WO2017168204A1

WO2017168204A1 - Ecmp multicast over existing mpls implementations

Info

Publication number: WO2017168204A1
Application number: PCT/IB2016/051752
Authority: WO
Inventors: David Ian Allan
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2016-03-28
Filing date: 2016-03-28
Publication date: 2017-10-05

Abstract

A method is implemented by a network device, where the network device implements multi- protocol label switching (MPLS) and equal cost multi-path (ECMP) in a source packet in routing (SPRING) domain. The method determines forwarding information for the network device. The method selects a multicast distribution tree, determines a set of next hops to reach a current downstream node with the role in the multicast distribution tree, selects one next hop from the set of next hops using an entropy source to determine the selected next hop, and inserts a next hop label forwarding entry (NHLFE) into a NHLFE table with label stack including the selected next hop to reach the current downstream node with the role in the multicast distribution tree.

Description

ECMP MULTICAST OVER EXISTING MPLS IMPLEMENTATIONS

FIELD

[0001] Embodiments of the invention relate to the field of interworking of communication networks; and more specifically, to the configuration of network nodes to implement forwarding of multicast in source packet in routing (SPRING) networks.

BACKGROUND

[0002] Numerous techniques and protocols exist for configuring networks to handle multicast traffic. For Internet Protocol (IP) and/or multiprotocol label switching (MPLS) implementations the existing solutions for multicast are based on multicast label distribution protocol (mLDP) or protocol independent multicast (PIM). These are all techniques that depend on a unicast shortest path first (SPF) computation followed by handshaking between peers to sort out a loop free multicast distribution tree (MDT) for each multicast source. In these approaches, a

comprehensive view of multicast connectivity does not exist at the node level, all decisions are entirely local and driven by the combination of the unicast forwarding solution derived from routing information and peer interactions.

[0003] Shortest path bridging (SPB) is a protocol related to computer networking for the configuration of computer networks that enables multipath routing. In one embodiment, the protocol is specified by the Institute of Electrical and Electronics Engineers (IEEE) 802. laq standard. This protocol replaces prior standards such as spanning tree protocols. SPB enables all paths in the computing network to be active with multiple equal costs paths being utilized through load sharing and similar technologies. The standard enables the implementation of logical Ethernet networks in Ethernet infrastructures using a link state protocol to advertise the topology and logical network memberships of the nodes in the network. SPB implements large scale multicast as part of implementing virtualized broadcast domains. A key distinguishing feature of the SPB standard is that the MDTs are computed from the information in the routing system's link state database via an all-pairs- shortest-path algorithm, which minimizes the amount of control messaging to converge multicast; the only real time peer interaction being advertisement of topology changes to the IGP database.

[0004] SPRING is an exemplary profile of the use of MPLS technology whereby global identifiers are used in the form of a global label assigned per label switched route (LSR) used for forwarding to that LSR. A full mesh of unicast tunnels is constructed via every node in the network computing the shortest path to every other node and installing the associated global labels accordingly. In the case of SPRING, this also allows explicit paths to be set up via the application of label stacks at the network ingress. Encompassed with this approach is the concept of a strict (every hop specified) or loose (some waypoints specified) route dependent on how exhaustively the ingress applied label stack specifies the path.

[0005] Proposals have been made to use global identifiers in the dataplane combined with the IEEE 802. laq technique of advertising multicast registrations in the interior gateway protocol (IGP) and replicating the "all pairs shortest path" approach of IEEE 802. laq to compute MDTs without the additional handshaking associated with legacy approaches to multicast. Such an approach would inherit a lot of desirable properties embodied in the IEEE 802. laq approach, primarily in the simplification of the amount of control plane exchange required to converge the network. Further proposals have been made to combine the IEEE 802. laq approach with SPRING tunneling such that multicast distribution tree construction is a hybrid of sparsely deployed multicast state and unicast tunnels significantly reducing the overall amount of multicast state in the network.

