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WO2017144944A1 - Procédé et appareil pour améliorer la convergence dans un réseau spring - Google Patents

Procédé et appareil pour améliorer la convergence dans un réseau spring Download PDF

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Publication number
WO2017144944A1
WO2017144944A1 PCT/IB2016/050982 IB2016050982W WO2017144944A1 WO 2017144944 A1 WO2017144944 A1 WO 2017144944A1 IB 2016050982 W IB2016050982 W IB 2016050982W WO 2017144944 A1 WO2017144944 A1 WO 2017144944A1
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WO
WIPO (PCT)
Prior art keywords
mdt
event
state
network
forwarding element
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PCT/IB2016/050982
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English (en)
Inventor
David Ian Allan
Original Assignee
Telefonaktiebolaget Lm Ericsson (Publ)
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Application filed by Telefonaktiebolaget Lm Ericsson (Publ) filed Critical Telefonaktiebolaget Lm Ericsson (Publ)
Priority to PCT/IB2016/050982 priority Critical patent/WO2017144944A1/fr
Publication of WO2017144944A1 publication Critical patent/WO2017144944A1/fr

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Classifications

    • 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
    • H04L45/028—Dynamic adaptation of the update intervals, e.g. event-triggered updates
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L43/00—Arrangements for monitoring or testing data switching networks
    • H04L43/08—Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters
    • H04L43/0805—Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters by checking availability
    • H04L43/0817—Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters by checking availability by checking functioning
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L43/00—Arrangements for monitoring or testing data switching networks
    • H04L43/20—Arrangements for monitoring or testing data switching networks the monitoring system or the monitored elements being virtualised, abstracted or software-defined entities, e.g. SDN or NFV
    • 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
    • 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

Definitions

  • Embodiments of the invention relate to the field of optimization and convergence in communication networks; and more specifically, to the optimization and convergence of multicast 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 segment ID (SID) associated with a node and used for forwarding to that node.
  • SID segment ID
  • 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/SIDs 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.
  • a method is executed by a network device in a network
  • the network device functions as a computing element for convergence after an event potentially affecting a multicast distribution tree (MDT) in the network.
  • MDT multicast distribution tree
  • the method maximizes reliability and minimizes an impact of a re-optimization of the convergence by sequencing the installation of updates to state in at least one forwarding element in the network to reduce lost data packets and delay of data packets during an update sequence.
  • the method includes receiving at the computing element the event potentially affecting the MDT, determining whether the event effects the state of the at least one forwarding element, categorizing an effect of the event on the state of the at least one forwarding element as a class of event, in response to the event effecting the state of the at least one forwarding element, and scheduling an update of the state of the at least one forwarding element according to the class of the event.
  • a network device is in a network implementing multicast using unicast tunneling.
  • the network device functions as a computing element for convergence after an event potentially affecting a multicast distribution tree (MDT) in the network.
  • the network device executes a method to maximize reliability and minimize an impact of a re-optimization of the convergence by sequencing the installation of updates to state in at least one forwarding element in the network to reduce lost data packets and delay of data packets during an update sequence.
  • the network device includes a non-transitory machine readable storage device having stored therein a multicast state scheduler, and a processor coupled to the non-transitory machine readable storage device.
  • the processor is configured to execute the multicast state scheduler.
  • the multicast state scheduler is configured to receive at the computing element the event potentially affecting the MDT, to determine whether the event effects the state of the at least one forwarding element, to categorize an effect of the event on the state of the at least one forwarding element as a class of event, in response to the event effecting the state of the at least one forwarding element, and to schedule an update of the state of the at least one forwarding element according to the class of the event.
  • a computing device is in communication with a network device in a network implementing multicast using unicast tunneling.
  • the computing device executes a plurality of virtual machines for implementing network function virtualization (NFV).
  • NFV network function virtualization
  • the network device functions as a computing element for convergence after an event potentially affecting a multicast distribution tree (MDT) in the network.
  • MDT multicast distribution tree
  • the network device executes a method to maximize reliability and minimize an impact of a re-optimization of the convergence by sequencing the installation of updates to state in at least one forwarding element in the network to reduce lost data packets and delay of data packets during an update sequence.
  • the network device includes a non-transitory machine readable storage device having stored therein a multicast state scheduler, and a processor coupled to the non-transitory machine readable storage device.
  • the processor is configured to execute a virtual machine in the plurality of virtual machines.
  • the virtual machine executes the multicast state scheduler.
