Patent Publication Number: US-2021173564-A1

Title: Using network device replication in distributed storage clusters

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 15/783,229, filed on Oct. 13, 2017, the content of which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present technology pertains to distributed storage, and in particular to data replication within a distributed storage cluster of a distributed storage system. 
     BACKGROUND 
     Currently, replication of data in storage clusters is performed by a network overlay through source-based replication. In using source-based replication to replicate data, a primary node within a storage cluster coordinates with different nodes in the cluster in order to replicate data within the cluster. A primary node within a storage cluster can communicate with each node in a cluster using unicast in order to coordinate data replication within the cluster. Specifically, a primary node can send the data to each node individually through unicast transmissions. Each node can then send back to the primary node an acknowledgement indicating receipt of the data to the primary node. Using a primary node as the sole node within a cluster for coordinating data replication within the cluster is inefficient. Specifically, using only a primary node to coordinate data replication as part of source-based replication is slow and utilizes larger amounts of resources as communication occurs as the primary node has to communicate with each node individually. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe the manner in which the above-recited and other advantages and features of the disclosure can be obtained, a more particular description of the principles briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only exemplary 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. 1A  illustrates an example cloud computing architecture; 
         FIG. 1B  illustrates an example fog computing architecture; 
         FIG. 2A  illustrates a diagram of an example Network Environment; 
         FIG. 2B  illustrates another example of a Network Environment; 
         FIG. 3  depicts a placement group of a distributed storage cluster as part of a distributed storage system; 
         FIG. 4  depicts an example underlying network-based data replication system; 
         FIG. 5  illustrates a flowchart for an example method of replicating data in a placement group of a distributed storage system using an underlying network of the distributed storage system; 
         FIG. 6  illustrates a flowchart for an example method of replicating data in a placement group of a distributed storage system through multicast messaging using an underlying network of the distributed storage system; 
         FIG. 7  illustrates an example computing system; and 
         FIG. 8  illustrates an example network device. 
     
    
    
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     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. 
     Various embodiments of the disclosure are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations may be used without parting from the spirit and scope of the disclosure. Thus, the following description and drawings are illustrative and are not to be construed as limiting. Numerous specific details are described to provide a thorough understanding of the disclosure. However, in certain instances, well-known or conventional details are not described in order to avoid obscuring the description. References to one or an embodiment in the present disclosure can be references to the same embodiment or any embodiment; and, such references mean at least one of the embodiments. 
     Reference to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. 
     The terms used in this specification generally have their ordinary meanings in the art, within the context of the disclosure, and in the specific context where each term is used. Alternative language and synonyms may be used for any one or more of the terms discussed herein, and no special significance should be placed upon whether or not a term is elaborated or discussed herein. In some cases, synonyms for certain terms are provided. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any terms discussed herein is illustrative only, and is not intended to further limit the scope and meaning of the disclosure or of any example term. Likewise, the disclosure is not limited to various embodiments given in this specification. 
     Without intent to limit the scope of the disclosure, examples of instruments, apparatus, methods and their related results according to the embodiments of the present disclosure are given below. Note that titles or subtitles may be used in the examples for convenience of a reader, which in no way should limit the scope of the disclosure. Unless otherwise defined, technical and scientific terms used herein have the meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In the case of conflict, the present document, including definitions will control. 
     Additional features and advantages of the disclosure will be set forth in the description which follows, and in part will be obvious from the description, or can be learned by practice of the herein disclosed principles. The features and advantages of the disclosure can be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the disclosure will become more fully apparent from the following description and appended claims, or can be learned by the practice of the principles set forth herein. 
     Overview 
     A method can include receiving data at a primary node of a placement group in a network overlay of a distributed storage cluster. The data can be provided from the primary node to a first slave node of a plurality of slaves nodes within the placement group in an underlying network of the distributed storage cluster. Subsequently, the data can be replicated using the underlying network by providing the data directly from the first slave node in the underlying network to at least one other slave node of the plurality of slave nodes within the placement group in the underlying network. 
     A system can receive data at a primary node of a placement group in a network overlay of a distributed storage cluster. The system can provide the data from the primary node to a first slave node of a plurality of slave nodes within the placement group in an underlying network of the distributed storage cluster. Subsequently, the data can be replicated using the underlying network by providing the data to at least one other slave node of the plurality of slave nodes in the underlying network directly from the first slave node in the underlying network using multicasting. 
     A system can receive data at a primary node of a placement group in a network overlay of a distributed storage cluster. The system can provide the data from the primary node to a first slave node of a plurality of slave nodes within the placement group in an underlying network of the distributed storage cluster. Subsequently, the data can be replicated using the underlying network by providing the data to at least one other slave node of the plurality of slave nodes in the underlying network directly from the first slave node in the underlying network using multicasting. The at least one other slave node can provide an acknowledgement message indicating receipt of the data from the first slave node through the underlying network back to the primary node. 
     Description 
     The disclosed technology addresses the need in the art for efficient data replication in distributed storage systems. The present technology involves system, methods, and computer-readable media for controlling replication of data in a distributed storage cluster of a distributed storage system through an underlying network of the distributed storage cluster. 
     A description of network environments and architectures for network data access and services, as illustrated in  FIGS. 1A, 1B, 2A, and 2B , is first disclosed herein. A discussion of systems and methods for using an underlying network to replicate data in distributed storage clusters, as shown in  FIGS. 3, 4, 5, and 6 , will then follow. The discussion then concludes with a brief description of example devices, as illustrated in  FIGS. 7 and 8 . These variations shall be described herein as the various embodiments are set forth. The disclosure now turns to  FIG. 1A . 