[0006] Given the above context, a node in the SPRING network could compute its role in implementing any given multicast (S, G) tree purely from information in the IGP. An algorithm that starts with all pairs shortest path computation augmented with algorithms to identify the nodes with specific roles of source, leaf and/or replication point may be employed by each node. Existing unicast tunnels may be used between sources, replication points and leaves of an MDT such that the overall amount of state in the network is minimized. One advantage to using tunnels as a component of MDT construction would be that such tunnels would be subject to equal cost multipath (ECMP) load spreading, improving the overall efficiency of the network. However many MPLS implementations may not anticipate a combination of multicast replication and applying ECMP treatment to each replicated packet as part of the overall incoming label map (ILM) to next hop label forwarding entry (NHLFE) forwarding paradigm as used in a MPLS architecture.

SUMMARY

[0007] In one embodiment, a method is implemented by a network device, where the network device implements multi-protocol label switching (MPLS) and equal cost multi-path (ECMP) in a source packet in routing (SPRING) domain. The method determines forwarding information for the network device. The method selects a multicast distribution tree, determines a set of next hops to reach a current downstream node with the role in the multicast distribution tree, selects one next hop from the set of next hops using an entropy source to determine the selected next hop, and inserts a next hop label forwarding entry (NHLFE) into a NHLFE table with label stack including the selected next hop to reach the current downstream node with the role in the multicast distribution tree.

[0008] In another embodiment, a network device implements multi-protocol label switching (MPLS) and equal cost multi-path (ECMP) in a source packet in routing (SPRING) domain. The method determines forwarding information for the network device. The network device includes a non- statutory machine-readable storage medium having stored therein a multicast forwarding information configuration manager, and a processor. The processor is coupled to the nonstatutory machine-readable storage medium. The processor is configured to execute the multicast forwarding information configuration manager. The multicast forwarding information configuration manager is configured to select a multicast distribution tree, determine a set of next hops to reach a current downstream node with the role in the multicast distribution tree, select one next hop from the set of next hops using an entropy source to determine the selected next hop, and insert a next hop label forwarding entry (NHLFE) into a NHLFE table with label stack including the selected next hop to reach the current downstream node with the role in the multicast distribution tree.

[0009] In one embodiment, a computing device is configured to execute a plurality of virtual machines. The plurality of virtual machines implements network function virtualization (NFV). The computing device is in communication with a network device implementing multi-protocol label switching (MPLS) and equal cost multi-path (ECMP) in a source packet in routing

(SPRING) domain. The method determines forwarding information for the network device. The computing device includes a non- statutory machine-readable storage medium having stored therein a multicast forwarding information configuration manager, and a processor. The processor is coupled to the non-statutory machine-readable storage medium. The processor is configured to execute a virtual machine from the plurality of virtual machines. The virtual machine is configured to execute the multicast forwarding information configuration manager. The multicast forwarding information configuration manager is configured to select a multicast distribution tree, determine a set of next hops to reach a current downstream node with the role in the multicast distribution tree, select one next hop from the set of next hops using an entropy source to determine the selected next hop, and insert a next hop label forwarding entry (NHLFE) into a NHLFE table with label stack including the selected next hop to reach the current downstream node with the role in the multicast distribution tree.

[0010] In a further embodiment, a control plane device is configured to implement a control plane of a software defined networking (SDN) network including a network device

implementing multi-protocol label switching (MPLS) and equal cost multi-path (ECMP) in a source packet in routing (SPRING) domain. The method determines forwarding information for the network device. The control plane device includes a non-statutory machine-readable storage medium having stored therein a multicast forwarding information configuration manager, and a processor. The processor is coupled to the non-statutory machine-readable storage medium. The processor is configured to execute the multicast forwarding information configuration manager. The multicast forwarding information configuration manager is configured to select a multicast distribution tree, determine a set of next hops to reach a current downstream node with the role in the multicast distribution tree, select one next hop from the set of next hops using an entropy source to determine the selected next hop, and insert a next hop label forwarding entry (NHLFE) into a NHLFE table with label stack including the selected next hop to reach the current downstream node with the role in the multicast distribution tree.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] 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:

[0012] Figure 1 is a diagram of the architecture associated with the operation of unicast and multicast configuration of incoming label map (ILM) and next hop forwarding label entry (NHFLE) tables for unicast and multicast.

