format, or any other preparations needed to prepare the insight data for consumption by an end user. At the output stage  312 , the generated insights may be provided to an end user. The end user may be, for example a network administrator, a third-party computing system, a computing system in the network, or any other entity configured to receive the insight data. In some cases, the insight data may be configured to be displayed on a screen or provided to a system for further processing, consumption, or storage. 
     As noted above, a network traffic monitoring system may be configured to continually collect network data and generate various insights based on the collected network data. This network data and the insights may be updated over time and each set of network data and/or insights may provide a network snapshot or view of the state of the network for a particular period of time. The network snapshot may be generated periodically over time or in response to one or more events. Events may include, for example, a change to a network policy or configuration; an application experiencing latency that exceeds an application latency threshold; the network experiencing latency that exceeds a network latency threshold; failure of server, network device, or other network element; and similar circumstances. Various network snapshots may further be compared in order to identify changes in the state of the network over time and be used to provide additional insights into the operations of the network. 
     However, each network snapshot for an entire network or network cluster, may be quite large in size. The network may include a large number of nodes and a sensor may be implemented on some or all of the nodes in the network. Nodes may include, for example, a virtual partition (e.g., VM or container); a hypervisor or shared kernel managing one or more virtual partitions and/or physical servers, an application-specific integrated circuit (ASIC) of a switch, router, gateway, or other networking device, or a packet capture (pcap) appliance (e.g., a standalone packet monitor, a device connected to a network devices monitoring port, a device connected in series along a main trunk of a datacenter, or similar device), servers, end-user devices, or other element of a network. The amount of data generated by these sensors and the insights that may be derived from the data may be quite large. Furthermore, the network state may be updated often, causing several network snapshots to be created and created often. 
     There are many technical limitations to transmitting and receiving that amount of data often enough for end users to stay in sync, especially when multiple network snapshots are generated in relatively quick succession. Additionally, in some cases, the network snapshots may be requested by a large number of end users or consumers of the network snapshots. Communication of such large amounts of data to multiple entities may be difficult for the network traffic monitoring system to transmit and difficult for each entity to receive, especially when the network traffic monitoring system and/or each receiving entity may crash or deal with transmission errors. Aspects of the subject technology address these technical problems by fragmenting each network snapshot into smaller chunks or segments and using a stream processing service to publish the network snapshots to one or more subscribers. 
       FIG. 4  illustrates an example of a network traffic monitoring system  410  providing network snapshots to subscribers  430 , in accordance various embodiments. An analytics engine  415  of a network monitoring system  410  may be configured to collect the network data generated by sensors deployed in a network, derive insights based on the network data, and generate network snapshots based on the network data and/or insights. The network snapshots may be generated periodically over time (e.g., every 15 minutes) and/or in response to network changes or events. Each network snapshot that is generated by the analytics engine  415  may be quite large in size. Accordingly, the analytics engine  415  may be configured to partition a network snapshot into smaller network snapshot segments (e.g., a 10 megabyte segment) and transmit the network snapshot segments to a stream processing service  420 . 
     According to some embodiment, the stream processing service  420  may be implemented in the network traffic monitoring system  410 , as part of the analytics engine  415 , or in the network managed by the network traffic monitoring system  410 . In other embodiments, however, the stream processing service  420  may be outside of the network managed by the network traffic monitoring system  410 . The stream processing service  420  is configured to receive network snapshots or network snapshot segments from the analytics engine  415  and publish the network snapshot segments to one or more subscribers via a snapshot stream  425 . 
     According to other embodiments, the analytics engine  415  may provide the network snapshots to the stream processing service  420  and the stream processing service  420  may partition each snapshot into smaller network snapshot segments for the snapshot stream  425 . 
     A subscriber  430  may be a device, application, or other entity that can make use of the network snapshots provided by the analytics engine  415 . For example, the subscriber  430  may use the network snapshots to update network policies, generate additional insights, or store for analysis. The stream reader  435  may be a component of the subscriber  430  that subscribes to the snapshot stream  425  of the stream processing service  420 . The stream reader  435  is further configured to receive messages from the stream processing service  420  that include one or more network snapshot segments and reconstruct the network snapshot based on the received network snapshot segments. The reconstruction of a network snapshot faces additional technical obstacles in cases where subscribers  430  start receiving network snapshot segments in the middle of a network snapshot or the sequence of network snapshot segments that are received is broken. 
