Network Working Group A. Lindem
Internet-Draft A. Roy
Intended status: Standards Track Cisco Systems
Expires: October 15, 2017 D. Goethals
Nokia
V. Reddy Vallem
Huawei, Inc
F. Baker
April 13, 2017
OSPFv3 LSA Extendibility
draft-ietf-ospf-ospfv3-lsa-extend-14.txt
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.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 15, 2017.
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Copyright Notice
Copyright (c) 2017 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
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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to this document. Code Components extracted from this document must
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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
1.3. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . . . 7
3.3. Attached-Routers TLV . . . . . . . . . . . . . . . . . . 8
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 . . . . . . . . . . . . . . . 15
3.10. IPv6-Forwarding-Address Sub-TLV . . . . . . . . . . . . . 16
3.11. IPv4-Forwarding-Address Sub-TLV . . . . . . . . . . . . . 16
3.12. Route-Tag Sub-TLV . . . . . . . . . . . . . . . . . . . . 17
4. OSPFv3 Extended LSAs . . . . . . . . . . . . . . . . . . . . 17
4.1. OSPFv3 E-Router-LSA . . . . . . . . . . . . . . . . . . . 17
4.2. OSPFv3 E-Network-LSA . . . . . . . . . . . . . . . . . . 19
4.3. OSPFv3 E-Inter-Area-Prefix-LSA . . . . . . . . . . . . . 20
4.4. OSPFv3 E-Inter-Area-Router-LSA . . . . . . . . . . . . . 21
4.5. OSPFv3 E-AS-External-LSA . . . . . . . . . . . . . . . . 22
4.6. OSPFv3 E-NSSA-LSA . . . . . . . . . . . . . . . . . . . . 23
4.7. OSPFv3 E-Link-LSA . . . . . . . . . . . . . . . . . . . . 24
4.8. OSPFv3 E-Intra-Area-Prefix-LSA . . . . . . . . . . . . . 26
5. Malformed OSPFv3 Extended LSA Handling . . . . . . . . . . . 27
6. LSA Extension Backward Compatibility . . . . . . . . . . . . 27
6.1. Full Extended LSA Migration . . . . . . . . . . . . . . . 27
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6.2. Extended LSA Spare-Mode Backward Compatibility . . . . . 28
6.3. LSA TLV Processing Backward Compatibility . . . . . . . . 28
7. Security Considerations . . . . . . . . . . . . . . . . . . . 29
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 30
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
10.1. Normative References . . . . . . . . . . . . . . . . . . 30
10.2. Informative References . . . . . . . . . . . . . . . . . 31
Appendix A. Appendix A - Global Configuration Parameters . . . . 31
Appendix B. Appendix B - Area Configuration Parameters . . . . . 31
Appendix C. Appendix C - Deprecated LSA Extension Backward
Compatibility . . . . . . . . . . . . . . . . . . . 32
C.1. Extended LSA Mixed-Mode Backward Compatibility . . . . . 34
C.1.1. Area Extended LSA Mixed-Mode Backward Compatibility . 34
C.2. Global Configuration Parameters . . . . . . . . . . . . . 35
C.3. Area Configuration Parameters . . . . . . . . . . . . . . 36
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 36
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.
A similar extension was previously proposed in support of multi-
topology routing. Additional requirements for 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 section A.4.1 in RFC
5340 [OSPFV3], have been retained. This requirement was included to
increase the expedience of IETF adoption and deployment.
The following aspects of OSPFv3 LSA extension are described:
1. Extended LSA Types
2. Extended LSA TLVs
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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", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC-KEYWORDS].
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.
1.3. 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, and Meng Zhang for review
and editorial comments.
The RFC text was produced using Marshall Rose's xml2rfc tool.
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
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one half the LSA function code space for the migration of the eight
original fixed-format LSAs. For backward compatibility, the U-bit
will be set in LS Type so that the LSAs will be flooded by OSPFv3
routers that do not understand them.
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
Type/Length/Value (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.
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This document defines the following top-level TLV types:
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
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 occurances of the TLV or
sub-TLVs.
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, is an
interface address. In RFC 5340, the LA-bit is only set in Intra-
Area-Prefix-LSAs (Section 4.4.3.9 in [OSPFV3]). This will allow a
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stable address to be advertised without having to configure a
separate loopback address in every OSPFv3 area.