[0013] Figure 2 is a diagram of one embodiment of a basic architecture associated with the operation of multicast configuration of ILM and NHFLE tables to support ECMP.

[0014] Figure 3 is a diagram of one embodiment of an improved multicast configuration of the ILM and NHFLE tables to support ECMP.

[0015] Figure 4 is a flowchart of one embodiment of a process for ILM and NHFLE table configuration for a node in a source packet in routing (SPRING) network.

[0016] 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.

[0017] Figure 5B illustrates an exemplary way to implement a special-purpose network device according to some embodiments of the invention.

[0018] Figure 5C illustrates various exemplary ways in which virtual network elements (VNEs) may be coupled according to some embodiments of the invention.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] Figure 6 illustrates a general purpose control plane device with centralized control plane (CCP) software 650), according to some embodiments of the invention.

DESCRIPTION OF EMBODIMENTS

[0023] The following description describes methods and apparatus for configuring the incoming label map and next hop label forwarding entry (NHLFE) tables in a network device in a source packet routing (SPRING) domain where multicast distribution tree (MDT) construction incorporates unicast tunnels as a component, and equal cost multipath (ECMP) is supported. The process provides a method for configuring the entries in the ILM tables and NHLFE tables that enables a multicast group label in the ILM tables to point to a set of entries in the NHLFE table that implement multicast and apply ECMP treatment.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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. [0029] 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).

[0030] 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.

[0031] SPRING Networks and Multicast

[0032] These embodiments work in combination with, but are not limited to other methods of utilizing unicast tunnels within a network to minimize multicast related state. The embodiments utilize the computation of multicast distribution trees (MDTs) and the exemplary information available in shortest path bridging (SPB) implementations such as IEEE 802. laq adapted to other technologies. In IEEE 802. laq multicast registrations are advertised in the interior gateway protocol (IGP), thus all nodes in the network have multicast group membership information about the other nodes in the network and are explicitly delegated with the task of determining their role in each MDT on the basis of both membership and topology information in the IGP.

[0033] IEEE 802. laq performs an all-pairs shortest path computation that determines a path from all nodes in a network to all other nodes in the network that selects a shortest path to each node from a source node. When combined with the tie breaking algorithms specified in

IEEE 802. laq the result is an acyclic shortest path tree. Multicast distribution trees can also be computed in a similar manner as they can be derived from the shortest path trees using the notion of reverse path forwarding. With the use of multicast protocol label switching (MPLS) a global multicast label is assigned by the management system and used on a per (S, G) multicast distribution tree basis. The (S, G) notation indicates an S - source and G - multicast group relation where the multicast tree has a single source and a group of listeners in a network. The multicast labels in the network are carried end to end (E2E) unmodified. This is inherent to the operation of SPRING. A multicast implementation MPLS could also be envisioned that combined IGP registrations, globally or centrally administered multicast labels and an LDP signaled unicast tunnel mesh. Further embodiments can encompass a network where service information is separately distributed from topology information, for example where service information is distributed by border gateway protocol (BGP) and topology information by interior gateway protocol (IGP).

[0034] The example embodiments utilize SPRING for unicast tunneling as a component of MDT construction. As a consequence of SPRING operation, upon nodal convergence to align with the view of the network available via the IGP, the local forwarding information base (LFIB) of each network device in the network will have at least one unicast SPRING-label switched route to each other LSR in the network. It is not necessary, but assumed that the network will also utilize penultimate-hop popping (PHP) on SPRING based LSPs where the outermost label is removed before being forwarded to the last hop to a destination.

[0035] After a shortest path first (SPF) tree (i.e., an (S, *) tree where S indicates the node is the source and * indicates the tree reaches all nodes) is computed for a given node that node can then determine via further processing of the resulting solution whether it is a source, a leaf and/or a replication node for each possible (S, G) MDT. If the node has one of these three roles in a given MDT it will then install the appropriate state for each, whereas if the node does not participate in the MDT in any of the three roles then no state needs to be installed for that MDT. The installed state where the node is a source or a replicating node utilizes established a priori unicast tunnels to deliver multicast packets to downstream non-adjacent leaves or replicating nodes. Tunnels do not need to be established for downstream immediately adjacent nodes that have a role in the MDT as they will have installed state for the MDT. Knowledge of the role of each node in the network in relation to a given MDT is an artifact of MDT determination.

