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Restart Signaling for Intermediate System to Intermediate System (IS-IS)
RFC 3847

Document type: RFC - Informational (July 2004; No errata)
Obsoleted by RFC 5306
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

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

This information refers to IESG processing after the RFC was initially published:
IESG State: RFC 3847 (Informational)
Responsible AD: Ross Callon
Send notices to: isis-chairs@tools.ietf.org

Network Working Group                                           M. Shand
Request for Comments: 3847                                   L. Ginsberg
Category: Informational                                    Cisco Systems
                                                               July 2004

                         Restart Signaling for
          Intermediate System to Intermediate System (IS-IS)

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2004).  All Rights Reserved.

Abstract

   This document describes a mechanism for a restarting router to signal
   to its neighbors that it is restarting, allowing them to reestablish
   their adjacencies without cycling through the down state, while still
   correctly initiating database synchronization.

   This document additionally describes a mechanism for a restarting
   router to determine when it has achieved LSP database synchronization
   with its neighbors and a mechanism to optimize LSP database
   synchronization, while minimizing transient routing disruption when a
   router starts.

Shand & Ginsberg             Informational                      [Page 1]
RFC 3847              Restart signaling for IS-IS              July 2004

Table of Contents

   1.  Conventions used in this Document. . . . . . . . . . . . . . .  2
   2.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Approach . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
       3.1.  Timers . . . . . . . . . . . . . . . . . . . . . . . . .  4
       3.2.  Restart TLV. . . . . . . . . . . . . . . . . . . . . . .  5
             3.2.1.  Use of RR and RA Bits. . . . . . . . . . . . . .  6
             3.2.2.  Use of SA Bit. . . . . . . . . . . . . . . . . .  7
       3.3.  Adjacency (re)Acquisition. . . . . . . . . . . . . . . .  8
             3.3.1.  Adjacency Reacquisition During Restart . . . . .  8
             3.3.2.  Adjacency Acquisition During Start . . . . . . . 10
             3.3.3.  Multiple Levels. . . . . . . . . . . . . . . . . 12
       3.4.  Database Synchronization . . . . . . . . . . . . . . . . 12
             3.4.1.  LSP Generation and Flooding and SPF Computation. 13
                     3.4.1.1. Restarting. . . . . . . . . . . . . . . 13
                     3.4.1.2. Starting. . . . . . . . . . . . . . . . 15
   4.  State Tables . . . . . . . . . . . . . . . . . . . . . . . . . 15
       4.1.  Running Router . . . . . . . . . . . . . . . . . . . . . 16
       4.2.  Restarting Router. . . . . . . . . . . . . . . . . . . . 17
       4.3.  Starting Router. . . . . . . . . . . . . . . . . . . . . 18
   5.  Security Considerations. . . . . . . . . . . . . . . . . . . . 18
   6.  IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 19
   7.  Normative References . . . . . . . . . . . . . . . . . . . . . 19
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20
   9.  Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 20
   10. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 21

1.  Conventions used in this Document

   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 BCP 14, RFC-2119 [3].

   If the control and forwarding functions in a router can be maintained
   independently, it is possible for the forwarding function state to be
   maintained across a resumption of control function operations.  This
   functionality is assumed when the terms "restart/restarting" are used
   in this document.

   The terms "start/starting" are used to refer to a router in which the
   control function has either commenced operations for the first time
   or has resumed operations but the forwarding functions have not been
   maintained in a prior state.

   The terms "(re)start/(re)starting" are used when the text is
   applicable to both a "starting" and a "restarting" router.

Shand & Ginsberg             Informational                      [Page 2]
RFC 3847              Restart signaling for IS-IS              July 2004

2.  Overview

   The Intermediate System to Intermediate System (IS-IS) routing
   protocol [RFC 1195, ISO/IEC 10589] is a link state intra-domain
   routing protocol.  Normally, when an IS-IS router is restarted,
   temporary disruption of routing occurs due to events in both the

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