NETWORKS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 62/428,476, filed November 30, 2016, which is hereby incorporated by reference.

TECHNICAL FIELD

[0002] Embodiments relate to the field of computer systems; and more specifically, to techniques for managing network devices added to a physical network topology, including initial device configuration, wiring validation based on network design policies, and provisioning of additional services to network devices.

BACKGROUND

[0003] The amount of network traffic handled by telecommunications service providers and other network operators continues to increase at a rapid pace. In addition to an ever growing number of users, new types of Internet consumption patterns (e.g., higher-definition streaming video, an increase in Internet of things (IoT) devices, 5th generation mobile networks (5G), etc.) are often straining existing service provider network infrastructures.

[0004] The strain on existing network infrastructures has caused telecommunications service providers to look to new access network technologies to meet increased network demands. One example of a technology used to improve performance of some access networks is the use of spine-and-leaf network architectures. At a high level, a spine-and-leaf network architecture creates a two-layer network topology of "leaf and "spine" switches, where the layer of leaf switches is fully meshed to a layer of spine switches. Among other benefits, the spine-and-leaf architecture ensures that access-layer leaf switches are no more than one hop away from one another, thereby minimizing latency and bottlenecks among the switches.

[0005] The use of spine-and-leaf and other modern network architectures has improved the ability of service providers to scale access networks. However, as the number of network devices and links in these networks increases, so too does the complexity of ensuring proper configuration of the networks. For example, a network administrator might add a leaf switch to a network and accidentally connect the leaf switch to another leaf switch, or one spine switch to another spine switch, resulting in an invalid spine-and-leaf network configuration. Furthermore, additional configuration of these devices (e.g., to configure network-specific parameters and provision additional services) is often dependent on a valid initial configuration. Traditional methods of network device configuration and wiring validation rely largely on manual configuration and inspection, both of which are error-prone and time consuming.

SUMMARY

[0006] Systems, methods, apparatuses, computer program products, and machine-readable media are provided for performing initial device configuration, wiring validation, and service provisioning of network devices added to a physical network. According to embodiments, a control and management entity (CME) component of a software defined networking (SDN) controller detects network devices added to a physical network topology and automatically configures the network devices with device-specific configuration. The CME further performs wiring validation to determine whether network links established between the network device and adjacent network devices satisfy one or more defined network design policies. If the wiring validation is successful, the CME sends network-specific configuration information to the network device. The CME may further provision the device to support services and other subscriber-specific information based on requests generated from operations support systems (OSS), business support systems (BSS), or other service orchestration systems. If the wiring validation is unsuccessful, the CME may perform operations including generating an alert to notify a network administrator of the errors in the wiring validation, generating a graphical interface displaying an indication of errors in the wiring validation, or combinations thereof.

[0007] According to some embodiments, a method in a software defined networking (SDN) controller implemented by one or more computing devices performs wiring validation of a network device added to a physical network. The method includes receiving, from the network device, a message identifying a physical network link established between the network device and a neighboring network device. The method also includes determining, by the SDN controller, whether the physical network link satisfies a network design policy. The network design policy includes rules relating to the topology of the physical network. The method also includes, in response to determining that the network link does not satisfy the network design policy, generating an alert indicating that the network link does not satisfy the network design policy.

[0008] According to some embodiments, a non-transitory machine readable medium provides instructions which, when executed by a processor of a device, causes, in a software defined networking (SDN) controller, the device to perform wiring validation of a network device added to a physical network by performing operations. The operations include receiving, from the network device, a message identifying a physical network link established between the network device and a neighboring network device. The operations also include determining, by the SDN controller, whether the physical network link satisfies a network design policy. The network design policy includes rules relating to the topology of the physical network. The operations also include, in response to determining that the network link does not satisfy the network design policy, generating an alert indicating that the network link does not satisfy the network design policy.

[0009] According to some embodiments, a device includes one or more processors and a non- transitory machine-readable storage medium. The non-transitory machine-readable medium provides instructions which, when executed by the one or more processors, causes the device to perform wiring validation of a network device added to a physical network by performing operations. The operations include receiving, from the network device, a message identifying a physical network link established between the network device and a neighboring network device. The operations also include determining, by the SDN controller, whether the physical network link satisfies a network design policy. The network design policy includes rules relating to the topology of the physical network. The operations also include, in response to determining that the network link does not satisfy the network design policy, generating an alert indicating that the network link does not satisfy the network design policy.

[0010] According to some embodiments, a device is adapted to perform wiring validation of a network device added to a physical network. The device includes a module to receive, from the network device, a message identifying a physical network link established between the network device and a neighboring network device. The device also includes a module to determine, by the SDN controller, whether the physical network link satisfies a network design policy. The network design policy includes rules relating to the topology of the physical network. The device also includes a module which, in response to determining that the network link does not satisfy the network design policy, generates an alert indicating that the network link does not satisfy the network design policy.

[0011] Accordingly, embodiments provide an automated approach for performing initial device configuration, wiring validation, and service provisioning for network devices and links added to a physical network.

[0012] Embodiments involve significantly less manual configuration compared to traditional network systems, thereby reducing the risk of misconfiguration of network devices and links between network devices in a physical network topology. This can reduce not only the initial cost of the network devices (e.g., by enabling service providers to use a variety of network device types from different vendors), but also future maintenance costs. These savings can be particularly significant in modern network operation centers using disaggregated architectures of network devices (e.g., leaf-and -spine, compute server, etc.) in which a number of network devices and network links is large and ever increasing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The invention may best be understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the invention. In the drawings:

[0014] Figure 1 is a block diagram illustrating a Fiber to the Distribution Point (FTTdp) architecture according to some embodiments.

[0015] Figure 2 is a block diagram illustrating a control and management entity (CME) module implemented as an application running in a SDN controller, the CME module enabling the initial configuration, wiring validation, and service provisioning of network devices and physical network links added to a network according to some embodiments.

[0016] Figure 3 is a flow-type diagram illustrating operations for auto-discovery and configuration of a network device according to some embodiments.

[0017] Figure 4 is a flow-type diagram illustrating operations to perform wiring validation of a network device added to a network according to some embodiments.

[0018] Figure 5A illustrates connectivity between network devices (NDs) within an exemplary network, as well as three exemplary implementations of the NDs, according to some embodiments of the invention.

[0019] Figure 5B illustrates an exemplary way to implement a special-purpose network device according to some embodiments of the invention.

[0020] Figure 5C illustrates various exemplary ways in which virtual network elements (VNEs) may be coupled according to some embodiments of the invention.

[0021] Figure 5D illustrates a network with a single network element (NE) on each of the NDs, and within this straight forward approach contrasts a traditional distributed approach (commonly used by traditional routers) with a centralized approach for maintaining reachability and forwarding information (also called network control), according to some embodiments of the invention.

[0022] Figure 5E illustrates the simple case of where each of the NDs implements a single NE, but a centralized control plane has abstracted multiple of the NEs in different NDs into (to represent) a single NE in one of the virtual network(s), according to some embodiments of the invention.

[0023] Figure 5F illustrates a case where multiple VNEs are implemented on different NDs and are coupled to each other, and where a centralized control plane has abstracted these multiple VNEs such that they appear as a single VNE within one of the virtual networks, according to some embodiments of the invention.

[0024] Figure 6 illustrates a general purpose control plane device with centralized control plane (CCP) software 650), according to some embodiments of the invention.

DETAILED DESCRIPTION

[0025] The following description describes techniques for performing initial configuration, wiring validation, and service provisioning for network devices and network device links added to a physical network. In the following description, numerous specific details such as logic implementations, opcodes, means to specify operands, resource partitioning/sharing/duplication implementations, types and interrelationships of system components, and logic

partitioning/integration choices are set forth in order to provide a more thorough understanding of the present invention. It will be appreciated, however, by one skilled in the art that the invention may be practiced without such specific details. In other instances, control structures, gate level circuits and full software instruction sequences have not been shown in detail in order not to obscure the invention. Those of ordinary skill in the art, with the included descriptions, will be able to implement appropriate functionality without undue experimentation.

