OSPFv3 Link State Advertisement (LSA) Extensibility
RFC 8362
| Document | Type | RFC - Proposed Standard (April 2018; No errata) | |
|---|---|---|---|
| Authors | Acee Lindem , Abhay Roy , Dirk Goethals , Veerendranatha Vallem , Fred Baker | ||
| Last updated | 2018-12-19 | ||
| Replaces | draft-acee-ospfv3-lsa-extend | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text html pdf htmlized (tools) htmlized bibtex | ||
| Reviews | |||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Peter Psenak | ||
| Shepherd write-up | Show (last changed 2017-11-26) | ||
| IESG | IESG state | RFC 8362 (Proposed Standard) | |
| Action Holders |
(None)
|
||
| Consensus Boilerplate | Yes | ||
| Telechat date | |||
| Responsible AD | Alvaro Retana | ||
| Send notices to | Peter Psenak <ppsenak@cisco.com>, aretana.ietf@gmail.com | ||
| IANA | IANA review state | Version Changed - Review Needed | |
| IANA action state | RFC-Ed-Ack | ||
Internet Engineering Task Force (IETF) A. Lindem
Request for Comments: 8362 A. Roy
Updates: 5340, 5838 Cisco Systems
Category: Standards Track D. Goethals
ISSN: 2070-1721 Nokia
V. Reddy Vallem
F. Baker
April 2018
OSPFv3 Link State Advertisement (LSA) Extensibility
Abstract
OSPFv3 requires functional extension beyond what can readily be done
with the fixed-format Link State Advertisement (LSA) as described in
RFC 5340. Without LSA extension, attributes associated with OSPFv3
links and advertised IPv6 prefixes must be advertised in separate
LSAs and correlated to the fixed-format LSAs. This document extends
the LSA format by encoding the existing OSPFv3 LSA information in
Type-Length-Value (TLV) tuples and allowing advertisement of
additional information with additional TLVs. Backward-compatibility
mechanisms are also described.
This document updates RFC 5340, "OSPF for IPv6", and RFC 5838,
"Support of Address Families in OSPFv3", by providing TLV-based
encodings for the base OSPFv3 unicast support and OSPFv3 address
family support.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8362.
Lindem, et al. Standards Track [Page 1]
RFC 8362 OSPFv3 LSA Extensibility April 2018
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 4
1.2. OSPFv3 LSA Terminology . . . . . . . . . . . . . . . . . 4
2. OSPFv3 Extended LSA Types . . . . . . . . . . . . . . . . . . 4
3. OSPFv3 Extended LSA TLVs . . . . . . . . . . . . . . . . . . 5
3.1. Prefix Options Extensions . . . . . . . . . . . . . . . . 6
3.1.1. N-bit Prefix Option . . . . . . . . . . . . . . . . . 7
3.2. Router-Link TLV . . . . . . . . . . . . . . . . . . . . . 8
3.3. Attached-Routers TLV . . . . . . . . . . . . . . . . . . 9
3.4. Inter-Area-Prefix TLV . . . . . . . . . . . . . . . . . . 10
3.5. Inter-Area-Router TLV . . . . . . . . . . . . . . . . . . 11
3.6. External-Prefix TLV . . . . . . . . . . . . . . . . . . . 12
3.7. Intra-Area-Prefix TLV . . . . . . . . . . . . . . . . . . 13
3.8. IPv6 Link-Local Address TLV . . . . . . . . . . . . . . . 14
3.9. IPv4 Link-Local Address TLV . . . . . . . . . . . . . . . 14
3.10. IPv6-Forwarding-Address Sub-TLV . . . . . . . . . . . . . 15
3.11. IPv4-Forwarding-Address Sub-TLV . . . . . . . . . . . . . 15
3.12. Route-Tag Sub-TLV . . . . . . . . . . . . . . . . . . . . 16
4. OSPFv3 Extended LSAs . . . . . . . . . . . . . . . . . . . . 16
4.1. OSPFv3 E-Router-LSA . . . . . . . . . . . . . . . . . . . 16
4.2. OSPFv3 E-Network-LSA . . . . . . . . . . . . . . . . . . 18
4.3. OSPFv3 E-Inter-Area-Prefix-LSA . . . . . . . . . . . . . 19
4.4. OSPFv3 E-Inter-Area-Router-LSA . . . . . . . . . . . . . 20
4.5. OSPFv3 E-AS-External-LSA . . . . . . . . . . . . . . . . 21
4.6. OSPFv3 E-NSSA-LSA . . . . . . . . . . . . . . . . . . . . 22
4.7. OSPFv3 E-Link-LSA . . . . . . . . . . . . . . . . . . . . 22
4.8. OSPFv3 E-Intra-Area-Prefix-LSA . . . . . . . . . . . . . 24
5. Malformed OSPFv3 Extended LSA Handling . . . . . . . . . . . 25
6. LSA Extension Backward Compatibility . . . . . . . . . . . . 25
6.1. Full Extended LSA Migration . . . . . . . . . . . . . . . 25
6.2. Extended LSA Sparse-Mode Backward Compatibility . . . . . 26
Lindem, et al. Standards Track [Page 2]
RFC 8362 OSPFv3 LSA Extensibility April 2018
6.3. LSA TLV Processing Backward Compatibility . . . . . . . . 26
7. Security Considerations . . . . . . . . . . . . . . . . . . . 27
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
8.1. OSPFv3 Extended LSA TLV Registry . . . . . . . . . . . . 27
8.2. OSPFv3 Extended LSA Sub-TLV Registry . . . . . . . . . . 28
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 29
9.1. Normative References . . . . . . . . . . . . . . . . . . 29
9.2. Informative References . . . . . . . . . . . . . . . . . 30
Appendix A. Global Configuration Parameters . . . . . . . . . . 31
Appendix B. Area Configuration Parameters . . . . . . . . . . . 31
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 32
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 33
1. Introduction
OSPFv3 requires functional extension beyond what can readily be done
with the fixed-format Link State Advertisement (LSA) as described in
RFC 5340 [OSPFV3]. Without LSA extension, attributes associated with
OSPFv3 links and advertised IPv6 prefixes must be advertised in
separate LSAs and correlated to the fixed-format LSAs. This document
extends the LSA format by encoding the existing OSPFv3 LSA
information in Type-Length-Value (TLV) tuples and allowing
advertisement of additional information with additional TLVs.