       FIG. 1A  illustrates a diagram of an example cloud computing architecture  100 . The architecture can include a cloud  102 . The cloud  102  can include one or more private clouds, public clouds, and/or hybrid clouds. Moreover, the cloud  102  can include cloud elements  104 - 114 . The cloud elements  104 - 114  can include, for example, servers  104 , virtual machines (VMs)  106 , one or more software platforms  108 , applications or services  110 , software containers  112 , and infrastructure nodes  114 . The infrastructure nodes  114  can include various types of nodes, such as compute nodes, storage nodes, network nodes, management systems, etc. 
     The cloud  102  can provide various cloud computing services via the cloud elements  104 - 114 , such as software as a service (SaaS) (e.g., collaboration services, email services, enterprise resource planning services, content services, communication services, etc.), infrastructure as a service (IaaS) (e.g., security services, networking services, systems management services, etc.), platform as a service (PaaS) (e.g., web services, streaming services, application development services, etc.), and other types of services such as desktop as a service (DaaS), information technology management as a service (ITaaS), managed software as a service (MSaaS), mobile backend as a service (MBaaS), etc. 
     The client endpoints  116  can connect with the cloud  102  to obtain one or more specific services from the cloud  102 . The client endpoints  116  can communicate with elements  104 - 114  via one or more public networks (e.g., Internet), private networks, and/or hybrid networks (e.g., virtual private network). The client endpoints  116  can include any device with networking capabilities, such as a laptop computer, a tablet computer, a server, a desktop computer, a smartphone, a network device (e.g., an access point, a router, a switch, etc.), a smart television, a smart car, a sensor, a GPS device, a game system, a smart wearable object (e.g., smartwatch, etc.), a consumer object (e.g., Internet refrigerator, smart lighting system, etc.), a city or transportation system (e.g., traffic control, toll collection system, etc.), an internet of things (IoT) device, a camera, a network printer, a transportation system (e.g., airplane, train, motorcycle, boat, etc.), or any smart or connected object (e.g., smart home, smart building, smart retail, smart glasses, etc.), and so forth. 
       FIG. 1B  illustrates a diagram of an example fog computing architecture  150 . The fog computing architecture  150  can include the cloud layer  154 , which includes the cloud  102  and any other cloud system or environment, and the fog layer  156 , which includes fog nodes  162 . The client endpoints  116  can communicate with the cloud layer  154  and/or the fog layer  156 . The architecture  150  can include one or more communication links  152  between the cloud layer  154 , the fog layer  156 , and the client endpoints  116 . Communications can flow up to the cloud layer  154  and/or down to the client endpoints  116 . 
     The fog layer  156  or “the fog” provides the computation, storage and networking capabilities of traditional cloud networks, but closer to the endpoints. The fog can thus extend the cloud  102  to be closer to the client endpoints  116 . The fog nodes  162  can be the physical implementation of fog networks. Moreover, the fog nodes  162  can provide local or regional services and/or connectivity to the client endpoints  116 . As a result, traffic and/or data can be offloaded from the cloud  102  to the fog layer  156  (e.g., via fog nodes  162 ). The fog layer  156  can thus provide faster services and/or connectivity to the client endpoints  116 , with lower latency, as well as other advantages such as security benefits from keeping the data inside the local or regional network(s). 
     The fog nodes  162  can include any networked computing devices, such as servers, switches, routers, controllers, cameras, access points, gateways, etc. Moreover, the fog nodes  162  can be deployed anywhere with a network connection, such as a factory floor, a power pole, alongside a railway track, in a vehicle, on an oil rig, in an airport, on an aircraft, in a shopping center, in a hospital, in a park, in a parking garage, in a library, etc. 
     In some configurations, one or more fog nodes  162  can be deployed within fog instances  158 ,  160 . The fog instances  158 ,  158  can be local or regional clouds or networks. For example, the fog instances  156 ,  158  can be a regional cloud or data center, a local area network, a network of fog nodes  162 , etc. In some configurations, one or more fog nodes  162  can be deployed within a network, or as standalone or individual nodes, for example. Moreover, one or more of the fog nodes  162  can be interconnected with each other via links  164  in various topologies, including star, ring, mesh or hierarchical arrangements, for example. 
     In some cases, one or more fog nodes  162  can be mobile fog nodes. The mobile fog nodes can move to different geographic locations, logical locations or networks, and/or fog instances while maintaining connectivity with the cloud layer  154  and/or the endpoints  116 . For example, a particular fog node can be placed in a vehicle, such as an aircraft or train, which can travel from one geographic location and/or logical location to a different geographic location and/or logical location. In this example, the particular fog node may connect to a particular physical and/or logical connection point with the cloud  154  while located at the starting location and switch to a different physical and/or logical connection point with the cloud  154  while located at the destination location. The particular fog node can thus move within particular clouds and/or fog instances and, therefore, serve endpoints from different locations at different times. 
