RFC 5340
OSPF for IPv6
Pages: 94
Proposed Standard
→ Errata
Obsoletes: 2740
Updated by: 6845 6860 7503 8362 9454
Proposed Standard
→ Errata
Obsoletes: 2740
Updated by: 6845 6860 7503 8362 9454
Part 1 of 4 – Pages 1 to 13
Network Working Group R. Coltun Request for Comments: 5340 Acoustra Productions Obsoletes: 2740 D. Ferguson Category: Standards Track Juniper Networks J. Moy Sycamore Networks, Inc A. Lindem, Ed. Redback Networks July 2008 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.Abstract
This document describes the modifications to OSPF to support version 6 of the Internet Protocol (IPv6). The fundamental mechanisms of OSPF (flooding, Designated Router (DR) election, area support, Short Path First (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. These modifications will necessitate incrementing the protocol version from version 2 to version 3. OSPF for IPv6 is also referred to as OSPF version 3 (OSPFv3). Changes between OSPF for IPv4, OSPF Version 2, and OSPF for IPv6 as described herein include the following. Addressing semantics have been removed from OSPF packets and the basic Link State Advertisements (LSAs). New LSAs have been created to carry IPv6 addresses and prefixes. OSPF now runs on a per-link basis rather than on a per-IP-subnet basis. Flooding scope for LSAs has been generalized. Authentication has been removed from the OSPF protocol and instead relies on IPv6's Authentication Header and Encapsulating Security Payload (ESP). Even with larger IPv6 addresses, most packets in OSPF for IPv6 are almost as compact as those in OSPF for IPv4. Most fields and packet- size limitations present in OSPF for IPv4 have been relaxed. In addition, option handling has been made more flexible.
All of OSPF for IPv4's optional capabilities, including demand circuit support and Not-So-Stubby Areas (NSSAs), are also supported in OSPF for IPv6.Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 4 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 2. Differences from OSPF for IPv4 . . . . . . . . . . . . . . . . 5 2.1. Protocol Processing Per-Link, Not Per-Subnet . . . . . . . 5 2.2. Removal of Addressing Semantics . . . . . . . . . . . . . 5 2.3. Addition of Flooding Scope . . . . . . . . . . . . . . . . 6 2.4. Explicit Support for Multiple Instances per Link . . . . . 6 2.5. Use of Link-Local Addresses . . . . . . . . . . . . . . . 7 2.6. Authentication Changes . . . . . . . . . . . . . . . . . . 7 2.7. Packet Format Changes . . . . . . . . . . . . . . . . . . 8 2.8. LSA Format Changes . . . . . . . . . . . . . . . . . . . . 9 2.9. Handling Unknown LSA Types . . . . . . . . . . . . . . . . 10 2.10. Stub/NSSA Area Support . . . . . . . . . . . . . . . . . . 11 2.11. Identifying Neighbors by Router ID . . . . . . . . . . . . 11 3. Differences with RFC 2740 . . . . . . . . . . . . . . . . . . 11 3.1. Support for Multiple Interfaces on the Same Link . . . . . 11 3.2. Deprecation of MOSPF for IPv6 . . . . . . . . . . . . . . 12 3.3. NSSA Specification . . . . . . . . . . . . . . . . . . . . 12 3.4. Stub Area Unknown LSA Flooding Restriction Deprecated . . 12 3.5. Link LSA Suppression . . . . . . . . . . . . . . . . . . . 