WO2017144947A1 - Procédé et appareil pour arbres maximaux en vue d'une multidiffusion spring calculée - Google Patents

Procédé et appareil pour arbres maximaux en vue d'une multidiffusion spring calculée Download PDF

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WO2017144947A1
WO2017144947A1 PCT/IB2016/050985 IB2016050985W WO2017144947A1 WO 2017144947 A1 WO2017144947 A1 WO 2017144947A1 IB 2016050985 W IB2016050985 W IB 2016050985W WO 2017144947 A1 WO2017144947 A1 WO 2017144947A1
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mdt
data packet
downstream
fib
network
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PCT/IB2016/050985
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David Ian Allan
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Telefonaktiebolaget Lm Ericsson (Publ)
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Publication of WO2017144947A1 publication Critical patent/WO2017144947A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
    • H04L41/12—Discovery or management of network topologies
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
    • H04L41/40—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks using virtualisation of network functions or resources, e.g. SDN or NFV entities
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/02—Topology update or discovery
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/16—Multipoint routing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/48—Routing tree calculation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/48—Routing tree calculation
    • H04L45/484—Routing tree calculation using multiple routing trees
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/02—Details
    • H04L12/16—Arrangements for providing special services to substations
    • H04L12/18—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast
    • H04L12/185—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast with management of multicast group membership
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
    • H04L41/08—Configuration management of networks or network elements
    • H04L41/0803—Configuration setting
    • H04L41/0813—Configuration setting characterised by the conditions triggering a change of settings
    • H04L41/0816—Configuration setting characterised by the conditions triggering a change of settings the condition being an adaptation, e.g. in response to network events
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
    • H04L41/08—Configuration management of networks or network elements
    • H04L41/0895—Configuration of virtualised networks or elements, e.g. virtualised network function or OpenFlow elements

Definitions

  • Embodiments of the invention relate to the field of multicast distribution tree generation in communication networks; and more specifically, to the implementation of multipoint to multipoint trees in source packet in routing (SPRING) networks.
  • SPRING source packet in routing
  • IP Internet Protocol
  • MPLS multiprotocol label switching
  • mLDP multicast label distribution protocol
  • PIM protocol independent multicast
  • SPF unicast shortest path first
  • MDT loop free multicast distribution tree
  • Shortest path bridging is a protocol related to computer networking for the configuration of computer networks that enables multipath routing.
  • 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.
  • IEEE Institute of Electrical and Electronics Engineers 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.
  • 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.
  • LSR label switched route
  • 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.
  • 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.
  • a node in the SPRING network could compute its role in implementing any given multicast (S, G) tree.
  • An algorithm that starts with all pairs shortest path computation augmented with algorithms to identify the nodes with specific roles of root, leave 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.
  • the art does not support multipoint to multipoint trees in SPRING networks.
  • a spanning tree In the domain of multipoint to multipoint trees a spanning tree can be considered to be fairly efficient in that the tree is completely bi-directional and employs split horizon forwarding such that traffic received by a node participating in the spanning tree will replicate the traffic on all interfaces except that of origin.
  • the closest analogy in other technologies is core based trees which rely on tunneling traffic to a common root which then mirrors traffic back to all leaves. However, this tunneling is inefficient as all traffic is backhauled to the root, and the sender will receive its own traffic back which it then must discard.
  • a method is implemented by a network device to compute a multicast distribution tree (MDT) that is a spanning tree in a source packet in routing (SPRING) network for a multicast group, where a first forwarding element has advertised itself as the root of the multicast group and at least one forwarding element has advertised a send and/or receive interest in the multicast group, the result of the spanning tree computation utilized to update the forwarding information base (FIB) of the network device.
  • MDT multicast distribution tree
  • SPRING source packet in routing
  • the method includes receiving a notice of a topology change for the SPRING network or a membership change for the multicast group, computing the MDT rooted at the first forwarding element, determining roles for each forwarding element that participates in the MDT, configuring the FIB to include a first set of entries that identify an upstream SID in a data packet received on any downstream interface of the MDT and that forward the data packet on the upstream interface of the MDT, configuring the FIB to include a second set of entries that identify the upstream SID in a data packet received on any downstream interface of the MDT and that forward the data packet with the upstream SID translated to the downstream SID, the data packet forwarded on the downstream interfaces of the MDT other than a downstream interface on which the data packet was received; and configuring the FIB to include a third set of entries that identify a downstream SID in a data packet received on any upstream interface of the MDT and that forward the data packet on the downstream interfaces of the MDT.
  • a method is implemented by a network device to compute a multicast distribution tree (MDT) that is a spanning tree in a source packet in routing (SPRING) network for a multicast group, where a first forwarding element has advertised itself as the root of the multicast group and at least one forwarding element has advertised a send and/or receive interest in the multicast group, the result of the spanning tree computation utilized to update the forwarding information base (FIB) of the network device.
  • MDT multicast distribution tree
  • SPRING source packet in routing
  • the method includes receiving a notice of a topology change for the SPRING network or a membership change for the multicast group, computing the MDT rooted at the first forwarding element, determining roles for each forwarding element that participates in the MDT, configuring the FIB to include a first set of entries that identify an upstream SID for each source in the MDT in a data packet and that forward the data packet on the downstream interfaces and upstream interfaces of the MDT other than an interface of the received data packet where a receive interest has been received where the upstream SID is translated to a downstream SID for forwarding on downstream interfaces; and configuring the FIB to include a second set of entries that identify a single downstream SID in a data packet received on an upstream interface of the MDT and that forward the data packet with the single downstream SID on all downstream interfaces of the MDT.