       FIG. 2A  illustrates a diagram of an example Network Environment  200 , such as a data center. In some cases, the Network Environment  200  can include a data center, which can support and/or host the cloud  102 . The Network Environment  200  can include a Fabric  220  which can represent the physical layer or infrastructure (e.g., underlay) of the Network Environment  200 . Fabric  220  can include Spines  202  (e.g., spine routers or switches) and Leafs  204  (e.g., leaf routers or switches) which can be interconnected for routing or switching traffic in the Fabric  220 . Spines  202  can interconnect Leafs  204  in the Fabric  220 , and Leafs  204  can connect the Fabric  220  to an overlay or logical portion of the Network Environment  200 , which can include application services, servers, virtual machines, containers, endpoints, etc. Thus, network connectivity in the Fabric  220  can flow from Spines  202  to Leafs  204 , and vice versa. The interconnections between Leafs  204  and Spines  202  can be redundant (e.g., multiple interconnections) to avoid a failure in routing. In some embodiments, Leafs  204  and Spines  202  can be fully connected, such that any given Leaf is connected to each of the Spines  202 , and any given Spine is connected to each of the Leafs  204 . Leafs  204  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  204  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  216 , and/or implemented or enforced by one or more devices, such as Leafs  204 . Leafs  204  can connect other elements to the Fabric  220 . For example, Leafs  204  can connect Servers  206 , Hypervisors  208 , Virtual Machines (VMs)  210 , Applications  212 , Network Device  214 , etc., with Fabric  220 . Such elements can reside in one or more logical or virtual layers or networks, such as an overlay network. In some cases, Leafs  204  can encapsulate and decapsulate packets to and from such elements (e.g., Servers  206 ) in order to enable communications throughout Network Environment  200  and Fabric  220 . Leafs  204  can also provide any other devices, services, tenants, or workloads with access to Fabric  220 . In some cases, Servers  206  connected to Leafs  204  can similarly encapsulate and decapsulate packets to and from Leafs  204 . For example, Servers  206  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  206  and an underlay layer represented by Fabric  220  and accessed via Leafs  204 . 
     Applications  212  can include software applications, services, containers, appliances, functions, service chains, etc. For example, Applications  212  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  212  can be distributed, chained, or hosted by multiple endpoints (e.g., Servers  206 , VMs  210 , etc.), or may run or execute entirely from a single endpoint. 
     VMs  210  can be virtual machines hosted by Hypervisors  208  or virtual machine managers running on Servers  206 . VMs  210  can include workloads running on a guest operating system on a respective server. Hypervisors  208  can provide a layer of software, firmware, and/or hardware that creates, manages, and/or runs the VMs  210 . Hypervisors  208  can allow VMs  210  to share hardware resources on Servers  206 , and the hardware resources on Servers  206  to appear as multiple, separate hardware platforms. Moreover, Hypervisors  208  on Servers  206  can host one or more VMs  210 . 
     In some cases, VMs  210  and/or Hypervisors  208  can be migrated to other Servers  206 . Servers  206  can similarly be migrated to other locations in Network Environment  200 . 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  206 , Hypervisors  208 , and/or VMs  210  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  200  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  216 , Servers  206 , Leafs  204 , etc. 
     Configurations in Network Environment  200  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  216 , which can implement or propagate such configurations through Network Environment  200 . In some examples, Controllers  216  can be Application Policy Infrastructure Controllers (APICs) in an ACI framework. In other examples, Controllers  216  can be one or more management components for associated with other SDN solutions, such as NSX Managers. 
     Such configurations can define rules, policies, priorities, protocols, attributes, objects, etc., for routing and/or classifying traffic in Network Environment  100 . For example, such configurations can define attributes and objects for classifying and processing traffic based on Endpoint Groups (EPGs), Security Groups (SGs), VM types, bridge domains (BDs), virtual routing and forwarding instances (VRFs), tenants, priorities, firewall rules, etc. Other example network objects and configurations are further described below. Traffic policies and rules can be enforced based on tags, attributes, or other characteristics of the traffic, such as protocols associated with the traffic, EPGs associated with the traffic, SGs associated with the traffic, network address information associated with the traffic, etc. Such policies and rules can be enforced by one or more elements in Network Environment  200 , such as Leafs  204 , Servers  206 , Hypervisors  208 , Controllers  216 , etc. As previously explained, Network Environment  200  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  200 . 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  204  can classify incoming traffic into different EPGs. The classification can be based on, for example, a network segment identifier such as a VLAN ID, VXLAN Network Identifier (VNID), NVGRE Virtual Subnet Identifier (VSID), MAC address, IP address, etc. 
     In some cases, classification in the ACI infrastructure can be implemented by Application Virtual Switches (AVS), which can run on a host, such as a server or switch. For example, an AVS can classify traffic based on specified attributes, and tag packets of different attribute EPGs with different identifiers, such as network segment identifiers (e.g., VLAN ID). Finally, Leafs  204  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  216 . Leaf  204  can classify to which EPG the traffic from a host belongs and enforce policies accordingly. 
     Another example SDN solution is based on VMWARE NSX. With VMWARE NSX, hosts can run a distributed firewall (DFW) which can classify and process traffic. Consider a case where three types of VMs, namely, application, database and web VMs, are put into a single layer-2 network segment. Traffic protection can be provided within the network segment based on the VM type. For example, HTTP traffic can be allowed among web VMs, and disallowed between a web VM and an application or database VM. To classify traffic and implement policies, VMWARE NSX can implement security groups, which can be used to group the specific VMs (e.g., web VMs, application VMs, database VMs). DFW rules can be configured to implement policies for the specific security groups. To illustrate, in the context of the previous example, DFW rules can be configured to block HTTP traffic between web, application, and database security groups. 
