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RFC 4970 - Extensions to OSPF for Advertising Optional Router Ca


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Network Working Group                                     A. Lindem, Ed.
Request for Comments: 4970                              Redback Networks
Category: Standards Track                                        N. Shen
                                                             JP. Vasseur
                                                           Cisco Systems
                                                             R. Aggarwal
                                                        Juniper Networks
                                                              S. Shaffer
                                                     BridgePort Networks
                                                               July 2007

    Extensions to OSPF for Advertising Optional Router Capabilities

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

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 document proposes extensions to OSPFv2 and
   OSPFv3 for advertising optional router capabilities.  A new Router
   Information (RI) Link State Advertisement (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
   autonomous system (AS)).

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Requirements Notation  . . . . . . . . . . . . . . . . . .  3
   2.  OSPF Router Information (RI) LSA . . . . . . . . . . . . . . .  3
     2.1.  OSPFv2 Router Information (RI) Opaque LSA  . . . . . . . .  3
     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  . . . .  7
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  7
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     6.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     6.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 11

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 so new optional capabilities cannot be
   advertised.  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 [RFC-KEYWORDS].

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                             -+
      |                             ...                               |

                   OSPFv2 Router Information Opaque LSA

   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...                           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                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.

2.2.  OSPFv3 Router Information (RI) Opaque LSA

   The OSPFv3 Router Information LSA has a function code of 12 while the
   S1/S2 bits are dependent on the desired flooding scope for the LSA.
   The U bit will be set indicating that 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                             -+
      |                             ...                               |

                       OSPFv3 Router Information LSA

   The format of the TLVs within the body of an RI LSA is 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
   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 protocol'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.  Bits
               are numbered left-to-right starting with the most
               significant bit being bit 0.

                OSPF Router Informational Capabilities TLV

   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 are assigned:

      Bit       Capabilities

      0         OSPF graceful restart capable [GRACE]
      1         OSPF graceful restart helper  [GRACE]
      2         OSPF Stub Router support [STUB]
      3         OSPF Traffic Engineering support [TE]
      4         OSPF point-to-point over LAN [P2PLAN]
      5         OSPF Experimental TE [EXP-TE]
      6-31      Unassigned (Standards Action)

                OSPF Router Informational Capabilities Bits

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
   S1 and S2 bits in the LSA type determine the flooding scope.  If AS-
   wide flooding scope is chosen, the originating router should also
   advertise area-scoped LSA(s) into any attached Not-So-Stubby Area
   (NSSA) area(s).  An OSPF router MAY advertise different capabilities
   when both NSSA area scoped LSA(s) and an AS-scoped LSA are
   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.

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 will need to be applied 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.

4.  Security Considerations

   This document describes both a generic mechanism for advertising
   router capabilities and a TLV for advertising informational
   capability bits.  The latter TLV is less critical than the topology
   information currently advertised by the base OSPF protocol.  The
   security considerations for the generic mechanism are dependent on
   the future application and, as such, should be described as
   additional capabilities are proposed for advertisement.  Security
   considerations for the base OSPF protocol are covered in [OSPF] and
   [OSPFV3].

5.  IANA Considerations

   The following IANA assignment was made from an existing registry:

      The OSPFv2 opaque LSA type 4 has been reserved for the OSPFv2 RI
      opaque LSA.

   The following registries have been defined for the following
   purposes:

   1.  Registry for OSPFv3 LSA Function Codes - This new top-level
       registry will be comprised of the fields Value, LSA function code
       name, and Document Reference.  The OSPFv3 LSA function code is
       defined in section A.4.2.1 of [OSPFV3].  The OSPFv3 LSA function
       code 12 has been reserved for the OSPFv3 Router Information (RI)
       LSA.