12 3.6. LSA Options and Prefix Options Updates . . . . . . . . . . 13 3.7. IPv6 Site-Local Addresses . . . . . . . . . . . . . . . . 13 4. Implementation Details . . . . . . . . . . . . . . . . . . . . 13 4.1. Protocol Data Structures . . . . . . . . . . . . . . . . . 14 4.1.1. The Area Data Structure . . . . . . . . . . . . . . . 15 4.1.2. The Interface Data Structure . . . . . . . . . . . . . 15 4.1.3. The Neighbor Data Structure . . . . . . . . . . . . . 16 4.2. Protocol Packet Processing . . . . . . . . . . . . . . . . 17 4.2.1. Sending Protocol Packets . . . . . . . . . . . . . . . 17 4.2.1.1. Sending Hello Packets . . . . . . . . . . . . . . 18 4.2.1.2. Sending Database Description Packets . . . . . . . 19 4.2.2. Receiving Protocol Packets . . . . . . . . . . . . . . 19 4.2.2.1. Receiving Hello Packets . . . . . . . . . . . . . 21 4.3. The Routing table Structure . . . . . . . . . . . . . . . 22 4.3.1. Routing Table Lookup . . . . . . . . . . . . . . . . . 23 4.4. Link State Advertisements . . . . . . . . . . . . . . . . 23 4.4.1. The LSA Header . . . . . . . . . . . . . . . . . . . . 23 4.4.2. The Link-State Database . . . . . . . . . . . . . . . 24 4.4.3. Originating LSAs . . . . . . . . . . . . . . . . . . . 25 4.4.3.1. LSA Options . . . . . . . . . . . . . . . . . . . 27 4.4.3.2. Router-LSAs . . . . . . . . . . . . . . . . . . . 27
4.4.3.3. Network-LSAs . . . . . . . . . . . . . . . . . . . 29
4.4.3.4. Inter-Area-Prefix-LSAs . . . . . . . . . . . . . . 30
4.4.3.5. Inter-Area-Router-LSAs . . . . . . . . . . . . . . 31
4.4.3.6. AS-External-LSAs . . . . . . . . . . . . . . . . . 32
4.4.3.7. NSSA-LSAs . . . . . . . . . . . . . . . . . . . . 33
4.4.3.8. Link-LSAs . . . . . . . . . . . . . . . . . . . . 34
4.4.3.9. Intra-Area-Prefix-LSAs . . . . . . . . . . . . . . 36
4.4.4. Future LSA Validation . . . . . . . . . . . . . . . . 40
4.5. Flooding . . . . . . . . . . . . . . . . . . . . . . . . . 40
4.5.1. Receiving Link State Update Packets . . . . . . . . . 40
4.5.2. Sending Link State Update Packets . . . . . . . . . . 41
4.5.3. Installing LSAs in the Database . . . . . . . . . . . 43
4.6. Definition of Self-Originated LSAs . . . . . . . . . . . . 43
4.7. Virtual Links . . . . . . . . . . . . . . . . . . . . . . 44
4.8. Routing Table Calculation . . . . . . . . . . . . . . . . 44
4.8.1. Calculating the Shortest-Path Tree for an Area . . . . 45
4.8.2. The Next-Hop Calculation . . . . . . . . . . . . . . . 44
4.8.3. Calculating the Inter-Area Routes . . . . . . . . . . 47
4.8.4. Examining Transit Areas' Summary-LSAs . . . . . . . . 48
4.8.5. Calculating AS External and NSSA Routes . . . . . . . 48
4.9. Multiple Interfaces to a Single Link . . . . . . . . . . . 48
4.9.1. Standby Interface State . . . . . . . . . . . . . . . 50
5. Security Considerations . . . . . . . . . . . . . . . . . . . 52
6. Manageability Considerations . . . . . . . . . . . . . . . . . 52
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 52
7.1. MOSPF for OSPFv3 Deprecation IANA Considerations . . . . . 53
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 53
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 55
9.1. Normative References . . . . . . . . . . . . . . . . . . . 55