Further, a source has knowledge of the set of leaves and is aware of leaf interest in a multicast group independently of the establishment of dataplane state.

[0036] Overview

[0037] Multiprotocol label switching (MPLS) implements point to multipoint (p2mp) and multipoint to multipoint (mp2mp) forwarding constructs for multicast. These can be signaled by multicast label distribution protocol (mLDP) or resource reservation protocol - traffic engineering (RSVP-TE). The embodiments are supported by a hybrid of multicast forwarding and unicast tunneling that make it possible to dramatically reduce the amount of state that needs to be installed in the overall network to implement a given multicast distribution tree, as described above. However it is not clear that this architecture could be deployed on all MPLS implementations with an expectation of both multicast replication and the application of ECMP treatment to each resulting copy of the multicast packet.

[0038] MPLS standards are comparatively silent on the internals of multicast

implementations. Although MPLS embodies tunneling by the nature of the label stack employed by MPLS, the combination of multicast replication, applying labels for a tunnel ingress and equal cost multipath (ECMP) processing for each tunnel may not necessarily be supported in all implementations or any given specified management. The embodiments provide a method and apparatus that enable a degree of load spreading at a node that is the ingress to multiple next hops to a downstream replication node, leaf or pinned waypoint in the described SPRING architecture.

[0039] Due to the computed nature of the described SPRING architecture it is possible for a computing node to know the set of next hops associated with each downstream node that has a role in a given multicast distribution tree. Therefore, rather than delegating the spreading of load exclusively to the dataplane in the presence of multiple next hops, the control plane can make forwarding selections in how it populates the forwarding information base (FIB) of that node to achieve multicast load spreading on existing MPLS implementations in a single ILM to NHLFE resolution step. In effect for the first downstream hop, ECMP for the data plane becomes a control plane responsibility.

[0040] Due to the distributed computed approach to multicast used in the SPRING architecture, the control plane knows the set of next hops for each downstream adjacency on a given MDT (i.e., each downstream node that plays a role in the MDT), and can load spread the aggregate of the multicast distribution tree (MDT) traffic directed to each next hop across the set of downstream interfaces on the basis of how it populates an existing FIB. This is purely a local behavior that does not need coordination with other nodes in the network. Thus, the embodiments provide advantages over the prior art by providing a specific method and apparatus for configuring the incoming label map (ILM) and next hop forwarding label entry (NHFLE) tables to support the combination of multicast and ECMP where each node in the SPRING architecture can independently implement this method.

[0041] SPRING multicast is implemented as a hybrid of replication points and unicast tunnels. Multicast in a SPRING architecture utilizes multicast distribution trees (MDTs) for distributing traffic for an associated multicast group where the MDTs identify those nodes in the SPRING architecture network that have a defined role in traffic forwarding for a multicast group.

Specifically, these roles are generally being a replicating node, root (source) or leaf node and a given node may have more than one role simultaneously. This basic definition of multicast for the SPRING architecture however may require modifications and enhancements to the MPLS forwarding of multicast traffic to deliver full ECMP operation in the SPRING network.

[0042] The reason for modifications and enhancements is that there would have to be a cascaded "one to many mapping followed by the many each mapping to a one of many decision" operations at each node where an ILM entry for a multicast label is mapped to multiple out going NHLFEs, each of which in an ECMP enabled network would potentially recursively map to multiple unicast NHLFEs from which one would be selected. However, ECMP has not been clearly defined and considered with multicast in SPRING architectures and the basic design of network devices in such networks is not prepared for such operations. IETF standards are relatively silent on multicast implementation, in particular for a multicast implementation combined with ECMP in a SPRING network architecture.