  • the multicast state scheduler is configured to receive at the computing element the event potentially affecting the MDT, to determine whether the event effects the state of the at least one forwarding element, to categorize an effect of the event on the state of the at least one forwarding element as a class of event, in response to the event effecting the state of the at least one forwarding element, and to schedule an update of the state of the at least one forwarding element according to the class of the event.
  • 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.
  • the network device implements multicast using unicast tunneling.
  • the network device functioning as a computing element for convergence after an event potentially affecting a multicast distribution tree (MDT) in the network.
  • the network device executes a method to maximize reliability and minimize an impact of a re-optimization of the convergence by sequencing the installation of updates to state in at least one forwarding element in the network to reduce lost data packets and delay of data packets during an update sequence.
  • the control plane device includes a non-transitory machine readable storage device having stored therein a multicast state scheduler, and a processor coupled to the non-transitory machine readable storage device.
  • the processor is configured to execute the multicast state scheduler.
  • the multicast state scheduler is configured to receive at the computing element the event potentially affecting the MDT, to determine whether the event effects the state of the at least one forwarding element, to categorize an effect of the event on the state of the at least one forwarding element as a class of event, in response to the event effecting the state of the at least one forwarding element, and to schedule an update of the state of the at least one forwarding element according to the class of the event.
  • Figure 1 is a flowchart of one embodiment of process for scheduling updates to state related to the effect of network convergence on a set of multicast distribution trees (MDTs) at a given node in the network topology.
  • MDTs multicast distribution trees
  • Figure 2 is a flowchart of one embodiment of the process for identifying the types of changes in a network and MDT caused by an event that initiates a network convergence.
  • Figure 3A is a flowchart of one embodiment of the process for handling membership changes.
  • Figure 3B is a flowchart of one embodiment of the process for handling membership addition and removal.
  • Figure 4 is a flowchart of one embodiment of the process for handling changes in the network topology.
  • Figure 5 is a flowchart of one embodiment of the process for handling link or node failures/removals in the network topology.
  • Figure 6 is a flowchart of one embodiment of the process for handling addition of nodes or links to the network topology.
  • Figure 7A illustrates connectivity between network devices (NDs) within an exemplary network, as well as three exemplary implementations of the NDs, according to some
  • Figure 7B illustrates an exemplary way to implement a special-purpose network device according to some embodiments of the invention.
  • FIG. 7C 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 7D 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 7E 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 7F 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 8 illustrates a general purpose control plane device with centralized control plane (CCP) software 850), according to some embodiments of the invention.
  • CCP centralized control plane
  • the following description describes methods and apparatus for improving optimization and re-optimization after a network convergence by identifying conditions where the scheduling of the updating of the state related to multicast can be ordered such that the updates have minimal or no impact on existing multicast traffic.
  • These embodiments apply to a network where multicast distribution tree construction is a hybrid of a root, leaves, and replication points interconnected with unicast tunnels.
  • the embodiments provide a process and apparatus that identify the types of events that caused the network to need to reconverge, then categorize the associated changes to state that need to be made such that these categories correspond to an ordering in time for the updates that ensure minimal disruption to the handling of existing data traffic in the network.
  • 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
  • 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) 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
  • 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 applying state update scheduling to improve convergence. These embodiments work in combination with other methods of utilizing unicast tunnels within a network where tunnels are employed to minimize multicast related state.
  • the embodiments utilize the computations 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.
  • MDTs multicast distribution trees
  • SPB shortest path bridging
  • 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 permitted the dataplane (S,G) forwarding state to be algorithmically constructed from information received in the control plane.
  • Other technologies such as multiprotocol label switching (MPLS) or source packet in routing (SPRING) can overload a single identifier to represent (S,G) such as a single MPLS label. Therefore the information distributed in the control plane would need to be augmented to reflect this.
  • multicast registrations in a SPRING network would identify both the multicast group and the global label or "multicast segment identifier" associated with a given root intended to use for the (S,G) MDT.
  • 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 and a group may have multiple sources.
  • 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 employ this mode of operation.
  • 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 a priori established 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.
  • network convergence i.e., the computation of the state necessary to implement the MDTs at each node in the network
  • a local repair of failures may occur, if necessary. For example, fast reroute and loop free alternate paths can be utilized to re-establish connectivity where a link or node has failed in the network.
  • Second, unicast re-optimization may occur. Unicast re-optimization involves the recalculation of unicast paths between all nodes in the network. Providing that leaves in an MDT have not been completely severed from the network, this process will restore service for a given MDT for all events other than failure of the root or a replication node.
  • multicast re-optimization occurs. This process determines the roles of nodes as replication points and similar functions of nodes in the network. This process will restore service for impacted MDTs not recovered by unicast convergence, and may re-optimize MDTs recovered by unicast convergence.
