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Versions: (draft-lindem-ospf-cap) 00 01 02 03 04 05 06 07 08 09 10 11 RFC 4970

Network Working Group                                 A. Lindem (Editor)
Internet-Draft                                                   N. Shen
Expires: June 3, 2006                                         J. Vasseur
                                                           Cisco Systems
                                                             R. Aggarwal
                                                        Juniper Networks
                                                              S. Shaffer
                                                     BridgePort Networks
                                                       November 30, 2005


    Extensions to OSPF for Advertising Optional Router Capabilities
                       draft-ietf-ospf-cap-08.txt

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   It is useful for routers in an OSPFv2 or OSPFv3 routing domain to
   know the capabilities of their neighbors and other routers in the
   routing domain.  This draft proposes extensions to OSPFv2 and OSPFv3



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   for advertising optional router capabilities.  A new Router
   Information (RI) LSA is proposed for this purpose.  In OSPFv2, the RI
   LSA will be implemented with a new opaque LSA type ID.  In OSPFv3,
   the RI LSA will be implemented with a new LSA type function code.  In
   both protocols, the RI LSA can be advertised at any of the defined
   flooding scopes (link, area, or AS).

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1   Requirements notation  . . . . . . . . . . . . . . . . . .  3
   2.  OSPF Router Information (RI) LSA . . . . . . . . . . . . . . .  4
     2.1   OSPFv2 Router Information (RI) Opaque LSA  . . . . . . . .  4
     2.2   OSPFv3 Router Information (RI) Opaque LSA  . . . . . . . .  5
     2.3   OSPF Router Informational Capabilities TLV . . . . . . . .  5
     2.4   Assigned OSPF Router Informational Capability Bits . . . .  6
     2.5   Flooding Scope of the Router Information LSA . . . . . . .  7
   3.  Router Information LSA Opaque Usage and Applicability  . . . .  8
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     6.1   Normative References . . . . . . . . . . . . . . . . . . . 11
     6.2   Informative References . . . . . . . . . . . . . . . . . . 11
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 11
   A.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 13
       Intellectual Property and Copyright Statements . . . . . . . . 14

























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1.  Introduction

   It is useful for routers in an OSPFv2 [OSPF] or OSPFv3 [OSPFV3]
   routing domain to know the capabilities of their neighbors and other
   routers in the routing domain.  This can be useful for both the
   advertisement and discovery of OSPFv2 and OSPFv3 capabilities.
   Throughout this document, OSPF will be used when the specification is
   applicable to both OSPFv2 and OSPFv3.  Similarly, OSPFv2 or OSPFv3
   will be used when the text is protocol specific.

   OSPF uses the options field in LSAs and hello packets to advertise
   optional router capabilities.  In the case of OSPFv2, all the bits in
   this field have been allocated and there is no way to advertise new
   optional capabilities.  This document proposes extensions to OSPF to
   advertise these optional capabilities via opaque LSAs in OSPFv2 and
   new LSAs in OSPFv3.  For existing OSPF capabilities, backward
   compatibility issues dictate that this advertisement is used
   primarily for informational purposes.  For future OSPF features, this
   advertisement MAY be used as the sole mechanism for advertisement and
   discovery.

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 RFC2119 [RFC2119].

























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2.  OSPF Router Information (RI) LSA

   OSPF routers MAY optionally advertise their optional capabilities in
   a link-scoped, area-scoped, or AS-scoped LSA.  For existing OSPF
   capabilities, this advertisement will be used primarily for
   informational purposes.  Future OSPF features could use the RI LSA as
   the sole mechanism for advertisement and discovery.  The RI LSA will
   be originated initially when an OSPF router instance is created and
   whenever one of the advertised capabilities is configured or changed.

2.1  OSPFv2 Router Information (RI) Opaque LSA

   OSPFv2 routers will advertise a link scoped, area-scoped, or AS-
   scoped Opaque-LSA [OPAQUE].  The OSPFv2 Router Information LSA has an
   Opaque type of 4 and Opaque ID of 0.