[0043] Figures 1 and 2 illustrate the issues related to implementing multicast and ECMP at the level of the ILM an NHLFE tables. Figure 1 is a diagram of the architecture associated with the operation of unicast and multicast configuration of incoming label map (ILM) and next hop forwarding label entry (NHFLE) tables for unicast and multicast. The ILM table is part of the packet processing pipeline of a network device. The process identifies an incoming label on a received packet. The incoming label is the outer most label in the MPLS label stack and identifies the destination node that the packet is destined for. The ILM table includes a set of entries for each label and a corresponding set of pointers to entries in the NHFLE table that correspond with the incoming label.

[0044] The NHFLE table is a table having a set of next hop forwarding label entries contain next-hop information (e.g., outbound interface and next-hop address) and label modification information. These entries may also include label encoding, L2 encapsulation information, and other information required for processing packets in the associated stream. Where an ILM entry points to multiple NHFLE table entries, the packet will be effectively replicated and with one instance being handled be each of the respective NHFLE. Both the ILM table and the NHFLE table are constituent parts of the FIB.

[0045] Returning to Figure 1, a unicast and multicast implementation are shown. In the unicast implementation, a separate level of logic must be implemented to support ECMP. An incoming label is utilized from the incoming packet to identify an ILM table entry. The ILM table entry identifies a set of one or more NHLFEs in the NHLFE table each representing a separate possible next hope to reach the destination identified by the incoming label. The ECMP logic then selects a single NHLFE to use by applying any load distributing algorithm typically using a source of entropy in the incoming packet as an input. The selection of the NHLFE thereby determines the outgoing interface and label stack to be utilized for forwarding the received data packet.

[0046] In the multicast implementation, the incoming label of the received packet is similarly compared to the ILM to find any matching entries for that incoming label. The matching entry will point to a set of NHLFEs that identify each of the next hops for which the packet is to be replicated. The packet is replicated and forward on each interface identified by the set of NHFLEs and a label stack for reaching the destination may be added to the packet. Thus, with these two embodiments, the unicast process utilizes the ILM and NHLFE tables to 'pick one' next hop for unicast and to 'use all' next hops for multicast. However, these basic scenarios do not provide a combination of both multicast and ECMP.

[0047] Figure 2 is a diagram of one embodiment of a basic architecture associated with the operation of multicast configuration of ILM and NHFLE tables to support ECMP. A basic implementation of the combination of prior art multicast and ECMP may result in a structure such as that illustrated in Figure 2. In this case, an incoming label is applied to the ILM to identify a set of entries in an intermediate table that then point into the NHLFE table. The ILM entry provides the 'use all' operation for replicating involved for multicast. The intermediate table then identifies the NHFLEs that are the ECMP possibilities. Finally, the ECMP logic selects one of the paths for each destination the packet is being replicated toward. Thus, this implementation combines facets of the unicast and multicast implementations. However, in existing network devices, there is no intermediate table as described in this example. Therefore, such an implementation is no feasible for existing network devices.

[0048] The embodiments provide a method for overcoming these deficiencies and functions with existing network device FIB architecture. The embodiments, can implement "the first hop" of ECMP in the control plane such that the interfaces used by each S,G tree are uniquely randomized across the set of outgoing interfaces for each next hop. For example, when performing label forwarding information base (LFIB) determination for each replicated copy of the packet that normally would then require dataplane ECMP processing to resolve the next hop, the process can select an interface from a set of multiple equal cost next hops on the basis of (S ^Λ G) MOD interface_count where S is the source IP address (S) of the multicast group, G is the IP address of the multicast group (G) and interface_count is the number of interfaces for a current node implementing the process. The multicast labels in the ILM effectively encodes S,G, so each label can refer to a unique set of NHLFEs and it is then possible to load spread at the granularity of S,G MDTs. Once the set of next hops for reaching each of the destination has been determined then the remainder of the process is analogous to unicast forwarding, such that the set of possible ECMP paths to reach each multicast destination can be load balanced using the modulo operation or similar operation. ECMP will work fine in any subsequent unicast hops, at the current node ECMP needs some randomization in the first hop to get reasonable load spreading. Subsequent hops would use one of an entropy label, a label stack, or a payload inspection to get a source of entropy to do additional load spreading where the combination of ECMP and multicast replication is not a factor.