  • the types of events that occur in a network that require network convergence or re-convergence fall broadly into the categories of group membership changes and topology changes. These events can be more specifically categorized and correlated with the requisite steps for addressing the changes and the priority of these steps in the reconvergence process.
  • Group membership changes are not accompanied by topology changes so there is no need for local repair or unicast optimization in these scenarios. Recognizing this at the outset enables these steps to be bypassed.
  • Topology changes add or remove links and/or nodes from the topology of the network as a whole. This may be either administrative or as the result of failure or repair. These changes may or may not directly involve the members of the multicast groups. There are three scenarios where topology changes occur: first, an addition or removal of a link and/or node that does not change the topology of an MDT (this encompasses equal cost multipath configurations in the topology); second, failure of a replication node in an MDT, which results in the addition, removal and/or modification to replication points in the MDT; and third, failure of a link that modifies the MDT topology, which results in the addition, removal and modification to replication points in the MDT.
  • the sequence of state modification can render a number of individual events hitless. Any node where the convergence action is to remove all state for an MDT as it is no longer a replication point can safely delay performing the state removal longer than the expected network convergence time as there are no strict coordination requirements with other state changes, it merely needs to occur after all other classes of change. This case addresses group membership changes such as the removal of a group member that in turn requires the removal of a replication point. Similarly, topology changes where a replication point has failed or a link has failed can have their effects mitigated. Thus, when performing multicast convergence as a result of any class of notification, a node may wait a pre-determined amount of time to remove state in the scenario when it transitioned from being a replication point for an MDT to not being a replication point.
  • a group membership change that results in the addition of a replication point can be addressed with high probability of no impact to existing multicast receivers if there is a delay added to multicast convergence between the installation of state in the new replication points and the installation of state in the existing replication nodes to decouple the dependency in time.
  • a node when performing multicast convergence upon notice of a group membership change, a node can determine whether it is a new replication node for an MDT and in this case install its state immediately, and the node can determine whether it is an existing replication node of an MDT that needs to alter its state, in this case the update to the state can be delayed. This delay in updating the state however would be less than a delay for a removal of state, which has less priority.
  • a topology change may result in the loss of a link or a tunnel transit node for a given MDT such that the topology of the MDT becomes non-optimal.
  • Restoration of connectivity will initially be addressed by unicast convergence. However, it is desirable both to re-optimize the MDT to make the multicast re-optimization hitless. In this scenario, the same methods for reducing the hitfullness of group membership changes can be applied. Addition of topology components will not affect existing MDTs until an optimization step is performed.
  • Nodes that have a role of a replication nodes will be able to determine the leaves and replication nodes are served by each downstream interface in the current installed topology solution.
  • a node may immediately install state that uniquely serves any leaf severed by the failure of the downstream replication node.
  • a node on a unique shortest path to a downstream leaf is determine to have failed, a node may immediately install state that uniquely serves that leaf.
  • FIG. 1 is a flowchart of one embodiment of process for scheduling updates to state related to a set of multicast distribution trees (MDTs) at a given node.
  • the process is implemented by a computing element that is responsible for the computation of the MDT during network convergence and re-optimization for a given forwarding element.
  • a computing element is a process implemented in any computing or network device where the process is for determining forwarding information for one or more forwarding elements.
  • a forwarding element is a process implemented in any network device or computing device where the process implements the forwarding of traffic, in particular for the context of the
  • multicast traffic in a network may be separately located or executed by the same computing device or networking device.
  • the process begins with a computing element receiving an event or notice of an event that instigates network convergence and potentially affects at least one multicast distribution tree (Block 101).
  • a network and the plurality of network elements that are part of the network may support and implement any number of MDTs.
  • the process is describe with relation to a single MDT being affected by network convergence, however, one skilled in the art would understand that the process can be applied to handle any number of MDTs in the network.
  • the following paragraphs will describe the scheduling of classes of forwarding state change in the context of a single forwarding element and its role in relation to the affected MDT.
  • Block 103 If the membership is not affected, then the process is determines whether the event modifies the network topology that the MDT is optimized for (Block 105). If either the membership of the MDT or the network topology utilized by the MDT is affected, then the process determines whether the event effects the state of the forwarding element (Block 107). If the state of the forwarding element is not affected or there was not affect on the membership of the MDT or the topology of the network underlying the MDT, then the process completes.
  • the effect is categorized based on if and how it affects the state of the forwarding element (Block 109).