  • a network device computes a multicast distribution tree (MDT) that is a spanning tree in a source packet in routing (SPRING) network for a multicast group, where a first forwarding element has advertised itself as the root of the multicast group and at least one forwarding element has advertised a send and/or receive interest in the multicast group.
  • MDT multicast distribution tree
  • SPRING source packet in routing
  • the result of the spanning tree computation is utilized to update the forwarding information base (FIB) of the network device.
  • the network device includes a non-transitory machine readable medium having stored therein a multicast spanning tree generator and the FIB, and a processor coupled to the non-transitory machine readable medium.
  • the processor is configured to execute the multicast spanning tree generator.
  • the multicast spanning tree generator is configured to receive a notice of a topology change for the SPRING network or a membership change for the multicast group, to compute the MDT rooted at the first forwarding element, to determine roles for each forwarding element that participates in the MDT, to configure the FIB to include a first set of entries that identify an upstream SID in a data packet received on any downstream interface of the MDT and that forward the data packet on the upstream interface of the MDT, to configure the FIB to include a second set of entries that identify the upstream SID in a data packet received on any downstream interface of the MDT and that forward the data packet with the upstream SID translated to the downstream SID, the data packet forwarded on the downstream interfaces of the MDT other than a downstream interface on which the data packet was received, and configure the FIB to include a third set of entries that identify a downstream SID in a data packet received on any upstream interface of the MDT and that forward the data packet on the downstream interfaces of the MDT.
  • a computing device is in communication with a network device.
  • the computing device executes a plurality of virtual machines for implementing network function virtualization (NFV).
  • the computing device computes a multicast distribution tree (MDT) that is a spanning tree in a source packet in routing (SPRING) network for a multicast group, where a first forwarding element has advertised itself as the root of the multicast group and at least one forwarding element has advertised a send and/or receive interest in the multicast group, the result of the spanning tree computation utilized to update the forwarding information base (FIB) of the network device.
  • MDT multicast distribution tree
  • SPRING source packet in routing
  • the computing device includes a non-transitory machine readable medium having stored therein a multicast spanning tree generator and the FIB, and a processor coupled to the non-transitory machine readable 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 spanning tree generator.
  • the multicast spanning tree generator is configured to receive a notice of a topology change for the SPRING network or a membership change for the multicast group, to compute the MDT rooted at the first forwarding element, to determine roles for each forwarding element that participates in the MDT, to configure the FIB to include a first set of entries that identify an upstream SID in a data packet received on any downstream interface of the MDT and that forward the data packet on the upstream interface of the MDT, to configure the FIB to include a second set of entries that identify the upstream SID in a data packet received on any downstream interface of the MDT and that forward the data packet with the upstream SID translated to the downstream SID, the data packet forwarded on the downstream interfaces of the MDT other than a downstream interface on which the data packet was received, and configure the FIB to include a third set of entries that identify a downstream SID in a data packet received on any upstream interface of the MDT and that forward the data packet on the downstream interfaces of the MDT.
  • a control plane device is configured to implement a control plane of a software defined networking (SDN) network including a network device in a network with a plurality of network devices, wherein the control plane device is configured to configure the network device to compute a multicast distribution tree (MDT) that is a spanning tree in a source packet in routing (SPRING) network for a multicast group, where a first forwarding element has advertised itself as the root of the multicast group and at least one forwarding element has advertised a send and/or receive interest in the multicast group.
  • MDT multicast distribution tree
  • SPRING source packet in routing
  • the result of the spanning tree computation is utilized to update the forwarding information base (FIB) of the network device.
  • the control plane device includes a non-transitory machine readable medium having stored therein a multicast spanning tree generator and the FIB, and a processor coupled to the non-transitory machine readable medium.
  • the processor is configured to execute the multicast spanning tree generator.
  • the multicast spanning tree generator is configured to receive a notice of a topology change for the SPRING network or a membership change for the multicast group, to compute the MDT rooted at the first forwarding element, to determine roles for each forwarding element that participates in the MDT, to configure the FIB to include a first set of entries that identify an upstream SID in a data packet received on any downstream interface of the MDT and that forward the data packet on the upstream interface of the MDT, to configure the FIB to include a second set of entries that identify the upstream SID in a data packet received on any downstream interface of the MDT and that forward the data packet with the upstream SID translated to the downstream SID, the data packet forwarded on the downstream interfaces of the MDT other than a downstream interface on which the data packet was received, and configure the FIB to include a third set of entries that identify a downstream SID in a data packet received on any upstream interface of the MDT and that forward the data packet on the downstream interfaces of the MDT.
  • Figure 1 is a flowchart of one embodiment of process for generating spanning trees for a SPRING network.
  • Figure 2 is a flowchart of one embodiment of another process for generating spanning trees for a SPRING network.
  • Figure 3A is a diagram of examples of spanning trees in protocol independent multicast (PIM).
  • PIM protocol independent multicast
  • Figure 3B is a diagram of an example of a generic spanning tree.
  • Figure 4 is a diagram of one example implementation of spanning trees and forwarding information base (FIB) management in a SPRING network.
  • FIB forwarding information base
  • Figure 5 is a diagram of another example implementation of spanning trees and forwarding information base (FIB) management in a SPRING network.
  • FIB forwarding information base
  • Figure 6A illustrates connectivity between network devices (NDs) within an exemplary network, as well as three exemplary implementations of the NDs, according to some
  • Figure 6B illustrates an exemplary way to implement a special-purpose network device according to some embodiments of the invention.
