Algorithm Related IGP-Adjacency SID Advertisement
draft-peng-lsr-algorithm-related-adjacency-sid-00

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LSR                                                            P. Shaofu
Internet-Draft                                                    C. Ran
Intended status: Standards Track                         ZTE Corporation
Expires: September 10, 2020                                March 9, 2020

           Algorithm Related IGP-Adjacency SID Advertisement
           draft-peng-lsr-algorithm-related-adjacency-sid-00

Abstract

   Segment Routing architecture supports the use of multiple routing
   algorithms, i.e, different constraint-based shortest-path
   calculations can be supported.  There are two standard algorithms:
   SPF and Strict-SPF, defined in Segment Routing architecture.  There
   are also other user defined algorithms according to Flex-algo
   applicaiton.  However, an algorithm identifier is often included as
   part of a Prefix-SID advertisement, that maybe not satisfy some
   scenarios where multiple algorithm share the same link resource.
   This document will complement that the algorithm identifier can be
   also included as part of a Adjacency-SID advertisement

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Shaofu & Ran           Expires September 10, 2020               [Page 1]
Internet-Draft            algo-related adj-sid                March 2020

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Adjacency Segment Identifier per Algorithm  . . . . . . . . .   3
     3.1.  ISIS Adjacency Segment Identifier per Algorithm . . . . .   3
       3.1.1.  ISIS Adjacency Segment Identifier (Adj-SID) per
               Algorithm Sub-TLV . . . . . . . . . . . . . . . . . .   4
       3.1.2.  ISIS Adjacency Segment Identifier (LAN-Adj-SID) per
               Algorithm Sub-TLV . . . . . . . . . . . . . . . . . .   4
     3.2.  OSPF Adjacency Segment Identifier per Algorithm . . . . .   5
       3.2.1.  OSPF Adj-SID Sub-TLV  . . . . . . . . . . . . . . . .   6
       3.2.2.  OSPF LAN Adj-SID Sub-TLV  . . . . . . . . . . . . . .   6
     3.3.  OSPFv3 Adjacency Segment Identifier per Algorithm . . . .   7
       3.3.1.  OSPFv3 Adj-SID Sub-TLV  . . . . . . . . . . . . . . .   7
       3.3.2.  OSPFv3 LAN Adj-SID Sub-TLV  . . . . . . . . . . . . .   8
   4.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . .   8
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Segment Routing architecture [RFC8402] supports the use of multiple
   routing algorithms, i.e, different constraint-based shortest-path
   calculations can be supported.  There are two standard algorithms,
   i.e, SPF and Strict-SPF, that defined in Segment Routing
   architecture.  For SPF, the packet is forwarded along the well known
   ECMP-aware Shortest Path First (SPF) algorithm employed by the IGPs.
   However, it is explicitly allowed for a midpoint to implement another
   forwarding based on local policy.  For Strict Shortest Path First
   (Strict-SPF), it mandates that the packet be forwarded according to
   the ECMP-aware SPF algorithm and instructs any router in the path to
   ignore any possible local policy overriding the SPF decision.

   There are also other user defined algorithms according to IGP Flex
   Algorithm [I-D.ietf-lsr-flex-algo].  IGP Flex Algorithm proposes a
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