  • the categorization can be any one of three or more classes of events. These three classes are referred to herein as a first, second and third class that relate generally to the sequence of the installing of state for the forwarding element offset in time from the receipt of notice of the network change, with the first class having the most immediate or prioritized installment timing and the third class having the last or least prioritized installment timing.
  • the update to the state of the forwarding element can be scheduled according to the class of the effect of the event, in other words in the order of the classes of event described above (Block 111).
  • the set of changes required are computed as part of the convergence process and this process works in tandem with that computation to structure the order in which the state is installed.
  • the three classes can include: a first class for immediate
  • FIG. 2 is a flowchart of one embodiment of the process for identifying the types of changes in a network and MDT.
  • the flowchart of Figure 2 is an example embodiment where the different classes are defined by timing delay constants. These timing delay constants may be labeled tl, t2, and t3 where tl ⁇ t2 ⁇ t3 where it is assumed that, for example, t2 has been dimensioned to be greater than the typical amount of time for the network to perform all computations associated with the network change and perform all forwarding state updates associated with the first class, and t3 has been dimensioned to be greater than the amount of time it would typically take the network to wait t2 and perform all tasks associated with t2.
  • the computing elements in the network each perform this process for their respective forwarding elements.
  • the process may begin in response to an event that affects the network.
  • the process determines whether the event requires a membership change for the MDT (Block 201).
  • a membership change involves the adding or removal of any member of the multicast group associated with the MDT. If there is a membership change then the process initiates a membership change sub-process (Block 209). If there is not a membership change, then the process determines whether a topology addition has occurred in the network
  • a topology addition would encompass any node or link being added to the network thereby altering/adding to the existing topology. If a topology addition has occurred, then the process begins a topology addition sub-process (Block 205). However, if no addition has occurred, then the remaining case is a topology removal, which triggers a topology removal sub-process (Block 207). This process of identifying the type of the changes in the network associated with an event can be performed in other sequences, with a single parallel test or can be similarly processed. In some cases, multiple sub-processes can be executed where more than one type of change has occurred due to an event or set of events.
  • FIG. 3A is a flowchart of one embodiment of the process for handling membership changes.
  • the event has been identified as having an affect on the membership of the multicast group.
  • the computation is to determine and schedule any changes to forwarding state in a forwarding element the computing element is responsible for.
  • This sub-process starts with the first forwarding element in the network and iterates through the forwarding elements in the network. Further the process iterates through each MDT that is rooted at the current forwarding element.
  • next MDT is selected (Block 312). If all of the MDT have been processed, then a check is made whether all forwarding elements have been processed (Block 310). If all of the forwarding elements have been processed then the process completes. Otherwise, the process selects the next forwarding element for processing (Block 314).
  • FIG. 3B is a flowchart of one embodiment of a sub-process for handling membership additions and removal. This sub-process is called from the process described herein above.
  • the sub-process performs an MDT re-computation for the forwarding element (Block 309).
  • a determination is made whether the MDT re-computation indicates that the forwarding element has transitioned to being a replication point for the MDT or where the forwarding element is already a replication point for the MDT whether the forwarding element has changed to serve a leaf that was not previously serviced (Block 311). If these conditions do not exist, then the process determines whether the forwarding element modifies any existing replication functions (Block 313).
  • the sub-process queues state to be installed at t2 (i.e., the second class). After queueing the installation of the state, the sub-process then completes.
  • the sub-process queues state for immediate installation at tl (i.e., the first class). The sub-process then completes.
  • FIG 4 is a flowchart of one embodiment of the process for handling topology changes.
  • This sub-process is implemented when the topology of the network has changed such that a forwarding element or link has been removed, changed or added that affects the MDT. Thus, from Figure 2, this sub-process is called by either a topology addition or topology removal. The process varies slightly depending on which of these two cases applies.
  • This sub- process also iterates through the forwarding elements of the network and begins with selecting a first forwarding element of the network (Block 401). The process then selects a first MDT to be processed that is rooted at the selected forwarding element (Block 403). This MDT is recomputed and compared with the previous MDT for the associated multicast group (Block 405).
  • a further sub-process is invoked to handle the specifics of link or forwarding element failure or topology addition in the network (Block 407).
  • a check is then made whether the processed MDT is the last MDT rooted at the current forwarding element (Block 413). If there are more MDTs rooted at the forwarding element, then the next MDT is selected (Block 411). If there are not further MDTs rooted at the current forwarding element, then a check is made whether the current forwarding element is the last forwarding element in the network to be processed (Block 415). If it is not the last forwarding element, then the next forwarding element to be processed is selected (Block 409). Otherwise, the sub-process completes.