9.2. Informative References . . . . . . . . . . . . . . . . . . 56
Appendix A. OSPF Data Formats . . . . . . . . . . . . . . . . . . 57
A.1. Encapsulation of OSPF Packets . . . . . . . . . . . . . . 57
A.2. The Options Field . . . . . . . . . . . . . . . . . . . . 58
A.3. OSPF Packet Formats . . . . . . . . . . . . . . . . . . . 60
A.3.1. The OSPF Packet Header . . . . . . . . . . . . . . . . 60
A.3.2. The Hello Packet . . . . . . . . . . . . . . . . . . . 62
A.3.3. The Database Description Packet . . . . . . . . . . . 63
A.3.4. The Link State Request Packet . . . . . . . . . . . . 65
A.3.5. The Link State Update Packet . . . . . . . . . . . . . 66
A.3.6. The Link State Acknowledgment Packet . . . . . . . . . 67
A.4. LSA Formats . . . . . . . . . . . . . . . . . . . . . . . 68
A.4.1. IPv6 Prefix Representation . . . . . . . . . . . . . . 69
A.4.1.1. Prefix Options . . . . . . . . . . . . . . . . . . 69
A.4.2. The LSA Header . . . . . . . . . . . . . . . . . . . . 70
A.4.2.1. LSA Type . . . . . . . . . . . . . . . . . . . . . 72
A.4.3. Router-LSAs . . . . . . . . . . . . . . . . . . . . . 73
A.4.4. Network-LSAs . . . . . . . . . . . . . . . . . . . . . 76
A.4.5. Inter-Area-Prefix-LSAs . . . . . . . . . . . . . . . . 77
A.4.6. Inter-Area-Router-LSAs . . . . . . . . . . . . . . . . 78
A.4.7. AS-External-LSAs . . . . . . . . . . . . . . . . . . . 79
A.4.8. NSSA-LSAs . . . . . . . . . . . . . . . . . . . . . . 82
A.4.9. Link-LSAs . . . . . . . . . . . . . . . . . . . . . . 82
A.4.10. Intra-Area-Prefix-LSAs . . . . . . . . . . . . . . . . 84
Appendix B. Architectural Constants . . . . . . . . . . . . . . . 86
Appendix C. Configurable Constants . . . . . . . . . . . . . . . 86
C.1. Global Parameters . . . . . . . . . . . . . . . . . . . . 86
C.2. Area Parameters . . . . . . . . . . . . . . . . . . . . . 87
C.3. Router Interface Parameters . . . . . . . . . . . . . . . 88
C.4. Virtual Link Parameters . . . . . . . . . . . . . . . . . 90
C.5. NBMA Network Parameters . . . . . . . . . . . . . . . . . 91
C.6. Point-to-Multipoint Network Parameters . . . . . . . . . . 92
C.7. Host Route Parameters . . . . . . . . . . . . . . . . . . 92
1. Introduction
This document describes the modifications to OSPF to support version
6 of the Internet Protocol (IPv6). The fundamental mechanisms of
OSPF (flooding, Designated Router (DR) election, area support,
(Shortest Path First) 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. These modifications will necessitate
incrementing the protocol version from version 2 to version 3. OSPF
for IPv6 is also referred to as OSPF version 3 (OSPFv3).
This document is organized as follows. Section 2 describes the
differences between OSPF for IPv4 (OSPF version 2) and OSPF for IPv6
(OSPF version 3) in detail. Section 3 describes the difference
between RFC 2740 and this document. Section 4 provides
implementation details for the changes. Appendix A gives the OSPF
for IPv6 packet and Link State Advertisement (LSA) formats. Appendix
B lists the OSPF architectural constants. Appendix C describes
configuration parameters.
1.1. Requirements Notation
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 [RFC-KEYWORDS].
