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Multi-Topology (MT) Routing in OSPF
RFC 4915

Document type: RFC - Proposed Standard (June 2007; No errata)
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: (None)
Consensus: Unknown
Document shepherd: No shepherd assigned

IESG State: RFC 4915 (Proposed Standard)
Responsible AD: Bill Fenner
Send notices to: ospf-chairs@tools.ietf.org

Network Working Group                                          P. Psenak
Request for Comments: 4915                                 Cisco Systems
Category: Standards Track                                   S. Mirtorabi
                                                        Force10 Networks
                                                                  A. Roy
                                                               L. Nguyen
                                                       P. Pillay-Esnault
                                                           Cisco Systems
                                                               June 2007

                  Multi-Topology (MT) Routing in OSPF

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document describes an extension to Open Shortest Path First
   (OSPF) in order to define independent IP topologies called Multi-
   Topologies (MTs).  The Multi-Topologies extension can be used for
   computing different paths for unicast traffic, multicast traffic,
   different classes of service based on flexible criteria, or an in-
   band network management topology.

   An optional extension to exclude selected links from the default
   topology is also described.

Psenak, et al.              Standards Track                     [Page 1]
RFC 4915          Multi-Topology (MT) Routing in OSPF          June 2007

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Differences between Multi-Topology and TOS-Based
           Routing  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.1.  Requirements Notation  . . . . . . . . . . . . . . . . . .  3
     2.2.  Terms  . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Base MT Functional Specifications  . . . . . . . . . . . . . .  4
     3.1.  MT Area Boundary . . . . . . . . . . . . . . . . . . . . .  4
     3.2.  Adjacency for MTs  . . . . . . . . . . . . . . . . . . . .  4
     3.3.  Sending OSPF Control Packets . . . . . . . . . . . . . . .  5
     3.4.  Advertising MT Adjacencies and the Corresponding IP
           Prefixes . . . . . . . . . . . . . . . . . . . . . . . . .  5
       3.4.1.  Inter-Area and External Routing  . . . . . . . . . . .  5
     3.5.  Flushing MT Information  . . . . . . . . . . . . . . . . .  6
     3.6.  MT SPF Computation . . . . . . . . . . . . . . . . . . . .  6
     3.7.  MT-ID Values . . . . . . . . . . . . . . . . . . . . . . .  6
     3.8.  Forwarding in MT . . . . . . . . . . . . . . . . . . . . .  6
   4.  Default Topology Link Exclusion Functional Specifications  . .  7
     4.1.  Exclusion of Links in the Default Topology . . . . . . . .  7
     4.2.  New Area Data Structure Parameter  . . . . . . . . . . . .  7
     4.3.  Adjacency Formation with Link Exclusion Capability . . . .  8
     4.4.  OSPF Control Packets Transmission over Excluded Links  . .  9
     4.5.  OSPF LSA Advertisement and SPF Computation for
           Excluded Links . . . . . . . . . . . . . . . . . . . . . .  9
   5.  Interoperability between MT-Capable and Non-MT-Capable
       Routers  . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     5.1.  Demand Circuit Compatibility Considerations  . . . . . . . 10
   6.  Migration from Non-MT-Area to MT-Area  . . . . . . . . . . . . 10
   7.  MT Network Management Considerations . . . . . . . . . . . . . 11
     7.1.  Create Dedicated Management Topology to Include All
           the Nodes  . . . . . . . . . . . . . . . . . . . . . . . . 11
     7.2.  Extend the Default Topology to All the Nodes . . . . . . . 11
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 12
     10.2. Informative References . . . . . . . . . . . . . . . . . . 12
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 13
   Appendix B.  OSPF Data Formats . . . . . . . . . . . . . . . . . . 13
     B.1.  Router-LSAs  . . . . . . . . . . . . . . . . . . . . . . . 13
     B.2.  Network-LSAs . . . . . . . . . . . . . . . . . . . . . . . 15
     B.3.  Summary-LSAs . . . . . . . . . . . . . . . . . . . . . . . 16
     B.4.  AS-external-LSAs . . . . . . . . . . . . . . . . . . . . . 17

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