       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             |     Options   |  9, 10 or 11  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       4       |                    0                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Advertising Router                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     LS sequence number                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         LS checksum           |             length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +-                            TLVs                             -+
      |                             ...                               |


   The format of the TLVs within the body of an RI LSA is the same as
   the format used by the Traffic Engineering Extensions to OSPF [TE].
   The LSA payload consists of one or more nested Type/Length/Value
   (TLV) triplets.  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...                           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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   The Length field defines the length of the value portion in octets
   (thus a TLV with no value portion would have a length of zero).  The
   TLV is padded to four-octet alignment;  padding is not included in
   the length field (so a three octet value would have a length of
   three, but the total size of the TLV would be eight octets).  Nested
   TLVs are also 32-bit aligned.  For example, a one byte value would
   have the length field set to 1, and three octets of padding would be
   added to the end of the value portion of the TLV.  Unrecognized types
   are ignored.

2.2  OSPFv3 Router Information (RI) Opaque LSA

   The OSPFv3 Router Information LSA has a function code of 12 while the
   S1/S2 bit are dependent on the desired flooding scope for the LSA.
   The U bit will be set indicating the OSPFv3 RI LSA should be flooded
   even if it is not understood.  The Link State ID (LSID) value for
   this LSA is 0.  This is unambiguous since an OSPFv3 router will only
   advertise a single RI LSA per flooding scope.


       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|S12|          12             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         0  (Link State ID)                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Advertising Router                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    LS sequence number                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        LS checksum           |             Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +-                            TLVs                             -+
      |                             ...                               |


   The format of the TLVs within the body of an RI LSA as defined in
   Section 2.1

   When a new Router Information LSA TLV is defined, the specification
   MUST explicitly state whether the TLV is applicable to OSPFv2 only,
   OSPFv3 only, or both OSPFv2 and OSPFv3.

2.3  OSPF Router Informational Capabilities TLV

   The first defined TLV in the body of an RI LSA is the Router



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   Informational Capabilities TLV.  A router advertising an RI LSA MAY
   include the Router Informational Capabilities TLV.  If included, it
   MUST be the first TLV in the LSA.  Additionally, the TLV MUST
   accurately reflect the OSPF router's capabilities in the scope
   advertised.  However, the informational capabilities advertised have
   no impact on the OSPF's operation - they are advertised purely for
   informational purposes

   The format of the Router Informational Capabilities TLV is as
   follows:


       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            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Informational Capabilities                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


      Type     A 16 bit field set to 1.
      Length   A 16 bit field that indicates the length of the value
               portion in octets and will be a multiple of 4 octets
               dependent on the number of capabilities advertised.
               Initially, the length will be 4 denoting 4 octets of
               informational capability bits.
      Value    A variable length sequence of capability bits rounded
               to a multiple of 4 octets padded with undefined bits.
               Initially, there are 4 octets of capability bits.


   The Router Informational Capabilities TLV MAY be followed by optional
   TLVs that further specify a capability.

2.4  Assigned OSPF Router Informational Capability Bits

   The following informational capability bits assigned:


      Bit       Capabilities

      1         OSPF graceful restart capable [GRACE]
      2         OSPF graceful restart helper  [GRACE]
      3         OSPF Stub Router support [STUB]
      4         OSPF Traffic Engineering support [TE]
      5         OSPF point-to-point over LAN [P2PLAN]
      6         OSPF Experimental TE [EXPTE]



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      7-31      Future assignments



2.5  Flooding Scope of the Router Information LSA

   The flooding scope for a Router Information LSA is determined by the
   LSA type.  For OSPFv2, type 9 (link-scoped), type 10 (area-scoped),
   or a type 11 (AS-scoped) opaque LSA may be flooded.  For OSPFv3, the
   flooding scope is determined by the S1 and S2 bits in the LSA type.
   If AS wide flooding scope is chosen, the originating router should
   also advertise area scoped LSA(s) into any attached NSSA area(s).  An
   OSPF router MAY advertise different capabilities when both NSSA area
   scoped LSA(s) and an AS scoped LSA is advertised.  This allows
   functional capabilities to be limited in scope.  For example, a
   router may be an area border router but only support traffic
   engineering (TE) in a subset of its attached areas.

   The choice of flooding scope is made by the advertising router and is
   a matter of local policy.  The originating router MAY advertise
   multiple RI LSAs as long as the flooding scopes differ.  TLV flooding
   scope rules will be specified on a per-TLV basis and MUST be
   specified in the accompanying specifications for new Router
   Information LSA TLVs.



