  • FIG. 6C illustrates various exemplary ways in which virtual network elements (VNEs) may be coupled according to some embodiments of the invention.
  • VNEs virtual network elements
  • Figure 6D 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.
  • NE network element
  • Figure 6E 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.
  • Figure 6F 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.
  • Figure 7 illustrates a general purpose control plane device with centralized control plane (CCP) software 750), according to some embodiments of the invention.
  • CCP centralized control plane
  • the following description describes methods and apparatus for implementing spanning trees and in particular multipoint to multipoint core rooted spanning trees.
  • the embodiments provide a process for computing minimum cost trees constructed from the root to the leaves that are bi-directional.
  • Nodes are configured such that every replication point on the upstream path to the root and the root itself performs split-horizon replication.
  • the nodes are configured to replicate multicast traffic on all logical and physical interfaces of the MDT with the exception of the interface of receipt. This requires a tree construction algorithm that avoids packet duplication on any physical or logical link, for which prior art exists.
  • the nodes are configured such that the root employs the same forwarding topology as a per source specific tree but constructed so that the connectivity is bi-directional, and employs split horizon forwarding at every replication point.
  • Split horizon in this context, refers to the technique of not sending traffic on the interface of receipt.
  • 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.
  • Bracketed text and blocks with dashed borders 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.
  • 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.
  • 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).
  • machine-readable media also called computer-readable media
  • machine-readable storage media e.g., magnetic disks, optical disks, read only memory (ROM), flash memory devices, phase change memory
  • machine-readable transmission media also called a carrier
  • carrier e.g., electrical, optical, radio, acoustical or other form of propagated signals - such as carrier waves, infrared signals.
  • 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.
  • 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.
  • volatile memory e.g., dynamic random access memory (DRAM), static random access memory (SRAM)
  • 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.
  • network connections to transmit and/or receive code and/or data using propagating signals.
  • One or more parts of an embodiment of the invention may be implemented using different combinations of software, firmware, and/or hardware.
  • a network device 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).
  • a network interface 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
  • 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.
  • IP addresses of that 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.
  • 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).
  • ECMP Equal Cost Multi Path
  • a packet flow is defined as a set of packets that share an ordering constraint.
  • 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.
  • the embodiments provide a method of construction of spanning trees in a network that uses both interior gateway protocol (IGP) driven computation, and unicast tunnels in the construction of MDTs.
  • the embodiments utilize the computations of multicast distribution trees (MDTs) and the exemplary information available in shortest path bridging (SPB)
  • IEEE 802. laq adapted to other technologies.
  • 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 information in the IGP.
  • IGP interior gateway protocol
  • 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.
  • 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.
  • MPLS multicast protocol label switching
  • 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). This is inherent to the operation of SPRING.
  • a multicast implementation MPLS could also be envisioned that combined IGP registrations and an LDP signaled unicast tunnel mesh could also be adapted to carry the labels E2E.
  • the example embodiments utilize SPRING for unicast tunneling.
  • 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. 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.
  • PDP penultimate-hop popping
  • 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
  • SPF shortest path first
  • the installed state where the node is a root 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 the all-pairs shortest path computation.
  • the example embodiments utilize SPRING for constructing spanning trees rooted on a designated node in the network. Spanning trees trade bandwidth efficiency and latency against state and in the case of the computed approach, convergence time as the computation of one tree is sufficient for all sources in a multicast group to send traffic to all receivers, therefore for classes of multicast service where the tradeoff can be made, the use of spanning trees can be employed.
  • Bi-directional trees such as protocol independent multicast (PIM) bi-directional trees, multicast label distribution protocol (mLDP) multipoint to multipoint trees and similar technology have inherent inefficiency in that all packets need to be tunneled to the rendezvous point which is also the MDT root before replication to the leaves begins. While the process is a standard paradigm whereby packets are simply tunneled to the rendezvous point, a further inefficiency is that any sender of data will receive and have to discard a copy of the any data it sends to the rendezvous point. In a general a spanning tree is also a rooted tree, but replication occurs at every branch point in the spanning tree reducing both the bandwidth required and overall average latency of the tree.
  • PIM protocol independent multicast
  • mLDP multicast label distribution protocol
  • the embodiments can employ efficient spanning tree construction techniques and minimal state techniques. These techniques can ensure that any tree constructed will only have one logical path to a leaf or set of leaves reachable by any individual physical or logical interface. Where there is more than one source downstream on a given interface, by the nature of spanning tree construction, all nodes will already have received a copy of any multicast packet for the group sent by any source whose connectivity in the spanning tree joins the current path downstream of the interface of arrival therefore there is no need to send any traffic on the physical or logical interface of arrival to ensure complete distribution of the traffic to all members of the multicast group served by the spanning tree.
  • the embodiments encompass at least two implementations for spanning trees.
  • an upstream multicast segment identifier (SID) and a downstream multicast SID are utilized. This separation reduces the vulnerability of transient loops.
  • the technique also utilizes a per interface incoming label map (ILM) to facilitate split horizon forwarding in the context of the defined MPLS architecture.
  • ILM per interface incoming label map
  • source specific SIDs and a single downstream SID are utilized. This embodiment also reduces the vulnerability of transient loops.
  • the embodiment works when the MPLS implementation in the network is restricted to using a common per platform ILM.