1.2. Terminology
This document attempts to use terms from both the OSPF for IPv4
specification ([OSPFV2]) and the IPv6 protocol specifications
([IPV6]). This has produced a mixed result. Most of the terms used
both by OSPF and IPv6 have roughly the same meaning (e.g.,
interfaces). However, there are a few conflicts. IPv6 uses "link" similarly to IPv4 OSPF's "subnet" or "network". In this case, we have chosen to use IPv6's "link" terminology. "Link" replaces OSPF's "subnet" and "network" in most places in this document, although OSPF's network-LSA remains unchanged (and possibly unfortunately, a new link-LSA has also been created). The names of some of the OSPF LSAs have also changed. See Section 2.8 for details. In the context of this document, an OSPF instance is a separate protocol instance complete with its own protocol data structures (e.g., areas, interfaces, neighbors), link-state database, protocol state machines, and protocol processing (e.g., SPF calculation).2. Differences from OSPF for IPv4
Most of the algorithms from OSPF for IPv4 [OSPFV2] have been preserved in OSPF for IPv6. 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. The following subsections describe the differences between this document and [OSPFV2].2.1. Protocol Processing Per-Link, Not Per-Subnet
IPv6 uses the term "link" to indicate "a communication facility or medium over which nodes can communicate at the link layer" ([IPV6]). "Interfaces" connect to links. Multiple IPv6 subnets can be assigned to a single link, and two nodes can talk directly over a single link, even if they do not share a common IPv6 subnet (IPv6 prefix). For this reason, OSPF for IPv6 runs per-link instead of the IPv4 behavior of per-IP-subnet. The terms "network" and "subnet" used in the IPv4 OSPF specification ([OSPFV2]) should generally be replaced by link. Likewise, an OSPF interface now connects to a link instead of an IP subnet. This change affects the receiving of OSPF protocol packets, the contents of Hello packets, and the contents of network-LSAs.2.2. Removal of Addressing Semantics
In OSPF for IPv6, addressing semantics have been removed from the OSPF protocol packets and the main LSA types, leaving a network- protocol-independent core. In particular:
o IPv6 addresses are not present in OSPF packets, except in LSA
payloads carried by the Link State Update packets. See
Section 2.7 for details.
o Router-LSAs and network-LSAs no longer contain network addresses,
but simply express topology information. See Section 2.8 for
details.
o OSPF Router IDs, Area IDs, and LSA Link State IDs remain at the
IPv4 size of 32 bits. They can no longer be assigned as (IPv6)
addresses.
o Neighboring routers are now always identified by Router ID.
Previously, they had been identified by an IPv4 address on
broadcast, NBMA (Non-Broadcast Multi-Access), and point-to-
multipoint links.
2.3. Addition of Flooding Scope
Flooding scope for LSAs has been generalized and is now explicitly
coded in the LSA's LS type field. There are now three separate
flooding scopes for LSAs:
o Link-local scope. LSA is only flooded on the local link and no
further. Used for the new link-LSA. See Section 4.4.3.8 for
details.
o Area scope. LSA is only flooded throughout a single OSPF area.
Used for router-LSAs, network-LSAs, inter-area-prefix-LSAs, inter-
area-router-LSAs, and intra-area-prefix-LSAs.
o AS scope. LSA is flooded throughout the routing domain. Used for
AS-external-LSAs. A router that originates AS scoped LSAs is
considered an AS Boundary Router (ASBR) and will set its E-bit in
router-LSAs for regular areas.
2.4. Explicit Support for Multiple Instances per Link
OSPF now supports the ability to run multiple OSPF protocol instances
on a single link. For example, this may be required on a NAP segment
shared between several providers. Providers may be supporting
separate OSPF routing domains that wish to remain separate even
though they have one or more physical network segments (i.e., links)
in common. In OSPF for IPv4, this was supported in a haphazard
fashion using the authentication fields in the OSPF for IPv4 header.