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3.  Router Information LSA Opaque Usage and Applicability

   The purpose of the Router Information (RI) LSA is to advertise
   information relating to the aggregate OSPF router.  Normally, this
   should be confined to TLVs with a single value or very few values.
   It is not meant to be a generic container to carry any and all
   information.  The intent is to both limit the size of the RI LSA to
   the point where an OSPF router will always be able to contain the
   TLVs in a single LSA and to keep the task of determining what has
   changed between LSA instances reasonably simple.  Hence, discretion
   and sound engineering judgment MUST be adhered to when deciding
   whether newly proposed TLV(s) in support of a new application are
   advertised in the RI LSA or warrant the creation of an application
   specific LSA.





































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4.  Security Considerations

   The function described in this document does not create any new
   security issues for the OSPF protocol.  Security considerations for
   the base OSPF protocol are covered in [OSPF] and [OSPFV3].














































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5.  IANA Considerations

   The following IANA assignments are to be made from existing
   registries:

   1.  The OSPFv2 opaque LSA type 4 will need to be reserved for the
       OSPFv2 RI opaque LSA.

   2.  The OSPFv3 LSA type function code 18 will need to be reserved for
       the OSPFv3 RI LSA.

   New registries are defined for the following purposes:

   1.  Registry for OSPF RI TLVs - The value of 1 for the capabilities
       TLV is defined herein.  All TLV additions are subject to OSPF WG
       review.

   2.  Registry for OSPF Router Informational Capability Bits - The
       values defined in Section 2.3.  All Router Informational
       Capability TLV additions are subject to OSPF WG review.































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6.  References

6.1  Normative References

   [OPAQUE]   Coltun, R., "The OSPF Opaque LSA Option", RFC 2370,
              July 1998.

   [OSPF]     Moy, J., "OSPF Version 2", RFC 2328, April 1998.

   [OSPFV3]   Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6",
              RFC 2740, December 1999.

   [RFC2119]  Bradner, S., "Key words for use in RFC's 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.

6.2  Informative References

   [EXPTE]   Srisuresh, P. and P. Joseph, "OSPF  OSPF-TE: An
             experimental extension to OSPF for Traffic Engineering",
             draft-srisuresh-ospf-te-07.txt (work in progress).

   [GRACE]   Moy, J., Pillay-Esnault, P., and A. Lindem, "Graceful OSPF
             Restart", RFC 3623, November 2003.

   [P2PLAN]  Shen, N. and A. Zinin, "Point-to-point operation over LAN
             in link-state routing protocols",
             draft-ietf-isis-igp-p2p-over-lan-05.txt (work in progress).

   [STUB]    Retana, A., Nguyen, L., White, R., Zinin, A., and D.
             McPherson, "OSPF Stub Router Advertisement", RFC 3137,
             June 2001.


Authors' Addresses

   Acee Lindem
   Cisco Systems
   7025 Kit Creek Road
   Research Triangle Park, NC  27709
   USA

   Email: acee@cisco.com






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   Naiming Shen
   Cisco Systems
   225 West Tasman Drive
   San Jose, CA  95134
   USA

   Email: naiming@cisco.com


   Jean-Philippe Vasseur
   Cisco Systems
   300 Beaver Brook Road
   Boxborough, MA  01719
   USA

   Email: jpv@cisco.com


   Rahul Aggarwal
   Juniper Networks
   1194 N. Mathilda Ave.
   Sunnyvale, CA  94089
   USA

   Email: rahul@juniper.net


   Scott Shaffer
   BridgePort Networks
   One Main Street, 7th Floor
   Cambridge, MA  02142
   USA

   Email: sshafferl@bridgeport-networks.com

















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Appendix A.  Acknowledgments

   The idea for this work grew out of a conversation with Andrew Partan
   and we would like to thank him for his contribution.  The authors
   would like to thanks Peter Psenak for his review and helpful comments
   on early versions of the draft.

   Comments from Abhay Roy, Vishwas Manral, Vivek Dubey, and Adrian
   Farrel have been incorporated into later draft versions.

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








































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