[0026] References in the specification to "one embodiment," "an embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0027] Bracketed text and blocks with dashed borders (e.g., large dashes, small dashes, dot- dash, and dots) may be used herein to illustrate optional operations that add additional features to embodiments of the invention. However, such notation should not be taken to mean that these are the only options or optional operations, and/or that blocks with solid borders are not optional in certain embodiments of the invention.

[0028] In the following description and claims, the terms "coupled" and "connected," along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. "Coupled" is used to indicate that two or more elements, which may or may not be in direct physical or electrical contact with each other, co-operate or interact with each other. "Connected" is used to indicate the establishment of communication between two or more elements that are coupled with each other.

[0029] Embodiments disclosed herein utilize a control and management entity (CME) component of a software defined networking (SDN) controller that can perform network device discovery, zero-touch provisioning of initial network device configuration, wiring validation, and service provisioning, among other features. In this manner, the CME helps to ensure that the physical topology of the network is properly configured as network devices and network links are added, modified, or removed from the network. In one embodiment, a CME is implemented as an application running in a software defined networking (SDN) controller.

[0030] For example, a network administrator might observe that an amount of network traffic in a data center is increasing and request the addition of one or more network devices for load balancing or other purposes. In response to the request from the network administrator, a data center technician might install additional network devices and add one or more physical connections between the network devices and other devices in the network. In one embodiment, newly added network devices undergo zero touch provisioning (ZTP) to establish initial network connectivity parameters and configuration.

[0031] In an embodiment, network devices added to a network send messages (e.g., Link Layer Discovery Protocol (LLDP) messages) identifying physical network links established between the network device and neighboring network devices. The CME receives these messages and, based on information contained in the messages, determines whether the network device and associated network links satisfy a network design policy. The network design policy includes rules relating to the topology of the physical network (e.g., rules indicating permissible network link configurations, valid port number ranges, allowed line speeds, etc.). In one embodiment, the network design policy is specified using a policy -based management architecture such as the policy -based management architecture (PMA) specified jointly by the Internet Engineering Task Force (IETF) and Distributed Management Task Force (DMTF).

[0032] In an embodiment, in response to determining that a network link does not satisfy the network design policy, the CME generates an alert. For example, the alert may include sending a message to a network administrator, generating a graphical display indicating the alert, or generating any other type of notification. The CME may also block the network link or network device not satisfying the network design policy, thereby preventing unintended network operation.

[0033] In an embodiment, in response to determining instead that the network link does satisfy the network design policy, the CME sends additional configuration information to the network device (e.g., using the Network Configuration Protocol (NETCONF) and "Yet Another Next Generation" (YANG), OpenFlow, and other configuration protocols). The ability to use NETCONF/YANG enables the SDN controller to send generic device configuration to devices supporting NETCONF/YANG, OpenFlow, and other protocols.

[0034] Embodiments generally are applicable to traditional network devices, "white box" network devices (e.g., generic hardware), or any other types of network devices supporting programmatic interfaces. The use of the CME to configure and validate network devices can significantly reduce the time to configure, validate, and provision services to network devices added to a physical network topology. Accordingly, embodiments are useful not only in traditional networks, but in IT data centers and next-generation central offices (NGCO) environments in which a number of network devices to be configured can be large. In many of these environments, service providers are increasingly using abstracted interfaces to enable the service providers to use network devices from a variety of different vendors. In this manner, network operators are able to both reduce capital expenditures by enabling the purchase of the most cost effective hardware that supports the programmatic interfaces, and reduce operating expenses by enabling the operators to seamlessly configure and manage large numbers of devices. Furthermore, service operators can better obtain an end-to-end picture of the network, and errors in the network easily can be detected and corrected.

[0035] Figure 1 is a block diagram illustrating a Fiber to the Distribution Point (FTTdp) system 100, including a next-generation central office (NGCO) 102 providing subscriber premises 104 access to the Internet 112. A FTTdp system 100 is one example system in which the approaches described herein are useful; however, the approaches may be applied to other networked systems.

[0036] For most access networks, extending fiber connections the entire way to subscriber premises 104 often is not possible or cost effective. FTTdp is an optical fiber/copper hybrid approach, where optical fiber arrives within meters of subscriber premises 104 and very-high- bit-rate digital subscriber line (VDSL) is used in the last meters over existing copper pairs. This approach often is more cost-effective than deploying fiber all the way to subscriber endpoint. FTTdp functions as a media converter, terminating a passive optical network (PON) fiber access line at a neighborhood distribution point unit (DPU) 106 and connecting to a standard based VDSL gateway in subscriber premises 104. In FTTdp-based access architectures, fiber backhaul technology feeds a distribution point which has copper drops of less than 200 meters. A distribution point unit (DPU) 106 is placed in the access network where copper drops are distributed to subscriber premises 104.

[0037] As shown in Figure 1, the NGCO 102 is architected as a mini data center, including a spine-and-leaf network architecture 108 comprising leaf switches connected in mesh to spine switches. In one embodiment, the network devices of the leaf-and-spine network 108 include white box network devices.

[0038] In an embodiment, a software defined networking (SDN) controller 110 manages and configures a variety of network devices (e.g., DPUs 106, network devices of leaf-and-spine network 108, L2/L3 switches, optical line terminations (OLTs), etc.). In one embodiment, the SDN controller 110 is based on the OpenDaylight Project, an open source project hosted by the Linux Foundation®. At a high level, the SDN controller 110 manages neighbor discovery and topology discovery, device configuration, and reachability and forwarding information for networks as a centralized control plane, among other functions. As described in more detail in reference to Figure 2, in one embodiment, a CME 204 component of a SDN controller 110 communicates with various network devices using various management protocols (e.g., NETCONF /YANG, OpenFlow®, LLDP, etc.) to manage and configure the network devices.

[0039] As shown in Figure 1, DPUs 106 can be Ethernet or PON fed. Thus, the DPU backhaul can be point-to-point Ethernet based or alternatively point-to-multipoint PON. Some of the embodiments described herein relate to the Ethernet-based backhaul or aggregation network.

[0040] Figure 2 is a block diagram illustrating a CME 204 implemented as an application running in a SDN controller 202. In an embodiment, a CME 204 enables the configuration, wiring validation, and service provisioning for network devices (e.g., network devices 210) and physical network links added, modified, or removed among devices of a network.

[0041] In an embodiment, a CME 204 runs as a virtual machine (VM) in the SDN

controller 202, and communicates with various different types of network devices 210 (e.g., Distribution Point Units (DPU), L2 switches, OLTs, Broadband Network Gateways (BNG), routers, etc.) using one or more network management protocols. For example, the CME 204 and network devices 210 might communicate configuration information using NETCONF/YANG, where the CME 204 operates a NETCONF Client function and the network devices 210 run a NETCONF server function. Additional information related to NETCONF/YANG can be found in RFC 6241 and RFC 6020. As yet another example, the network devices 210 might communicate link layer information to the CME 204 using a link layer protocol such as Link Layer Discovery Protocol (LLDP).

[0042] In an embodiment, the SDN controller 202 includes a repository 208 of information relating to network devices 210, along with associated configuration files, operational status information, and performance statistics.

[0043] In an embodiment, ongoing connectivity is maintained between the CME 204 and network devices 210. For example, once a network device 210 is powered on, a connection is established with the CME 204 and regular keep-alive messages are sent between the network device and CME 204. In one embodiment, the management protocol used by the CME 204 and network devices 210 is NETCONF running over Secure Shell (SSH), which includes a keep- alive mechanism.