     Various embodiments of the subject technology address these and other technical obstacles by having the analytics engine  415  annotate or tag each network snapshot segment with metadata that may be used by the stream reader  435  to reconstruct a network snapshot. The metadata may include, for example a “start” label, an “end” label, and/or a number associated with the location of the network snapshot segment within the network snapshot. For example, a first segment of a network snapshot may be tagged with the “start” label and a last segment of the network snapshot may be tagged with the “end” label. Each segment of a snapshot may also be numbered (e.g., from 0 to n, where n is assigned to the last segment). The network segments of the network snapshot are then provided to the stream processing service  420  for distribution in a snapshot output stream  425 . 
     Once the stream reader  435  subscribes to the snapshot stream  425  or otherwise begins receiving stream messages from the stream processing service  420 , the stream reader  435  may use the tags (e.g., start/end tags) and/or the enumeration of a received network snapshot segment to determine which network snapshot segment has been received and which network snapshot segments, if any, should be requested from the stream processing service. For example, if the first network snapshot segment received by the stream reader  435  is segment 5, the stream reader  435  may transmit requests for segments 0-4 from the stream processing service  420  or request transmission of the stream starting from 5 segments back from the recently received network snapshot segment (e.g., rewinding the stream). Once a network snapshot segment tagged with the “end” label is received, the stream reader  435  may compile the network snapshot segments into a network snapshot. 
       FIG. 5  illustrates an example of a process  500  for compiling a network snapshot, in accordance with an embodiment. It should be understood that, for any process discussed herein, there can be additional, fewer, or alternative steps performed in similar or alternative orders, or in parallel, within the scope of the various embodiments unless otherwise stated. The process  500  can be performed by a computing device, and particularly, a subscriber device (e.g., the subscriber  430  of  FIG. 4 ), a stream reader application (e.g., the stream reader  435  of  FIG. 4 ), or similar system. 
     The subscriber device may subscribe to a snapshot stream provided by a stream processing service. The stream processing service may be configured to publish network snapshot segments to potentially a large number of subscribers. The network snapshot segments may be provided to subscribers in a series of messages that each include a network snapshot segment and metadata for the network snapshot segment (e.g., labels, tags, enumerations, segment identifiers, network snapshot identifiers, etc.) that may be used to indicate a position of the network snapshot segment within the snapshot stream. 
     Once the subscriber device is subscribed to the snapshot stream, at operation  505 , the subscriber device may receive a message containing a network snapshot segment from a stream processing service. Based on the metadata also contained in the message, the subscriber device may identify an offset associated with the network snapshot segment received in the message at operation  510 . Based on the offset, the subscriber device may determine whether the network snapshot segment is the first segment for the network snapshot or whether additional network snapshot segments should be requested at operation  515 . 
     For example, if the metadata for the network snapshot segment contains a “start” label or a “0” for the enumerated snapshot offset identifier, the subscriber device may determine that the offset for the network snapshot segment is 0, indicating that the network snapshot segment received in the message is the first network snapshot segment for a network snapshot. Accordingly, the subscriber device has not missed any network snapshot segments for the current network snapshot. The subscriber device can continue to operation  525  and receive subsequent network snapshot segments for the network snapshot from the snapshot stream and compile the network snapshot without having to request other network snapshot segments that the subscriber device has missed. 
     If, on the other hand, the metadata for the network snapshot segment does not contain the “start” label or the “0” value for the enumerated snapshot segment offset identifier, the subscriber device may determine that the network snapshot segment received in the message is not the first network snapshot segment for the network snapshot. If the subscriber device has not received the previous network snapshot segments for the network snapshot, the subscriber device may request additional messages containing the previous network snapshot segments from the stream processing service at operation  520 . 
     There may be several reasons for the subscriber device not having received one or more of the previous network snapshot segments. For example, the subscriber device may have just subscribed to the snapshot stream and the network snapshot segment received at operation  505  may be the first segment received for the network snapshot. The subscriber device or the stream reader associated with the subscriber device may have just restarted operation or one or more of the previous snapshot segments may not have been transmitted properly based on network failures, interface failures, or errors by the subscriber device or the stream processing service. 