  • the per-interface ILM has advantages as it reduces the overall amount of state in the system. FIBs may otherwise get larger at nodes that are closer to the root of the spanning tree. However, the per-interface ILM may not be applicable to all scenarios.
  • FIB entries there are two types of relevant forwarding information base (FIB) entries, upstream SID and downstream SID entries. These entries define the next hop on a per upstream SID or downstream SID basis. These entries are mapped to one of four types of outgoing FIB entries.
  • an upstream physical FIB entry defines the next upstream node in the MDT that is physically adjacent to the node of the FIB.
  • an upstream logical entry defines the next upstream node in the MDT that is not physically adjacent and will be reached via a tunnel which may egress the node via one of a set of one or more physical interfaces and may require additional processing (e.g. ECMP) to resolve to a physical interface.
  • ECMP additional processing
  • downstream physical entry that defines the next downstream node in the MDT that is physically adjacent to the node with the FIB.
  • the downstream logical entry which defines the next downstream node in the MDT that is not physically adjacent and will be reached via a tunnel which may egress the node via one of a set of one or more physical interfaces.
  • the elements of the embodiment using separate upstream and downstream SIDs involves configuration of nodes and interior gateway (IGP) advertisement.
  • IGP interior gateway
  • a given node is configured to advertise itself via the IGP as the root for an MDT of a type 'spanning tree' for a multicast group G, with an upstream SID 'u' and a downstream SID 'd.' This is the root node for the spanning tree type MDT.
  • Other nodes advertise themselves as senders and/or receivers of the multicast group G via the IGP.
  • the advertisements may use a null SID value for consistency in encoding structure with existing mechanisms. Once these advertisements have been made, the nodes in the
  • SPRING network may compute the spanning tree as if it were a (S,G) MDT with the node designated as the spanning tree root as the source, and determine their role in the tree for the multicast group G.
  • a node participating in the topology of the spanning tree will have zero (if the root) or one upstream interface and zero (non-bud leaf, where a bud node is one that is both a leaf and a replication point) or more than one downstream interface, where both upstream and downstream interfaces can be physical or logical.
  • FIG. 1 is a diagram of one embodiment of a process for configuring an FIB and the computation of the nodes for the upstream and downstream SID embodiment where per- interface ILMs are deployed in the network.
  • the process involves a set of computing elements and forwarding elements.
  • the computing elements are responsible for the implementation of the process and configuring of the forwarding elements.
  • the computing elements may be implemented in the same network device as the forwarding element or separately implemented.
  • the forwarding elements are the processes that implement the forwarding of data traffic in the SPRING network based on their FIBs.
  • the 'nodes' of a network are synonymous with the forwarding elements.
  • each forwarding element In response to each forwarding element receiving a notice of topology or membership change for a SPRING network (Block 101), the process begins to compute a multicast distribution tree rooted at a first designated root forwarding element (Block 103). The computation generates a spanning tree rooted on the root forwarding element. The process determines a role for each forwarding element that participates in the MDT (i.e., a leaf, replicating node or root) (Block 105). The process then configures the FIB to implement a set of mappings.
  • the FIB may be configured to include a first set of entries that identify the upstream SID in data packets received on any downstream interface (logical or physical) of the MDT and that forward the identified data packets on the upstream interface of the MDT (Block 107).
  • the FIB may also be configured to include a second set of entries that identify the upstream SID in data packets received on any downstream interface (logical or physical) of the MDT and that forward the identified data packets on each downstream interface (logical or physical) exclusive of the interface of arrival of the MDT (Block 109).
  • the upstream SID of the received data packets is translated to the downstream SID before forwarding.
  • the FIB may be configured to include a third set of entries that identify the downstream SID in data packets received on any upstream interface (logical or physical) of the MDT and that forward the identified data packets on each downstream interface of the MDT (Block 111).
  • the elements of the embodiment using source specific and downstream SIDs involves configuration of nodes and interior gateway (IGP) advertisement.
  • a given node is configured to advertise itself via the IGP as the root for an MDT of a type 'spanning tree' for a multicast group G, with a downstream SID 'r.' This is the root node for the spanning tree type MDT.
  • Other nodes advertise themselves as senders and/or receivers of the multicast group g via IGP.
  • the advertisements may use separate upstream SID values for each node "node/g" and a common downstream SID value used for forwarding all traffic in the direction of away from the root. Once these advertisements have been made, the nodes in the SPRING network may compute the spanning tree and their role in the tree for the multicast group g.
  • FIG. 2 is a diagram of one embodiment of a process for configuring an FIB and the computation of the nodes for the source specific and downstream SID embodiment.
  • the process begins to compute a multicast distribution tree rooted at a first designated root forwarding element (Block 203).
  • the computation generates a spanning tree rooted on the root forwarding element that reaches all receivers in the served group.
  • the process determines a role for each forwarding element that participates in the MDT (i.e., a leaf, replicating node or root) (Block 205).
  • the process then configures the FIB to include a first set of entries that identify an upstream SID for each downstream source in the MDT in a data packet and that forward the data packet on the downstream interfaces in the MDT using the
  • FIG. 3A is a diagram of a core based tree implemented in protocol independent multicast (PEVI) that is bi-directional (BI-DIR). In the basic core based tree shown here a tunnel exists from a source S to the root. Upstream and downstream refer to the direction to or direction from the root, respectively. Replication is performed on downstream interfaces in the MDT.
  • PEVI protocol independent multicast
  • Figure 3B is a diagram of a further core based tree implemented in a PIM BI-DIR.