[0044] In an embodiment, a CME 204 includes wiring validation and performance management functions. For example, southbound interfaces (e.g., NETCONF /YANG,

OpenFlow®, etc.) of the SDN controller 202 can be used to program the underlying transport elements. The SDN controller 202 further includes northbound interfaces with other management software (e.g., cloud infrastructure management software, operator service orchestration software, etc.) through a representational state transfer (REST) interface 206. In an embodiment, the northbound interfaces include an interface with a GUI 212 for displaying various types of information related to the network devices 210.

[0045] Figure 3 is a flow-type diagram illustrating operations for automatic discovery, wiring validation, configuration, and management of network devices added to a physical network according to some embodiments. In some embodiments, some or all of the operations of Figure 3 may be performed by a CME 204 of a SDN controller 202. Thus, the operations in this flow diagram and others may be described with reference to the exemplary embodiments of the other figures. However, it should be understood that the operations of the flow diagram can be performed by embodiments other than those discussed with reference to the other figures, and the embodiments discussed with reference to these other figures can perform operations different than those discussed with reference to the flow diagrams.

[0046] At block 302, a request is received to add a network device or network link to a network. For example, the request for the addition of the network device or network link might be generated by a network administrator based on a determination that additional network resources are needed (e.g., due to bandwidth constraints, network congestion, network policies, etc.). In some situations, the network administrator generating the request may be a different person from an IT center technician or other person who, based on the request, adds the network device to the physical network topology and decides how to physically wire the network device to adjacent network devices. In other examples, the same person may generate the request to add a network device and add the network device to the network.

[0047] At block 304, the network device added to the network topology at block 302 is initially configured. In one embodiment, zero touch provisioning (ZTP) techniques can be used to automate the initial configuration of the network device. In general, an initial configuration includes network device-specific parameters, protocol agents (LLDP, OpenFlow®, NETCONF), and other interfaces and local software for basic operation of the network device. [0048] For example, when a newly added network device is powered on, the network device can be configured to contact a Dynamic Host Configuration Protocol (DHCP) server (e.g., a DHCP server 216), a Trivial File Transfer Protocol (TFTP) server, and an SDN server, among other possible networked devices, for initial configuration information. A DHCP server can assign an IP management address to the network device, which the network device can use to contact a TFTP server to retrieve an appropriate initial configuration file designated for the type of network device. The following illustrates an example table used by a TFTP server to retrieve an appropriate initial configuration file based on a network device role, media access control (MAC) address, IP address, or combinations thereof.

[0049]

[0050] As shown in the table, a TFTP server selects a configuration template file for the network device based on information about the device included in the request. The following is a fragment from an example configuration template file:

[0051] #Network node type: FTTPdp (DPU)

[0052] #MAC address: [00:02:5d:f7:af:cd]

[0053] #IP address: IP=10.125.144.236

[0054] #IP-address of TFTP server: 66=" 10.125.144.230"

[0055] #Boots with: BootFileName="DPUl-config.xml"

[0056] DomainServer=10.125.144.230

[0057] As shown above, the example configuration template file includes information identifying the network node type (e.g., a DPU device), MAC address, IP address, and a boot file name, among other information. In an embodiment, a TFTP server sends a configuration file specific for the network device and, in response to receiving the configuration file, the network device reboots and applies the received configuration.

[0058] At block 306, the network device connects to adjacent network devices and links. For example, once the network device is booted with the configuration file obtained from the TFTP server, the network device can establish network links with adjacent network devices. In general, the network device establishes links with adjacent network devices based on how the network device is physically wired to neighboring network devices in block 302. [0059] At block 308, in response to establishing a network link with an adjacent device in block 304, the network device sends an LLDP notification which is received by the SDN controller. In one embodiment, the CME 204 of the SDN controller 202 receives the LLDP notification, where the notification includes information about the network link. The CME 204 uses the LLDP notification to discover the physical network topology and stores information relating to the topology in a repository 208.

[0060] The following is an example of information contained in an LLDP message: "lldp- neighbor-activity notification via NETCONF: <Local host-name><Neighbor-host- name><Localport> <Remote port><Link Status>". As shown, information contained in an LLDP notification message can include a local hostname, a neighbor hostname, a local port, a remote port, and a link status. In some embodiments, LLDP messages may include other information relating to the network devices such as IP addresses, MAC addresses, and so forth.

[0061] At block 310, in response to receiving the LLDP message, the SDN controller performs wiring validation based on a network design policy. A process for performing wiring validation is described in more detail hereinafter with reference to Figure 4. At a high level, if the wiring validation is successful, then the SDN controller sends additional configuration to the network device at block 312. If the wiring validation is not successful, then at block 314 the SDN controller blocks the network device from operation, blocks the network link from operation, generates an alert, or combinations thereof.

[0062] At block 316, the SDN controller may cause display of a graphical interface displaying a representation of at least a portion of the physical network topology. As shown in block 316 of Figure 3, an example graphical interface displays several indications of network links (e.g., links L1-L3) established between spine switches (e.g., Swl and Sw2) and leaf switches (e.g., Sw3 and Sw4) which passed wiring validation (e.g., because the network links did not violate any network design policies at block 310). The graphical interface at block 316 further displays an indication of an invalid link L4 established between two leaf switches Sw3 and Sw4, for example, represented by a line with an X in the middle. The graphical display in block 316 is provided for illustrative purposes only; other example displays might display network links and wiring validation information for a network topology using different graphical representations.

[0063] Figure 4 is a flow-type diagram illustrating operations for performing wiring validation of a network device added to a physical network according to some embodiments. In some embodiments, some or all of the operations of Figure 4 may be performed by a CME 204 of a SDN controller 202. The operations illustrated in Figure 4 provide additional details related to the operations described above, for example, with respect to blocks 310-316 of Figure 3. [0064] At block 402, the SDN controller receives a message identifying a network link established between the network device and a neighboring network device. In an embodiment, a CME 204 of an SDN controller 202 listens for LLDP messages generated by network devices 210. As indicated above, network devices 210 generate LLDP notification messages in response to the network devices establishing network links with adjacent network devices. For example, a network device 210 might establish network links with adjacent network devices when the network device is added to the network, or in response to subsequent modifications to the network topology.

[0065] At block 404, the SDN controller determines whether the network link satisfies a network design policy specified for the network. In an embodiment, the network design policy includes rules relating to the topology of the physical network.

[0066] In one embodiment, a network design policy can be specified using IETF's Policy Management Architecture (PMA), which is based on an object oriented model utilizing Lightweight Directory Access Protocol (LDAP). LDAP is a client-server protocol designed for accessing directories over a network. In this example, a network administrator can create, view, and edit policies from a directory service using LDAP. Each policy rule component <condition, action> can be stored as an LDAP object. Furthermore, a network administrator or other user can create policy groups, which define sets of related policy rules.

[0067] Examples of rules which might be included in a network design policy include (a) allowed configurations of network links (e.g., DPU to Access Switch, Access Switch to Aggregate Switch, Aggregation Switch to OLT, Leaf to Spine, etc.); (b) port number ranges reserved for DPUs (e.g., DPU1 : 1-10), port number range from DPU to other nodes (e.g., DPU1 : 11-30); (c) allowed line speeds (e.g., Access: 1G, Aggregation 10G, OLT: 40G, etc.); (d) allowed Optics per port (e.g., ShortRange, LongRange, xSFP, etc.); (e) other policy rules.

[0068] At block 406, if the network link does not satisfy the network design policy, then the SDN controller can optionally block the network link or network device from operation. For example, if the SDN controller determines that a particular network link violates a network design policy, the controller might send instructions (e.g., using NETCONF/YANG or another configuration protocol) to prevent the network device from sending network traffic using the invalid link.

[0069] At block 408, further in response to determining that the network link does not satisfy the network design policy, the SDN controller can optionally generate a notification indicating that the network link does not satisfy the network design policy. In an embodiment, the notification can include an email or other message-based alert (e.g., sent to a network administrator), an alert displayed in a management console, an indication displayed on a graphical representation of the network (e.g., as shown in block 316 of Figure 3), or any other type of notification or combination thereof.