     Returning now to  FIG. 2A , Network Environment  200  can deploy different hosts via Leafs  204 , Servers  206 , Hypervisors  208 , VMs  210 , Applications  212 , and Controllers  216 , such as VMWARE ESXi hosts, WINDOWS HYPER-V hosts, bare metal physical hosts, etc. Network Environment  200  may interoperate with a variety of Hypervisors  208 , Servers  206  (e.g., physical and/or virtual servers), SDN orchestration platforms, etc. Network Environment  200  may implement a declarative model to allow its integration with application design and holistic network policy. 
     Controllers  216  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  216  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  216  can define and manage application-level model(s) for configurations in Network Environment  200 . 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  200 , including configurations and settings for virtual appliances. 
     As illustrated above, Network Environment  200  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  216  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  206  (e.g., physical or logical), Hypervisors  208 , VMs  210 , containers (e.g., Applications  212 ), 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. 2B  illustrates another example of Network Environment  200 . In this example, Network Environment  200  includes Endpoints  222  connected to Leafs  204  in Fabric  220 . Endpoints  222  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  222  can be an object that represents a physical device (e.g., server, client, switch, etc.), an application (e.g., web application, database application, etc.), a logical or virtual resource (e.g., a virtual switch, a virtual service appliance, a virtualized network function (VNF), a VM, a service chain, etc.), a container running a software resource (e.g., an application, an appliance, a VNF, a service chain, etc.), storage, a workload or workload engine, etc. Endpoints  122  can have an address (e.g., an identity), a location (e.g., host, network segment, virtual routing and forwarding (VRF) instance, domain, etc.), one or more attributes (e.g., name, type, version, patch level, OS name, OS type, etc.), a tag (e.g., security tag), a profile, etc. 
     Endpoints  222  can be associated with respective Logical Groups  218 . Logical Groups  218  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  1  can contain client endpoints, Logical Group 2 can contain web server endpoints, Logical Group  3  can contain application server endpoints, Logical Group N can contain database server endpoints, etc. In some examples, Logical Groups  218  are EPGs in an ACI environment and/or other logical groups (e.g., SGs) in another SDN environment. 
     Traffic to and/or from Endpoints  222  can be classified, processed, managed, etc., based Logical Groups  218 . For example, Logical Groups  218  can be used to classify traffic to or from Endpoints  222 , apply policies to traffic to or from Endpoints  222 , define relationships between Endpoints  222 , define roles of Endpoints  222  (e.g., whether an endpoint consumes or provides a service, etc.), apply rules to traffic to or from Endpoints  222 , apply filters or access control lists (ACLs) to traffic to or from Endpoints  222 , define communication paths for traffic to or from Endpoints  222 , enforce requirements associated with Endpoints  222 , implement security and other configurations associated with Endpoints  222 , etc. 
     In an ACI environment, Logical Groups  218  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. 
     The networks shown in  FIGS. 2A and 2B  can be used to implement, at least in part, a distributed data storage system. A distributed data storage system can include clusters of nodes, otherwise referred to as distributed storage clusters. A distributed data storage system can be implemented as a distributed database. For example, a distributed data storage system can be implemented as a non-relational database that stores and accesses data as key-value pairs. Additionally, a distributed data storage system can be implemented across peer network data stores. For example, a distributed storage system can include peers acting as nodes within a distributed storage cluster that are connected and form the distributed storage cluster through an applicable network, such as the networks shown in  FIGS. 2A and 2B . 
     A distributed storage system can replicate data stored within the system. Specifically, nodes within one or a plurality of clusters of nodes can store the same data, as part of replicating the data within the distributed data storage system. In replicating data, e.g. within a distributed storage cluster, a distribute data storage system can provide both increased fault tolerance and high availability of data. For example, in the event that one node storing data is unavailable, then another node storing the data can be used to provide or otherwise make the data accessible. 
     In typical distributed storage systems a network overlay of the distributed storage systems controls all or most aspects of replication of data within an underlying network of the distributed storage systems. In particular, data replication in current distributed data storage systems is controlled through source-based replication. In using source-based replication to replicate data, a primary node can communicate with each node to control data replication. In particular, a primary node can use unicast to communicate with each node as part of control data replication. Each node can then send back an acknowledgement indicating receipt of the data to the primary node, e.g. using unicast. This is an inefficient use of resources. Specifically, the primary node is burdened with originating all communications and transfers of data for purposes of replicating data. 
       FIG. 3  depicts a placement group  300  of a distributed storage cluster as part of a distributed storage system. The placement group  300  shown in  FIG. 3  is configured to use an underlying network of a distributed storage system to replicate data within the distributed storage system. In particular, the placement group  300  is configured to use an underlying network formed by slave nodes of the distributed storage system to replicate data within the placement group  300 . 
     The placement group  300  shown in  FIG. 3  includes a primary node  302  and an underlying network  304 . The placement group  300  can be part of a distributed storage system, e.g. a distributed storage system implemented through the networks shown in  FIGS. 2A and 2B . The primary node  302  can be included as part of a network overlay of a distributed storage cluster of a distributed storage system. For example, the primary node  302  can be part of a plurality of primary nodes in distributed storage clusters forming a network overlay for the distributed storage clusters. The primary node  302  can serve as a primary node for a plurality of placement groups, potentially simultaneously. For example, the primary node  302  can provide data to different placement groups for replication of data in the different placement groups. 