  • FIG. 5 is a flowchart of one embodiment of the sub-process for handling link or node failures in the topology.
  • This sub-process is executed where there is a forwarding element or link failure as part of the topology change sub-process.
  • the sub-process begins being called where there is a link or forwarding element failure in the network (Block 501).
  • the network topology and the MDT have been updated and this updated topology and MDT are examined to identify the impacted leaves of the MDT (Block 503).
  • a determination is then made whether the current forwarding element as selected in the topology change sub-process needs to add state that uniquely serves impacted leaves (Block 505). Where this is the case, the state to be installed is queued for immediate installation at tl (i.e., the first class) (Block 507).
  • a check is then made whether the forwarding element needs to add other state
  • Block 509 This is any other state than the state needed to uniquely serve impacted leaves. If there is other state to be added, this state can be added at t2 (i.e., second class) (Block 511). A check is then made whether the selected forwarding element can remove state that uniquely served impacted leaves (Block 513), although it should be noted that this is an optimization, and such state could also be removed at t2. If this is the case, then the process queues this state for immediate removal at tl (i.e., first class) (Block 515). Then a check is made whether the forwarding element needs to remove any other state (Block 517) but without transitioning to not having a role in the MDT. This can be any state other than the state related to uniquely serviced leaves.
  • FIG. 6 is a flowchart of one embodiment of the sub-process for handling addition of nodes to a topology.
  • This sub-process is executed where the network has changed such that topology needs to be added to the network, which may affect the MDT.
  • the sub-process is invoked by the topology change sub-process as described herein above (Block 601A check is made using the new MDT to determine whether the forwarding element is transitioning to being a replication point for the new MDT (Block 605). In this case, the process queues the state to be installed to effect this transition for immediate installation at tl (i.e., first class).
  • the process determines whether the forwarding element is modifying existing replication functions (Block 609). If there are modifications to the existing replication functions, then the process queues state for addition at or after t2 (i.e., second class) (Block 611). Where there is no modification to replication function, then the process determines whether the forwarding element needs to only remove state (Block 613). For example, where the forwarding element is no longer a replication point after the topology addition. In this case, the process queues state removal at or after t3 (i.e., third class) (Block 615). In all cases after all of the state has been queued, the process completes and returns to the topology change sub- process.
  • nodes may implement a reverse path forwarding check (RPFC) in which multicast MPLS label is only accepted on certain upstream labels.
  • RPFC reverse path forwarding check
  • each node can determine the impact of a failure and can tailor how it installs state to respond to the impact such that it minimizes the impact on multicast distribution.
  • State for leaves for which service has been interrupted is scheduled immediately at tl (i.e., first class).
  • tl i.e., first class
  • node can take advantages of the properties of sparsely defined state in these networks to make adds, modifications and similar changes less intrusive on multicast distribution by sequencing how state is added and removed when responding to the local impact of network events.
  • Figure 7A illustrates connectivity between network devices (NDs) within an exemplary network, as well as three exemplary implementations of the NDs, according to some
  • Figure 7A shows NDs 700A-H, and their connectivity by way of lines between 700A-700B, 700B-700C, 700C-700D, 700D-700E, 700E-700F, 700F-700G, and 700A-700G, as well as between 700H and each of 700A, 700C, 700D, and 700G.
  • These NDs are physical devices, and the connectivity between these NDs can be wireless or wired (often referred to as a link).
  • NDs 700A, 700E, and 700F An additional line extending from NDs 700A, 700E, and 700F 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).
  • ASICs application-specific integrated-circuits
  • OS special-purpose operating system
  • COTS common off-the-shelf
  • the special-purpose network device 702 includes networking hardware 710 comprising compute resource(s) 712 (which typically include a set of one or more processors), forwarding resource(s) 714 (which typically include one or more ASICs and/or network processors), and physical network interfaces (NIs) 716 (sometimes called physical ports), as well as non- transitory machine readable storage media 718 having stored therein networking software 720.
  • 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 700A-H.
  • WNIC wireless network interface controller
  • NIC network interface controller
  • the networking software 720 may be executed by the networking hardware 710 to instantiate a set of one or more networking software instance(s) 722.
  • Each of the networking software instance(s) 722, and that part of the networking hardware 710 that executes that network software instance form a separate virtual network element 730A-R.
  • VNEs 730A-R includes a control communication and configuration module 732A-R
  • a given virtual network element (e.g., 730A) includes the control communication and configuration module (e.g., 732A), a set of one or more forwarding table(s) (e.g., 734A), and that portion of the networking hardware 710 that executes the virtual network element (e.g., 73 OA).