[0070] At block 410, if the network link satisfies the network design policy, then the SDN controller sends configuration information to the network device. In an embodiment, the CME 204 of the SDN controller 202 can send the configuration information, including other network related protocols and parameters, using NETCONF/YANG or any other configuration management protocol. Examples of configuration parameters and services that can be sent to the network device based on determining that the network link satisfies the network design policy includes, but is not limited to, quality of service (QoS) parameters, virtual local area network (VLAN) configurations, access control list (ACL) permissions, interior gateway protocol (IGP) settings, and media access control (MAC) filters.

[0071] The examples described in Figure 3 and Figure 4 illustrate operations for performing physical wiring validation of physical network devices added to a network topology. Examples of physical connectivity between physical network devices is described in subsequent sections, for example, in reference to Figure 5A. In an embodiment, similar operations to those describe with reference to physical wiring validation can be performed to validate logical network configurations. For example, a design policy can be specified to indicate permissible VLAN configurations within a service provider's network. In this example, in addition to validating the physical wiring of the physical network devices, an initial configuration of a VLAN space might also be validated before sending additional configuration information, as described in block 410 of Figure 4.

[0072] In an embodiment, after wiring validation, a network administrator or service orchestration entity (e.g., northbound to the SDN controller 202) might send a request to the CME 204 for service creation on a DPU of network devices 210 (e.g., to add triple play services for a given subscriber). In this example, the CME 204 might enable one or more service instances on customer facing ports and configure associated parameters based on the service profile for a given service. For example, a video service might require creation of service VLAN (SVLAN) and shaping parameters for downstream interfaces, and creation of a customer VLAN (CVLAN) on a customer facing port (e.g., one VLAN per service).

[0073] In an embodiment, a CME 204 monitors LLDP notifications for topology updates, periodically checks for expired network links, and notifies a topology manager 214 in response to topology updates. For example, a network link expires when the link does not receive an update from the switch for three LLDP speaker cycles. The CME 204 can be notified of changes to the topology via Simple Network Management Protocol (SNMP) traps. In an embodiment, any graphical displays of the network topology can be updated accordingly. [0074] In an embodiment, the CME 204 collects performance statistics related to DPUs and other access network devices or network elements. The collected information can be stored in a DPU repository for each device and active interface. For example, the following performance statistics can be collected and parsed using Interfaces Group (IF)-Management Information Base (MIBs) (detailed in the table below as defined in RFC 2863), and information related to interface counters can be populated into the CME 204 repository 208: (a) DPU/switch supporting total number of bytes received and transmitted on its backhaul interface; (b) DPU/switch supporting counters of a total number of bytes received and transmitted on each activated user port; (c) collecting data for a 15 minute interval while storing a previous 15 minute interval totals for all counts; (d) OAM requirements based on TR-156.

[0075] An electronic device stores and transmits (internally and/or with other electronic devices over a network) code (which is composed of software instructions and which is sometimes referred to as computer program code or a computer program) and/or data using machine -readable media (also called computer-readable media), such as machine-readable storage media (e.g., magnetic disks, optical disks, read only memory (ROM), flash memory devices, phase change memory) and machine -readable transmission media (also called a carrier) (e.g., electrical, optical, radio, acoustical or other form of propagated signals - such as carrier waves, infrared signals). Thus, an electronic device (e.g., a computer) includes hardware and software, such as a set of one or more processors coupled to one or more machine-readable storage media to store code for execution on the set of processors and/or to store data. For instance, an electronic device may include non-volatile memory containing the code since the non-volatile memory can persist code/data even when the electronic device is turned off (when power is removed), and while the electronic device is turned on that part of the code that is to be executed by the processor(s) of that electronic device is typically copied from the slower nonvolatile memory into volatile memory (e.g., dynamic random access memory (DRAM), static random access memory (SRAM)) of that electronic device. Typical electronic devices also include a set or one or more physical network interface(s) to establish network connections (to transmit and/or receive code and/or data using propagating signals) with other electronic devices. One or more parts of an embodiment of the invention may be implemented using different combinations of software, firmware, and/or hardware.

[0076] A network device (ND) is an electronic device that communicatively interconnects other electronic devices on the network (e.g., other network devices, end-user devices). Some network devices are "multiple services network devices" that provide support for multiple networking functions (e.g., routing, bridging, switching, Layer 2 aggregation, session border control, Quality of Service, and/or subscriber management), and/or provide support for multiple application services (e.g., data, voice, and video). Examples of network devices include, but are not limited to, distribution point units (DPUs), L2/L3 switches, optical line terminations (OLT), Broadband Network Gateways (BNG), leaf-and-spine switches, and routers.

[0077] Figure 5A illustrates connectivity between network devices (NDs) within an exemplary network, as well as three exemplary implementations of the NDs, according to some embodiments of the invention. Figure 5A shows NDs 500A-H, and their connectivity by way of lines between 500A-500B, 500B-500C, 500C-500D, 500D-500E, 500E-500F, 500F-500G, and 500A-500G, as well as between 500H and each of 500A, 500C, 500D, and 500G. These NDs are physical devices, and the connectivity between these NDs can be wireless or wired (often referred to as a link). An additional line extending from NDs 500A, 500E, and 500F illustrates that these NDs act as ingress and egress points for the network (and thus, these NDs are sometimes referred to as edge NDs; while the other NDs may be called core NDs).

[0078] Two of the exemplary ND implementations in Figure 5A are: 1) a special-purpose network device 502 that uses custom application-specific integrated-circuits (ASICs) and a special-purpose operating system (OS); and 2) a general purpose network device 504 that uses common off-the-shelf (COTS) processors and a standard OS. [0079] The special -purpose network device 502 includes networking hardware 510 comprising compute resource(s) 512 (which typically include a set of one or more processors), forwarding resource(s) 514 (which typically include one or more ASICs and/or network processors), and physical network interfaces (NIs) 516 (sometimes called physical ports), as well as non- transitory machine readable storage media 518 having stored therein networking software 520. A physical NI is hardware in a ND through which a network connection (e.g., wirelessly through a wireless network interface controller (WNIC) or through plugging in a cable to a physical port connected to a network interface controller (NIC)) is made, such as those shown by the connectivity between NDs 500A-H. During operation, the networking software 520 may be executed by the networking hardware 510 to instantiate a set of one or more networking software instance(s) 522. Each of the networking software instance(s) 522, and that part of the networking hardware 510 that executes that network software instance (be it hardware dedicated to that networking software instance and/or time slices of hardware temporally shared by that networking software instance with others of the networking software instance(s) 522), form a separate virtual network element 530A-R. Each of the virtual network element(s) (VNEs) 530A- R includes a control communication and configuration module 532A-R (sometimes referred to as a local control module or control communication module) and forwarding table(s) 534A-R, such that a given virtual network element (e.g., 53 OA) includes the control communication and configuration module (e.g., 532A), a set of one or more forwarding table(s) (e.g., 534A), and that portion of the networking hardware 510 that executes the virtual network element (e.g., 530A).

