Network Working Group R. Coltun
Requests for Comments: 2740 Siara Systems
Category: Standards Track D. Ferguson
Juniper Networks
J. Moy
Sycamore Networks
December 1999
OSPF for IPv6
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 Internet Society (1999). All Rights Reserved.
Abstract
This document describes the modifications to OSPF to support version
6 of the Internet Protocol (IPv6). The fundamental mechanisms of
OSPF (flooding, DR election, area support, SPF calculations, etc.)
remain unchanged. However, some changes have been necessary, either
due to changes in protocol semantics between IPv4 and IPv6, or simply
to handle the increased address size of IPv6.
Changes between OSPF for IPv4 and this document include the
following. Addressing semantics have been removed from OSPF packets
and the basic LSAs. New LSAs have been created to carry IPv6
addresses and prefixes. OSPF now runs on a per-link basis, instead of
on a per-IP-subnet basis. Flooding scope for LSAs has been
generalized. Authentication has been removed from the OSPF protocol
itself, instead relying on IPv6's Authentication Header and
Encapsulating Security Payload.
Most packets in OSPF for IPv6 are almost as compact as those in OSPF
for IPv4, even with the larger IPv6 addresses. Most field-XSand
packet-size limitations present in OSPF for IPv4 have been relaxed.
In addition, option handling has been made more flexible.
Coltun, et al. Standards Track [Page 1]RFC 2740 OSPF for IPv6 December 1999
All of OSPF for IPv4's optional capabilities, including on-demand
circuit support, NSSA areas, and the multicast extensions to OSPF
(MOSPF) are also supported in OSPF for IPv6.
Table of Contents
1 Introduction ........................................... 4
1.1 Terminology ............................................ 4
2 Differences from OSPF for IPv4 ......................... 4
2.1 Protocol processing per-link, not per-subnet ........... 5
2.2 Removal of addressing semantics ........................ 5
2.3 Addition of Flooding scope ............................. 5
2.4 Explicit support for multiple instances per link ....... 6
2.5 Use of link-local addresses ............................ 6
2.6 Authentication changes ................................. 7
2.7 Packet format changes .................................. 7
2.8 LSA format changes ..................................... 8
2.9 Handling unknown LSA types ............................ 10
2.10 Stub area support ..................................... 10
2.11 Identifying neighbors by Router ID .................... 11
3 Implementation details ................................ 11
3.1 Protocol data structures .............................. 12
3.1.1 The Area Data structure ............................... 13
3.1.2 The Interface Data structure .......................... 13
3.1.3 The Neighbor Data Structure ........................... 14
3.2 Protocol Packet Processing ............................ 15
3.2.1 Sending protocol packets .............................. 15
3.2.1.1 Sending Hello packets ................................. 16
3.2.1.2 Sending Database Description Packets .................. 17
3.2.2 Receiving protocol packets ............................ 17
3.2.2.1 Receiving Hello Packets ............................... 19
3.3 The Routing table Structure ........................... 19
3.3.1 Routing table lookup .................................. 20
3.4 Link State Advertisements ............................. 20
3.4.1 The LSA Header ........................................ 21
3.4.2 The link-state database ............................... 22
3.4.3 Originating LSAs ...................................... 22
3.4.3.1 Router-LSAs ........................................... 25
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