     The underlying network  304  includes a first slave node  306 , a second slave node  308 , and a third slave node  310 . The second slave node  308  can be coupled to the primary node  302  through the first slave node  306 . One or a combination of the primary node  302 , the first slave node  306 , the second slave node  308 , and the third slave node  310  can be formed in the data link layer or layer 2 of a network environment in which the placement group  300  is implemented. Additionally, one or a combination of the primary node  302 , the first slave node  306 , the second slave node  308 , and the third slave node  310  can be formed in the network layer or layer 3 of a network environment in which the placement group  300  is implemented. 
     The placement group  300  shown in  FIG. 3  is configured to replicate data within the placement group  300  using the underlying network  304  instead of source-based replication. The primary node  302  can receive data to be replicated within the placement group  300 . Further, the primary node  302  can provide the data to the underlying network  304 , where subsequently the underlying network  304  can replicate the data using the single copy of the data received from the primary node  302 . As part of using the underlying network  304  to replicate data instead of using source-based replication, the primary node  302  does not need to provide or otherwise can refrain from providing multiple copies of the data to the underlying network  304  corresponding to each time the data is replicated within the underlying network  304 . This can lead to lower amounts of consumed network resources and improved speeds in actually replicating the data within the placement group  300 . 
     As part of using the underlying network  304  to replicate data within the placement group  300 , the primary node  302  can provide data only to the first slave node  306  as illustrated in  FIG. 3 . The primary node  302  can provide data to the first slave node  306  according to an IP multicast group or an IP multicast group mapping associated with the placement group  300 . An IP multicast group mapping can include or otherwise be associated with a multicast tree of a plurality of slave nodes in the underlying network  304  and routes, potentially shortest paths, for communicating with the slave nodes in the underlying network  304 . For example, an IP multicast group mapping for the placement group  300  can include the first slave node  306  and the second slave node  308  and an indication that the second slave node  308  is downstream from the first slave node  306 . Additionally, an IP multicast group mapping can include a destination IP address associated with the IP multicast group mapping. In using an IP multicast group mapping to send data, the primary node  302  can set a destination IP address of the data as the IP multicast group address, and the data can subsequently be sent to the first slave node  306  as part of sending the data to the IP multicast group. 
     An IP multicast group can be uniquely associated with the placement group  300 . In particular, an IP multicast group associated with the placement group  300  can only include nodes within the placement group  300 . A node can belong to multiple IP multicast groups corresponding to different placement groups associated with the node. For example, the first slave node  306  can serve as a slave node for not only the placement group  300  shown in  FIG. 3 , but also for another placement group. As a result, the first slave node  306  can be included as part of an IP multicast group uniquely associated with the placement group  300  shown in  FIG. 3  and another IP multicast group uniquely associated with the other placement group. 
     Nodes can be added to and removed from an IP multicast group. More specifically, nodes can be added to and removed from an IP multicast group as they are added to and removed from a placement group associated with the IP multicast group. For example, after the third slave node  310  is added to the placement group  300  it can subsequently subscribe to an IP multicast group associated with the placement group  300 . Once a node subscribes to an IP multicast group, the node can be added to a multicast tree associated with the IP multicast group. For example, when the second slave node  308  joins an IP multicast group associated with the placement group  300 , then the second slave node  308  can be added to a multicast tree to indicate the second slave node is downstream from the first slave node  306  as part of a shortest path to the second slave node  308 . 
     A primary node of a placement group can refrain from subscribing to an IP multicast group associated with the placement group. As a result, an IP multicast group can be specific to an underlying network. For example, the primary node  302  can refrain from subscribing to an IP multicast group uniquely associated with the placement group  300  in order to maintain a multicast tree specific to one or a combination of the first slave node  306 , the second slave node  308 , and the third slave node  310  within the underlying network  304 . 
     Nodes can subscribe to the IP multicast group using an applicable method of subscribing a node to a multicast group such as an applicable Internet Group Management Protocol (hereinafter referred to as “IGMP”), e.g. IGMPv3, IGMPv2, and IGMPPv1. Nodes can subscribe to an IP multicast group when the IP multicast group is created or otherwise associated with a placement group associated with the nodes. For example, the first slave node  306 , the second slave node  308 , and the third slave node  310  can subscribe to an IP multicast group associated with the placement group  300  after the placement group  300  is mapped to or otherwise associated with the IP multicast group. 
     In subscribing nodes to an IP multicast group, an IP multicast group mapping for the IP multicast group can be distributed to the nodes. An IP multicast group mapping for an IP multicast group can be distributed to nodes using source based replication. For example, the first slave node  306  and the second slave node  308  can receive an IP multicast group mapping as part of individual unicast transmissions sent from the primary node  302  to each of the first slave node  306  and the second slave node  308 . A multicast group mapping used in subscribing nodes to an IP multicast group can be sent to the nodes using unicast transmissions. Subsequently, the nodes can subscribe an IP multicast group based on receipt of an IP multicast group mapping for the IP multicast group. 
     The primary node  302  can be configured to only send data to a slave node in the underlying network  304  that has downstream slave nodes. For example, the primary node  302  can send data to be replicated to the first slave node  306  because the first slave node  306  has a node downstream, the second slave node  308 . Further in the example, the primary node  302  can refrain from sending the data to the third slave node  310  as the third slave node  310  lacks downstream nodes. In only sending data to a slave node in the underlying network  304  that has downstream slave nodes, the primary node  302  can ensure that data can be replicated across a plurality of slave nodes in the underlying network  304 . Further, in only sending data to a slave node in the underlying network  304  that has downstream slave nodes, the primary node  302  only has to send the data once to the underlying network  304  for purposes of replicating the data in the underlying network  304 . As a result, the primary node  302  can utilize fewer resources in replicating data in the underlying network  304  while potentially replicating the data in the underlying network  304  more quickly. 