[0080] The special -purpose network device 502 is often physically and/or logically considered to include: 1) a ND control plane 524 (sometimes referred to as a control plane) comprising the compute resource(s) 512 that execute the control communication and configuration module(s) 532A-R; and 2) a ND forwarding plane 526 (sometimes referred to as a forwarding plane, a data plane, or a media plane) comprising the forwarding resource(s) 514 that utilize the forwarding table(s) 534A-R and the physical NIs 516. By way of example, where the ND is a router (or is implementing routing functionality), the ND control plane 524 (the compute resource(s) 512 executing the control communication and configuration module(s) 532A-R) is typically responsible for participating in controlling how data (e.g., packets) is to be routed (e.g., the next hop for the data and the outgoing physical NI for that data) and storing that routing information in the forwarding table(s) 534A-R, and the ND forwarding plane 526 is responsible for receiving that data on the physical NIs 516 and forwarding that data out the appropriate ones of the physical NIs 516 based on the forwarding table(s) 534A-R. [0081] Figure 5B illustrates an exemplary way to implement the special-purpose network device 502 according to some embodiments of the invention. Figure 5B shows a special-purpose network device including cards 538 (typically hot pluggable). While in some embodiments the cards 538 are of two types (one or more that operate as the ND forwarding plane 526

(sometimes called line cards), and one or more that operate to implement the ND control plane 524 (sometimes called control cards)), alternative embodiments may combine functionality onto a single card and/or include additional card types (e.g., one additional type of card is called a service card, resource card, or multi -application card). A service card can provide specialized processing (e.g., Layer 4 to Layer 7 services (e.g., firewall, Internet Protocol Security (IPsec), Secure Sockets Layer (SSL) / Transport Layer Security (TLS), Intrusion Detection System (IDS), peer-to-peer (P2P), Voice over IP (VoIP) Session Border Controller, Mobile Wireless Gateways (Gateway General Packet Radio Service (GPRS) Support Node (GGSN), Evolved Packet Core (EPC) Gateway)). By way of example, a service card may be used to terminate IPsec tunnels and execute the attendant authentication and encryption algorithms. These cards are coupled together through one or more interconnect mechanisms illustrated as backplane 536 (e.g., a first full mesh coupling the line cards and a second full mesh coupling all of the cards).

[0082] Returning to Figure 5 A, the general purpose network device 504 includes hardware 540 comprising a set of one or more processor(s) 542 (which are often COTS processors) and network interface controller(s) 544 (NICs; also known as network interface cards) (which include physical NIs 546), as well as non-transitory machine readable storage media 548 having stored therein software 550. During operation, the processor(s) 542 execute the software 550 to instantiate one or more sets of one or more applications 564A-R. While one embodiment does not implement virtualization, alternative embodiments may use different forms of virtualization. For example, in one such alternative embodiment the virtualization layer 554 represents the kernel of an operating system (or a shim executing on a base operating system) that allows for the creation of multiple instances 562A-R called software containers that may each be used to execute one (or more) of the sets of applications 564A-R; where the multiple software containers (also called virtualization engines, virtual private servers, or jails) are user spaces (typically a virtual memory space) that are separate from each other and separate from the kernel space in which the operating system is run; and where the set of applications running in a given user space, unless explicitly allowed, cannot access the memory of the other processes. In another such alternative embodiment the virtualization layer 554 represents a hypervisor (sometimes referred to as a virtual machine monitor (VMM)) or a hypervisor executing on top of a host operating system, and each of the sets of applications 564A-R is run on top of a guest operating system within an instance 562A-R called a virtual machine (which may in some cases be considered a tightly isolated form of software container) that is run on top of the hypervisor - the guest operating system and application may not know they are running on a virtual machine as opposed to running on a "bare metal" host electronic device, or through para-virtualization the operating system and/or application may be aware of the presence of virtualization for optimization purposes. In yet other alternative embodiments, one, some or all of the applications are implemented as unikernel(s), which can be generated by compiling directly with an application only a limited set of libraries (e.g., from a library operating system (LibOS) including drivers/libraries of OS services) that provide the particular OS services needed by the application. As a unikernel can be implemented to run directly on hardware 540, directly on a hypervisor (in which case the unikernel is sometimes described as running within a LibOS virtual machine), or in a software container, embodiments can be implemented fully with unikernels running directly on a hypervisor represented by virtualization layer 554, unikernels running within software containers represented by instances 562A-R, or as a combination of unikernels and the above-described techniques (e.g., unikernels and virtual machines both run directly on a hypervisor, unikernels and sets of applications that are run in different software containers).

[0083] The instantiation of the one or more sets of one or more applications 564A-R, as well as virtualization if implemented, are collectively referred to as software instance(s) 552. Each set of applications 564A-R, corresponding virtualization construct (e.g., instance 562A-R) if implemented, and that part of the hardware 540 that executes them (be it hardware dedicated to that execution and/or time slices of hardware temporally shared), forms a separate virtual network element(s) 560A-R.

[0084] The virtual network element(s) 560A-R perform similar functionality to the virtual network element(s) 530A-R - e.g., similar to the control communication and configuration module(s) 532A and forwarding table(s) 534A (this virtualization of the hardware 540 is sometimes referred to as network function virtualization (NFV)). Thus, NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which could be located in Data centers, NDs, and customer premise equipment (CPE). While embodiments of the invention are illustrated with each instance 562A-R corresponding to one VNE 560A-R, alternative embodiments may implement this correspondence at a finer level granularity (e.g., line card virtual machines virtualize line cards, control card virtual machine virtualize control cards, etc.); it should be understood that the techniques described herein with reference to a correspondence of instances 562A-R to VNEs also apply to embodiments where such a finer level of granularity and/or unikernels are used. [0085] In certain embodiments, the virtualization layer 554 includes a virtual switch that provides similar forwarding services as a physical Ethernet switch. Specifically, this virtual switch forwards traffic between instances 562A-R and the NIC(s) 544, as well as optionally between the instances 562A-R; in addition, this virtual switch may enforce network isolation between the VNEs 560A-R that by policy are not permitted to communicate with each other (e.g., by honoring virtual local area networks (VLANs)).

[0086] The third exemplary ND implementation in Figure 5 A is a hybrid network device 506, which includes both custom ASICs/special-purpose OS and COTS processors/standard OS in a single ND or a single card within an ND. In certain embodiments of such a hybrid network device, a platform VM (i.e., a VM that that implements the functionality of the special-purpose network device 502) could provide for para-virtualization to the networking hardware present in the hybrid network device 506.

[0087] Regardless of the above exemplary implementations of an ND, when a single one of multiple VNEs implemented by an ND is being considered (e.g., only one of the VNEs is part of a given virtual network) or where only a single VNE is currently being implemented by an ND, the shortened term network element (NE) is sometimes used to refer to that VNE. Also in all of the above exemplary implementations, each of the VNEs (e.g., VNE(s) 530A-R, VNEs 560A-R, and those in the hybrid network device 506) receives data on the physical NIs (e.g., 516, 546) and forwards that data out the appropriate ones of the physical NIs (e.g., 516, 546). For example, a VNE implementing IP router functionality forwards IP packets on the basis of some of the IP header information in the IP packet; where IP header information includes source IP address, destination IP address, source port, destination port (where "source port" and "destination port" refer herein to protocol ports, as opposed to physical ports of a ND), transport protocol (e.g., user datagram protocol (UDP), Transmission Control Protocol (TCP), and differentiated services code point (DSCP) values.

[0088] Figure 5C illustrates various exemplary ways in which VNEs may be coupled according to some embodiments of the invention. Figure 5C shows VNEs 570A.1-570A.P (and optionally VNEs 570A.Q-570A.R) implemented in ND 500A and VNE 570H.1 in ND 500H. In Figure 5C, VNEs 570A.1-P are separate from each other in the sense that they can receive packets from outside ND 500A and forward packets outside of ND 500A; VNE 570A.1 is coupled with VNE 570H.1, and thus they communicate packets between their respective NDs; VNE 570A.2-570A.3 may optionally forward packets between themselves without forwarding them outside of the ND 500A; and VNE 570A.P may optionally be the first in a chain of VNEs that includes VNE 570A.Q followed by VNE 570A.R (this is sometimes referred to as dynamic service chaining, where each of the VNEs in the series of VNEs provides a different service - e.g., one or more layer 4-7 network services). While Figure 5C illustrates various exemplary relationships between the VNEs, alternative embodiments may support other relationships (e.g., more/fewer VNEs, more/fewer dynamic service chains, multiple different dynamic service chains with some common VNEs and some different VNEs).