Backward-compatibility mechanisms are also described.
This document updates RFC 5340, "OSPF for IPv6", and RFC 5838,
"Support of Address Families in OSPFv3", by providing TLV-based
encodings for the base OSPFv3 support [OSPFV3] and OSPFv3 address
family support [OSPFV3-AF].
A similar extension was previously proposed in support of multi-
topology routing. Additional requirements for the OSPFv3 LSA
extension include source/destination routing, route tagging, and
others.
A final requirement is to limit the changes to OSPFv3 to those
necessary for TLV-based LSAs. For the most part, the semantics of
existing OSPFv3 LSAs are retained for their TLV-based successor LSAs
described herein. Additionally, encoding details, e.g., the
representation of IPv6 prefixes as described in Appendix A.4.1 in RFC
5340 [OSPFV3], have been retained. This requirement was included to
increase the expedience of IETF adoption and deployment.
Lindem, et al. Standards Track [Page 3]
RFC 8362 OSPFv3 LSA Extensibility April 2018
The following aspects of the OSPFv3 LSA extension are described:
1. Extended LSA Types
2. Extended LSA TLVs
3. Extended LSA Formats
4. Backward Compatibility
1.1. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
1.2. OSPFv3 LSA Terminology
The TLV-based OSPFv3 LSAs described in this document will be referred
to as Extended LSAs. The OSPFv3 fixed-format LSAs [OSPFV3] will be
referred to as Legacy LSAs.
2. OSPFv3 Extended LSA Types
In order to provide backward compatibility, new LSA codes must be
allocated. There are eight fixed-format LSAs defined in RFC 5340
[OSPFV3]. For ease of implementation and debugging, the LSA function
codes are the same as the fixed-format LSAs only with 32, i.e., 0x20,
added. The alternative to this mapping was to allocate a bit in the
LS Type indicating the new LSA format. However, this would have used
one half the LSA function code space for the migration of the eight
original fixed-format LSAs. For backward compatibility, the U-bit
MUST be set in the LS Type so that the LSAs will be flooded by OSPFv3
routers that do not understand them.
Lindem, et al. Standards Track [Page 4]
RFC 8362 OSPFv3 LSA Extensibility April 2018
LSA function code LS Type Description
----------------------------------------------------
33 0xA021 E-Router-LSA
34 0xA022 E-Network-LSA
35 0xA023 E-Inter-Area-Prefix-LSA
36 0xA024 E-Inter-Area-Router-LSA
37 0xC025 E-AS-External-LSA
38 N/A Unused (Not to be allocated)
39 0xA027 E-Type-7-LSA
40 0x8028 E-Link-LSA
41 0xA029 E-Intra-Area-Prefix-LSA
OSPFv3 Extended LSA Types
3. OSPFv3 Extended LSA TLVs
The format of the TLVs within the body of the Extended LSAs is the
same as the format used by the Traffic Engineering Extensions to OSPF
[TE]. The variable TLV section consists of one or more nested TLV
tuples. Nested TLVs are also referred to as sub-TLVs. The format of
each TLV is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Format
The Length field defines the length of the value portion in octets
(thus, a TLV with no value portion would have a length of 0). The
TLV is padded to 4-octet alignment; padding is not included in the
Length field (so a 3-octet value would have a length of 3, but the
total size of the TLV would be 8 octets). Nested TLVs are also
32-bit aligned. For example, a 1-byte value would have the Length
field set to 1, and 3 octets of padding would be added to the end of
the value portion of the TLV.
This document defines the following top-level TLV types:
o 0 - Reserved
o 1 - Router-Link TLV
Lindem, et al. Standards Track [Page 5]
RFC 8362 OSPFv3 LSA Extensibility April 2018
o 2 - Attached-Routers TLV
o 3 - Inter-Area-Prefix TLV
o 4 - Inter-Area-Router TLV
o 5 - External-Prefix TLV
o 6 - Intra-Area-Prefix TLV
o 7 - IPv6 Link-Local Address TLV
o 8 - IPv4 Link-Local Address TLV
Additionally, this document defines the following sub-TLV types:
o 0 - Reserved
o 1 - IPv6-Forwarding-Address sub-TLV
o 2 - IPv4-Forwarding-Address sub-TLV
o 3 - Route-Tag sub-TLV
In general, TLVs and sub-TLVs MAY occur in any order, and the
specification should define whether the TLV or sub-TLV is required
and the behavior when there are multiple occurrences of the TLV or
sub-TLV. While this document only describes the usage of TLVs and
sub-TLVs, sub-TLVs may be nested to any level as long as the sub-TLVs
are fully specified in the specification for the subsuming sub-TLV.
For backward compatibility, an LSA is not considered malformed from a
TLV perspective unless either a required TLV is missing or a
specified TLV is less than the minimum required length. Refer to
Section 6.3 for more information on TLV backward compatibility.