     The first slave node  306  can receive data to be replicated in the underlying network  304  from the primary node  302 . The first slave node  306  can receive data from the primary node  302 , potentially as part of a multicasting to an IP multicast group associated with the placement group  300  and including the first slave node  306 . The first slave node  306  can locally store the data received from the primary node  302  at the first slave node  306 . Subsequently, the first slave node  306  can send the data to the second slave node  308  where the data can be save locally as part of replicating the data in the underlying network. The first slave node  306  can send data to the second slave node  308  using network broadcasting. More specifically, the first slave node  306  and the second slave node can be implemented in a data link layer of a distributed storage system and subsequently use network broadcasting to communicate and exchange data with each other. 
     The first slave node  306  can send data to the second slave node  308  as part of a multicast message. Further, the first slave node  306  can send data to the second slave node  308  using a multicast tree included as part of an IP multicast group mapping for an IP multicast group including the first slave node  306  and the second slave node  308 . For example, the first slave node  306  can use a multicast tree to identify that the second slave node  308  is downstream from the first slave node  306 , and subsequently send the data to the second slave node  308 . 
     Both the first slave node  306  and the second slave node  308  can send an acknowledgement message indicating receipt of data to be replicated in the underlying network  304 . More specifically, the first slave node  306  can send an acknowledgment message after receiving data from the primary node  302  and the second slave node  308  can send an acknowledgment message after receiving data from the first slave node  306 . The first slave node  306  and the second slave node  308  can send acknowledgment messages indicating receipt of data back to the primary node  302 . The acknowledgment message sent back to the primary node  302  from the first slave node  306  and the second slave node  308  can each be sent as unicast messages. 
     Any one of the slave nodes in the underlying network  304  can be implemented through routers configured to communicate using source specific multicast (hereinafter referred to as “SSM”). In using SSM to communicate, slave nodes in the underlying network  304  can receive data directly from the source, e.g. the primary node  302 . More specifically, slave nodes in the underlying network  304  can receive data directly from a source instead of receiving the data from a rendezvous point. This can further reduce an amount of network resources used in replicating data in the underlying network  304  while potentially increasing speeds at which the data is replicated in the underlying network  304 . 
       FIG. 4  depicts an example underlying network-based data replication system  400 . The underlying network-based data replication system  400  can replicate data received from a primary node of a placement group using an underlying network of the placement group. In replicating data using an underlying network, the underlying network-based data replication system  400  eliminates the need for a primary node to replicate data in a placement group using source-based data replication. More specifically, by replicating data using an underlying network, the underlying network-based data replication system  400  eliminates the need for a primary node to send data multiple times to an underlying network, e.g. through multiple unicast messages, in order to replicate the data in the underlying network. 
     The underlying network-based data replication system  400  shown in  FIG. 4  can be implemented at one or a combination of slave nodes in an underlying network, e.g. the first slave node  306  in the underlying network  304  of the placement group  300  shown in  FIG. 3 . Additionally, the underlying network-based data replication system  400  can be implemented at a primary node of a placement group  300 , e.g. the primary node  302  of the placement group shown in  FIG. 3 . Further, the underlying network-based data replication system  400  can be implemented, at least in part, at a remote system, e.g. in the cloud. 
     The underlying network-based data replication system  400  shown in  FIG. 4  includes a multicast group mapper  402 , a multicast group storage  404 , a data replicator  406 , a data receipt acknowledger  408 . The multicast group mapper  402  can manage an IP multicast group of a placement group for purposes of controlling data replication in an underlying network of the placement group. Specifically, the multicast group mapper  402  can map or otherwise uniquely associate an IP multicast group with a placement group. In being uniquely associated with an IP multicast group, each placement group of a plurality of placement groups can be associated with a different IP multicast group. This allows for controlled data replication within specific placement groups using IP multicast groups. 
     In response to mapping an IP multicast group to a placement group or vice versa, the multicast group mapper  402  can facilitate subscription of all or a subset of slave nodes in the placement group to the IP multicast group. Specifically, the multicast group mapper  402  can send a mapping of an IP multicast group to a placement group to all or a subset of nodes, e.g. slave nodes, in the placement group. The multicast group mapper  402  can send a mapping of an IP multicast group to a placement group through unicast messages, e.g. source based replication, to corresponding nodes in the placement group. In response to receiving a mapping of an IP multicast group to a placement group, nodes in the placement group can subsequently subscribe to the IP multicast group using the multicast group mapper. Specifically, the nodes can use an applicable IGMP method for subscribing to an IP multicast group through the multicast group mapper  402 . 
     The multicast group mapper  402  can add nodes to an IP multicast group mapped to a placement group, as nodes are added to the placement group. Specifically, when a node joins a placement group, the multicast group mapper  402  can send a mapping of an IP multicast group uniquely associated with the placement group to the newly joined node. The newly joined node can subsequently subscribe to the IP multicast group through the multicast group mapper  402 . 
