IS-IS Extensions for Path MTU
draft-hu-lsr-isis-path-mtu-00

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Last updated 2018-06-30
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Network Working Group                                              Z. Hu
Internet-Draft                                                    Huawei
Intended status: Informational                                    Y. Zhu
Expires: January 1, 2019                                   China Telecom
                                                                   Z. Li
                                                                  L. Dai
                                                                  Huawei
                                                           June 30, 2018

                     IS-IS Extensions for Path MTU
                     draft-hu-lsr-isis-path-mtu-00

Abstract

   Segment routing (SR) leverages the source routing mechanism.  It
   allows for a flexible definition of end-to-end paths with IGP
   topologies by encoding paths as sequences of topological sub-paths
   which is called segments.  These segments are advertised by the link-
   state routing protocols (IS-IS and OSPF).  Unlike the MPLS, SR does
   not have the specific path construction signaling so that it cannot
   support the Path MTU.  This draft provides the necessary IS-IS
   extensions about the Path MTU that need to be used on SR.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on January 1, 2019.

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Internet-Draft        IS-IS Extensions for Path MTU            June 2018

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Extendsion of IS-IS . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Protocol Extension  . . . . . . . . . . . . . . . . . . .   4
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Segment routing (SR) leverages the source routing mechanism.  SR
   allows for a flexible definition of end-to-end paths within IGP
   topologies by encoding paths as sequences of toplogical sub-paths
   which is called segments.  These segments are advertised by the link-
   state routing protocols (IS-SI and OSPF).  The SR architecture as
   well as the routing policy is proposed in
   [I-D.ietf-spring-segment-routing] and
   [I-D.filsfils-spring-segment-routing-policy].  Two types of segments
   are defined, Prefix segments and Adjacency segments.  Prefix segments
   represent an ecmp-aware shortest-path to a prefix, as per the state
   of the IGP topology.  Adjacency segments represent a hop over a
   specific adjacency between two nodes in the IGP.  A prefix segment is
   typically a multi-hop path while an adjacency segment, in most of the
   cases, is a one-hop path.  SR can compute the paths from end to end
   and without requiring any LDP or RSVP-TE signaling.  SR supports per-
   flow explict routing while just maintaining per-flow state only at
   the source node.

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