                     +-----------+-------------------------------------+
                     | Range     | Assignment Policy                   |
                     +-----------+-------------------------------------+
                     | 0         | Reserved (not to be assigned)       |
                     |           |                                     |
                     | 1-9       | Already assigned                    |
                     |           |                                     |
                     | 10-11     | Unassigned (Standards Action)       |
                     |           |                                     |
                     | 12        | OSPFv3 RI LSA (Assigned herein)     |
                     |           |                                     |
                     | 13-255    | Unassigned (Standards Action)       |
                     |           |                                     |
                     | 256-8175  | Reserved (No assignments)           |
                     |           |                                     |
                     | 8176-8183 | Experimentation (No assignments)    |
                     |           |                                     |
                     | 8184-8191 | Vendor Private Use (No assignments) |
                     +-----------+-------------------------------------+

                           OSPFv3 LSA Function Codes

       *  OSPFv3 LSA function codes in the range 256-8175 are not to be
          assigned at this time.  Before any assignments can be made in
          this range, there MUST be a Standards Track RFC that specifies
          IANA Considerations that cover the range being assigned.

       *  OSPFv3 LSA function codes in the range 8176-8181 are for
          experimental use; these will not be registered with IANA and
          MUST NOT be mentioned by RFCs.

       *  OSPFv3 LSAs with an LSA Function Code in the Vendor Private
          Use range 8184-8191 MUST include the Vendor Enterprise Code as
          the first 4 octets following the 20 octets of LSA header.

       *  If a new LSA Function Code is documented, the documentation
          MUST include the valid combinations of the U, S2, and S1 bits
          for the LSA.  It SHOULD also describe how the Link State ID is
          to be assigned.

   2.  Registry for OSPF RI TLVs - This top-level registry will be
       comprised of the fields Value, TLV Name, and Document Reference.
       The value of 1 for the capabilities TLV is defined herein.

                     +-------------+-----------------------------------+
                     | Range       | Assignment Policy                 |
                     +-------------+-----------------------------------+
                     | 0           | Reserved (not to be assigned)     |
                     |             |                                   |
                     | 1           | Already assigned                  |
                     |             |                                   |
                     | 2-32767     | Unassigned (Standards Action)     |
                     |             |                                   |
                     | 32768-32777 | Experimentation (No assignements) |
                     |             |                                   |
                     | 32778-65535 | Reserved (Not to be assigned)     |
                     +-----------+-------------------------------------+

                                 OSPF RI TLVs

       *  Types in the range 32768-32777 are for experimental use; these
          will not be registered with IANA and MUST NOT be mentioned by
          RFCs.

       *  Types in the range 32778-65535 are reserved and are not to be
          assigned at this time.  Before any assignments can be made in
          this range, there MUST be a Standards Track RFC that specifies
          IANA Considerations that covers the range being assigned.

   3.  Registry for OSPF Router Informational Capability Bits - This
       sub-registry of the OSPF RI TLV registry will be comprised of the
       fields Bit Number, Capability Name, and Document Reference.  The
       values are defined in Section 2.4.  All Router Informational
       Capability TLV additions are to be assigned through standards
       action.

6.  References

6.1.  Normative References

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

   [OSPF]          Moy, J., "OSPF Version 2", STD 54, RFC 2328,
                   April 1998.

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

   [RFC-KEYWORDS]  Bradner, S., "Key words for use in RFC's to Indicate
                   Requirement Levels", BCP 14, RFC 2119, March 1997.

   [TE]            Katz, D., Kompella, K., and D. Yeung, "Traffic
                   Engineering Extensions to OSPF", RFC 3630,
                   September 2003.

6.2.  Informative References

   [EXP-TE]        Srisuresh, P. and P. Joseph, "OSPF-xTE: Experimental
                   Extension to OSPF for Traffic Engineering", RFC 4973,
                   July 2007.

   [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", Work
                   in Progress, April 2006.

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

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 document.

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

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

Authors' Addresses

   Acee Lindem (editor)
   Redback Networks
   102 Carric Bend Court
   Cary, NC  27519
   USA

   EMail: acee@redback.com

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

   EMail: naiming@cisco.com

   Jean-Philippe Vasseur
   Cisco Systems
   1414 Massachusetts Avenue
   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: sshaffer@bridgeport-networks.com

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