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 (pending IANA
allocation). This corresponds to the 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) 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, 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 which has the N-bit set
in the PrefixOptions. Similarly, the N-bit is propagated in the
PrefixOptions when an OSPFv3 NSSA ABR originates an Extended-AS-
External-LSA corresponding to an NSSA route as described in section 3
of RFC 3101 ([NSSA]). The N-bit is 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 useful for applications such as
identifying the prefixes corresponding to Node Segment Identifiers
(SIDs) in Segment Routing [SEGMENT-ROUTING].
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,
section A.4.3, [OSPFV3]. The Router-Link TLV is only applicable to
the E-Router-LSA (Section 4.1). Inclusion in other Extended LSAs
MUST be ignored.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 (Router-Link) | TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | 0 | Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. sub-TLVs .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Router-Link TLV
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, section A.4.4,
[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
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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.
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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 Section A.4.1, [OSPFV3] and an OSPFv3
Inter-Area-Prefix-LSA, as defined in section A.4.5, [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
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3.5. Inter-Area-Router TLV
The Inter-Area-Router TLV defines a single OSPFv3 Autonomous System
Boundary Router (ASBR) reachable in another area. The field
definitions correspond directly to the content of an OSPFv3 Inter-
Area-Router-LSA, as defined in section A.4.6, [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
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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 Section A.4.1, [OSPFV3] and an OSPFv3 AS-
External-LSA, as defined in section A.4.7, [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)
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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 Section A.4.1, [OSPFV3] and an OSPFv3 Link-
LSA, as defined in section A.4.9, [OSPFV3]. The Intra-Area-Prefix
TLV is only applicable to the E-Link-LSA (Section 4.7) and the
Additionally, the PrefixOptions are extended as described in
Section 3.1. E-Intra-Area-Prefix-LSA (Section 4.8). 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
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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
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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
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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 section 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.
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 -+
| |
+- -+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Forwarding Address Tag TLV
3.11. IPv4-Forwarding-Address Sub-TLV
The IPv4 Forwarding Address TLV has identical semantics to the
optional forwarding address in section A.4.7 of [OSPFV3]. The IPv4
Forwarding Address TLV is 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 IPv3 address
families as defined in [OSPFV3-AF] It MUST be ignored for other
address families.
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Forwarding Address Tag TLV
3.12. Route-Tag Sub-TLV
The optional Route Tag sub-TLV has identical semantics to the
optional External Route Tag in section 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.
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 specifed 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 section A.4.3 of
[OSPFV3]. However, unlike the existing Router-LSA, it is fully
extendable and represented as TLVs.
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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 differnt 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 TLVs.
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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 section A.4.4 of
[OSPFV3]. However, unlike the existing Network-LSA, it is fully
extendable 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 differnt 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
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.
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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
section A.4.5 of [OSPFV3]. However, unlike the existing Inter-Area-
Prefix-LSA, it is fully extendable 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 differnt 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 SPF computation.
Like the existing Inter-Area-Prefix-LSA, the LSA length is used to
determine the end of the LSA including TLV. 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.
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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-LSAE defined in
section A.4.6 of [OSPFV3]. However, unlike the Inter-Area-Router-
LSA, it is fully extendable 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 differnt 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 TLV. 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.
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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 section A.4.7
of [OSPFV3]. However, unlike the existing AS-External-LSA, it is
fully extendable 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 differnt 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 processes such as
incremental SPF computation.
Like the existing AS-External-LSA, the LSA length is used to
determine the end of the LSA including sub-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 as exists
between the NSSA-LSA defined in section 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.
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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 section A.4.9 of
[OSPFV3]. However, unlike the existing Link-LSA, it is extendable
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 differnt 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
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 all 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
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following the first MUST be ignored. For OSPFv3 IPv6 address
families as defined in [OSPFV3-AF], this TLV MUST 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.
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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
section A.4.10 of [OSPFV3] except for the Referenced LS Type.
However, unlike the Intra-Area-Prefix-LSA, it is fully extendable 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 differnt 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 all TLVs.
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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. 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 any required TLV or 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 enabled 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 (RIB) 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.
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6.2. Extended LSA Spare-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 addtional functionality. Furthermore, the
extended LSAs will only include those TLVs which require further
specification for that new functionality. Hence, this mode of
compatibility is know as "sparse-mode". The advantage of sparse-mode
is that functionality utilizing the OSPFv3 extended LSAs can be added
to an existing OSFPv3 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 are 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 occurence SHOULD
be logged with enough information to identify the LSA by type,
originator, and sequence number and the TLV or Sub-TLV in error.