  • the illustrated process defines a set of replication point such that upstream packet are replicated on all but interfaces of arrival at MDT replication points. Downstream packets are replicated on all downstream interfaces.
  • FIG. 4 is a diagram of an example of the process for the upstream and downstream SID embodiment.
  • a network topology is show, where node (i.e., forwarding element) A and D are leaves in the MDT.
  • Node E is a replication point and for this example the computing (i.e., computing element) as well.
  • Nodes B and C have no role in this MDT.
  • the upstream identifier is "U" and the downstream SID is "D.”
  • the link between node E and node A is virtual and represented as a downstream logical interface.
  • the FIB maintained by this node includes the illustrated entries. These are the FIB entries for example node E.
  • the first entry is for physical interface 1 which is a link to node B.
  • the upstream SID U is associated with this entry and the replication instructions to replicate traffic from interface 1 to interface 3 and 4.
  • the second entry is associated with the upstream SID U and the replication instructions to replicate traffic from interface 2 to interfaces 3 and 4.
  • the third entry is association with the upstream SID U and the replication instructions indicate to replicate received traffic to interfaces 1 or 2 (based on ECMP) and interface 4.
  • the fourth entry is associated with downstream SID d with the replication instructions to replicate received traffic on interface 4 to interfaces 1 or 2 (based on ECMP) and interface 3.
  • FIG. 5 is a diagram of an example of the process for the source and downstream SID embodiment.
  • a network topology is shown, where node (i.e., forwarding element) A and D are leaves in the MDT.
  • Node E is a replication point and for this example the computing node (i.e., computing element) as well.
  • Nodes B and C have no role in this MDT.
  • the upstream identifiers are "a" and "d” and the downstream SID is "r.”
  • the link between node E and node A is virtual and represented as a downstream logical interface.
  • the FIB maintained by this node E includes the illustrated entries. These are the FIB entries for example node E.
  • the first entry is for any interface.
  • the upstream SID "a” is associated with this entry and the replication instructions to replicate traffic from any interface to interface 3 and 4.
  • the second entry is associated with the upstream SID "d” and the replication instructions to replicate traffic from any interface to interfaces 1 or 2 (based on ECMP) and 4.
  • the third entry is association with the downstream SID "r” and the replication instructions indicate to replicate received traffic to interfaces 1 or 2 (based on ECMP) and interface 3.
  • each node can independently determine its role in the spanning tree and generate forwarding entries for its FIB to implement split horizon forwarding.
  • refinement of the rules for logical interfaces is provided for explicitly to address the case of spanning trees constructed with unicast tunnels as a constituent component. It is possible to extend the spanning tree construction technique to include "flat trees" via collapsing the concept of logical interface to only refer to physical interfaces.
  • Figure 6A illustrates connectivity between network devices (NDs) within an exemplary network, as well as three exemplary implementations of the NDs, according to some
  • Figure 6A shows NDs 600A-H, and their connectivity by way of lines between 600A-600B, 600B-600C, 600C-600D, 600D-600E, 600E-600F, 600F-600G, and 600A-600G, as well as between 600H and each of 600A, 600C, 600D, and 600G.
  • These NDs are physical devices, and the connectivity between these NDs can be wireless or wired (often referred to as a link).
  • NDs 600A, 600E, and 600F An additional line extending from NDs 600A, 600E, and 600F 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).
  • Two of the exemplary ND implementations in Figure 6A are: 1) a special-purpose network device 602 that uses custom application-specific integrated-circuits (ASICs) and a special-purpose operating system (OS); and 2) a general purpose network device 604 that uses common off-the-shelf (COTS) processors and a standard OS.
  • ASICs application-specific integrated-circuits
  • OS special-purpose operating system
  • COTS common off-the-shelf
  • the special-purpose network device 602 includes networking hardware 610 comprising compute resource(s) 612 (which typically include a set of one or more processors), forwarding resource(s) 614 (which typically include one or more ASICs and/or network processors), and physical network interfaces (NIs) 616 (sometimes called physical ports), as well as non- transitory machine readable storage media 618 having stored therein networking software 620.
  • 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 600A-H.
  • WNIC wireless network interface controller
  • NIC network interface controller
  • the networking software 620 may be executed by the networking hardware 610 to instantiate a set of one or more networking software instance(s) 622.
  • Each of the networking software instance(s) 622, and that part of the networking hardware 610 that executes that network software instance form a separate virtual network element 630A-R.
  • VNEs 630A-R includes a control communication and configuration module 632A-R
  • a given virtual network element (e.g., 630A) includes the control communication and configuration module (e.g., 632A), a set of one or more forwarding table(s) (e.g., 634A), and that portion of the networking hardware 610 that executes the virtual network element (e.g., 630A).
  • the special-purpose network device 601 can implement a multicast spanning tree generator 664.
  • the multicast spanning tree generator 664 can be a program or similar set of instructions that implement the methods described herein above in reference to Figures 1-5 that provide spanning tree generation in a SPRING network.
  • generator 664 can be stored by the non-transitory machine readable storage media 618 and executed by the compute resources 612.
  • the special-purpose network device 602 is often physically and/or logically considered to include: 1) a ND control plane 624 (sometimes referred to as a control plane) comprising the compute resource(s) 612 that execute the control communication and configuration
  • ND forwarding plane 626 (sometimes referred to as a forwarding plane, a data plane, or a media plane) comprising the forwarding resource(s) 614 that utilize the forwarding table(s) 634A-R and the physical NIs 616.