3.1. Prefix Options Extensions
The prefix options are extended from Appendix A.4.1.1 [OSPFV3]. The
applicability of the LA-bit is expanded, and it SHOULD be set in
Inter-Area-Prefix TLVs and MAY be set in External-Prefix TLVs when
the advertised host IPv6 address, i.e., PrefixLength = 128 for the
IPv6 Address Family or PrefixLength = 32 for the IPv4 Address Family
[OSPFV3-AF], is an interface address. In RFC 5340, the LA-bit is
only set in Intra-Area-Prefix-LSAs (Section 4.4.3.9 of [OSPFV3]).
This will allow a stable address to be advertised without having to
configure a separate loopback address in every OSPFv3 area.
Lindem, et al. Standards Track [Page 6]
RFC 8362 OSPFv3 LSA Extensibility April 2018
3.1.1. N-bit Prefix Option
Additionally, the N-bit prefix option is defined. The figure below
shows the position of the N-bit in the prefix options (value 0x20).
0 1 2 3 4 5 6 7
+--+--+--+--+--+--+--+--+
| | | N|DN| P| x|LA|NU|
+--+--+--+--+--+--+--+--+
The Prefix Options Field
The N-bit is set in PrefixOptions for a host address
(PrefixLength=128 for the IPv6 Address Family or PrefixLength=32 for
the IPv4 Address Family [OSPFV3-AF]) that identifies the advertising
router. While it is similar to the LA-bit, there are two
differences. The advertising router MAY choose NOT to set the N-bit
even when the above conditions are met. If the N-bit is set and the
PrefixLength is NOT 128 for the IPv6 Address Family or 32 for the
IPv4 Address Family [OSPFV3-AF], the N-bit MUST be ignored.
Additionally, the N-bit is propagated in the PrefixOptions when an
OSPFv3 Area Border Router (ABR) originates an Inter-Area-Prefix-LSA
for an Intra-Area route that has the N-bit set in the PrefixOptions.
Similarly, the N-bit is propagated in the PrefixOptions when an
OSPFv3 Not-So-Stubby Area (NSSA) ABR originates an E-AS-External-LSA
corresponding to an NSSA route as described in Section 3 of RFC 3101
[NSSA]. The N-bit is added to the Inter-Area-Prefix TLV
(Section 3.4), External-Prefix TLV (Section 3.6), and
Intra-Area-Prefix-TLV (Section 3.7). The N-bit is used as hint to
identify the preferred address to reach the advertising OSPFv3
router. This would be in contrast to an anycast address
[IPV6-ADDRESS-ARCH], which could also be a local address with the
LA-bit set. It is useful for applications such as identifying the
prefixes corresponding to Node Segment Identifiers (SIDs) in Segment
Routing [SEGMENT-ROUTING]. There may be future applications
requiring selection of a prefix associated with an OSPFv3 router.
Lindem, et al. Standards Track [Page 7]
RFC 8362 OSPFv3 LSA Extensibility April 2018
3.2. Router-Link TLV
The Router-Link TLV defines a single router link, and the field
definitions correspond directly to links in the OSPFv3 Router-LSA;
see Appendix A.4.3 of [OSPFV3]. The Router-Link TLV is only
applicable to the E-Router-LSA (Section 4.1). Inclusion in other
Extended LSAs MUST be ignored.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 (Router-Link) | TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | 0 | Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Sub-TLVs .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Router-Link TLV
Lindem, et al. Standards Track [Page 8]
RFC 8362 OSPFv3 LSA Extensibility April 2018
3.3. Attached-Routers TLV
The Attached-Routers TLV defines all the routers attached to an
OSPFv3 multi-access network. The field definitions correspond
directly to content of the OSPFv3 Network-LSA; see Appendix A.4.4 of
[OSPFV3]. The Attached-Routers TLV is only applicable to the
E-Network-LSA (Section 4.2). Inclusion in other Extended LSAs MUST
be ignored.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 2 (Attached-Routers) | TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Adjacent Neighbor Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Additional Adjacent Neighbors .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Attached-Routers TLV
There are two reasons for not having a separate TLV or sub-TLV for
each adjacent neighbor. The first is to discourage using the
E-Network-LSA for more than its current role of solely advertising
the routers attached to a multi-access network. The router's metric
as well as the attributes of individual attached routers should be
advertised in their respective E-Router-LSAs. The second reason is
that there is only a single E-Network-LSA per multi-access link with
the Link State ID set to the Designated Router's Interface ID, and
consequently, compact encoding has been chosen to decrease the
likelihood that the size of the E-Network-LSA will require IPv6
fragmentation when advertised in an OSPFv3 Link State Update packet.
Lindem, et al. Standards Track [Page 9]
RFC 8362 OSPFv3 LSA Extensibility April 2018
3.4. Inter-Area-Prefix TLV
The Inter-Area-Prefix TLV defines a single OSPFV3 inter-area prefix.
The field definitions correspond directly to the content of an OSPFv3
IPv6 Prefix, as defined in Appendix A.4.1 of [OSPFV3], and an OSPFv3
Inter-Area-Prefix-LSA, as defined in Appendix A.4.5 of [OSPFV3].
Additionally, the PrefixOptions are extended as described in
Section 3.1. The Inter-Area-Prefix TLV is only applicable to the
E-Inter-Area-Prefix-LSA (Section 4.3). Inclusion in other Extended
LSAs MUST be ignored.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 (Inter-Area Prefix) | TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 | Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PrefixLength | PrefixOptions | 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Prefix |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Sub-TLVs .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Inter-Area-Prefix TLV
Lindem, et al. Standards Track [Page 10]
RFC 8362 OSPFv3 LSA Extensibility April 2018
3.5. Inter-Area-Router TLV
The Inter-Area-Router TLV defines a single OSPFv3 Autonomous System
Boundary Router (ASBR) that is reachable in another area. The field
definitions correspond directly to the content of an OSPFv3
Inter-Area-Router-LSA, as defined in Appendix A.4.6 of [OSPFV3]. The
Inter-Area-Router TLV is only applicable to the
E-Inter-Area-Router-LSA (Section 4.4). Inclusion in other Extended
LSAs MUST be ignored.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 4 (Inter-Area Router) | TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 | Options |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 | Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Sub-TLVs .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Inter-Area-Router TLV
Lindem, et al. Standards Track [Page 11]
RFC 8362 OSPFv3 LSA Extensibility April 2018
3.6. External-Prefix TLV
The External-Prefix TLV defines a single OSPFv3 external prefix.