  • the special-purpose network device 701 can implement a multicast state
  • the multicast state scheduler 764 can be a program or similar set of instructions that implement the methods described herein above in reference to Figures 1-6 that provide a method and system for scheduling multicast state installation in a SPRING network.
  • the multicast state scheduler 764 can be stored by the non-transitory machine readable storage media 718 and executed by the compute resources 712.
  • the special-purpose network device 702 is often physically and/or logically considered to include: 1) a ND control plane 724 (sometimes referred to as a control plane) comprising the compute resource(s) 712 that execute the control communication and configuration
  • ND forwarding plane 726 (sometimes referred to as a forwarding plane, a data plane, or a media plane) comprising the forwarding resource(s) 714 that utilize the forwarding table(s) 734A-R and the physical NIs 716.
  • the ND control plane 724 (the compute resource(s) 712 executing the control communication and configuration module(s) 732A-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) 734A-R, and the ND forwarding plane 726 is responsible for receiving that data on the physical NIs 716 and forwarding that data out the appropriate ones of the physical NIs 716 based on the forwarding table(s) 734A-R.
  • data e.g., packets
  • the ND forwarding plane 726 is responsible for receiving that data on the physical NIs 716 and forwarding that data out the appropriate ones of the physical NIs 716 based on the forwarding table(s) 734A-R.
  • Figure 7B illustrates an exemplary way to implement the special-purpose network device 702 according to some embodiments of the invention.
  • Figure 7B shows a special- purpose network device including cards 738 (typically hot pluggable). While in some embodiments the cards 738 are of two types (one or more that operate as the ND forwarding plane 726 (sometimes called line cards), and one or more that operate to implement the ND control plane 724 (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 704 includes 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 software 750.
  • processor(s) 742 execute the software 750 to instantiate one or more sets of one or more applications 764A-R. While one embodiment does not implement virtualization, alternative embodiments may use different forms of virtualization.
  • 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 that may each be used to execute one (or more) of the sets of applications 764A-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 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 each of the sets of applications 764A-R is run on top of a guest operating system within an instance 762A-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
  • 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 740, 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 754, unikernels running within software containers represented by instances 762A-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 instantiation of the one or more sets of one or more applications 764A-R, as well as virtualization if implemented, are collectively referred to as software instance(s) 752.
  • the virtual network element(s) 760A-R perform similar functionality to the virtual network element(s) 730A-R - e.g., similar to the control communication and configuration module(s) 732A and forwarding table(s) 734A (this virtualization of the hardware 740 is sometimes referred to as network function virtualization (NFV)).
  • NFV network function virtualization
  • CPE customer premise equipment
  • each instance 762A-R corresponding to one VNE 760A-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 762A-R to VNEs also apply to embodiments where such a finer level of granularity and/or unikernels are used.
  • the virtualization layer 754 includes a virtual switch that provides similar forwarding services as a physical Ethernet switch. Specifically, this virtual switch forwards traffic between instances 762A-R and the NIC(s) 744, as well as optionally between the instances 762A-R; in addition, this virtual switch may enforce network isolation between the VNEs 760A-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 704 can implement a multicast state
  • the multicast state scheduler 768 can be a program or similar set of instructions that implement the methods described herein above in reference to Figures 1-6 that provide a method and system for scheduling multicast state installation in a SPRING network.
  • the multicast state scheduler 768 can be stored by the non-transitory machine readable storage media 748 and executed by the compute resources 742.
  • the third exemplary ND implementation in Figure 7A is a hybrid network device 706, 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 702 could provide for para-virtualization to the networking hardware present in the hybrid network device 706.
  • NE network element
  • each of the VNEs receives data on the physical NIs (e.g., 716, 746) and forwards that data out the appropriate ones of the physical NIs (e.g., 716, 746).
  • 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 7C illustrates various exemplary ways in which VNEs may be coupled according to some embodiments of the invention.
  • Figure 7C shows VNEs 770A.1-770A.P (and optionally VNEs 770A.Q-770A.R) implemented in ND 700A and VNE 770H.1 in ND 700H.
  • VNEs 770A.1-P are separate from each other in the sense that they can receive packets from outside ND 700A and forward packets outside of ND 700A; VNE 770A.1 is coupled with VNE 770H.1, and thus they communicate packets between their respective NDs; VNE 770A.2-770A.3 may optionally forward packets between themselves without forwarding them outside of the ND 700A; and VNE 770A.P may optionally be the first in a chain of VNEs that includes VNE 770A.Q followed by VNE 770A.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 7C 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 VNE
  • the NDs of Figure 7A 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.