     In mapping an IP multicast group to a placement group, the multicast group mapper  402  can maintain an IP multicast group mapping for the IP multicast group, as indicated by multicast group data stored in the multicast group storage  404 . Specifically, the multicast group mapper  402  can maintain a mapping including all nodes in a placement group, e.g. identifiers or addresses of the nodes, that are subscribed to an IP multicast group and an address of the IP multicast group. Additionally, the multicast group mapper  402  can maintain a multicast tree, as part of an IP multicast group mapping, indicating network or connectivity relationships between nodes that have subscribed to an IP multicast group. For example, the multicast group mapper  402  can maintain a multicast tree indicating which slave nodes in a placement group are downstream from other slave nodes in the placement group. 
     The data replicator  406  can receive and transmit data for replication within a placement group using an underlying network. The data replicator  406  can be implemented at one or a plurality of slave nodes in an underlying network and receive data to be replicated in a placement group from a primary node of the placement group. The data replicator  406  can receive data to be replicated from a primary node as either a unicast transmissions or multicasting. For example, the data replicator  406  can be implemented at a first slave node in an underlying network and can receive data through a multicasting addressed to an IP multicast group including the first slave node. 
     The data replicator  406  can propagate received data through an underlying network by providing received data to other slave nodes in the underlying network, effectively replicating the data in the underlying network. The data replicator  406  can transmit data to other slave nodes in the underlying network as part of multicasting. Additionally, the data replicator  406  can use an IP multicast group mapping, e.g. as indicated by multicast group data stored in the multicast group storage  404 , to send data to other slave nodes in an underlying network as part of multicasting. For example, the data replicator can use a multicast tree for an IP multicast group to send received data to other downstream slave nodes in the IP multicast group. As the data replicator  406  can propagate received data through an underlying network to replicate the data through the underlying network, a primary node only has to provide the data to data replicator  406  once in order to replicate the data in the underlying network. This reduces an amount of network resources used in replicating the data and can potentially lead to faster replication times for the data. 
     The data receipt acknowledger  408  can send acknowledgements of receipt of data at various slave nodes in the underlying network. Specifically, the data receipt acknowledger  408  can be implemented at slave nodes in an underlying network and be configured to provide an acknowledgment when data to be replicated in the underlying network is received at the slave nodes. For example, the data receipt acknowledger  408  can provide an acknowledgment when data is received at a slave node through multicasting from another slave node in an underlying network, as part of replicating the data in the underlying network. The data receipt acknowledger  408  can send acknowledgements of receipt of data at various slave nodes back to a primary node for a placement group. More specifically, the data receipt acknowledger  408  can send the acknowledgement back to the primary node through unicast transmissions. As a result, each acknowledgement can correspond to a single slave node and indicate each slave node that has received data as part of replicating data through an underlying network. 
       FIG. 5  illustrates a flowchart for an example method of replicating data in a placement group of a distributed storage system using an underlying network of the distributed storage system. The method shown in  FIG. 5  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 steps, those of ordinary skill in the art will appreciate that  FIG. 5  and the modules shown therein can be executed in any order and can include fewer or more modules than illustrated. 
     Each module shown in  FIG. 5  represents one or more steps, processes, methods or routines in the method. For the sake of clarity and explanation purposes, the modules in  FIG. 5  are described with reference to the placement group  300  shown in  FIG. 3  and the underlying network-based data replication system  400  shown in  FIG. 4 . 
     At step  500 , a primary node of a placement group in a network overlay of a distributed storage cluster received data to be replicated in the distributed storage cluster. The placement group can be included as part of a plurality of distributed storage clusters that form part of a distributed storage system. Additionally, a placement group including a primary node can be implemented using a network environment as shown in  FIGS. 2A and 2B . 
     At step  502 , the data is provided from the primary node to a first slave node of a plurality of slave nodes within the placement group in an underlying network of the distributed storage cluster. A data replicator  406  can receive the data at a first slave node of a plurality of slave nodes within the placement group in an underlying network of the distributed storage cluster. The data can be provided from the primary node to a first slave node of a plurality of slave nodes within the placement group as part of multicasting. For example, the primary node can set a destination address of a multicast transmission including the data as an address of a multicast group of the placement group. 
     At step  504 , the data replicator  406  replicates the data using the underlying network by providing the data to at least one other slave node of the plurality of slave nodes within the placement group in the underlying network directly from the first slave node in the underlying network. In providing the data using the underlying network to at least one other slave node of the plurality of slave nodes in the underlying network, the primary node only has to provide the data once to the underlying network. Accordingly network resource usage in replicating the data can be reduced and an increase in speed in replicating the data can be achieved. 
       FIG. 6  illustrates a flowchart for an example method of replicating data in a placement group of a distributed storage system through multicast messaging using an underlying network of the distributed storage system. The method shown in  FIG. 6  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 steps, those of ordinary skill in the art will appreciate that  FIG. 6  and the modules shown therein can be executed in any order and can include fewer or more modules than illustrated. 
     Each module shown in  FIG. 6  represents one or more steps, processes, methods or routines in the method. For the sake of clarity and explanation purposes, the modules in  FIG. 6  are described with reference to the placement group  300  shown in  FIG. 3  and the underlying network-based data replication system  400  shown in  FIG. 4 . 
