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Versions: (draft-baker-ipv6-ospf-extensible) 00 01 02 draft-ietf-ospf-ospfv3-lsa-extend

Network Working Group                                          A. Lindem
Internet-Draft                                                  Ericsson
Intended status: Standards Track                            S. Mirtorabi
Expires: March 14, 2014                                           A. Roy
                                                                F. Baker
                                                           Cisco Systems
                                                      September 10, 2013


                        OSPFv3 LSA Extendibility
                  draft-acee-ospfv3-lsa-extend-02.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 LSA.  This document extends
   the LSA format by allowing the optional inclusion of Type-Length-
   Value (TLV) tuples in the LSAs.  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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   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 March 14, 2014.

Copyright Notice

   Copyright (c) 2013 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



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   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.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
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   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Requirements notation  . . . . . . . . . . . . . . . . . .  4
     1.2.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . .  4
   2.  OSPFv3 Extended LSA Types  . . . . . . . . . . . . . . . . . .  6
   3.  OSPFv3 Extended LSA TLV  . . . . . . . . . . . . . . . . . . .  7
   4.  OSPFv3 E-Router-LSA  . . . . . . . . . . . . . . . . . . . . .  8
   5.  OSPFv3 E-Network-LSA . . . . . . . . . . . . . . . . . . . . . 10
   6.  OSPFv3 E-Inter-Area-Prefix-LSA . . . . . . . . . . . . . . . . 12
   7.  OSPFv3 E-Inter-Area-Router-LSA . . . . . . . . . . . . . . . . 14
   8.  OSPFv3 E-AS-External-LSA . . . . . . . . . . . . . . . . . . . 16
   9.  OSPFv3 E-NSSA-LSA  . . . . . . . . . . . . . . . . . . . . . . 18
   10. OSPFv3 E-Link-LSA  . . . . . . . . . . . . . . . . . . . . . . 19
   11. OSPFv3 E-Intra-Area-Prefix-LSA . . . . . . . . . . . . . . . . 22
   12. LSA Extension Backward Compatibility . . . . . . . . . . . . . 23
     12.1. Extended LSA Mixed-Mode Backward Compatibility . . . . . . 24
     12.2. LSA TLV Processing Backward Compatibility  . . . . . . . . 24
   13. Security Considerations  . . . . . . . . . . . . . . . . . . . 25
   14. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 26
   15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     15.1. Normative References . . . . . . . . . . . . . . . . . . . 27
     15.2. Informative References . . . . . . . . . . . . . . . . . . 27
   Appendix A.  Configurable Constants  . . . . . . . . . . . . . . . 28
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29


























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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 LSA.  This document
   extends the LSA format by allowing the optional inclusion of Type-
   Length-Value (TLV) tuples in the LSAs.  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 LSA 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 Formats

   3.  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.  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, and Anton Smirnov for
   review of the draft versions and discussions of backward
   compatibility.



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   The RFC text was produced using Marshall Rose's xml2rfc tool.


















































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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 was to allocate a bit in the LSA 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
   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






















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3.  OSPFv3 Extended LSA TLV

   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.  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.  Unrecognized types are ignored.
























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4.  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, section 4.4.3.2 in [OSPFV3].
   However, unlike the existing 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|         0x21            |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Link State ID                            |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Advertising Router                          |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    LS Sequence Number                          |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        LS Checksum             |            Length             |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  0  |Nt|x|V|E|B|            Options                            |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .                                                                .
      .                            TLVs                                .
      .                                                                .
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                            Extended Router-LSA

   All LSA Header fields are the same as defined for the Router-LSA.
   The following top-level TLVs are defined:

   o  0 - Reserved

   o  1 - Router-Link TLV













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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

   Like the existing Router-LSA, the LSA length is used to determine the
   end of the LSA including TLVs.  The Router-Link TLV is only
   applicable to the E-Router-LSA.  Inclusion in other Extended LSAs
   MUST be ignored.



























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5.  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, section 4.4.3.3 in [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

   All LSA Header fields are the same as defined for the Network-LSA.
   The following top-level TLVs are defined:

   o  2 - Attached-Routers TLV


       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                    .
      .                                                               .



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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                           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 her 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 of the size of the E-Network-LSA requiring IPv6
   fragmentation when advertised in an OSPFv3 Link State Update packet.

   Like the existing Network-LSA, the LSA length is used to determine
   the end of the LSA including TLVs.  The Attached-Routers TLV is only
   applicable to the E-Network-LSA.  Inclusion in other Extended LSAs
   MUST be ignored.