Another use for running multiple OSPF instances is if you want, for one reason or another, to have a single link belong to two or more OSPF areas. Support for multiple protocol instances on a link is accomplished via an "Instance ID" contained in the OSPF packet header and OSPF interface data structures. Instance ID solely affects the reception of OSPF packets and applies to normal OSPF interfaces and virtual links.2.5. Use of Link-Local Addresses
IPv6 link-local addresses are for use on a single link, for purposes of neighbor discovery, auto-configuration, etc. IPv6 routers do not forward IPv6 datagrams having link-local source addresses [IP6ADDR]. Link-local unicast addresses are assigned from the IPv6 address range FE80/10. OSPF for IPv6 assumes that each router has been assigned link-local unicast addresses on each of the router's attached physical links [IP6ADDR]. On all OSPF interfaces except virtual links, OSPF packets are sent using the interface's associated link-local unicast address as the source address. A router learns the link-local addresses of all other routers attached to its links and uses these addresses as next-hop information during packet forwarding. On virtual links, a global scope IPv6 address MUST be used as the source address for OSPF protocol packets. Link-local addresses appear in OSPF link-LSAs (see Section 4.4.3.8). However, link-local addresses are not allowed in other OSPF LSA types. In particular, link-local addresses MUST NOT be advertised in inter-area-prefix-LSAs (Section 4.4.3.4), AS-external-LSAs (Section 4.4.3.6), NSSA-LSAs (Section 4.4.3.7), or intra-area-prefix- LSAs (Section 4.4.3.9).2.6. Authentication Changes
In OSPF for IPv6, authentication has been removed from the OSPF protocol. The "AuType" and "Authentication" fields have been removed from the OSPF packet header, and all authentication-related fields have been removed from the OSPF area and interface data structures. When running over IPv6, OSPF relies on the IP Authentication Header (see [IPAUTH]) and the IP Encapsulating Security Payload (see [IPESP]) as described in [OSPFV3-AUTH] to ensure integrity and authentication/confidentiality of routing exchanges.
Protection of OSPF packet exchanges against accidental data corruption is provided by the standard IPv6 Upper-Layer checksum (as described in Section 8.1 of [IPV6]), covering the entire OSPF packet and prepended IPv6 pseudo-header (see Appendix A.3.1).2.7. Packet Format Changes
OSPF for IPv6 runs directly over IPv6. Aside from this, all addressing semantics have been removed from the OSPF packet headers, making it essentially "network-protocol-independent". All addressing information is now contained in the various LSA types only. In detail, changes in OSPF packet format consist of the following: o The OSPF version number has been incremented from 2 to 3. o The Options field in Hello packets and Database Description packets has been expanded to 24 bits. o The Authentication and AuType fields have been removed from the OSPF packet header (see Section 2.6). o The Hello packet now contains no address information at all. Rather, it now includes an Interface ID that the originating router has assigned to uniquely identify (among its own interfaces) its interface to the link. This Interface ID will be used as the network-LSA's Link State ID if the router becomes the Designated Router on the link. o Two Options bits, the "R-bit" and the "V6-bit", have been added to the Options field for processing router-LSAs during the SPF calculation (see Appendix A.2). If the "R-bit" is clear, an OSPF speaker can participate in OSPF topology distribution without being used to forward transit traffic; this can be used in multi- homed hosts that want to participate in the routing protocol. The V6-bit specializes the R-bit; if the V6-bit is clear, an OSPF speaker can participate in OSPF topology distribution without being used to forward IPv6 datagrams. If the R-bit is set and the V6-bit is clear, IPv6 datagrams are not forwarded but datagrams belonging to another protocol family may be forwarded. o The OSPF packet header now includes an "Instance ID" that allows multiple OSPF protocol instances to be run on a single link (see Section 2.4).