[0089] The NDs of Figure 5A, for example, may form part of the Internet or a private network; and other electronic devices (not shown; such as end user devices including workstations, laptops, netbooks, tablets, palm tops, mobile phones, smartphones, phablets, multimedia phones, Voice Over Internet Protocol (VOIP) phones, terminals, portable media players, Global Positioning System (GPS) units, wearable devices, gaming systems, set-top boxes, Internet enabled household appliances) may be coupled to the network (directly or through other networks such as access networks) to communicate over the network (e.g., the Internet or virtual private networks (VPNs) overlaid on (e.g., tunneled through) the Internet) with each other (directly or through servers) and/or access content and/or services. Such content and/or services are typically provided by one or more servers (not shown) belonging to a service/content provider or one or more end user devices (not shown) participating in a peer-to-peer (P2P) service, and may include, for example, public webpages (e.g., free content, store fronts, search services), private webpages (e.g., username/password accessed webpages providing email services), and/or corporate networks over VPNs. For instance, end user devices may be coupled (e.g., through customer premise equipment coupled to an access network (wired or wirelessly)) to edge NDs, which are coupled (e.g., through one or more core NDs) to other edge NDs, which are coupled to electronic devices acting as servers. However, through compute and storage virtualization, one or more of the electronic devices operating as the NDs in Figure 5A may also host one or more such servers (e.g., in the case of the general purpose network device 504, one or more of the software instances 562A-R may operate as servers; the same would be true for the hybrid network device 506; in the case of the special-purpose network device 502, one or more such servers could also be run on a virtualization layer executed by the compute resource(s) 512); in which case the servers are said to be co-located with the VNEs of that ND.

[0090] A virtual network is a logical abstraction of a physical network (such as that in Figure 5A) that provides network services (e.g., L2 and/or L3 services). A virtual network can be implemented as an overlay network (sometimes referred to as a network virtualization overlay) that provides network services (e.g., layer 2 (L2, data link layer) and/or layer 3 (L3, network layer) services) over an underlay network (e.g., an L3 network, such as an Internet Protocol (IP) network that uses tunnels (e.g., generic routing encapsulation (GRE), layer 2 tunneling protocol (L2TP), IPSec) to create the overlay network). [0091] A network virtualization edge (NVE) sits at the edge of the underlay network and participates in implementing the network virtualization; the network-facing side of the NVE uses the underlay network to tunnel frames to and from other NVEs; the outward-facing side of the NVE sends and receives data to and from systems outside the network. A virtual network instance (VNI) is a specific instance of a virtual network on a NVE (e.g., a NE/VNE on an ND, a part of a NE/VNE on a ND where that NE/VNE is divided into multiple VNEs through emulation); one or more VNIs can be instantiated on an NVE (e.g., as different VNEs on an ND). A virtual access point (VAP) is a logical connection point on the NVE for connecting external systems to a virtual network; a VAP can be physical or virtual ports identified through logical interface identifiers (e.g., a VLAN ID).

[0092] Examples of network services include: 1) an Ethernet LAN emulation service (an Ethernet-based multipoint service similar to an Internet Engineering Task Force (IETF) Multiprotocol Label Switching (MPLS) or Ethernet VPN (EVPN) service) in which external systems are interconnected across the network by a LAN environment over the underlay network (e.g., an NVE provides separate L2 VNIs (virtual switching instances) for different such virtual networks, and L3 (e.g., IP/MPLS) tunneling encapsulation across the underlay network); and 2) a virtualized IP forwarding service (similar to IETF IP VPN (e.g., Border Gateway Protocol (BGP)/MPLS IPVPN) from a service definition perspective) in which external systems are interconnected across the network by an L3 environment over the underlay network (e.g., an NVE provides separate L3 VNIs (forwarding and routing instances) for different such virtual networks, and L3 (e.g., IP/MPLS) tunneling encapsulation across the underlay network)). Network services may also include quality of service capabilities (e.g., traffic classification marking, traffic conditioning and scheduling), security capabilities (e.g., filters to protect customer premises from network - originated attacks, to avoid malformed route announcements), and management capabilities (e.g., full detection and processing).

[0093] Fig. 5D illustrates a network with a single network element on each of the NDs of Figure 5A, and within this straight forward approach contrasts a traditional distributed approach (commonly used by traditional routers) with a centralized approach for maintaining reachability and forwarding information (also called network control), according to some embodiments of the invention. Specifically, Figure 5D illustrates network elements (NEs) 570A-H with the same connectivity as the NDs 500A-H of Figure 5A.

[0094] Figure 5D illustrates that the distributed approach 572 distributes responsibility for generating the reachability and forwarding information across the NEs 570A-H; in other words, the process of neighbor discovery and topology discovery is distributed. [0095] For example, where the special -purpose network device 502 is used, the control communication and configuration module(s) 532A-R of the ND control plane 524 typically include a reachability and forwarding information module to implement one or more routing protocols (e.g., an exterior gateway protocol such as Border Gateway Protocol (BGP), Interior Gateway Protocol(s) (IGP) (e.g., Open Shortest Path First (OSPF), Intermediate System to Intermediate System (IS-IS), Routing Information Protocol (RIP), Label Distribution Protocol (LDP), Resource Reservation Protocol (RSVP) (including RS VP-Traffic Engineering (TE): Extensions to RSVP for LSP Tunnels and Generalized Multi-Protocol Label Switching

(GMPLS) Signaling RSVP-TE)) that communicate with other NEs to exchange routes, and then selects those routes based on one or more routing metrics. Thus, the NEs 570A-H (e.g., the compute resource(s) 512 executing the control communication and configuration module(s) 532A-R) perform their responsibility for participating in controlling how data (e.g., packets) is to be routed (e.g., the next hop for the data and the outgoing physical NI for that data) by distributively determining the reachability within the network and calculating their respective forwarding information. Routes and adjacencies are stored in one or more routing structures (e.g., Routing Information Base (RIB), Label Information Base (LIB), one or more adjacency structures) on the ND control plane 524. The ND control plane 524 programs the ND forwarding plane 526 with information (e.g., adjacency and route information) based on the routing structure(s). For example, the ND control plane 524 programs the adjacency and route information into one or more forwarding table(s) 534A-R (e.g., Forwarding Information Base (FIB), Label Forwarding Information Base (LFIB), and one or more adjacency structures) on the ND forwarding plane 526. For layer 2 forwarding, the ND can store one or more bridging tables that are used to forward data based on the layer 2 information in that data. While the above example uses the special -purpose network device 502, the same distributed approach 572 can be implemented on the general purpose network device 504 and the hybrid network device 506.

[0096] Figure 5D illustrates that a centralized approach 574 (also known as software defined networking (SDN)) that decouples the system that makes decisions about where traffic is sent from the underlying systems that forwards traffic to the selected destination. The illustrated centralized approach 574 has the responsibility for the generation of reachability and forwarding information in a centralized control plane 576 (sometimes referred to as a SDN control module, controller, network controller, OpenFlow® controller, SDN controller, control plane node, network virtualization authority, or management control entity), and thus the process of neighbor discovery and topology discovery is centralized. The centralized control plane 576 has a south bound interface 582 with a data plane 580 (sometime referred to the infrastructure layer, network forwarding plane, or forwarding plane (which should not be confused with a ND forwarding plane)) that includes the NEs 570A-H (sometimes referred to as switches, forwarding elements, data plane elements, or nodes). The centralized control plane 576 includes a network controller 578, which includes a centralized reachability and forwarding information module 579 that determines the reachability within the network and distributes the forwarding information to the NEs 570A-H of the data plane 580 over the south bound interface 582 (which may use the OpenFlow® protocol). Thus, the network intelligence is centralized in the centralized control plane 576 executing on electronic devices that are typically separate from the NDs.

[0097] In one embodiment, the SDN controller 202 of Figure 2 can be implemented as a network controller 578. For example, the network controller 578 can include a control and management entity (CME) 204, as described in more detail in reference to Figure 2. The CME 204 communicates with various network devices and network elements over a south bound interface 582, which may use various configuration protocols including NETCONF/YANG, OpenFlow®, LLDP, etc.