With the exception of omitted fields noted below, the field
definitions correspond directly to the content of an OSPFv3 IPv6
Prefix, as defined in Appendix A.4.1 of [OSPFV3], and an OSPFv3
AS-External-LSA, as defined in Appendix A.4.7 of [OSPFV3]. The
External-Prefix TLV is only applicable to the E-AS-External-LSA
(Section 4.5) and the E-NSSA-LSA (Section 4.6). Additionally, the
PrefixOptions are extended as described in Section 3.1. Inclusion in
other Extended LSAs MUST be ignored.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 (External Prefix) | TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |E| | | Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PrefixLength | PrefixOptions | 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Prefix |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Sub-TLVs .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
External-Prefix TLV
In the External-Prefix TLV, the optional IPv6/IPv4 Forwarding Address
and External Route Tag are now sub-TLVs. Given the Referenced LS
Type and Referenced Link State ID from the AS-External-LSA have never
been used or even specified, they have been omitted from the
External-Prefix TLV. If there were ever a requirement for a
referenced LSA, it could be satisfied with a sub-TLV.
The following sub-TLVs are defined for optional inclusion in the
External-Prefix TLV:
o 1 - IPv6-Forwarding-Address sub-TLV (Section 3.10)
o 2 - IPv4-Forwarding-Address sub-TLV (Section 3.11)
o 3 - Route-Tag sub-TLV (Section 3.12)
Lindem, et al. Standards Track [Page 12]
RFC 8362 OSPFv3 LSA Extensibility April 2018
3.7. Intra-Area-Prefix TLV
The Intra-Area-Prefix TLV defines a single OSPFv3 intra-area prefix.
The field definitions correspond directly to the content of an OSPFv3
IPv6 Prefix, as defined in Appendix A.4.1 of [OSPFV3], and an OSPFv3
Link-LSA, as defined in Appendix A.4.9 of [OSPFV3]. The
Intra-Area-Prefix TLV is only applicable to the E-Link-LSA
(Section 4.7) and the E-Intra-Area-Prefix-LSA (Section 4.8).
Additionally, the PrefixOptions are extended as described in
Section 3.1. Inclusion in other Extended LSAs MUST be ignored.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 6 (Intra-Area Prefix) | TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 | Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PrefixLength | PrefixOptions | 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Prefix |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Sub-TLVs .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Intra-Area-Prefix TLV
Lindem, et al. Standards Track [Page 13]
RFC 8362 OSPFv3 LSA Extensibility April 2018
3.8. IPv6 Link-Local Address TLV
The IPv6 Link-Local Address TLV is to be used with IPv6 address
families as defined in [OSPFV3-AF]. The IPv6 Link-Local Address TLV
is only applicable to the E-Link-LSA (Section 4.7). Inclusion in
other Extended LSAs MUST be ignored.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 7 (IPv6 Local-Local Address) | TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+- -+
| |
+- IPv6 Link-Local Interface Address -+
| |
+- -+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Sub-TLVs .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6 Link-Local Address TLV
3.9. IPv4 Link-Local Address TLV
The IPv4 Link-Local Address TLV is to be used with IPv4 address
families as defined in [OSPFV3-AF]. The IPv4 Link-Local Address TLV
is only applicable to the E-Link-LSA (Section 4.7). Inclusion in
other Extended LSAs MUST be ignored.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 8 (IPv4 Local-Local Address) | TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Link-Local Interface Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Sub-TLVs .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv4 Link-Local Address TLV
Lindem, et al. Standards Track [Page 14]
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3.10. IPv6-Forwarding-Address Sub-TLV
The IPv6-Forwarding-Address TLV has identical semantics to the
optional forwarding address in Appendix A.4.7 of [OSPFV3]. The IPv6-
Forwarding-Address TLV is applicable to the External-Prefix TLV
(Section 3.6). Specification as a sub-TLV of other TLVs is not
defined herein. The sub-TLV is optional and the first specified
instance is used as the forwarding address as defined in [OSPFV3].
Instances subsequent to the first MUST be ignored.
The IPv6-Forwarding-Address TLV is to be used with IPv6 address
families as defined in [OSPFV3-AF]. It MUST be ignored for other
address families. The IPv6-Forwarding-Address TLV length must meet a
minimum length (16 octets), or it will be considered malformed as
described in Section 6.3.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 - Forwarding Address | sub-TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+- -+
| |
+- Forwarding Address -+
| |
+- -+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6-Forwarding-Address TLV
3.11. IPv4-Forwarding-Address Sub-TLV
The IPv4-Forwarding-Address TLV has identical semantics to the
optional forwarding address in Appendix A.4.7 of [OSPFV3]. The
IPv4-Forwarding-Address TLV is applicable to the External-Prefix TLV
(Section 3.6). Specification as a sub-TLV of other TLVs is not
defined herein. The sub-TLV is optional, and the first specified
instance is used as the forwarding address as defined in [OSPFV3].
Instances subsequent to the first MUST be ignored.
The IPv4-Forwarding-Address TLV is to be used with IPv4 address
families as defined in [OSPFV3-AF]. It MUST be ignored for other
address families. The IPv4-Forwarding-Address TLV length must meet a
minimum length (4 octets), or it will be considered malformed as
described in Section 6.3.