Ideally, the log entry would include the hexidecimal or binary
representation of the LSA including the malformed TLS or Sub-TLV.
6. Documents specifying future TLVs or Sub-TLVs MUST specify the
requirements for usage of those TLVs or Sub-TLVs.
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7. Future TLV 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, extendible 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.
This specification also creates two registries OSPFv3 Extended-LSAs
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.
The OSPFv3 Extended-LSA TLV registry will define top-level TLVs for
Extended-LSAs and should be placed in the existing OSPFv3 IANA
registry. New values can be allocated via IETF Consensus or IESG
Approval.
Nine values are allocated by this specification:
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
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
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The OSPFv3 Extended-LSA sub-TLV registry will define sub-TLVs at any
level of nesting for Extended-LSAs and should be placed in the
existing OSPFv3 IANA registry. New values can be allocated via IETF
Review.
Three values are allocated by this specification:
o 0 - Reserved
o 1 - Forwarding Address
o 2 - Route Tag
The OSPFv3 Prefix Options registry will define a new code point for
the N-bit. The value 0x20 is suggested.
9. Contributors
Contributors' Addresses
Sina Mirtorabi
Cisco Systems
170 Tasman Drive
San Jose, CA 95134
USA
Email: sina@cisco.com
10. References
10.1. Normative References
[GRACEFUL-RESTART]
Lindem, A. and P. Pillay-Esnault, "OSPFv3 Graceful
Restart", RFC 5187, June 2008.
[NSSA] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option",
RFC 3101, January 2003.
[OSPFV3] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, July 2008.
[OSPFV3-AF]
Lindem, A., Mirtorabi, S., Roy, A., Barnes, M., and R.
Aggarwal, "Support of Address Families in OSPFv3", RFC
5838, April 2010.
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[RFC-KEYWORDS]
Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[TE] Katz, D., Yeung, D., and K. Kompella, "Traffic Engineering
Extensions to OSPF", RFC 3630, September 2003.
10.2. Informative References
[MT-OSPFV3]
Mirtorabi, S. and A. Roy, "Multi-topology routing in
OSPFv3 (MT-OSPFV3)", draft-ietf-ospf-mt-ospfv3-03.txt
(work in progress), January 2008.
[OSPF-DIGITAL-SIGNATURE]
Murphy, S., Badger, M., and B. Wellington, "OSPF with
Digital Signatures", RFC 2154, June 1997.
[OSPF-PREFIX-LINK]
Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPF Prefix/Link
Attributes", RFC 7684, December 2015.
[SEGMENT-ROUTING]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPFv3
Extensions for Segment Routing", draft-ietf-ospf-ospfv3-
segment-routing-extensions-06.txt (work in progress), July
2016.
Appendix A. Appendix A - Global Configuration Parameters
The global configurable parameter ExtendedLSASupport will be 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. Appendix B - Area Configuration Parameters
The area configurable parameter AreaExtendedLSASupport will be added
to the OSPFv3 protocol. If ExtendedLSASupport 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
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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 when ExtendedLSASupport is enabled
is contradictory and MAY be prohibited by the implementation.
Appendix C. Appendix C - Deprecated 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.
Three distinct backward compatibility modes are supported dependent
on the OSPFv3 routing domain migration requirements. For simplicity
and to avoid the scaling impact of maintaining both TLV and non-TLV
based versions of the same LSA within a routing domain, the basic
backward compatibility mode will not allow mixing of LSA formats.
Different LSA formats could still be supported with multiple OSPFv3
instances and separate OSPFv3 routing domains. Additionally, a more
flexible mode is provided in Appendix C.1, where both formats of LSA
coexist. In order to facilitate backward compatibility, the OSPFv3
options field (as described in Appendix A.2 of RFC 5340 [OSPFV3]),
will contain two additional options bits. The EL-bits will be used
to indicate that the OSPFv3 router's level of Extended LSA support.
An OSPFv3 router configured to support extended LSAs MUST set its
options field EL-bits in OSPFv3 Hello and Database Description
packets as follows:
B'00'
None - Extended LSAs are not originated nor used in the SPF
calculation (except for future functionalities as described in
Section 6.2) .