     As an illustrative example, the metadata for the network snapshot segment may contain a snapshot offset identifier value of “8.” The subscriber device may determine that the offset for the network snapshot segment is 8, indicating that there are 8 previous network snapshot segments (e.g., network snapshot segments with offset identifier values 0-7) for the current network snapshot before the current network snapshot. If the subscriber device has not received these previous network snapshot segments, the subscriber device may request them from the stream processing service at operation  520 . These network stream segments may be provided out-of-stream. That is, the stream processing service may provide them separately to the subscriber device upon request, outside the normal sequential operation of the snapshot stream. 
     While the requested network snapshot segments are being sent by the stream processing service and/or after they are received by the subscriber device, the subscriber device can continue receiving additional message from the snapshot stream at operation  525 . Once the last network snapshot segment for a network snapshot is received, the subscriber device may compile the network snapshot segments into a network snapshot at operation  530 . The subscriber device may identify the last network snapshot segment for the network snapshot because the metadata associated with the network snapshot segment may include an “end” or “last” label. 
     After the network snapshot segments for a first network snapshot are received and compiled, the subscriber device may continue to receive messages from the snapshot stream containing additional network snapshot segments for subsequent network snapshots. As a result, a series of network snapshots generated by a network traffic monitoring system may be provided to a stream processing service and provided to one or more subscribers in network snapshot segments that may be compiled by the subscriber system. These network snapshots may further processed or analyzed by the subscriber device for further use by the subscriber device or downstream consumers. For example, according to some embodiments, after a network snapshot is compiled, the subscriber device or the stream reader associated with the subscriber device may convert the network snapshot into a generic format that may be consumed by a group of diverse downstream consumers. 
     As noted above, the network snapshots may represent the state of a network or information associated with the network during a particular time period. Accordingly, multiple network snapshots that are compiled by the subscriber system may be compared in order to identify changes in the state of the network over time and be used to provide additional insights into the operations of the network. The subscriber system may further be configured to compare two or more network snapshots, identify the differences between the network snapshots, and provide the differences to a downstream consumer. 
       FIG. 6  illustrates an example of a process  600  for identifying a difference between network snapshots, in accordance with an embodiment. It should be understood that, for any process discussed herein, there can be additional, fewer, or alternative steps performed in similar or alternative orders, or in parallel, within the scope of the various embodiments unless otherwise stated. The process  600  can be performed by a computing device, and particularly, a subscriber device (e.g., the subscriber  430  of  FIG. 4 ), a stream reader application (e.g., the stream reader  435  of  FIG. 4 ), or similar system. 
     At operation  605 , a stream reader or similar system may receive from a stream processing system a set of messages that contain network snapshot segments. The messages may be received based on process  500  of  FIG. 5  or a similar process. At operation  610 , the stream reader may compile the network snapshot segments into two or more network snapshots. For the sake of illustrating the process of  FIG. 6 , a first network snapshot and a second network snapshot may be compiled. 
     At operation  615 , the stream reader compares the compiled network snapshots to identify a difference between the first network snapshot and the second network snapshot. This difference may represent a change in a network policy or other data associated with the network. At operation  620 , the difference may then be provided to one or more consumer systems. In some cases, the difference may be converted into a generic format that is more accessible to the consumer systems. The consumer systems may be downstream consumers of network information and may be configured to use the difference to update network information stored by the consumer system rather than store the entire network snapshot. By using the difference to update the network information rather than an entire network snapshot, network resources (e.g., bandwidth), memory, processing time, and other computing resources may be conserved or more efficiently utilized. 
     According to some embodiments, downstream consumers systems of the network information may be interested in different portions of the network snapshots. For example, one consumer system may be interested in one set of endpoint groups in the network while another consumer system may be interested in another set of endpoint groups. These two sets of endpoint groups may or may not have overlapping portions. In order to reduce the information provided to the consumer system and further improve the efficient use of computing resources, the stream reader may filter out portions of the network snapshots or the identified differences between network snapshots provided to each consumer system based on filtering criteria associated with each consumer system. The filtering criteria may include, for example, endpoint group identifiers, a list of IP addresses of interest, a list of network policies of interest, or any other criteria that may be used to filter, categorize, or group network information or insights generated by the network traffic monitoring system. 
     Various embodiments relate to a computer-implemented method comprising receiving a set of messages associated with an output stream of a stream processing service, wherein each message in the set of messages includes a network snapshot segment. The method includes compiling the network snapshot segments from the set of messages into a first network snapshot and a second network snapshot, identifying a difference between the first network snapshot and the second network snapshot, and providing the difference to a consumer system. 