Lindem, et al. Standards Track [Page 15]
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 2 - Forwarding Address | sub-TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Forwarding Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv4-Forwarding-Address TLV
3.12. Route-Tag Sub-TLV
The optional Route-Tag sub-TLV has identical semantics to the
optional External Route Tag in Appendix A.4.7 of [OSPFV3]. The
Route-Tag sub-TLV is applicable to the External-Prefix TLV
(Section 3.6). Specification as a sub-TLV of other TLVs is not
defined herein. The sub-TLV is optional, and the first specified
instance is used as the Route Tag as defined in [OSPFV3]. Instances
subsequent to the first MUST be ignored.
The Route-Tag TLV length must meet a minimum length (4 octets), or it
will be considered malformed as described in Section 6.3.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 - Route Tag | sub-TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Route Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Route-Tag Sub-TLV
4. OSPFv3 Extended LSAs
This section specifies the OSPFv3 Extended LSA formats and encoding.
The Extended OSPFv3 LSAs corresponded directly to the original OSPFv3
LSAs specified in [OSPFV3].
4.1. OSPFv3 E-Router-LSA
The E-Router-LSA has an LS Type of 0xA021 and has the same base
information content as the Router-LSA defined in Appendix A.4.3 of
[OSPFV3]. However, unlike the existing Router-LSA, it is fully
extensible and represented as TLVs.
Lindem, et al. Standards Track [Page 16]
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Age |1|0|1| 0x21 |
+-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number |
+-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Checksum | Length |
+-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 |Nt|x|V|E|B| Options |
+-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. TLVs .
. .
+-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Extended Router-LSA
Other than having a different LS Type, all LSA Header fields are the
same as defined for the Router-LSA. Initially, only the top-level
Router-Link TLV (Section 3.2) is applicable, and an E-Router-LSA may
include multiple Router-Link TLVs. Like the existing Router-LSA, the
LSA length is used to determine the end of the LSA including any
TLVs. Depending on the implementation, it is perfectly valid for an
E-Router-LSA to not contain any Router-Link TLVs. However, this
would imply that the OSPFv3 router doesn't have any adjacencies in
the corresponding area and is forming an adjacency or adjacencies
over an unnumbered link(s). Note that no E-Router-LSA stub link is
advertised for an unnumbered link.
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4.2. OSPFv3 E-Network-LSA
The E-Network-LSA has an LS Type of 0xA022 and has the same base
information content as the Network-LSA defined in Appendix A.4.4 of
[OSPFV3]. However, unlike the existing Network-LSA, it is fully
extensible and represented as TLVs.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Age |1|0|1| 0x22 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 | Options |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. TLVs .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
E-Network-LSA
Other than having a different LS Type, all LSA Header fields are the
same as defined for the Network-LSA. Like the existing Network-LSA,
the LSA length is used to determine the end of the LSA including any
TLVs. Initially, only the top-level Attached-Routers TLV
(Section 3.3) is applicable. If the Attached-Router TLV is not
included in the E-Network-LSA, it is treated as malformed as
described in Section 5. Instances of the Attached-Router TLV
subsequent to the first MUST be ignored.
Lindem, et al. Standards Track [Page 18]
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4.3. OSPFv3 E-Inter-Area-Prefix-LSA
The E-Inter-Area-Prefix-LSA has an LS Type of 0xA023 and has the same
base information content as the Inter-Area-Prefix-LSA defined in
Appendix A.4.5 of [OSPFV3]. However, unlike the existing
Inter-Area-Prefix-LSA, it is fully extensible and represented as
TLVs.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Age |1|0|1| 0x23 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. TLVs .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
E-Inter-Area-Prefix-LSA
Other than having a different LS Type, all LSA Header fields are the
same as defined for the Inter-Area-Prefix-LSA. In order to retain
compatibility and semantics with the current OSPFv3 specification,
each Inter-Area-Prefix LSA MUST contain a single Inter-Area-Prefix
TLV. This will facilitate migration and avoid changes to functions
such as incremental Shortest Path First (SPF) computation.
Like the existing Inter-Area-Prefix-LSA, the LSA length is used to
determine the end of the LSA including any TLVs. Initially, only the
top-level Inter-Area-Prefix TLV (Section 3.4) is applicable. If the
Inter-Area-Prefix TLV is not included in the E-Inter-Area-Prefix-LSA,
it is treated as malformed as described in Section 5. Instances of
the Inter-Area-Prefix TLV subsequent to the first MUST be ignored.
Lindem, et al. Standards Track [Page 19]
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4.4. OSPFv3 E-Inter-Area-Router-LSA
The E-Inter-Area-Router-LSA has an LS Type of 0xA024 and has the same
base information content as the Inter-Area-Router-LSA defined in
Appendix A.4.6 of [OSPFV3]. However, unlike the
Inter-Area-Router-LSA, it is fully extensible and represented as
TLVs.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Age |1|0|1| 0x24 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. TLVs .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
E-Inter-Area-Router-LSA
Other than having a different LS Type, all LSA Header fields are the
same as defined for the Inter-Area-Router-LSA. In order to retain
compatibility and semantics with the current OSPFv3 specification,
each Inter-Area-Router-LSA MUST contain a single Inter-Area-Router
TLV. This will facilitate migration and avoid changes to functions
such as incremental SPF computation.
Like the existing Inter-Area-Router-LSA, the LSA length is used to
determine the end of the LSA including any TLVs. Initially, only the
top-level Inter-Area-Router TLV (Section 3.5) is applicable. If the
Inter-Area-Router TLV is not included in the E-Inter-Area-Router-LSA,
it is treated as malformed as described in Section 5. Instances of
the Inter-Area-Router TLV subsequent to the first MUST be ignored.