  • the ND control plane 624 (the compute resource(s) 612 executing the control communication and configuration module(s) 632A-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) 634A-R, and the ND forwarding plane 626 is responsible for receiving that data on the physical NIs 616 and forwarding that data out the appropriate ones of the physical NIs 616 based on the forwarding table(s) 634A-R.
  • data e.g., packets
  • the ND forwarding plane 626 is responsible for receiving that data on the physical NIs 616 and forwarding that data out the appropriate ones of the physical NIs 616 based on the forwarding table(s) 634A-R.
  • Figure 6B illustrates an exemplary way to implement the special-purpose network device 602 according to some embodiments of the invention.
  • Figure 6B shows a special- purpose network device including cards 638 (typically hot pluggable). While in some embodiments the cards 638 are of two types (one or more that operate as the ND forwarding plane 626 (sometimes called line cards), and one or more that operate to implement the ND control plane 624 (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).
  • 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)).
  • 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)
  • GPRS General Pack
  • the general purpose network device 604 includes 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 software 650.
  • processor(s) 642 execute the software 650 to instantiate one or more sets of one or more applications 664A-R. While one embodiment does not implement virtualization, alternative embodiments may use different forms of virtualization.
  • 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 that may each be used to execute one (or more) of the sets of applications 664A-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.
  • the multiple software containers also called virtualization engines, virtual private servers, or jails
  • user spaces typically a virtual memory space
  • 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 each of the sets of applications 664A-R is run on top of a guest operating system within an instance 662A-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.
  • a hypervisor sometimes referred to as a virtual machine monitor (VMM)
  • VMM virtual machine monitor
  • 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.
  • libraries e.g., from a library operating system (LibOS) including drivers/libraries of OS services
  • unikernel can be implemented to run directly on hardware 640, 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 654, unikernels running within software containers represented by instances 662A-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).
  • the virtual network element(s) 660A-R perform similar functionality to the virtual network element(s) 630A-R - e.g., similar to the control communication and configuration module(s) 632A and forwarding table(s) 634A (this virtualization of the hardware 640 is sometimes referred to as network function virtualization (NFV)).
  • NFV network function virtualization
  • CPE customer premise equipment
  • each instance 662A-R corresponding to one VNE 660A-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 662A-R to VNEs also apply to embodiments where such a finer level of granularity and/or unikernels are used.
  • the virtualization layer 654 includes a virtual switch that provides similar forwarding services as a physical Ethernet switch. Specifically, this virtual switch forwards traffic between instances 662A-R and the NIC(s) 644, as well as optionally between the instances 662A-R; in addition, this virtual switch may enforce network isolation between the VNEs 660A-R that by policy are not permitted to communicate with each other (e.g., by honoring virtual local area networks (VLANs)).
  • VLANs virtual local area networks
  • the general purpose network device 604 can implement a multicast spanning tree generator 664A-R.
  • the multicast spanning tree generator 664A-R can be a program or similar set of instructions that implement the methods described herein above in reference to Figures 1- 5 that provide for the generation of spanning trees for use in multicast distribution of frames in a SPRING network.
  • the multicast spanning tree generator 664A-R can be stored by the non- transitory machine readable storage media 648 and executed by the software instances 652 and processors 642.
  • the third exemplary ND implementation in Figure 6A is a hybrid network device 606, which includes both custom ASICs/special-purpose OS and COTS processors/standard OS in a single ND or a single card within an ND.
  • a platform VM i.e., a VM that that implements the functionality of the special-purpose network device 602 could provide for para-virtualization to the networking hardware present in the hybrid network device 606.
  • NE network element
  • each of the VNEs receives data on the physical NIs (e.g., 616, 646) and forwards that data out the appropriate ones of the physical NIs (e.g., 616, 646).
  • 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.
  • transport protocol e.g., user datagram protocol (UDP), Transmission Control Protocol (TCP), and differentiated services (DSCP) values.
  • Figure 6C illustrates various exemplary ways in which VNEs may be coupled according to some embodiments of the invention.
  • Figure 6C shows VNEs 670A.1-670A.P (and optionally VNEs 670A.Q-670A.R) implemented in ND 600A and VNE 670H.1 in ND 600H.
  • VNEs 670A.1-P are separate from each other in the sense that they can receive packets from outside ND 600A and forward packets outside of ND 600A; VNE 670A.1 is coupled with VNE 670H.1, and thus they communicate packets between their respective NDs; VNE 670A.2-670A.3 may optionally forward packets between themselves without forwarding them outside of the ND 600A; and VNE 670A.P may optionally be the first in a chain of VNEs that includes VNE 670A.Q followed by VNE 670A.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 6C 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 V
  • the NDs of Figure 6A 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.
  • VOIP Voice Over Internet Protocol
  • VPNs virtual private networks
  • 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.,
  • 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.
  • one or more of the electronic devices operating as the NDs in Figure 6A may also host one or more such servers (e.g., in the case of the general purpose network device 604, one or more of the software instances 662A-R may operate as servers; the same would be true for the hybrid network device 606; in the case of the special-purpose network device 602, one or more such servers could also be run on a virtualization layer executed by the compute resource(s) 612); in which case the servers are said to be co-located with the VNEs of that ND.
  • the servers are said to be co-located with the VNEs of that ND.
  • a virtual network is a logical abstraction of a physical network (such as that in
  • 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).
  • IP Internet Protocol
  • GRE generic routing encapsulation
  • L2TP layer 2 tunneling protocol
  • IPSec Internet Protocol
  • a network virtualization edge 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 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 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).