2.8. LSA Format Changes
All addressing semantics have been removed from the LSA header, router-LSAs, and network-LSAs. These two LSAs now describe the routing domain's topology in a network-protocol-independent manner. New LSAs have been added to distribute IPv6 address information and data required for next-hop resolution. The names of some of IPv4's LSAs have been changed to be more consistent with each other. In detail, changes in LSA format consist of the following: o The Options field has been removed from the LSA header, expanded to 24 bits, and moved into the body of router-LSAs, network-LSAs, inter-area-router-LSAs, and link-LSAs. See Appendix A.2 for details. o The LSA Type field has been expanded (into the former Options space) to 16 bits, with the upper three bits encoding flooding scope and the handling of unknown LSA types (see Section 2.9). o Addresses in LSAs are now expressed as [prefix, prefix length] instead of [address, mask] (see Appendix A.4.1). The default route is expressed as a prefix with length 0. o Router-LSAs and network-LSAs now have no address information and are network protocol independent. o Router interface information MAY be spread across multiple router- LSAs. Receivers MUST concatenate all the router-LSAs originated by a given router when running the SPF calculation. o A new LSA called the link-LSA has been introduced. Link-LSAs have link-local flooding scope; they are never flooded beyond the link with which they are associated. Link-LSAs have three purposes: 1) they provide the router's link-local address to all other routers attached to the link, 2) they inform other routers attached to the link of a list of IPv6 prefixes to associate with the link, and 3) they allow the router to advertise a collection of Options bits to associate with the network-LSA that will be originated for the link. See Section 4.4.3.8 for details. o In IPv4, the router-LSA carries a router's IPv4 interface addresses, the IPv4 equivalent of link-local addresses. These are only used when calculating next hops during the OSPF routing calculation (see Section 16.1.1 of [OSPFV2]), so they do not need to be flooded past the local link. Hence, using link-LSAs to distribute these addresses is more efficient. Note that link- local addresses cannot be learned through the reception of Hellos
in all cases. On NBMA links, next-hop routers do not necessarily
exchange Hellos. Rather, these routers learn of each other's
existence by way of the Designated Router (DR).
o The Options field in the network LSA is set to the logical OR of
the Options that each router on the link advertises in its link-
LSA.
o Type-3 summary-LSAs have been renamed "inter-area-prefix-LSAs".
Type-4 summary LSAs have been renamed "inter-area-router-LSAs".
o The Link State ID in inter-area-prefix-LSAs, inter-area-router-
LSAs, NSSA-LSAs, and AS-external-LSAs has lost its addressing
semantics and now serves solely to identify individual pieces of
the Link State Database. All addresses or Router IDs that were
formerly expressed by the Link State ID are now carried in the LSA
bodies.
o Network-LSAs and link-LSAs are the only LSAs whose Link State ID
carries additional meaning. For these LSAs, the Link State ID is
always the Interface ID of the originating router on the link
being described. For this reason, network-LSAs and link-LSAs are
now the only LSAs whose size cannot be limited: a network-LSA MUST
list all routers connected to the link and a link-LSA MUST list
all of a router's addresses on the link.
o A new LSA called the intra-area-prefix-LSA has been introduced.
This LSA carries all IPv6 prefix information that in IPv4 is
included in router-LSAs and network-LSAs. See Section 4.4.3.9 for
details.
o Inclusion of a forwarding address or external route tag in AS-
external-LSAs is now optional. In addition, AS-external-LSAs can
now reference another LSA, for inclusion of additional route
attributes that are outside the scope of the OSPF protocol. For
example, this reference could be used to attach BGP path
attributes to external routes.
2.9. Handling Unknown LSA Types
Handling of unknown LSA types has been made more flexible so that,
based on the LS type, unknown LSA types are either treated as having
link-local flooding scope, or are stored and flooded as if they were
understood. This behavior is explicitly coded in the LSA Handling
bit of the link state header's LS type field (see the U-bit in
Appendix A.4.2.1).