[0049] The embodiments do not require coordination between any network devices in the SPRING network, the process is purely a local process specific to the implementing network device. Downstream nodes will "promiscuously accept" tunneled packets and do not need any explicit knowledge of how load spreading (or lack of it) occurred upstream. The embodiments provide comparable resilience such that fast reroute (FRR) and similar technologies would continue to function. The FRR process would rely on multicast convergence to move off the backup tunnel instead of unicast convergence. In other words, because ECMP treatment will be applied to tunneled multicast packets by any existing unicast implementation at all subsequent hops, the process only needs to address the tunnel ingress implementation. By performing load spreading at the ingress at a reasonable level of granularity via control plane selection of the set of NHLFEs can be used for each S,G label for the first hop of an ECMP tunnel. This process can be considered a virtuous or self-referential circle, as this issues is a byproduct of computing and tunneling for multicast in the SPRING network. Thus, this issue is specific to the operation of the SPRING architecture that is only possible to solve because each of the nodes are separately computing the network forwarding information.

[0050] Figure 3 is a diagram of one embodiment of an improved multicast configuration of the ILM and NHFLE tables to support ECMP. In this example, the ILM table contains a set of labels 1-6 that are associated with a set of entries in the NHFLE table. Label 4 and label 6 refer to identical MDTs with the same set of leaves. In these two example MDTs associated with labels 4 and 6, there are three leaves in the MDT. The other labels in the ILM are each associated with other MDTs that are not pertinent to this example.

[0051] The illustrated entries in the NHLFE table are enumerated 1-6 with each entry having next hop information. Entries 1 and 3 in the NHLFE table are valid next hops for reaching the first leaf of the MDT referenced by labels 4 and 6. Similarly, entry 4 is the single next hop for reaching the second leaf of the MDT associated with labels 4 and 6. Entries 5 and 6 in the NHFLE table identify additional valid next hops for the third leaf of the MDT.

[0052] The process of the embodiments, described further herein below, resolves each next unicast hop such that it is unique for each multicast group identifier (e.g., the service identifier (SID)). For label 4 in the ILM, the process selected entry 1 from the set of valid entries [1, 3] for reaching the first leaf and selected entry 5 from the set of valid entries [5, 6] for reaching the third leaf. This relationship is established at the time the entries in the ILM are generated or updated such that ECMP is supported without requiring computation and selection at the time of forwarding and without requiring an additional intermediate table that is not available in network devices.

[0053] Figure 4 is a flowchart of one embodiment of a process for ILM and NHFLE table configuration for a node in a source packet in routing (SPRING) network. In one embodiment the process begins at a network device by computing multicast distribution trees for each multicast group in the SPRING network (Block 99). The process then iterates through the MDTs, and downstream nodes with a role in the current MDT (referred to also as downstream adjacencies). The process selects a next or current MDT (Block 101) to process, and a next downstream node with a role in the MDT (Block 105).

[0054] A determination is then made a set of possible next hops to reach the selected downstream node with a role in the MDT (Block 107). These next hops are next hops on equal cost paths for reaching the selected downstream node. One of the next hops is then selected from this set using an entropy source to ensure load spreading across the set of possible next hops (Block 109). For example, the process may use a modulo operation over the set of possible next hops using a multicast group identifier such as S, G as the input. This enables load spreading while all traffic for a given multicast group will follow the same path. The entropy source is common to all packets for a single MDT such as the multicast SID. Such an entropy source will permit the dataplane mapping to correspond to what the control plane configures. In one example embodiment, the multicast SID would be the entropy source that has the most entropy of those that could be correlated between the control plane and the dataplane and is therefore utilized.

[0055] With the next hop selected, then an entry can be inserted into the NHLFE table with label stacks including the selected next hop to reach the selected downstream node with the role in the MDT (Block 111). Thus, the NHLFE includes the forwarding interface and label manipulation instructions to adjust the label stack such that the packet will follow a unicast path to the selected downstream node. A check is then made whether all downstream nodes with a role in the MDT have been processed (Block 113). If all of the downstream nodes have not been processed then the process selects a next downstream node (Block 103).