     The first network snapshot may correspond to a state of a network during a first time period and the second network snapshot may correspond to the state of the network during a second time period. The state of the network may include network policies for the network. The difference between the first network snapshot and the second network snapshot may indicate a change in a state of a network. 
     The method may further include receiving, from the consumer system, filtering criteria for the first network snapshot and the second network snapshot and filtering the difference between the first network snapshot and the second network snapshot based on the filtering criteria. The method may further include receiving, from the consumer system, filtering criteria for the first network snapshot and the second network snapshot and filtering the first network snapshot and the second network snapshot based on the filtering criteria. The filtering criteria may include a list of IP addresses associated with the consumer system. 
     The method may further include receiving a first message associated with the output stream, wherein the first message includes a first network snapshot segment and an offset for the first network snapshot segment, determining, based on the offset, that at least one additional network snapshot segment associated with the output stream has not been previously received, and transmit, to the stream processing service, a request for the at least one additional network snapshot segment. The request of the at least one additional network snapshot segment may be for an out-of-stream message outside a sequence of messages associated with the output stream, wherein the out-of-stream message includes the at least one additional network snapshot segment. 
     Various embodiments relate to a non-transitory computer-readable medium having computer readable instructions that, upon being executed by a processor, cause the processor to receive a set of network snapshot segments from an output stream of a stream processing service, compile the set of network snapshot segments from the output stream into a first network snapshot and a second network snapshot, and compare the first network snapshot and the second network snapshot to identify a difference between the first network snapshot and the second network snapshot. 
     Additional instructions may cause the processor to provide the difference to a consumer system, receive, from a consumer system, filtering criteria for the first network snapshot and the second network snapshot, or filter the first network snapshot and the second network snapshot based on the filtering criteria. Each network snapshot segment in the set of network snapshot segments may be associated with an offset, and wherein the first network snapshot and the second network snapshot is compiled based on the offsets for each network snapshot segment in the set of network snapshot segments. 
     Various embodiments relate to a system comprising a processor and memory including instructions that, upon being executed by the processor, cause the system to receive, from a consumer system, filtering criteria for network information generated by a network traffic monitoring system, receive a set of messages associated with an output stream of a stream processing service, wherein each message in the set of messages includes a network snapshot segment, compile the network snapshot segments from the set of messages into a first network snapshot and a second network snapshot, identify a difference between the first network snapshot and the second network snapshot, wherein the difference complies with the filtering criteria, and provide the difference to an end user. The filtering criteria may be a list of IP addresses associated from the consumer system. 
       FIG. 7A  and  FIG. 7B  illustrate systems in accordance with various embodiments. The more appropriate system will be apparent to those of ordinary skill in the art when practicing the various embodiments. Persons of ordinary skill in the art will also readily appreciate that other systems are possible. 
       FIG. 7A  illustrates an example architecture for a bus computing system  700  wherein the components of the system are in electrical communication with each other using a bus  705 . The computing system  700  can include a processing unit (CPU or processor)  710  and a system bus  705  that may couple various system components including the system memory  715 , such as read only memory (ROM) in a storage device  770  and random access memory (RAM)  775 , to the processor  710 . The computing system  700  can include a cache  712  of high-speed memory connected directly with, in close proximity to, or integrated as part of the processor  710 . The computing system  700  can copy data from the memory  715  and/or the storage device  730  to the cache  712  for quick access by the processor  710 . In this way, the cache  712  can provide a performance boost that avoids processor delays while waiting for data. These and other modules can control or be configured to control the processor  710  to perform various actions. Other system memory  715  may be available for use as well. The memory  715  can include multiple different types of memory with different performance characteristics. The processor  710  can include any general purpose processor and a hardware module or software module, such as module  1   732 , module  2   734 , and module  3   736  stored in storage device  730 , configured to control the processor  710  as well as a special-purpose processor where software instructions are incorporated into the actual processor design. The processor  710  may essentially 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 system  700 , an input device  745  can represent any number of input mechanisms, such as a microphone for speech, a touch-protected screen for gesture or graphical input, keyboard, mouse, motion input, speech and so forth. An output device  735  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 system  700 . The communications interface  740  can govern and manage the user input and system output. There may be no restriction on operating on any particular hardware arrangement and therefore the basic features here may easily be substituted for improved hardware or firmware arrangements as they are developed. 
