Network Working Group P. Pillay-Esnault
Request for Comments: 5187 Cisco Systems
Category: Standards Track A. Lindem
Redback Networks
June 2008
OSPFv3 Graceful Restart
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.
Abstract
This document describes the OSPFv3 graceful restart. The OSPFv3
graceful restart is identical to that of OSPFv2 except for the
differences described in this document. These differences include
the format of the grace Link State Advertisements (LSAs) and other
considerations.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Grace Link State Advertisement . . . . . . . . . . . . . . . . 2
2.1. Grace LSA - LS Type . . . . . . . . . . . . . . . . . . . . 2
2.2. Grace LSA Format . . . . . . . . . . . . . . . . . . . . . 3
3. Additional Considerations for OSPFv3 Graceful Restart . . . . . 4
3.1. Preservation of LSA ID to Prefix Correspondence . . . . . . 4
3.2. Preservation of Interface IDs for Link-LSAs,
Network-LSAs, and Router-LSAs . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . . 6
Pillay-Esnault & Lindem Standards Track [Page 1]RFC 5187 OSPFv3 Graceful Restart June 20081. Introduction
Graceful OSPF restart [GRACE] describes a mechanism to restart the
control plane of an OSPFv2 [OSPFv2] router that still has its
forwarding plane intact with a minimum of disruption to the network.
In general, the methods described in [GRACE] work for OSPFv3 [OSPFv3]
as well. However, OSPFv3 will use a grace-LSA with a different
format to signal that a router is initiating (or is about to
initiate) a graceful restart. This document describes other OSPFv3
differences as well.
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 [RFC2119].
2. Grace Link State Advertisement
An OSPFv3 router initiating a graceful restart of its OSPFv3 software
originates grace-LSAs. A grace-LSA requests that the router's
neighbors aid in its graceful restart by continuing to advertise the
router as fully adjacent during the specified grace period. The
grace-LSA contains the restarting router grace-period and the reason
code indicating the reason for the graceful restart.
In OSPFv3 (refer to section 2.11 of [OSPFv3]), neighboring routers on
any link are always identified by their router IDs. This contrasts
with the OSPFv2 behavior where neighbors on point-to-point networks
and virtual links are identified by their Router IDs, while neighbors
on broadcast, Non-Broadcast Multi-Access (NBMA), and point-to-
multipoint links are identified by their IPv4 interface addresses.
Consequently, there is no requirement for the router-address TLV
[GRACE] for OSPFv3 graceful restart.
The TLV formats of the grace-LSA described in [GRACE] remain
unchanged.
2.1. Grace LSA - LS Type
A grace-LSA is defined as an LSA with the LS type equal to 0x000b.
LSA function code LS Type Description
------------------------------------------
11 0x000b GRACE-LSA
Grace-LSA Type and Function Code
Pillay-Esnault & Lindem Standards Track [Page 2]RFC 5187 OSPFv3 Graceful Restart June 2008
The S2-bit and S1-bit are set to 0 to indicate link-local flooding
scope. The U-bit is set to 0 since it isn't applicable to LSAs with
datatracker.ietf.org