[0056] If all downstream nodes have been processed, then the multicast group labels are inserted into the ILM table to point to each of the NHLFE table entries that have been created for the MDT corresponding to the multicast group label (Block 117). A check is made whether all MDTs have been processed (Block 119), if not, then the next MDT is selected (Block 101). If all of the MDTs have been processed, then the update to the FIB is complete. [0057] Architecture

[0058] 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).

[0059] Two of the exemplary ND implementations in Figure 5 A 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.

[0060] 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., 530A) 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., 53 OA). [0061] In some embodiments, the network software instance(s) 522 implement a multicast forwarding information configuration manager 564A. The multicast forwarding information configuration manager 564A can implement the MPLS and ECMP configuration processes described herein above.

[0062] 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.

[0063] 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). [0064] Returning to Figure 5A, 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). [0065] 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 564 A-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. In some embodiments, the software instance(s) 522 implement a multicast forwarding information configuration manager 564A as one of the applications 564A- R. The multicast forwarding information configuration manager 564A can implement the MPLS and ECMP configuration processes described herein above.

[0066] 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.

[0067] 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)).

[0068] The third exemplary ND implementation in Figure 5A 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. [0069] 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 (DSCP) values.

[0070] 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).

[0071] 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, 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.

[0072] 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).

[0073] 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).

[0074] 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 IP VPN) 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).

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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).

[0080] In some embodiments, the centralized control plane 576 implement a multicast forwarding information configuration manager 581. The multicast forwarding information configuration manager 581 can implement the MPLS and ECMP configuration processes described herein above. In further embodiments, the multicast forwarding information configuration manager 581 can be implemented at the application layer 586 with other applications 588.

[0081] 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.

[0082] 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).

[0083] 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.

[0084] 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).

[0085] 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. [0086] 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.

[0087] 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).

[0088] 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.

[0089] 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 unikemel can run directly on hardware 640, directly on a hypervisor represented by virtualization layer 654 (in which case the unikemel 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 unikemel 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.

[0090] 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.

[0091] In some embodiments, the control plane device 604 implement a multicast forwarding information configuration manager 681. The multicast forwarding information configuration manager 681 can implement the MPLS and ECMP configuration processes described herein above. In further embodiments, the multicast forwarding information configuration manager 681 can be implemented in other aspects of the control plane device 604.

[0092] 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.

[0093] 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).

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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

[0098] Next hop selection by the routing system for a given destination may resolve to one path (that is, a routing protocol may generate one next hop on a shortest path); but if the routing system determines there are multiple viable next hops (that is, the routing protocol generated forwarding solution offers more than one next hop on a shortest path - multiple equal cost next hops), some additional criteria is used - for instance, in a connectionless network, Equal Cost Multi Path (ECMP) (also known as Equal Cost Multi Pathing, multipath forwarding and IP multipath) may be used (e.g., typical implementations use as the criteria particular header fields to ensure that the packets of a particular packet flow are always forwarded on the same next hop to preserve packet flow ordering). For purposes of multipath forwarding, a packet flow is defined as a set of packets that share an ordering constraint. As an example, the set of packets in a particular TCP transfer sequence need to arrive in order, else the TCP logic will interpret the out of order delivery as congestion and slow the TCP transfer rate down.

[0099] For example, 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.).

[00100] 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.

Claims

CLAIMS is claimed is:

A method implemented by a network device, the network device implementing multiprotocol label switching (MPLS) and equal cost multi-path (ECMP) in a source packet in routing (SPRING) domain, the method to determine forwarding information for the network device, the method comprising:

selecting (101) a multicast distribution tree;

determining (107) a set of next hops to reach a current downstream node with a role in the multicast distribution tree;

selecting (109) one next hop from the set of next hops using an entropy source to

determine the selected next hop; and

inserting (111) a next hop label forwarding entry (NHLFE) into a NHLFE table with label stack including the selected next hop to reach the current downstream node with the role in the multicast distribution tree.

The method of claim 1, further comprising:

selecting (105) the current downstream node with the role in the multicast distribution tree.

The method of claim 1, wherein the method further comprises:

inserting (117) a multicast group label into an incoming label map (ILM) table to point to each NHLFE entry for a multicast group associated with the multicast distribution tree.

The method of claim 1, wherein the entropy source is a multicast distribution tree identifier.

