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SCHEME FOR DEFINING SEGMENT ROUTED P2MP TRAFFIC ENGINEERING LABEL SWITCHED PATHS

IP.com Disclosure Number: IPCOM000235727D
Publication Date: 2014-Mar-24
Document File: 11 page(s) / 1M

Publishing Venue

The IP.com Prior Art Database

Related People

Tarek Saad: AUTHOR [+3]

Abstract

A new Multicast Adjacency Segment Identifier (MAdj-SID) as well as a new segment stack encoding scheme using nested subtree(s) are provided to make forwarding of Segment Routed (SR) multicast packets onto Segment Routed Point-to-Multipoint Traffic Engineering (SR P2MP TE) Label Switched Paths (LSPs) feasible and practical. This scheme is practical since it makes the SR segment stack depth independent of the number of replications (branches) or replication hops (branch points) in the P2MP LSP.

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SCHEME FOR DEFINING SEGMENT ROUTED P2MP TRAFFIC ENGINEERING LABEL SWITCHED PATHS

AUTHORS:

Tarek Saad

Siva Sivabalan
Rakesh Gandhi

CISCO SYSTEMS, INC.

ABSTRACT

    A new Multicast Adjacency Segment Identifier (MAdj-SID) as well as a new segment stack encoding scheme using nested subtree(s) are provided to make forwarding of Segment Routed (SR) multicast packets onto Segment Routed Point-to-Multipoint Traffic Engineering (SR P2MP TE) Label Switched Paths (LSPs) feasible and practical. This scheme is practical since it makes the SR segment stack depth independent of the number of replications (branches) or replication hops (branch points) in the P2MP LSP.

DETAILED DESCRIPTION

    Segment routing (SR) defines an evolutionary technology that allows Multi- Protocol Label Switching (MPLS) forwarding while eliminating many control plane complexities. Traffic Engineered Point-to-Multipoint (P2MP) trees may deviate in their paths from the Internal Gateway Protocol (IGP)-computed Shortest Path Tree (SPT) towards their egress destinations. This may necessitate explicitly routing the P2MP subtree(s) towards respective egress destination(s).

    In SR, the path(s) to a specific destination does not depend on a hop-by-hop signaling technique (e.g., LDP or RSVP-TE), but rather on a set of segments that are advertised by the IGP routing protocol. For SR P2MP Traffic Engineering Label Switch Paths (TE LSPs), this imposes additional challenges to achieve, specifically with respect to 1) the size of label stack required to define a full P2MP TE SR LSP, 2) the encoding scheme used for pushing the SR labels that defines the SR P2MP TE tree, and 3) the complexity and amount of the work preformed at each node upon receiving and replicating SR P2MP packets.

Copyright 2014 Cisco Systems, Inc.

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    Presented herein is a solution to efficiently encode and forward P2MP packets on to SR-defined P2MP TE LSPs whose paths are set at the ingress node or Path Computation Element (PCE) router using a set of SR segments.


I. Multicast Adjacency Segment Identifier

    Segment Routing defines two types of Segment Identifiers (SID): Node-SID and Adjacency SID or Adj-SID. Proposed herein is a new segment identifier to represent a Multicast Adjacency Segment Identifier (MAdj-SID). The MAdj-SID represents a replication on to a set of router adjacencies.

FIG. 1 Example of MADJ-SID (A_m)

    In FIG. 1, for example, the MAdj-SID (A_m1) on router A represents a multicast replication onto legs AB (Replication Leg #0), AC (Replication Leg #1), and
AD (Replication Leg #2). A_m1 and its associated replication legs are flooded as MAdj-SID using IGP.

MCast_adj_segment sub-TLV: {
{A_m1, AB_ID(0), AC_ID(1), AD_ID(2)} }

MCast_adj_segment sub-TLV: {
{A_m2, AB_ID(0), AD_ID(2)}

Copyright 2014 Cisco Systems, Inc.

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}

MCast_adj_segment sub-TLV: { {A_m3, AC_ID(1), AD_ID(2)} }

MCast_adj_segment sub-TLV: { {A_m4, AB_ID(0), AC_ID(1)} }

FIG. 2 Example of MAdj-SID subTLVs

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