B'01'
MixedModeOriginateOnly - Both Extended and Legacy LSAs are
originated. Legacy LSAs are used in the SPF computation.
B'10'
MixedModeOriginateSPF - Both extended and Legacy LSAs are
originated. Extended LSAs are used in the SPF computation.
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B'11'
Full - Only extended LSAs are originated and used in the SPF
computation.
If Full is specified for ExtendedLSASupport, the OSPFv3 router MUST
NOT form adjacencies with OSPFv3 Routers sending OSPFv3 Hello and
Database Description packets with the options field EL-bits set to
MixedModeOriginateOnly or None. Similarly, if MixModeOriginateSPF is
specified for ExtendedLSASupport, the OSPFv3 router MUST NOT form
adjacencies with OSPFv3 Routers sending OSPFv3 Hello and Database
Description packets with the options field EL-bits set to None
(B'00'). In this manner, OSPFv3 routers using new encodings can be
completely isolated from those OSPFv3 routers depending on the RFC
5340 encoding and not setting their options field EL-bits since the
default setting indicates no support for extended LSAs.
Finally, a mode supporting existing OSPFv3 routing domains is
provided. This mode, subsequently referred to as "sparse-mode", will
use the TLV-based LSAs solely in support of new functionality
Section 6.2. In this compatibility mode, the EL-bits will be
advertised as B'00' since the backward compatibility with the Legacy
LSAs is not supported or required.
1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+--+-+-+--+-+-+-+-+--+
| | | | | | | | | | | | EL|AT|L|AF|*|*|DC|R|N|x|E|V6|
+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+--+-+-+--+-+-+-+-+--+
The Options field
EL-bits
These bits indicate the level of Extended LSA support.
B'00' - Extended LSAs are not originate nor used in the
SPF calculation (except for new functionalities
for future functions as described in Section 6.2).
B'01' - Both extended and Legacy LSAs are originated.
Non-extended LSAs are used in the SPF computation.
B'10' - Both extended and Legacy LSAs are originated.
Extended LSAs are used in the SPF computation.
B'11' - Only extended LSA are originated and used in the
SPF computation.
Options Field EL-bits
The EL-bits will also be set in the LSA options field in Extended and
Legacy LSAs. While the value of the EL-bits has no functional
significance in the LSA options field, visibility of every OSPFv3
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Router's extended LSA support is expected to be very useful for
management and troubleshooting during the migration period.
C.1. Extended LSA Mixed-Mode Backward Compatibility
An implementation MAY support configuration allowing a graceful
transition from the Legacy (non-TLV-based) LSAs to the extended (TLV-
based) LSAs in an OSPFv3 routing domain. In these routing domains,
the OSPFv3 routers configured with a value of MixedModeOriginateOnly
or MixedModeOriginateSPF for ExtendedLSASupport, (Appendix C.2), MUST
originate both the extended and legacy versions of the OSPFv3 LSAs
described herein. For the purposes of Shortest Path First (SPF)
computation, the Legacy LSAs are used for SPF computation when
MixedModeOriginateOnly is configured and the extended LSAs are used
when MixedModeOriginateSPF is specified. The Extended LSAs MAY be
used for functions other than routing computation as long as backward
compatibility is specified in the documents specifying those
functions.
In this manner, OSPFv3 routing domains utilizing the new encodings
can be gradually migrated with a worst-case overhead cost of
approximately doubling the number of LSAs in the routing domain. The
transition within an OSPFv3 routing domain would progress as follows:
1. Configure OSPFv3 Router ExtendedLSASupport to
MixedModeOriginateOnly so that routers originate the extended
LSAs.
2. When all the OSPFv3 Routers have been reconfigured to
MixedModeOriginateOnly, gradually reconfigure OSPFv3 Routers to
use the extended LSAs by configuring ExtendedLSASupport to
MixedModeOriginateSPF. This can be done on a small subset of
OSPFv3 Routers and the route tables can be verified.
3. When all the OSPFv3 Routers have been reconfigured to
MixedModeOriginateSPF and the routing has been verified,
reconfigure OSPFv3 Routers to purge or simply not refresh the
Legacy LSA by configuring ExtendedLSASupport to Full.
In order to prevent OSPFv3 routing domain routing loops, the
advertised metrics in the Extended LSAs and Legacy LSAs MUST be
identical.