[0098] For example, where the special -purpose network device 502 is used in the data plane 580, each of the control communication and configuration module(s) 532A-R of the ND control plane 524 typically include a control agent that provides the VNE side of the south bound interface 582. In this case, the ND control plane 524 (the compute resource(s) 512 executing the control communication and configuration module(s) 532A-R) performs its responsibility for participating in controlling how data (e.g., packets) is to be routed (e.g., the next hop for the data and the outgoing physical NI for that data) through the control agent communicating with the centralized control plane 576 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 579 (it should be understood that in some embodiments of the invention, the control communication and configuration module(s) 532A-R, in addition to communicating with the centralized control plane 576, may also play some role in determining reachability and/or calculating forwarding information - albeit less so than in the case of a distributed approach; such embodiments are generally considered to fall under the centralized approach 574, but may also be considered a hybrid approach).

[0099] While the above example uses the special -purpose network device 502, the same centralized approach 574 can be implemented with the general purpose network device 504 (e.g., each of the VNE 560A-R performs its responsibility for controlling how data (e.g., packets) is to be routed (e.g., the next hop for the data and the outgoing physical NI for that data) by communicating with the centralized control plane 576 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 579; it should be understood that in some embodiments of the invention, the VNEs 560A-R, in addition to communicating with the centralized control plane 576, may also play some role in determining reachability and/or calculating forwarding information - albeit less so than in the case of a distributed approach) and the hybrid network device 506. In fact, the use of SDN techniques can enhance the NFV techniques typically used in the general purpose network device 504 or hybrid network device 506 implementations as NFV is able to support SDN by providing an infrastructure upon which the SDN software can be run, and NFV and SDN both aim to make use of commodity server hardware and physical switches.

[00100] Figure 5D also shows that the centralized control plane 576 has a north bound interface 584 to an application layer 586, in which resides application(s) 588. The centralized control plane 576 has the ability to form virtual networks 592 (sometimes referred to as a logical forwarding plane, network services, or overlay networks (with the NEs 570A-H of the data plane 580 being the underlay network)) for the application(s) 588. Thus, the centralized control plane 576 maintains a global view of all NDs and configured NEs/VNEs, and it maps the virtual networks to the underlying NDs efficiently (including maintaining these mappings as the physical network changes either through hardware (ND, link, or ND component) failure, addition, or removal).

[00101] While Figure 5D shows the distributed approach 572 separate from the centralized approach 574, the effort of network control may be distributed differently or the two combined in certain embodiments of the invention. For example: 1) embodiments may generally use the centralized approach (SDN) 574, but have certain functions delegated to the NEs (e.g., the distributed approach may be used to implement one or more of fault monitoring, performance monitoring, protection switching, and primitives for neighbor and/or topology discovery); or 2) embodiments of the invention may perform neighbor discovery and topology discovery via both the centralized control plane and the distributed protocols, and the results compared to raise exceptions where they do not agree. Such embodiments are generally considered to fall under the centralized approach 574, but may also be considered a hybrid approach.

[00102] While Figure 5D illustrates the simple case where each of the NDs 500A-H implements a single NE 570A-H, it should be understood that the network control approaches described with reference to Figure 5D also work for networks where one or more of the NDs 500A-H implement multiple VNEs (e.g., VNEs 530A-R, VNEs 560A-R, those in the hybrid network device 506). Alternatively or in addition, the network controller 578 may also emulate the implementation of multiple VNEs in a single ND. Specifically, instead of (or in addition to) implementing multiple VNEs in a single ND, the network controller 578 may present the implementation of a VNE/NE in a single ND as multiple VNEs in the virtual networks 592 (all in the same one of the virtual network(s) 592, each in different ones of the virtual network(s) 592, or some combination). For example, the network controller 578 may cause an ND to implement a single VNE (a NE) in the underlay network, and then logically divide up the resources of that NE within the centralized control plane 576 to present different VNEs in the virtual network(s) 592 (where these different VNEs in the overlay networks are sharing the resources of the single VNE/NE implementation on the ND in the underlay network).

[00103] On the other hand, Figures 5E and 5F respectively illustrate exemplary abstractions of NEs and VNEs that the network controller 578 may present as part of different ones of the virtual networks 592. Figure 5E illustrates the simple case of where each of the NDs 500A-H implements a single NE 570A-H (see Figure 5D), but the centralized control plane 576 has abstracted multiple of the NEs in different NDs (the NEs 570A-C and G-H) into (to represent) a single NE 5701 in one of the virtual network(s) 592 of Figure 5D, according to some embodiments of the invention. Figure 5E shows that in this virtual network, the NE 5701 is coupled to NE 570D and 570F, which are both still coupled to NE 570E.

[00104] Figure 5F illustrates a case where multiple VNEs (VNE 570A.1 and VNE 570H.1) are implemented on different NDs (ND 500A and ND 500H) and are coupled to each other, and where the centralized control plane 576 has abstracted these multiple VNEs such that they appear as a single VNE 570T within one of the virtual networks 592 of Figure 5D, according to some embodiments of the invention. Thus, the abstraction of a NE or VNE can span multiple NDs.

[00105] While some embodiments of the invention implement the centralized control plane 576 as a single entity (e.g., a single instance of software running on a single electronic device), alternative embodiments may spread the functionality across multiple entities for redundancy and/or scalability purposes (e.g., multiple instances of software running on different electronic devices).

[00106] Similar to the network device implementations, the electronic device(s) running the centralized control plane 576, and thus the network controller 578 including the centralized reachability and forwarding information module 579, may be implemented a variety of ways (e.g., a special purpose device, a general-purpose (e.g., COTS) device, or hybrid device). These electronic device(s) would similarly include compute resource(s), a set or one or more physical NICs, and a non-transitory machine-readable storage medium having stored thereon the centralized control plane software. For instance, Figure 6 illustrates, a general purpose control plane device 604 including hardware 640 comprising a set of one or more processor(s) 642 (which are often COTS processors) and network interface controller(s) 644 (NICs; also known as network interface cards) (which include physical NIs 646), as well as non-transitory machine readable storage media 648 having stored therein centralized control plane (CCP) software 650.

[00107] In embodiments that use compute virtualization, the processor(s) 642 typically execute software to instantiate a virtualization layer 654 (e.g., in one embodiment the virtualization layer 654 represents the kernel of an operating system (or a shim executing on a base operating system) that allows for the creation of multiple instances 662A-R called software containers (representing separate user spaces and also called virtualization engines, virtual private servers, or jails) that may each be used to execute a set of one or more applications; in another embodiment the virtualization layer 654 represents a hypervisor (sometimes referred to as a virtual machine monitor (VMM)) or a hypervisor executing on top of a host operating system, and an application is run on top of a guest operating system within an instance 662A-R called a virtual machine (which in some cases may be considered a tightly isolated form of software container) that is run by the hypervisor ; in another embodiment, an application is implemented as a unikernel, which can be generated by compiling directly with an application only a limited set of libraries (e.g., from a library operating system (LibOS) including drivers/libraries of OS services) that provide the particular OS services needed by the application, and the unikernel can run directly on hardware 640, directly on a hypervisor represented by virtualization layer 654 (in which case the unikernel is sometimes described as running within a LibOS virtual machine), or in a software container represented by one of instances 662A-R). Again, in embodiments where compute virtualization is used, during operation an instance of the CCP software 650 (illustrated as CCP instance 676A) is executed (e.g., within the instance 662A) on the virtualization layer 654. In embodiments where compute virtualization is not used, the CCP instance 676A is executed, as a unikernel or on top of a host operating system, on the "bare metal" general purpose control plane device 604. The instantiation of the CCP instance 676A, as well as the virtualization layer 654 and instances 662A-R if implemented, are collectively referred to as software instance(s) 652.