  • Examples of network services include: 1) an Ethernet LAN emulation service (an Ethernet-based multipoint service similar to an Internet Engineering Task Force (IETF)
  • IETF Internet Engineering Task Force
  • MPLS Multiprotocol Label Switching
  • EVPN Ethernet VPN
  • 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)).
  • IETF IP VPN e.g., Border Gateway Protocol (BGP)/MPLS IP VPN
  • 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).
  • 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
  • management capabilities e.g., full detection and processing
  • FIG. 6D illustrates a network with a single network element on each of the NDs of Figure 6A, 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.
  • Figure 6D illustrates network elements (NEs) 670A-H with the same connectivity as the NDs 600A-H of Figure 6A.
  • Figure 6D illustrates that the distributed approach 672 distributes responsibility for generating the reachability and forwarding information across the NEs 670A-H; in other words, the process of neighbor discovery and topology discovery is distributed.
  • the control communication and configuration module(s) 632A-R of the ND control plane 624 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
  • Border Gateway Protocol BGP
  • IGP Interior Gateway Protocol
  • OSPF Open Shortest Path First
  • IS-IS Intermediate System to Intermediate System
  • RIP Routing Information Protocol
  • LDP Label Distribution Protocol
  • RSVP Resource Reservation Protocol
  • TE Extensions to RSVP for LSP Tunnels and Generalized Multi-Protocol Label Switching
  • GPLS Signaling RSVP-TE
  • NEs 670A-H e.g., the compute resource(s) 612 executing the control communication and configuration
  • module(s) 632A-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 624.
  • the ND control plane 624 programs the ND forwarding plane 626 with information (e.g., adjacency and route information) based on the routing structure(s).
  • the ND control plane 624 programs the adjacency and route information into one or more forwarding table(s) 634A-R (e.g., Forwarding Information Base (FIB), Label Forwarding Information Base (LFIB), and one or more adjacency structures) on the ND forwarding plane 626.
  • 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 602, the same distributed approach 672 can be implemented on the general purpose network device 604 and the hybrid network device 606.
  • FIG. 6D illustrates that a centralized approach 674 (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 674 has the responsibility for the generation of reachability and forwarding information in a centralized control plane 676 (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.
  • a centralized control plane 676 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
  • the centralized control plane 676 has a south bound interface 682 with a data plane 680 (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 670A-H (sometimes referred to as switches, forwarding elements, data plane elements, or nodes).
  • the centralized control plane 676 includes a network controller 678, which includes a centralized reachability and forwarding information module 679 that determines the reachability within the network and distributes the forwarding information to the NEs 670A-H of the data plane 680 over the south bound interface 682 (which may use the OpenFlow protocol).
  • the network intelligence is centralized in the centralized control plane 676 executing on electronic devices that are typically separate from the NDs.
  • each of the control communication and configuration module(s) 632A-R of the ND control plane 624 typically include a control agent that provides the VNE side of the south bound interface 682.
  • the ND control plane 624 (the compute resource(s) 612 executing the control communication and configuration module(s) 632A-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 676 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 679 (it should be understood that in some embodiments of the invention, the control communication and configuration module(s) 632A-R, in addition to communicating with the centralized control plane 676, 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 674, but may also be considered a hybrid approach).
  • data e.g., packets
  • the control agent communicating with the centralized control plane 676 to receive the forward
  • the same centralized approach 674 can be implemented with the general purpose network device 604 (e.g., each of the VNE 660A-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 676 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 679; it should be understood that in some embodiments of the invention, the VNEs 660A-R, in addition to communicating with the centralized control plane 676, 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 606.
  • the general purpose network device 604 e.g., each of the VNE 660A-R performs its responsibility for controlling how data (e.g., packets) is to be routed (e.g., the next hop for
  • NFV is able to support SDN by providing an infrastructure upon which the SDN software can be run
  • NFV and SDN both aim to make use of commodity server hardware and physical switches.
  • Figure 6D also shows that the centralized control plane 676 has a north bound interface 684 to an application layer 686, in which resides application(s) 688.
  • the centralized control plane 676 has the ability to form virtual networks 692 (sometimes referred to as a logical forwarding plane, network services, or overlay networks (with the NEs 670A-H of the data plane 680 being the underlay network)) for the application(s) 688.
  • virtual networks 692 sometimes referred to as a logical forwarding plane, network services, or overlay networks (with the NEs 670A-H of the data plane 680 being the underlay network)
  • the centralized control plane 676 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).
  • Figure 6D shows the distributed approach 672 separate from the centralized approach 674
  • the effort of network control may be distributed differently or the two combined in certain embodiments of the invention.
  • embodiments may generally use the centralized approach (SDN) 674, 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.
  • SDN centralized approach
  • Such embodiments are generally considered to fall under the centralized approach 674, but may also be considered a hybrid approach.
  • Figure 6D illustrates the simple case where each of the NDs 600A-H implements a single NE 670A-H
  • the network control approaches described with reference to Figure 6D also work for networks where one or more of the NDs 600A-H implement multiple VNEs (e.g., VNEs 630A-R, VNEs 660A-R, those in the hybrid network device 606).
  • the network controller 678 may also emulate the implementation of multiple VNEs in a single ND.
  • the network controller 678 may present the implementation of a VNE/NE in a single ND as multiple VNEs in the virtual networks 692 (all in the same one of the virtual network(s) 692, each in different ones of the virtual
  • the network controller 678 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 676 to present different VNEs in the virtual network(s) 692 (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).