  • 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
  • VOIP
  • 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 7A may also host one or more such servers (e.g., in the case of the general purpose network device 704, one or more of the software instances 762A-R may operate as servers; the same would be true for the hybrid network device 706; in the case of the special-purpose network device 702, one or more such servers could also be run on a virtualization layer executed by the compute resource(s) 712); 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. 7D illustrates a network with a single network element on each of the NDs of Figure 7A, 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 7D illustrates network elements (NEs) 770A-H with the same connectivity as the NDs 700A-H of Figure 7A.
  • Figure 7D illustrates that the distributed approach 772 distributes responsibility for generating the reachability and forwarding information across the NEs 770A-H; in other words, the process of neighbor discovery and topology discovery is distributed.
  • the control communication and configuration module(s) 732A-R of the ND control plane 724 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
  • the NEs 770A-H (e.g., the compute resource(s) 712 executing the control communication and configuration
  • module(s) 732A-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 724.
  • the ND control plane 724 programs the ND forwarding plane 726 with information (e.g., adjacency and route information) based on the routing structure(s).
  • the ND control plane 724 programs the adjacency and route information into one or more forwarding table(s) 734A-R (e.g., Forwarding Information Base (FIB), Label Forwarding Information Base (LFIB), and one or more adjacency structures) on the ND forwarding plane 726.
  • 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 702, the same distributed approach 772 can be implemented on the general purpose network device 704 and the hybrid network device 706.
  • Figure 7D illustrates that a centralized approach 774 (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 774 has the responsibility for the generation of reachability and forwarding information in a centralized control plane 776 (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 776 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 776 has a south bound interface 782 with a data plane 780 (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 770A-H (sometimes referred to as switches, forwarding elements, data plane elements, or nodes).
  • the centralized control plane 776 includes a network controller 778, which includes a centralized reachability and forwarding information module 779 that determines the reachability within the network and distributes the forwarding information to the NEs 770A-H of the data plane 780 over the south bound interface 782 (which may use the OpenFlow protocol).
  • the network intelligence is centralized in the centralized control plane 776 executing on electronic devices that are typically separate from the NDs.
  • each of the control communication and configuration module(s) 732A-R of the ND control plane 724 typically include a control agent that provides the VNE side of the south bound interface 782.
  • the ND control plane 724 (the compute resource(s) 712 executing the control communication and configuration module(s) 732A-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 776 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 779 (it should be understood that in some embodiments of the invention, the control communication and configuration module(s) 732A-R, in addition to communicating with the centralized control plane 776, 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 774, but may also be considered a hybrid approach).
  • data e.g., packets
  • the control agent communicating with the centralized control plane 776 to receive the forward
  • the same centralized approach 774 can be implemented with the general purpose network device 704 (e.g., each of the VNE 760A-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 776 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 779; it should be understood that in some embodiments of the invention, the VNEs 760A-R, in addition to communicating with the centralized control plane 776, 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 706.
  • the general purpose network device 704 e.g., each of the VNE 760A-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 7D also shows that the centralized control plane 776 has a north bound interface 784 to an application layer 786, in which resides application(s) 788.
  • the centralized control plane 776 has the ability to form virtual networks 792 (sometimes referred to as a logical forwarding plane, network services, or overlay networks (with the NEs 770A-H of the data plane 780 being the underlay network)) for the application(s) 788.
  • virtual networks 792 sometimes referred to as a logical forwarding plane, network services, or overlay networks (with the NEs 770A-H of the data plane 780 being the underlay network)
  • the centralized control plane 776 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 7D shows the distributed approach 772 separate from the centralized approach 774
  • 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) 774, 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 774, but may also be considered a hybrid approach.
  • Figure 7D illustrates the simple case where each of the NDs 700A-H implements a single NE 770A-H
  • the network control approaches described with reference to Figure 7D also work for networks where one or more of the NDs 700A-H implement multiple VNEs (e.g., VNEs 730A-R, VNEs 760A-R, those in the hybrid network device 706).
  • the network controller 778 may also emulate the implementation of multiple VNEs in a single ND.
  • the network controller 778 may present the implementation of a VNE/NE in a single ND as multiple VNEs in the virtual networks 792 (all in the same one of the virtual network(s) 792, each in different ones of the virtual
  • the network controller 778 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 776 to present different VNEs in the virtual network(s) 792 (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 778 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 776 to present different VNEs in the virtual network(s) 792 (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 776 can implement a multicast state scheduler 781.