The IPv4 OSPF behavior of simply discarding unknown types is unsupported due to the desire to mix router capabilities on a single link. Discarding unknown types causes problems when the Designated Router supports fewer options than the other routers on the link.2.10. Stub/NSSA Area Support
In OSPF for IPv4, stub and NSSA areas were designed to minimize link- state database and routing table sizes for the areas' internal routers. This allows routers with minimal resources to participate in even very large OSPF routing domains. In OSPF for IPv6, the concept of stub and NSSA areas is retained. In IPv6, of the mandatory LSA types, stub areas carry only router-LSAs, network-LSAs, inter-area-prefix-LSAs, link-LSAs, and intra-area- prefix-LSAs. NSSA areas are restricted to these types and, of course, NSSA-LSAs. This is the IPv6 equivalent of the LSA types carried in IPv4 stub areas: router-LSAs, network-LSAs, type 3 summary-LSAs and for NSSA areas: stub area types and NSSA-LSAs.2.11. Identifying Neighbors by Router ID
In OSPF for IPv6, neighboring routers on a given link are always identified by their OSPF Router ID. This contrasts with the IPv4 behavior where neighbors on point-to-point networks and virtual links are identified by their Router IDs while neighbors on broadcast, NBMA, and point-to-multipoint links are identified by their IPv4 interface addresses. This change affects the reception of OSPF packets (see Section 8.2 of [OSPFV2]), the lookup of neighbors (Section 10 of [OSPFV2]), and the reception of Hello packets (Section 10.5 of [OSPFV2]). The Router ID of 0.0.0.0 is reserved and SHOULD NOT be used.3. Differences with RFC 2740
OSPFv3 implementations based on RFC 2740 will fully interoperate with implementations based on this specification. There are, however, some protocol additions and changes (all of which are backward compatible).3.1. Support for Multiple Interfaces on the Same Link
This protocol feature was only partially specified in the RFC 2740. The level of specification was insufficient to implement the feature. Section 4.9 specifies the additions and clarifications necessary for implementation. They are fully compatible with RFC 2740.
3.2. Deprecation of MOSPF for IPv6
This protocol feature was only partially specified in RFC 2740. The level of specification was insufficient to implement the feature. There are no known implementations. Multicast Extensions to OSPF (MOSPF) support and its attendant protocol fields have been deprecated from OSPFv3. Refer to Section 4.4.3.2, Section 4.4.3.4, Section 4.4.3.6, Section 4.4.3.7, Appendix A.2, Appendix A.4.2.1, Appendix A.4.3, Appendix A.4.1.1, and Section 7.1.3.3. NSSA Specification
This protocol feature was only partially specified in RFC 2740. The level of specification was insufficient to implement the function. This document includes an NSSA specification unique to OSPFv3. This specification coupled with [NSSA] provide sufficient specification for implementation. Refer to Section 4.8.5, Appendix A.4.3, Appendix A.4.8, and [NSSA].3.4. Stub Area Unknown LSA Flooding Restriction Deprecated
In RFC 2740 [OSPFV3], flooding of unknown LSA was restricted within stub and NSSA areas. The text describing this restriction is included below. However, unlike in IPv4, IPv6 allows LSAs with unrecognized LS types to be labeled "Store and flood the LSA, as if type understood" (see the U-bit in Appendix A.4.2.1). Uncontrolled introduction of such LSAs could cause a stub area's link-state database to grow larger than its component routers' capacities. To guard against this, the following rule regarding stub areas has been established: an LSA whose LS type is unrecognized can only be flooded into/throughout a stub area if both a) the LSA has area or link-local flooding scope and b) the LSA has U-bit set to 0. See Section 3.5 for details. This restriction has been deprecated. OSPFv3 routers will flood link and area scope LSAs whose LS type is unrecognized and whose U-bit is set to 1 throughout stub and NSSA areas. There are no backward- compatibility issues other than OSPFv3 routers still supporting the restriction may not propagate newly defined LSA types.3.5. Link LSA Suppression
The LinkLSASuppression interface configuration parameter has been added. If LinkLSASuppression is configured for an interface and the interface type is not broadcast or NBMA, origination of the link-LSA
may be suppressed. The LinkLSASuppression interface configuration parameter is described in Appendix C.3. Section 4.8.2 and Section 4.4.3.8 were updated to reflect the parameter's usage.3.6. LSA Options and Prefix Options Updates
The LSA Options and Prefix Options fields have been updated to reflect recent protocol additions. Specifically, bits related to MOSPF have been deprecated, Options field bits common with OSPFv2 have been reserved, and the DN-bit has been added to the prefix- options. Refer to Appendix A.2 and Appendix A.4.1.1.3.7. IPv6 Site-Local Addresses
All references to IPv6 site-local addresses have been removed.
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