Lindem, et al. Standards Track [Page 20]
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4.5. OSPFv3 E-AS-External-LSA
The E-AS-External-LSA has an LS Type of 0xC025 and has the same base
information content as the AS-External-LSA defined in Appendix A.4.7
of [OSPFV3]. However, unlike the existing AS-External-LSA, it is
fully extensible and represented as TLVs.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Age |1|1|0| 0x25 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. TLVs .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
E-AS-External-LSA
Other than having a different LS Type, all LSA Header fields are the
same as defined for the AS-External-LSA. In order to retain
compatibility and semantics with the current OSPFv3 specification,
each LSA MUST contain a single External-Prefix TLV. This will
facilitate migration and avoid changes to OSPFv3 functions such as
incremental SPF computation.
Like the existing AS-External-LSA, the LSA length is used to
determine the end of the LSA including any TLVs. Initially, only the
top-level External-Prefix TLV (Section 3.6) is applicable. If the
External-Prefix TLV is not included in the E-External-AS-LSA, it is
treated as malformed as described in Section 5. Instances of the
External-Prefix TLV subsequent to the first MUST be ignored.
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4.6. OSPFv3 E-NSSA-LSA
The E-NSSA-LSA will have the same format and TLVs as the Extended
AS-External-LSA (Section 4.5). This is the same relationship that
exists between the NSSA-LSA, as defined in Appendix A.4.8 of
[OSPFV3], and the AS-External-LSA. The NSSA-LSA will have type
0xA027, which implies area flooding scope. Future requirements may
dictate that supported TLVs differ between the E-AS-External-LSA and
the E-NSSA-LSA. However, future requirements are beyond the scope of
this document.
4.7. OSPFv3 E-Link-LSA
The E-Link-LSA has an LS Type of 0x8028 and will have the same base
information content as the Link-LSA defined in Appendix A.4.9 of
[OSPFV3]. However, unlike the existing Link-LSA, it is fully
extensible and represented as TLVs.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Age |1|0|0| 0x28 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Rtr Priority | Options |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. TLVs .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
E-Link-LSA
Other than having a different LS Type, all LSA Header fields are the
same as defined for the Link-LSA.
Only the Intra-Area-Prefix TLV (Section 3.7), IPv6 Link-Local Address
TLV (Section 3.8), and IPv4 Link-Local Address TLV (Section 3.9) are
applicable to the E-Link-LSA. Like the Link-LSA, the E-Link-LSA
Lindem, et al. Standards Track [Page 22]
RFC 8362 OSPFv3 LSA Extensibility April 2018
affords advertisement of multiple intra-area prefixes. Hence,
multiple Intra-Area-Prefix TLVs (Section 3.7) may be specified, and
the LSA length defines the end of the LSA including any TLVs.
A single instance of the IPv6 Link-Local Address TLV (Section 3.8)
SHOULD be included in the E-Link-LSA. Instances following the first
MUST be ignored. For IPv4 address families as defined in
[OSPFV3-AF], this TLV MUST be ignored.
Similarly, only a single instance of the IPv4 Link-Local Address TLV
(Section 3.9) SHOULD be included in the E-Link-LSA. Instances
following the first MUST be ignored. For OSPFv3 IPv6 address
families as defined in [OSPFV3-AF], this TLV SHOULD be ignored.
If the IPv4/IPv6 Link-Local Address TLV corresponding to the OSPFv3
Address Family is not included in the E-Link-LSA, it is treated as
malformed as described in Section 5.
Future specifications may support advertisement of routing and
topology information for multiple address families. However, this is
beyond the scope of this document.
Lindem, et al. Standards Track [Page 23]
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4.8. OSPFv3 E-Intra-Area-Prefix-LSA
The E-Intra-Area-Prefix-LSA has an LS Type of 0xA029 and has the same
base information content as the Intra-Area-Prefix-LSA defined in
Appendix A.4.10 of [OSPFV3] except for the Referenced LS Type.
However, unlike the Intra-Area-Prefix-LSA, it is fully extensible and
represented as TLVs. The Referenced LS Type MUST be either an
E-Router-LSA (0xA021) or an E-Network-LSA (0xA022).
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Age |1|0|1| 0x29 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 | Referenced LS Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Referenced Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Referenced Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. TLVs .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
E-Intra-Area-Prefix-LSA
Other than having a different LS Type, all LSA Header fields are the
same as defined for the Intra-Area-Prefix-LSA.
Like the Intra-Area-Prefix-LSA, the E-Intra-Area-Link-LSA affords
advertisement of multiple intra-area prefixes. Hence, multiple
Intra-Area-Prefix TLVs may be specified, and the LSA length defines
the end of the LSA including any TLVs.
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RFC 8362 OSPFv3 LSA Extensibility April 2018
5. Malformed OSPFv3 Extended LSA Handling
Extended LSAs that have inconsistent length or other encoding errors,
as described herein, MUST NOT be installed in the Link State
Database, acknowledged, or flooded. Reception of malformed LSAs
SHOULD be counted and/or logged for examination by the administrator
of the OSPFv3 routing domain. Note that for the purposes of length
validation, a TLV or sub-TLV should not be considered invalid unless
the length exceeds the length of the LSA or does not meet the minimum
length requirements for the TLV or sub-TLV. This allows for sub-TLVs
to be added as described in Section 6.3.
Additionally, an LSA MUST be considered malformed if it does not
include all of the required TLVs and sub-TLVs.
6. LSA Extension Backward Compatibility
In the context of this document, backward compatibility is solely
related to the capability of an OSPFv3 router to receive, process,
and originate the TLV-based LSAs defined herein. Unrecognized TLVs
and sub-TLVs are ignored. Backward compatibility for future OSPFv3
extensions utilizing the TLV-based LSAs is out of scope and must be
covered in the documents describing those extensions. Both full and,
if applicable, partial deployment SHOULD be specified for future TLV-
based OSPFv3 LSA extensions.