  • a single VNE a NE
  • the network controller 678 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 676 to present different VNEs in the virtual network(s) 692 (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).
  • the centralized control plane 676 can implement a spanning tree generator 681.
  • the spanning tree generator 681 can be a program or similar set of instructions that implement the methods described herein above in reference to Figures 1-5 that provide for the generation of spanning trees for distribution of multicast frames in a SPRING network.
  • Figures 6E and 6F respectively illustrate exemplary abstractions of NEs and VNEs that the network controller 678 may present as part of different ones of the virtual networks 692.
  • Figure 6E illustrates the simple case of where each of the NDs 600A-H implements a single NE 670A-H (see Figure 6D), but the centralized control plane 676 has abstracted multiple of the NEs in different NDs (the NEs 670A-C and G-H) into (to represent) a single NE 6701 in one of the virtual network(s) 692 of Figure 6D, according to some embodiments of the invention.
  • Figure 6E shows that in this virtual network, the NE 6701 is coupled to NE 670D and 670F, which are both still coupled to NE 670E.
  • Figure 6F illustrates a case where multiple VNEs (VNE 670A.1 and VNE 670H.1) are implemented on different NDs (ND 600 A and ND 600H) and are coupled to each other, and where the centralized control plane 676 has abstracted these multiple VNEs such that they appear as a single VNE 670T within one of the virtual networks 692 of Figure 6D, according to some embodiments of the invention.
  • the abstraction of a NE or VNE can span multiple NDs.
  • the electronic device(s) running the centralized control plane 676 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.
  • FIG. 7 illustrates, a general purpose control plane device 704 including hardware 740 comprising a set of one or more processor(s) 742 (which are often COTS processors) and network interface controller(s) 744 (NICs; also known as network interface cards) (which include physical NIs 746), as well as non-transitory machine readable storage media 748 having stored therein centralized control plane (CCP) software 750.
  • processors which are often COTS processors
  • NICs network interface controller
  • NICs network interface controller
  • CCP centralized control plane
  • the processor(s) 742 typically execute software to instantiate a virtualization layer 754 (e.g., in one embodiment the virtualization layer 754 represents the kernel of an operating system (or a shim executing on a base operating system) that allows for the creation of multiple instances 762A-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 754 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 762A-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
  • VMM virtual machine monitor
  • an instance of the CCP software 750 (illustrated as CCP instance 776A) is executed (e.g., within the instance 762A) on the virtualization layer 754.
  • the CCP instance 776A is executed, as a unikernel or on top of a host operating system, on the "bare metal" general purpose control plane device 704.
  • the instantiation of the CCP instance 776A, as well as the virtualization layer 754 and instances 762A-R if implemented, are collectively referred to as software instance(s) 752.
  • the CCP instance 776A includes a network controller instance 778.
  • the network controller instance 778 includes a centralized reachability and forwarding information module instance 779 (which is a middleware layer providing the context of the network controller 678 to the operating system and communicating with the various NEs), and an CCP application layer 780 (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).
  • this CCP application layer 780 within the centralized control plane 676 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.
  • the centralized control plane 676 transmits relevant messages to the data plane 680 based on CCP application layer 780 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 680 may receive different messages, and thus different forwarding information.
  • the data plane 680 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.
  • the general purpose control plane device 404 can implement a spanning tree generator 481.
  • the 481 can be a program or similar set of instructions that implement the methods described herein above in reference to Figures 1-5 that provide generation of spanning trees for distribution of multicast frames in a SPRING network.
  • generator 481 can be stored by the non-transitory machine readable storage media 448 and executed by the software instances 452 and processors 442.
  • 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).
  • MAC media access control
  • 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.
  • TCP transmission control protocol
  • an unknown packet for example, a "missed packet” or a "match-miss” as used in OpenFlow parlance
  • the packet (or a subset of the packet header and content) is typically forwarded to the centralized control plane 676.
  • the centralized control plane 676 will then program forwarding table entries into the data plane 680 to accommodate packets belonging to the flow of the unknown packet. Once a specific forwarding table entry has been programmed into the data plane 680 by the centralized control plane 676, the next packet with matching credentials will match that forwarding table entry and take the set of actions associated with that matched entry.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)

Abstract

L'invention concerne un procédé mis en œuvre par un dispositif de réseau pour calculer un arbre de distribution de multidiffusion (MDT) qui est un arbre maximal dans un réseau avec paquets source en routage (SPRING) pour un groupe de multidiffusion où un premier élément de transfert s'est annoncé comme la racine du groupe de multidiffusion et au moins un élément de transfert a annoncé un intérêt d'émission et/ou de réception pour le groupe de multidiffusion. Le résultat du calcul d'arbre maximal est utilisé pour mettre à jour la base d'informations de transfert (FIB) du dispositif de réseau.
PCT/IB2016/050985 2016-02-23 2016-02-23 Procédé et appareil pour arbres maximaux en vue d'une multidiffusion spring calculée WO2017144947A1 (fr)

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US10673742B2 (en) 2015-09-10 2020-06-02 Telefonaktiebolaget Lm Ericsson (Publ) Multicast state reduction via tunneling in a routed system
US11128576B2 (en) 2015-11-25 2021-09-21 Telefonaktiebolaget Lm Ericsson (Publ) Method and system for completing loosely specified MDTS
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US10904136B2 (en) 2018-08-06 2021-01-26 Telefonaktiebolaget Lm Ericsson (Publ) Multicast distribution tree versioning for minimizing multicast group traffic disruption

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