C.1.1. Area Extended LSA Mixed-Mode Backward Compatibility
An implementation MAY also support configuration allowing graceful
transition from the Legacy LSAs to the extended LSAs within a single
area. In these areas, the parameter AreaExtendedLSASupport
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(Appendix C.3) may be configured to take precedence over the global
parameter ExtendedLSASupport. However, the AreaExtendedLSASupport
will only apply to link and area scoped LSAs within the area and area
based SPF calculations. The default is for the
AreaExtendedLSASupport to be inherited from the ExtendedLSASupport.
The configuration of ExtendedLSASupport will apply to AS-External
LSAs even when AreaExtendedLSASupport takes precedence.
When preforming a graceful restart [GRACEFUL-RESTART], an OSPFv3
router configured with MixedModeOriginate will use the Legacy LSAs to
determine whether or not the graceful restart has completed
successfully. Similarly, an OSPFv3 router configured with
MixedModeOriginateSPF will use the extended LSAs. In other words,
successful OSPFv3 graceful restart determination will follow the SPF
calculation.
C.2. Global Configuration Parameters
An additional global configurable parameter will be added to the
OSPFv3 protocol.
ExtendedLSASupport
This is an enumeration type indicating the extent to which the
OSPFv3 instance supports the TLV format described herein for
Extended LSAs. The valid values for the enumeration are:
* None - Extended LSAs will not be originated or used in the SPF
calculation. This is the default. When OSPFv3 functions
requiring extended LSA are configured, and the
ExtendedLSASuppport is "None", extended LSAs may be used as
described in Section 6.2.
* MixedModeOriginateOnly - Both extended and Legacy LSAs will be
originated. OSPFv3 adjacencies will be formed with OSPFv3
routers not supporting this specification. The Legacy LSAs are
used for the SPF computation.
* MixedModeOriginateSPF - Both Extended LSAs and Legacy LSAs will
be originated. OSPFv3 adjacencies will be formed with OSPFv3
routers not supporting this specification. The Extended LSAs
are used for the SPF computation.
* Full - Extended LSAs will be originated and adjacencies will
ndot be formed with OSPFv3 routers not supporting this
specification. Only Extended LSAs will be originated.
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C.3. Area Configuration Parameters
An additional area configurable parameter will be added to the OSPFv3
protocol.
AreaExtendedLSASupport
This is an enumeration type indicating the extent to which the
OSPFv3 area supports the TLV format described herein for Extended
LSAs. The valid value for the enumeration are:
* InheritGlobal - The AreaExtendedLSASupport will be inherited
from ExtendedLSASupport. This is the default.
* None - Extended LSAs will not be originated or used in the SPF
calculation. This is the default. When OSPFv3 functions
requiring extended LSA are configured, and the
ExtendedLSASuppport is "None", the spare-mode compatability is
in effect Section 6.2.
* MixedModeOriginateOnly - Both extended and legacy link and area
scoped LSAs will be originated. OSPFv3 adjacencies will be
formed with OSPFv3 routers not supporting this specification.
The Legacy LSAs are used for the area SPF computation.
* MixedModeOriginateSPF - Both extended and legacy link and area
scoped LSAs will be originated. OSPFv3 adjacencies will be
formed with OSPFv3 routers not supporting this specification.
The Extended LSAs are used for the area SPF computation.
* Full - Link and area scoped Extended LSAs will be originated
and adjacencies will not be formed with OSPFv3 routers not
supporting this specification. Only Extended LSAs will be
originated.
For regular areas, i.e., areas where AS scoped LSAs are flooded,
configuring None or MixedModeOriginateOnly for AreaExtendedLSASupport
when Full is specified for ExtendedLSASupport is contradictory and
MAY be prohibited by the implementation.
Authors' Addresses
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Acee Lindem
Cisco Systems
301 Midenhall Way
Cary, NC 27513
USA
Email: acee@cisco.com
Abhay Roy
Cisco Systems
170 Tasman Drive
San Jose, CA 95134
USA
Email: akr@cisco.com
Dirk Goethals
Nokia
Copernicuslaan 50
Antwerp 2018
Belgium
Email: dirk.goethals@nokia.com
Veerendranatha Reddy Vallem
Huawei, Inc
Email: veerendranatharv@huawei.com
Fred Baker
Santa Barbara, California 93117
USA
Email: FredBaker.IETF@gmail.com
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