     At step  600 , the multicast group mapper  402  maps a placement group in an underlying network of a distributed storage cluster to a unique IP multicast group to create an IP multicast group mapping. As part of mapping a placement group to a unique IP multicast group, nodes within the placement group can subscribe to the IP multicast group. Specifically, a mapping of a placement group to a unique IP multicast group can be provided to slave nodes in the placement group who can subsequently subscribe to the IP multicast group. In mapping a placement group to a unique IP multicast group, a multicast tree for the unique IP multicast group can be maintained. More specifically, a multicast tree indicating slave nodes downstream from other slave nodes in an IP multicast group can be maintained as slave nodes subscribe to the IP multicast group. 
     At step  602 , a primary node of the placement group in a network overlay of a distributed storage cluster received data to be replicated in the distributed storage cluster. The placement group can be included as part of a plurality of distributed storage clusters that form part of a distributed storage system. Additionally, the placement group including a primary node can be implemented using a network environment as shown in  FIGS. 2A and 2B . 
     At step  604 , the data is provided from the primary node to a first slave node of the plurality of slave nodes within the placement group in an underlying network of the distributed storage cluster. A data replicator  406  can receive the data at a first slave node of the plurality of slave nodes within the placement group in an underlying network of the distributed storage cluster. The data can be provided from the primary node to a first slave node of the plurality of slave nodes within the placement group as part of multicasting. For example, the primary node can set a destination address of a multicast transmission including the data as an address of the IP multicast group of the placement group. 
     At step  606 , the data replicator  406  replicates the data using the underlying network by providing the data to at least one other slave node of the plurality of slave nodes within the placement group in the underlying network directly from the first slave node in the underlying network according to the IP multicast group mapping. The data can be provided at least one other slave node using a multicast tree included as part of the IP multicast group mapping. For example, the data can be provided to slave nodes downstream from the first slave node using a multicast tree included as part of the IP multicast group mapping. 
     The disclosure now turns to  FIGS. 7 and 8 , which illustrate example network devices and computing devices, such as switches, routers, load balancers, client devices, and so forth. 
       FIG. 7  illustrates a computing system architecture  700  wherein the components of the system are in electrical communication with each other using a connection  705 , such as a bus. Exemplary system  700  includes a processing unit (CPU or processor)  710  and a system connection  705  that couples various system components including the system memory  715 , such as read only memory (ROM)  720  and random access memory (RAM)  725 , to the processor  710 . The system  700  can include a cache of high-speed memory connected directly with, in close proximity to, or integrated as part of the processor  710 . The 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 can provide a performance boost that avoids processor  710  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 or software service, such as service  1   732 , service  2   734 , and service  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 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  700 , an input device  745  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  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 device  700 . The communications interface  740  can generally govern and manage the user input and system output. There is no restriction on operating on any particular hardware arrangement and therefore the basic features here may easily be substituted for improved hardware or firmware arrangements as they are developed. 
     Storage device  730  is 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 services  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 connection  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 , connection  705 , output device  735 , and so forth, to carry out the function. 
       FIG. 8  illustrates an example network device  800  suitable for performing switching, routing, load balancing, and other networking operations. Network device  800  includes a central processing unit (CPU)  804 , interfaces  802 , and a bus  810  (e.g., a PCI bus). When acting under the control of appropriate software or firmware, the CPU  804  is responsible for executing packet management, error detection, and/or routing functions. The CPU  804  preferably accomplishes all these functions under the control of software including an operating system and any appropriate applications software. CPU  804  may include one or more processors  808 , such as a processor from the INTEL X86 family of microprocessors. In some cases, processor  808  can be specially designed hardware for controlling the operations of network device  800 . In some cases, a memory  806  (e.g., non-volatile RAM, ROM, etc.) also forms part of CPU  804 . However, there are many different ways in which memory could be coupled to the system. 
     The interfaces  802  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  800 . Among the interfaces that may be provided are Ethernet interfaces, frame relay interfaces, cable interfaces, DSL interfaces, token ring interfaces, and the like. In addition, various very high-speed interfaces may be provided such as fast token ring interfaces, wireless interfaces, Ethernet interfaces, Gigabit Ethernet interfaces, ATM interfaces, HSSI interfaces, POS interfaces, FDDI interfaces, WIFI interfaces, 3G/4G/5G cellular interfaces, CAN BUS, LoRA, and the like. Generally, these interfaces may include ports appropriate for communication with the appropriate media. In some cases, they may also include an independent processor and, in some instances, volatile RAM. The independent processors may control such communications intensive tasks as packet switching, media control, signal processing, crypto processing, and management. By providing separate processors for the communications intensive tasks, these interfaces allow the master microprocessor  804  to efficiently perform routing computations, network diagnostics, security functions, etc. 
     Although the system shown in  FIG. 8  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  800 . 
     Regardless of the network device&#39;s configuration, it may employ one or more memories or memory modules (including memory  806 ) configured to store program instructions for the general-purpose network operations and mechanisms for roaming, route optimization and routing functions described herein. The program instructions may control the operation of an operating system and/or one or more applications, for example. The memory or memories may also be configured to store tables such as mobility binding, registration, and association tables, etc. Memory  806  could also hold various software containers and virtualized execution environments and data. 
     The network device  800  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  800  via the bus  810 , to exchange data and signals and coordinate various types of operations by the network device  800 , such as routing, switching, and/or data storage operations, for example. 
     For clarity of explanation, in some instances the present technology 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. 
     Claim language reciting “at least one of” refers to at least one of a set and indicates that one member of the set or multiple members of the set satisfy the claim. For example, claim language reciting “at least one of A and B” means A, B, or A and B.