Signaling MSD (Maximum SID Depth) using OSPF
draft-ietf-ospf-segment-routing-msd-00

The information below is for an old version of the document
Document Type Active Internet-Draft (ospf WG)
Last updated 2016-11-15
Stream IETF
Intended RFC status (None)
Formats pdf htmlized bibtex
Reviews
Stream WG state WG Document
Document shepherd No shepherd assigned
IESG IESG state I-D Exists
Consensus Boilerplate Unknown
Telechat date
Responsible AD (None)
Send notices to (None)
OSPF Working Group                                           J. Tantsura
Internet-Draft                                               U. Chunduri
Intended status: Standards Track                              Individual
Expires: May 20, 2017                                  November 16, 2016

              Signaling MSD (Maximum SID Depth) using OSPF
                 draft-ietf-ospf-segment-routing-msd-00

Abstract

   This document proposes a way to expose Maximum SID Depth (MSD)
   supported by a node at node and/or link level by an OSPF Router.  In
   a Segment Routing (SR) enabled network a centralized controller that
   programs SR tunnels at the head-end node needs to know the MSD
   information at node level and/or link level to push the label stack
   of an appropriate depth .  Here the term OSPF means both OSPFv2 and
   OSPFv3.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 20, 2017.

Copyright Notice

   Copyright (c) 2016 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
   (http://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

Tantsura & Chunduri       Expires May 20, 2017                  [Page 1]
Internet-Draft                                             November 2016

   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions used in this document . . . . . . . . . . . .   3
       1.1.1.  Terminology . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Node MSD TLV  . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  LINK MSD sub-TLV  . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Node MSD vs Link MSD conflict resolution  . . . . . . . . . .   4
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   When Segment Routing tunnels are computed by a centralized
   controller, it is crucial that the controller knows the MSD "Maximum
   SID Depth" of the node or link SR tunnel exits over, so it doesn't
   download a path with SID (label stack) of a depth more than the node
   or link used is capable of imposing.  This document describes how to
   use OSPF to expose the MSD of the node or link to a centralized
   controller.

   PCEP SR extensions [I-D.ietf-pce-segment-routing] has defined MSD, to
   signal in SR PCE Capability TLV, METRIC Object.  However, If PCEP is
   not supported by a node (head-end of the SR tunnel) and controller
   does not participate in IGP routing it has no way to learn the MSD of
   the node or link configured.  BGP-LS [RFC7752] defines a way to
   expose topology and associated different attributes, capabilities of
   the nodes in that topology to a centralized controller and MSD has
   been defined in [I-D.tantsura-bgp-ls-segment-routing-msd].  For this
   information to be advertised by BGP for the all nodes and links of
   the network, where this is provisioned, OSPF module should have this
   information in the LSDB.

   [I-D.ietf-ospf-mpls-elc] defines, RLSDC which indicates how many
   labels a node can read to take a decision to insert an Entropy Label
   (EL) and is different than how many labels a node can push as defined
   by MSD in this draft.

Tantsura & Chunduri       Expires May 20, 2017                  [Page 2]
Show full document text