6.1. Full Extended LSA Migration
If ExtendedLSASupport is enabled (Appendix A), OSPFv3 Extended LSAs
will be originated and used for the SPF computation. Individual OSPF
Areas can be migrated separately with the Legacy AS-External-LSAs
being originated and used for the SPF computation. This is
accomplished by enabling AreaExtendedLSASupport (Appendix B).
An OSPFv3 routing domain or area may be non-disruptively migrated
using separate OSPFv3 instances for the Extended LSAs. Initially,
the OSPFv3 instances with ExtendedLSASupport will have a lower
preference, i.e., higher administrative distance, than the OSPFv3
instances originating and using the Legacy LSAs. Once the routing
domain or area is fully migrated and the OSPFv3 Routing Information
Bases (RIBs) have been verified, the OSPFv3 instances using the
Extended LSAs can be given preference. When this has been completed
and the routing within the OSPF routing domain or area has been
verified, the original OSPFv3 instance using Legacy LSAs can be
removed.
Lindem, et al. Standards Track [Page 25]
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6.2. Extended LSA Sparse-Mode Backward Compatibility
In this mode, OSPFv3 will use the Legacy LSAs for the SPF computation
and will only originate Extended LSAs when LSA origination is
required in support of additional functionality. Furthermore, those
Extended LSAs will only include the top-level TLVs (e.g., Router-Link
TLVs or Inter-Area TLVs), which are required for that new
functionality. However, if a top-level TLV is advertised, it MUST
include required sub-TLVs, or it will be considered malformed as
described in Section 5. Hence, this mode of compatibility is known
as "sparse-mode". The advantage of sparse-mode is that functionality
utilizing the OSPFv3 Extended LSAs can be added to an existing OSPFv3
routing domain without the requirement for migration. In essence,
this compatibility mode is very much like the approach taken for
OSPFv2 [OSPF-PREFIX-LINK]. As with all the compatibility modes,
backward compatibility for the functions utilizing the Extended LSAs
must be described in the IETF documents describing those functions.
6.3. LSA TLV Processing Backward Compatibility
This section defines the general rules for processing LSA TLVs. To
ensure compatibility of future TLV-based LSA extensions, all
implementations MUST adhere to these rules:
1. Unrecognized TLVs and sub-TLVs are ignored when parsing or
processing Extended LSAs.
2. Whether or not partial deployment of a given TLV is supported
MUST be specified.
3. If partial deployment is not supported, mechanisms to ensure the
corresponding feature is not deployed MUST be specified in the
document defining the new TLV or sub-TLV.
4. If partial deployment is supported, backward compatibility and
partial deployment MUST be specified in the document defining the
new TLV or sub-TLV.
5. If a TLV or sub-TLV is recognized but the length is less than the
minimum, then the LSA should be considered malformed, and it
SHOULD NOT be acknowledged. Additionally, the occurrence SHOULD
be logged with enough information to identify the LSA by type,
Link State ID, originator, and sequence number and identify the
TLV or sub-TLV in error. Ideally, the log entry would include
the hexadecimal or binary representation of the LSA including the
malformed TLV or sub-TLV.
Lindem, et al. Standards Track [Page 26]
RFC 8362 OSPFv3 LSA Extensibility April 2018
6. Documents specifying future TLVs or Sub-TLVs MUST specify the
requirements for usage of those TLVs or sub-TLVs.
7. Future TLVs or sub-TLVs must be optional. However, there may be
requirements for sub-TLVs if an optional TLV is specified.
7. Security Considerations
In general, extensible OSPFv3 LSAs are subject to the same security
concerns as those described in RFC 5340 [OSPFV3]. Additionally,
implementations must assure that malformed TLV and sub-TLV
permutations do not result in errors that cause hard OSPFv3 failures.
If there were ever a requirement to digitally sign OSPFv3 LSAs as
described for OSPFv2 LSAs in RFC 2154 [OSPF-DIGITAL-SIGNATURE], the
mechanisms described herein would greatly simplify the extension.
8. IANA Considerations
This specification defines nine OSPFv3 Extended LSA types as
described in Section 2. These have been added to the existing OSPFv3
LSA Function Codes registry.
The specification defines a code point for the N-bit in the OSPFv3
Prefix-Options registry. The value 0x20 has been assigned.
This specification also creates two registries for OSPFv3 Extended
LSA TLVs and sub-TLVs. The TLV and sub-TLV code points in these
registries are common to all Extended LSAs, and their respective
definitions must define where they are applicable.
8.1. OSPFv3 Extended LSA TLV Registry
The "OSPFv3 Extended LSA TLVs" registry defines top-level TLVs for
Extended LSAs and has been placed in the existing OSPFv3 IANA
registry.
Nine values have been allocated:
o 0 - Reserved
o 1 - Router-Link TLV
o 2 - Attached-Routers TLV
o 3 - Inter-Area-Prefix TLV
o 4 - Inter-Area-Router TLV
Lindem, et al. Standards Track [Page 27]
RFC 8362 OSPFv3 LSA Extensibility April 2018
o 5 - External-Prefix TLV
o 6 - Intra-Area-Prefix TLV
o 7 - IPv6 Link-Local Address TLV
o 8 - IPv4 Link-Local Address TLV
Types in the range 9-32767 are allocated via IETF Review or IESG
Approval [RFC8126].
Types in the range 32768-33023 are Reserved for Experimental Use;
these will not be registered with IANA and MUST NOT be mentioned by
RFCs.
Types in the range 33024-45055 are to be assigned on a First Come
First Served (FCFS) basis.
Types in the range 45056-65535 are not to be assigned at this time.
Before any assignments can be made in the 33024-65535 range, there
MUST be an IETF specification that specifies IANA Considerations that
cover the range being assigned.