[00108] In some embodiments, the CCP instance 676A includes a network controller instance 678. The network controller instance 678 includes a centralized reachability and forwarding information module instance 679 (which is a middleware layer providing the context of the network controller 578 to the operating system and communicating with the various NEs), and an CCP application layer 680 (sometimes referred to as an application layer) over the middleware layer (providing the intelligence required for various network operations such as protocols, network situational awareness, and user - interfaces). At a more abstract level, this CCP application layer 680 within the centralized control plane 576 works with virtual network view(s) (logical view(s) of the network) and the middleware layer provides the conversion from the virtual networks to the physical view.

[00109] The centralized control plane 576 transmits relevant messages to the data plane 580 based on CCP application layer 680 calculations and middleware layer mapping for each flow. A flow may be defined as a set of packets whose headers match a given pattern of bits; in this sense, traditional IP forwarding is also flow-based forwarding where the flows are defined by the destination IP address for example; however, in other implementations, the given pattern of bits used for a flow definition may include more fields (e.g., 10 or more) in the packet headers. Different NDs/NEs/VNEs of the data plane 580 may receive different messages, and thus different forwarding information. The data plane 580 processes these messages and programs the appropriate flow information and corresponding actions in the forwarding tables (sometime referred to as flow tables) of the appropriate NE/VNEs, and then the NEs/VNEs map incoming packets to flows represented in the forwarding tables and forward packets based on the matches in the forwarding tables.

[00110] Standards such as OpenFlow® define the protocols used for the messages, as well as a model for processing the packets. The model for processing packets includes header parsing, packet classification, and making forwarding decisions. Header parsing describes how to interpret a packet based upon a well-known set of protocols. Some protocol fields are used to build a match structure (or key) that will be used in packet classification (e.g., a first key field could be a source media access control (MAC) address, and a second key field could be a destination MAC address).

[00111] Packet classification involves executing a lookup in memory to classify the packet by determining which entry (also referred to as a forwarding table entry or flow entry) in the forwarding tables best matches the packet based upon the match structure, or key, of the forwarding table entries. It is possible that many flows represented in the forwarding table entries can correspond/match to a packet; in this case the system is typically configured to determine one forwarding table entry from the many according to a defined scheme (e.g., selecting a first forwarding table entry that is matched). Forwarding table entries include both a specific set of match criteria (a set of values or wildcards, or an indication of what portions of a packet should be compared to a particular value/values/wildcards, as defined by the matching capabilities - for specific fields in the packet header, or for some other packet content), and a set of one or more actions for the data plane to take on receiving a matching packet. For example, an action may be to push a header onto the packet, for the packet using a particular port, flood the packet, or simply drop the packet. Thus, a forwarding table entry for IPv4/IPv6 packets with a particular transmission control protocol (TCP) destination port could contain an action specifying that these packets should be dropped.

[00112] Making forwarding decisions and performing actions occurs, based upon the forwarding table entry identified during packet classification, by executing the set of actions identified in the matched forwarding table entry on the packet.

[00113] However, when an unknown packet (for example, a "missed packet" or a "match- miss" as used in OpenFlow® parlance) arrives at the data plane 580, the packet (or a subset of the packet header and content) is typically forwarded to the centralized control plane 576. The centralized control plane 576 will then program forwarding table entries into the data plane 580 to accommodate packets belonging to the flow of the unknown packet. Once a specific forwarding table entry has been programmed into the data plane 580 by the centralized control plane 576, the next packet with matching credentials will match that forwarding table entry and take the set of actions associated with that matched entry.

[00114] A network interface (NI) may be physical or virtual; and in the context of IP, an interface address is an IP address assigned to a NI, be it a physical NI or virtual NI. A virtual NI may be associated with a physical NI, with another virtual interface, or stand on its own (e.g., a loopback interface, a point-to-point protocol interface). A NI (physical or virtual) may be numbered (a NI with an IP address) or unnumbered (a NI without an IP address). A loopback interface (and its loopback address) is a specific type of virtual NI (and IP address) of a NE/VNE (physical or virtual) often used for management purposes; where such an IP address is referred to as the nodal loopback address. The IP address(es) assigned to the NI(s) of a ND are referred to as IP addresses of that ND; at a more granular level, the IP address(es) assigned to NI(s) assigned to a NE/VNE implemented on a ND can be referred to as IP addresses of that NE/VNE.

[00115] Each VNE (e.g., a virtual router, a virtual bridge (which may act as a virtual switch instance in a Virtual Private LAN Service (VPLS) is typically independently administrable. For example, in the case of multiple virtual routers, each of the virtual routers may share system resources but is separate from the other virtual routers regarding its management domain, AAA (authentication, authorization, and accounting) name space, IP address, and routing database(s). Multiple VNEs may be employed in an edge ND to provide direct network access and/or different classes of services for subscribers of service and/or content providers.

[00116] Within certain NDs, "interfaces" that are independent of physical NIs may be configured as part of the VNEs to provide higher-layer protocol and service information (e.g., Layer 3 addressing). The subscriber records in the AAA server identify, in addition to the other subscriber configuration requirements, to which context (e.g., which of the VNEs/NEs) the corresponding subscribers should be bound within the ND. As used herein, a binding forms an association between a physical entity (e.g., physical NI, channel) or a logical entity (e.g., circuit such as a subscriber circuit or logical circuit (a set of one or more subscriber circuits)) and a context's interface over which network protocols (e.g., routing protocols, bridging protocols) are configured for that context. Subscriber data flows on the physical entity when some higher-layer protocol interface is configured and associated with that physical entity.

[00117] Some NDs provide support for implementing VPNs (Virtual Private Networks) (e.g., Layer 2 VPNs and/or Layer 3 VPNs). For example, the ND where a provider's network and a customer's network are coupled are respectively referred to as PEs (Provider Edge) and CEs (Customer Edge). In a Layer 2 VPN, forwarding typically is performed on the CE(s) on either end of the VPN and traffic is sent across the network (e.g., through one or more PEs coupled by other NDs). Layer 2 circuits are configured between the CEs and PEs (e.g., an Ethernet port, an ATM permanent virtual circuit (PVC), a Frame Relay PVC). In a Layer 3 VPN, routing typically is performed by the PEs. By way of example, an edge ND that supports multiple VNEs may be deployed as a PE; and a VNE may be configured with a VPN protocol, and thus that VNE is referred as a VPN VNE.

[00118] Some NDs provide support for VPLS (Virtual Private LAN Service). For example, in a VPLS network, end user devices access content/services provided through the VPLS network by coupling to CEs, which are coupled through PEs coupled by other NDs. VPLS networks can be used for implementing triple play network applications (e.g., data applications (e.g., highspeed Internet access), video applications (e.g., television service such as IPTV (Internet Protocol Television), VoD (Video-on-Demand) service), and voice applications (e.g., VoIP (Voice over Internet Protocol) service)), VPN services, etc. VPLS is a type of layer 2 VPN that can be used for multi-point connectivity. VPLS networks also allow end use devices that are coupled with CEs at separate geographical locations to communicate with each other across a Wide Area Network (WAN) as if they were directly attached to each other in a Local Area Network (LAN) (referred to as an emulated LAN).

[00119] In VPLS networks, each CE typically attaches, possibly through an access network (wired and/or wireless), to a bridge module of a PE via an attachment circuit (e.g., a virtual link or connection between the CE and the PE). The bridge module of the PE attaches to an emulated LAN through an emulated LAN interface. Each bridge module acts as a "Virtual Switch Instance" (VSI) by maintaining a forwarding table that maps MAC addresses to pseudowires and attachment circuits. PEs forward frames (received from CEs) to destinations (e.g., other CEs, other PEs) based on the MAC destination address field included in those frames. [00120] While the flow diagrams in the figures show a particular order of operations performed by certain embodiments of the invention, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.).

[00121] While the invention has been described in terms of several embodiments, those skilled in the art will recognize that the invention is not limited to the embodiments described, can be practiced with modification and alteration within the spirit and scope of the appended claims. The description is thus to be regarded as illustrative instead of limiting.