The method of claim 4, wherein the multicast distribution tree identifier are multicast source internet protocol (IP) address and multicast group IP address.

A network device implementing multi-protocol label switching (MPLS) and equal cost multi-path (ECMP) in a source packet in routing (SPRING) domain, the network device to implement a method to determine forwarding information for the network device, the network device comprising:

a non-statutory machine -readable storage medium (518) having stored therein a multicast forwarding information configuration manager (564A); and a processor (512) coupled to the non-statutory machine-readable storage medium, the processor configured to execute the multicast forwarding information configuration manager, the multicast forwarding information configuration manager configured to select a multicast distribution tree, determine a set of next hops to reach a current downstream node with a role in the multicast distribution tree, select one next hop from the set of next hops using an entropy source to determine the selected next hop, and insert a next hop label forwarding entry (NHLFE) into a NHLFE table with label stack including the selected next hop to reach the current downstream node with the role in the multicast distribution tree.

7. The network device of claim 6, wherein the multicast forwarding information

configuration manager is further to select the current downstream node with the role in the multicast distribution tree.

8. The network device of claim 6, wherein the multicast forwarding information

configuration manager is to insert a multicast group label into an incoming label map (ILM) table to point to each NHLFE entry for a multicast group associated with the multicast distribution tree.

9. The network device of claim 6, wherein the entropy source is a multicast distribution tree identifier.

10. The network device of claim 9, wherein the multicast distribution tree identifier are

multicast source internet protocol (IP) address and multicast group IP address.

11. A computing device configured to execute a plurality of virtual machines, the plurality of virtual machines implementing network function virtualization (NFV), the computing device in communication with a network device implementing multi-protocol label switching (MPLS) and equal cost multi-path (ECMP) in a source packet in routing (SPRING) domain, a method to determine forwarding information for the network device, the computing device comprising:

a non-statutory machine -readable storage medium (548) having stored therein a multicast forwarding information configuration manager (564A); and

a processor (542) coupled to the non-statutory machine-readable storage medium, the processor configured to execute a virtual machine from the plurality of virtual machines, the virtual machine configured to execute the multicast forwarding information configuration manager, the multicast forwarding information configuration manager configured to select a multicast distribution tree, determine a set of next hops to reach a current downstream node with a role in the multicast distribution tree, select one next hop from the set of next hops using an entropy source to determine the selected next hop, and insert a next hop label forwarding entry (NHLFE) into a NHLFE table with label stack including the selected next hop to reach the current downstream node with the role in the multicast distribution tree.

12. The computing device of claim 11, wherein the multicast forwarding information

13. The computing device of claim 11, wherein the multicast forwarding information

14. The computing device of claim 11, wherein the entropy source is a multicast distribution tree identifier.

15. The computing device of claim 14, wherein the multicast distribution tree identifier are multicast source internet protocol (IP) address and multicast group IP address.

16. A control plane device is configured to implement a control plane of a software defined networking (SDN) network including a network device implementing multi-protocol label switching (MPLS) and equal cost multi-path (ECMP) in a source packet in routing (SPRING) domain, a method to determine forwarding information for the network device, the control plane device comprising:

a non-statutory machine -readable storage medium (648) having stored therein a multicast forwarding information configuration manager (681); and

a processor (642) coupled to the non-statutory machine-readable storage medium, the processor configured to execute the multicast forwarding information configuration manager, the multicast forwarding information configuration manager configured to select a multicast distribution tree, determine a set of next hops to reach a current downstream node with a role in the multicast distribution tree, select one next hop from the set of next hops using an entropy source to determine the selected next hop, and insert a next hop label forwarding entry (NHLFE) into a NHLFE table with label stack including the selected next hop to reach the current downstream node with the role in the multicast distribution tree.

17. The control plane device of claim 16, wherein the multicast forwarding information

18. The control plane device of claim 16, wherein the multicast forwarding information

19. The control plane device of claim 16, wherein the entropy source is a multicast

distribution tree identifier.

20. The control plane device of claim 17, wherein the multicast distribution tree identifier are multicast source internet protocol (IP) address and multicast group IP address.