8.2. OSPFv3 Extended LSA Sub-TLV Registry
The "OSPFv3 Extended LSA Sub-TLVs" registry defines sub-TLVs at any
level of nesting for Extended LSAs and has been placed in the
existing OSPFv3 IANA registry.
Four values have been allocated:
o 0 - Reserved
o 1 - IPv6-Forwarding-Address sub-TLV
o 2 - IPv4-Forwarding-Address sub-TLV
o 3 - Route-Tag sub-TLV
Types in the range 4-32767 are allocated via IETF Review or IESG
Approval.
Types in the range 32768-33023 are Reserved for Experimental Use;
these will not be registered with IANA and MUST NOT be mentioned by
RFCs.
Types in the range 33024-45055 are to be assigned on an FCFS basis.
Lindem, et al. Standards Track [Page 28]
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Types in the range 45056-65535 are not to be assigned at this time.
Before any assignments can be made in the 33024-65535 range, there
MUST be an IETF specification that specifies IANA Considerations that
cover the range being assigned.
9. References
9.1. Normative References
[NSSA] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option",
RFC 3101, DOI 10.17487/RFC3101, January 2003,
<https://www.rfc-editor.org/info/rfc3101>.
[OSPFV3] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>.
[OSPFV3-AF]
Lindem, A., Ed., Mirtorabi, S., Roy, A., Barnes, M., and
R. Aggarwal, "Support of Address Families in OSPFv3",
RFC 5838, DOI 10.17487/RFC5838, April 2010,
<https://www.rfc-editor.org/info/rfc5838>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[TE] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
DOI 10.17487/RFC3630, September 2003,
<https://www.rfc-editor.org/info/rfc3630>.
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9.2. Informative References
[IPV6-ADDRESS-ARCH]
Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>.
[MT-OSPFV3]
Mirtorabi, S. and A. Roy, "Multi-topology routing in
OSPFv3 (MT-OSPFv3)", Work in Progress, draft-ietf-ospf-mt-
ospfv3-03, July 2007.
[OSPF-DIGITAL-SIGNATURE]
Murphy, S., Badger, M., and B. Wellington, "OSPF with
Digital Signatures", RFC 2154, DOI 10.17487/RFC2154, June
1997, <https://www.rfc-editor.org/info/rfc2154>.
[OSPF-PREFIX-LINK]
Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
2015, <https://www.rfc-editor.org/info/rfc7684>.
[SEGMENT-ROUTING]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPFv3
Extensions for Segment Routing", Work in Progress,
draft-ietf-ospf-ospfv3-segment-routing-extensions-11,
January 2018.
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Appendix A. Global Configuration Parameters
The global configurable parameter ExtendedLSASupport is added to the
OSPFv3 protocol. If ExtendedLSASupport is enabled, the OSPFv3 router
will originate OSPFv3 Extended LSAs and use the LSAs for the SPF
computation. If ExtendedLSASupport is not enabled, a subset of
OSPFv3 Extended LSAs may still be originated and used for other
functions as described in Section 6.2.
Appendix B. Area Configuration Parameters
The area configurable parameter AreaExtendedLSASupport is added to
the OSPFv3 protocol. If AreaExtendedLSASupport is enabled, the
OSPFv3 router will originate link and area OSPFv3 Extended LSAs and
use the LSAs for the SPF computation. Legacy AS-Scoped LSAs will
still be originated and used for the AS-External-LSA computation. If
AreaExtendedLSASupport is not enabled, a subset of OSPFv3 link and
area Extended LSAs may still be originated and used for other
functions as described in Section 6.2.
For regular areas, i.e., areas where AS-scoped LSAs are flooded,
disabling AreaExtendedLSASupport for a regular OSPFv3 area (not a
Stub or NSSA area) when ExtendedLSASupport is enabled is
contradictory and SHOULD be prohibited by implementations.
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Acknowledgments
OSPFv3 TLV-based LSAs were first proposed in "Multi-topology routing
in OSPFv3 (MT-OSPFv3)" [MT-OSPFV3].
Thanks for Peter Psenak for significant contributions to the
backward-compatibility mechanisms.
Thanks go to Michael Barnes, Mike Dubrovsky, Anton Smirnov, and Tony
Przygienda for review of the draft versions and discussions of
backward compatibility.
Thanks to Alan Davey for review and comments including the suggestion
to separate the Extended LSA TLV definitions from the Extended LSAs
definitions.
Thanks to David Lamparter for review and suggestions on backward
compatibility.
Thanks to Karsten Thomann, Chris Bowers, Meng Zhang, and Nagendra
Kumar for review and editorial comments.
Thanks to Alia Atlas for substantive Routing Area Director (AD)
comments prior to IETF last call.
Thanks to Alvaro Retana and Suresh Krishnan for substantive comments
during IESG Review.
Thanks to Mehmet Ersue for the Operations and Management (OPS)
Directorate review.
Contributors
Sina Mirtorabi
Cisco Systems
170 Tasman Drive
San Jose, CA 95134
United States of America
Email: sina@cisco.com
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Authors' Addresses
Acee Lindem
Cisco Systems
301 Midenhall Way
Cary, NC 27513
United States of America
Email: acee@cisco.com
Abhay Roy
Cisco Systems
170 Tasman Drive
San Jose, CA 95134
United States of America
Email: akr@cisco.com
Dirk Goethals
Nokia
Copernicuslaan 50
Antwerp 2018
Belgium
Email: dirk.goethals@nokia.com
Veerendranatha Reddy Vallem
Bangalore
India
Email: vallem.veerendra@gmail.com
Fred Baker
Santa Barbara, California 93117
United States of America
Email: FredBaker.IETF@gmail.com
Lindem, et al. Standards Track [Page 33]