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6.  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, section
   4.4.3.4 in [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

   All LSA Header fields are the same as defined for the Network-LSA.
   The following top-level TLVs are defined:

   o  3 - Inter-Area Prefix TLV

















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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       3 (Inter-Area Prefix)   |       TLV Length              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      0        |                  Metric                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | PrefixLength  | PrefixOptions |              0                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Address Prefix                         |
      |                             ...                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .                                                               .
      .                            sub-TLVs                           .
      .                                                               .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                           Inter-Area Prefix TLV

   In order to retain compatibility and semantics with the current
   OSPFv3 specification, each 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.  The Inter-Area-Prefix
   TLV is only applicable to the E-Inter-Area-Prefix-LSA.  Inclusion in
   other Extended LSAs MUST be ignored.























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7.  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, section
   4.4.3.5 in [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

   All LSA Header fields are the same as defined for the Inter-Area-
   Router-LSA.  The following top-level TLVs are defined:

   o  4 - Inter-Area Router TLV

















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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       3 (Inter-Area Router)   |       TLV Length              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      0        |                Options                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      0        |                Metric                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Destination Router ID                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .                                                               .
      .                            sub-TLVs                           .
      .                                                               .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                           Inter-Area Router TLV

   In order to retain compatibility and semantics with the current
   OSPFv3 specification, each 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 sub-TLVs.  The Inter-Area-
   Router TLV is only applicable to the E-Inter-Area-Router-LSA.
   Inclusion in other Extended LSAs MUST be ignored.
























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8.  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, section 4.4.3.6 in
   [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

   All LSA Header fields are the same as defined for the AS-External-
   LSA.  The following top-level TLVs are defined:

   o  5 - External Prefix TLV

















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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       5 (External Prefix)     |       TLV Length              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         |E|F|T|                Metric                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | PrefixLength  | PrefixOptions |             0                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Address Prefix                         |
      |                             ...                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +-                                                             -+
      |                                                               |
      +-                Forwarding Address (Optional)                -+
      |                                                               |
      +-                                                             -+
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 External Route Tag (Optional)                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .                                                               .
      .                            sub-TLVs                           .
      .                                                               .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                            External Prefix TLV

   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 functions
   such as incremental SPF computation.  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.

   Like the existing AS-External-LSA, the LSA length is used to
   determine the end of the LSA including sub-TLVs.  The External-Prefix
   TLV is only applicable to the E-AS-External-LSA and the E-NSSA-LSA.
   Inclusion in other Extended LSAs MUST be ignored.









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9.  OSPFv3 E-NSSA-LSA

   The E-NSSA-LSA will have the same format and TLVs as the Extended AS-
   External-LSA Section 8.  This is the same relationship as exists
   between the NSSA-LSA, section 4.4.3.7 in [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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10.  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, section 4.4.3.8 in [OSPFV3].
   However, unlike the existing Link-LFA, 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

   The following top-level TLVs are defined:

   o  6 - Intra-Area Prefix TLV

   o  7 - IPv6 Link-Local Address TLV

   o  8 - IPv4 Link-Local Address TLV













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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       6 (Intra-Area Prefix)   |       TLV Length              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      0        |                  Metric                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | PrefixLength  | PrefixOptions |              0                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Address Prefix                         |
      |                             ...                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .                                                               .
      .                            sub-TLVs                           .
      .                                                               .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                           Intra-Area Prefix TLV

   Like the Link-LSA, the E-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.  The Intra-Area-Prefix TLV is only applicable to the E-Link-LSA
   and the E-Intra-Area-Prefix-LSA.  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

   The IPv6 Link-Local Address TLV is to be used with IPv6 address



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   families as defined in [OSPFV3-AF].  The IPv6 Link-Local Address TLV
   is only applicable to the E-Link-LSA.  Inclusion in other Extended
   LSAs MUST be ignored.  Only a single instance of the IPv6 Link-Local
   Address family SHOULD be included in the E-Link-LSA.  Instances
   preceding the first MUST be ignored.  For IPv4 address families as
   defined in [OSPFV3-AF], this TLV SHOULD be ignored.  Future
   specifications may support advertisement of routing and topology
   information for multiple address families.  However, this is beyond
   the scope of this document.


       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

   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.  Inclusion in other Extended
   LSAs MUST be ignored.  Only a single instance of the IPv4 Link-Local
   Address family SHOULD be included in the E-Link-LSA.  Instances
   preceding the first MUST be ignored.  For IPv6 address families as
   defined in [OSPFV3-AF].  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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11.  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, section
   4.4.3.9 in [OSPFV3].  However, unlike the Intra-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|         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

   All LSA Header fields are the same as defined for the Intra-Area-
   Prefix-LSA.  The following top-level TLVs are defined:

   o  6 - Intra-Area-Prefix TLV (defined in Section 10)

   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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12.  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.  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 covered for future OSPFv3 LSA extensions.