  • the multicast state scheduler 781 can be a program or similar set of instructions that implement the methods described herein above in reference to Figures 1-6 that provide a method and system for scheduling multicast state installation in a SPRING network.
  • scheduler 781 can be stored by the non-transitory machine readable storage media and executed by the compute resource.
  • Figures 7E and 7F respectively illustrate exemplary abstractions of NEs and VNEs that the network controller 778 may present as part of different ones of the virtual networks 792.
  • Figure 7E illustrates the simple case of where each of the NDs 700A-H implements a single NE 770A-H (see Figure 7D), but the centralized control plane 776 has abstracted multiple of the NEs in different NDs (the NEs 770A-C and G-H) into (to represent) a single NE 7701 in one of the virtual network(s) 792 of Figure 7D, according to some
  • Figure 7E shows that in this virtual network, the NE 7701 is coupled to NE 770D and 770F, which are both still coupled to NE 770E.
  • Figure 7F illustrates a case where multiple VNEs (VNE 770A.1 and VNE 770H.1) are implemented on different NDs (ND 700A and ND 700H) and are coupled to each other, and where the centralized control plane 776 has abstracted these multiple VNEs such that they appear as a single VNE 770T within one of the virtual networks 792 of Figure 7D, 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 776 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.
  • Figure 8 illustrates, a general purpose control plane device 804 including hardware 840 comprising a set of one or more processor(s) 842 (which are often COTS processors) and network interface controller(s) 844 (NICs; also known as network interface cards) (which include physical NIs 846), as well as non-transitory machine readable storage media 848 having stored therein centralized control plane (CCP) software 850.
  • processor(s) 842 which are often COTS processors
  • NICs network interface controller
  • NICs network interface controller
  • non-transitory machine readable storage media 848 having stored therein centralized control plane (CCP) software 850.
  • CCP centralized control plane
  • the processor(s) 842 typically execute software to instantiate a virtualization layer 854 (e.g., in one embodiment the virtualization layer 854 represents the kernel of an operating system (or a shim executing on a base operating system) that allows for the creation of multiple instances 862A-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 854 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 862A-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
  • CCP instance 876A an instance of the CCP software 850 (illustrated as CCP instance 876A) is executed (e.g., within the instance 862A) on the virtualization layer 854.
  • CCP instance 876A is executed, as a unikernel or on top of a host operating system, on the "bare metal" general purpose control plane device 804. The instantiation of the CCP instance 876A, as well as the virtualization layer 854 and
  • instances 862A-R if implemented, are collectively referred to as software instance(s) 852.
  • the CCP instance 876A includes a network controller instance 878.
  • the network controller instance 878 includes a centralized reachability and forwarding information module instance 879 (which is a middleware layer providing the context of the network controller 778 to the operating system and communicating with the various NEs), and an CCP application layer 880 (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 880 within the centralized control plane 776 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 776 transmits relevant messages to the data plane 780 based on CCP application layer 880 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 780 may receive different messages, and thus different forwarding information.
  • the data plane 780 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 804 can implement a multicast state scheduler 881.
  • the multicast state scheduler 881 can be a program or similar set of instructions that implement the methods described herein above in reference to Figures 1-6 that provide a method and system for scheduling multicast state installation in a SPRING network.
  • the multicast state scheduler 881 can be stored by the non-transitory machine readable storage media 848 and executed by the compute resources 842.
  • 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

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Abstract

La présente invention concerne un procédé qui est exécuté par un dispositif de réseau dans un réseau mettant en œuvre une multidiffusion à l'aide de tunnels d'unidiffusion. Le dispositif de réseau fonctionne en tant qu'élément de calcul pour une convergence après un événement perturbant potentiellement un arbre de distribution de multidiffusion (MDT) dans le réseau. Le procédé rend maximale la fiabilité et rend minimal un impact d'une ré-optimisation de la convergence par un séquencement de l'installation de mises à jour à un état dans au moins un élément de transfert dans le réseau pour réduire la perte de paquets de données et le retard de paquets de données durant une séquence de mise à jour. Le procédé consiste à recevoir potentiellement l'événement dans l'élément de calcul.
PCT/IB2016/050982 2016-02-23 2016-02-23 Procédé et appareil pour améliorer la convergence dans un réseau spring WO2017144944A1 (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
US10904136B2 (en) 2018-08-06 2021-01-26 Telefonaktiebolaget Lm Ericsson (Publ) Multicast distribution tree versioning for minimizing multicast group traffic disruption
US11128576B2 (en) 2015-11-25 2021-09-21 Telefonaktiebolaget Lm Ericsson (Publ) Method and system for completing loosely specified MDTS

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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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