     Storage device  730  can be a non-volatile memory and can be a hard disk or other types of computer readable media which can store data that are accessible by a computer, such as magnetic cassettes, flash memory cards, solid state memory devices, digital versatile disks, cartridges, random access memories (RAMs)  725 , read only memory (ROM)  720 , and hybrids thereof. 
     The storage device  730  can include software modules  732 ,  734 ,  736  for controlling the processor  710 . Other hardware or software modules are contemplated. The storage device  730  can be connected to the system bus  705 . 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  710 , bus  705 , output device  735 , and so forth, to carry out the function. 
       FIG. 7B  illustrates an example architecture for a chipset computing system  750  that can be used in accordance with an embodiment. The computing system  750  can include a processor  755 , representative of any number of physically and/or logically distinct resources capable of executing software, firmware, and hardware configured to perform identified computations. The processor  755  can communicate with a chipset  760  that can control input to and output from the processor  755 . In this example, the chipset  760  can output information to an output device  765 , such as a display, and can read and write information to storage device  770 , which can include magnetic media, and solid state media, for example. The chipset  760  can also read data from and write data to RAM  775 . A bridge  780  for interfacing with a variety of user interface components  785  can be provided for interfacing with the chipset  760 . The user interface components  785  can include a keyboard, a microphone, touch detection and processing circuitry, a pointing device, such as a mouse, and so on. Inputs to the computing system  750  can come from any of a variety of sources, machine generated and/or human generated. 
     The chipset  760  can also interface with one or more communication interfaces  790  that can have different physical interfaces. The communication interfaces  790  can include interfaces for wired and wireless LANs, for broadband wireless networks, as well as personal area networks. Some applications of the methods for generating, displaying, and using the GUI disclosed herein can include receiving ordered datasets over the physical interface or be generated by the machine itself by processor  755  analyzing data stored in the storage device  770  or the RAM  775 . Further, the computing system  700  can receive inputs from a user via the user interface components  785  and execute appropriate functions, such as browsing functions by interpreting these inputs using the processor  755 . 
     It will be appreciated that computing systems  700  and  750  can have more than one processor  710  and  755 , respectively, or be part of a group or cluster of computing devices networked together to provide greater processing capability. 
     For clarity of explanation, in some instances the various embodiments may be presented as including individual functional blocks including functional blocks comprising devices, device components, steps or routines in a method embodied in software, or combinations of hardware and software. 
     In some embodiments the computer-readable storage devices, mediums, and memories can include a cable or wireless signal containing a bit stream and the like. However, when mentioned, non-transitory computer-readable storage media expressly exclude media such as energy, carrier signals, electromagnetic waves, and signals per se. 
     Methods according to the above-described examples can be implemented using computer-executable instructions that are stored or otherwise available from computer readable media. Such instructions can comprise, for example, instructions and data which cause or otherwise configure a general purpose computer, special purpose computer, or special purpose processing device to perform a certain function or group of functions. Portions of computer resources used can be accessible over a network. The computer executable instructions may be, for example, binaries, intermediate format instructions such as assembly language, firmware, or source code. Examples of computer-readable media that may be used to store instructions, information used, and/or information created during methods according to described examples include magnetic or optical disks, flash memory, USB devices provided with non-volatile memory, networked storage devices, and so on. 
     Devices implementing methods according to these disclosures can comprise hardware, firmware, and/or software, and can take any of a variety of form factors. Typical examples of such form factors include laptops, smart phones, small form factor personal computers, personal digital assistants, rackmount devices, standalone devices, and so on. Functionality described herein also can be embodied in peripherals or add-in cards. Such functionality can also be implemented on a circuit board among different chips or different processes executing in a single device, by way of further example. 
     The instructions, media for conveying such instructions, computing resources for executing them, and other structures for supporting such computing resources are means for providing the functions described in these disclosures. 
     Although a variety of examples and other information was used to explain aspects within the scope of the appended claims, no limitation of the claims should be implied based on particular features or arrangements in such examples, as one of ordinary skill would be able to use these examples to derive a wide variety of implementations. Further and although some subject matter may have been described in language specific to examples of structural features and/or method steps, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to these described features or acts. For example, such functionality can be distributed differently or performed in components other than those identified herein. Rather, the described features and steps are disclosed as examples of components of systems and methods within the scope of the appended claims.