   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 formats could still be supported with
   multiple OSPFv3 instances and separate OSPFv3 routing domains.
   Additionally, a more complex mode is provided in Section 12.1, where
   both formats of LSA coexist.  An OSPFv3 instance will be configured
   to use either the Non-TLV-based LSAs, TLV-based LSAs, or support both
   (Appendix A).  In order to facilitate backward compatibility, the
   OSPFv3 options field (as described in Appendix A.2 of RFC 5340
   [OSPFV3]), will contain an additional options bits.  The EL-bit will
   be used to indicate that the advertising OSPFv3 Router can receive,
   process, and originate TLV-based LSAs.  An OSPFv3 router configured
   to support TLV-based LSAs WILL set its option field EL-bit in OSPFv3
   Hello and Database Description packets.  If "Normal" 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-bit clear.  In this manner, OSPFv3 routing
   domains utilizing the new encoding will be completely isolated from
   those using the RFC 5340 encodings.


                         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-bit
        This bit is indicates whether or not the OSPFv3 router
        supports the Extended LSA format with the bit set condition
        indicating support.

                           Options Field EL-bit






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12.1.  Extended LSA Mixed-Mode Backward Compatibility

   An implementation MAY support configuration allowing a mixture of
   OSPFv3 routers supporting and not supporting TLV-based LSAs in the
   same OSPFv3 routing domain.  In these deployments, the OSPFv3 routers
   configured with a value of MixedMode or MixedModeDegraded for
   ExtendedLSASupport, (Appendix A), MUST originate both the TLV-based
   and non-TLV-based versions of the OSPFv3 LSAs described herein.  For
   the purposes of Shortest Path First (SPF) computation, if the
   configured value is MixedMode, the TLV-based LSAs MUST be used by
   OSPFv3 routers supporting this specification.  If MixedModeDegraded
   is configured, the non-TLV-based versions of the OSPFv3 LSAs are used
   for SPF computation.  OSPFv3 routers configured for mixed mode
   operation also MUST form adjacencies with OSPFv3 Routers sending
   OSPFv3 Hello and Database Description packets with the options field
   EL-bit clear.  In this manner, OSPFv3 routing domains utilizing the
   new encodings can be gradually migrated with a worst-case cost of
   approximately doubling the number of LSAs in the routing domain.

12.2.  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.













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13.  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 which 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.








































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14.  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 Extend-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 initial values are 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

   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

   The OSPFv3 Extend-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
   Consensus or IESG Approval.

   One initial value is allocated:

   o  0 - Reserved








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15.  References

15.1.  Normative References

   [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.

   [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.

15.2.  Informative References

   [MT-OSPFV3]
              Mirtorabi, S. and A. Roy, "Multi-topology routing in
              OSPFv3 (MT-OSPFV3)", draft-ietf-ospf-mt-ospfv3-04.txt
              (work in progress).

   [OSPF-DIGITAL-SIGNATURE]
              Murphy, S., Badger, M., and B. Wellington, "OSPF with
              Digital Signatures", RFC 2154, June 1997.






















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Appendix A.  Configurable Constants

   An additional global configurable constant 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 value for the enumeration are:

      *  None - Non-extended LSAs will not be originated or used in the
         SPF calculation.

      *  Normal - Extended LSAs will be originated and adjacencies will
         not be formed with OSPFv3 routers not supporting this
         specification.

      *  MixedMode - Both extended and non-extended 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.

      *  MixedModeDegraded - Both extended and non-extended LSAs will be
         originated.  OSPFv3 adjacencies will be formed with OSPFv3
         routers not supporting this specification.  The non-extended
         LSAs are used for the SPF computation.
























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Authors' Addresses

   Acee Lindem
   Ericsson
   301 Midenhall Way
   Cary, NC  27513
   USA

   Email: acee.lindem@ericsson.com


   Sina Mirtorabi
   Cisco Systems
   170 Tasman Drive
   San Jose, CA  95134
   USA

   Email: sina@cisco.com


   Abhay Roy
   Cisco Systems
   170 Tasman Drive
   San Jose, CA  95134
   USA

   Email: akr@cisco.com


   Fred Baker
   Cisco Systems
   Santa Barbara, CA  93117
   USA

   Email: fred@cisco.com
















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