Network Working Group                                      Acee Lindem
Internet Draft                                            Naiming Shen
Expiration Date: April December 2004                        Redback Networks
                                                        Rahul Aggarwal
                                                      Juniper Networks
                                                         Scott Shaffer
                                                Level 3 Communications
                                                            JP Vasseur
                                                    Cisco Systems, Inc

       Extensions to OSPF for Advertising Optional Router Capabilities


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   It is useful for routers in an OSPF routing domain to know the
   capabilities of their neighbors and other routers in the OSPF
   routing domain.  This draft proposes extensions to OSPF for
   advertising optional router capabilities.  A new Router
   Information (RI) opaque LSA is proposed for this purpose.

Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   this document are to be interpreted as described in RFC-2119 [3].

1. Motivation

   It is useful for routers in an OSPF routing domain to know the
   capabilities of their neighbors and other routers in the OSPF
   routing domain.  This can be useful for various applications:

   o In MPLS Traffic Engineering (TE), it can be used as a discovery
     mechanism [7, 8] to announce a LSR's TE capabilities like
     Path Computation Server capability (Capability of an LSR to be
     a Path Computation Server for TE LSP path computation) or the
     intention of an LSR to be part of a particular MPLS TE mesh group.

   o For network management and troubleshooting.  It gives operators a
     network wide view of OSPF capabilities on different routers.
     The presence of a capability on a given router implies
     that the software version supports the capability and the router
     is configured to support it.  On the other hand, the absence of an
     expected capability on a particular router can imply either
     misconfiguration or an incorrect software version.  Hence, this
     capability information can be used to track problems resulting from
     misconfiguration or an incorrect software version.

   OSPF uses the options field in the hello packet to advertise optional
   router capabilities [1].  However, all the bits in this field have
   been allocated and there is no way to advertise new optional
   or MPLS TE capabilities.  This document proposes extensions to OSPF
   to advertise these optional capabilities.  For existing OSPF
   capabilities, this advertisement will be used primarily for
   informational purposes.  For MPLS TE features, it is used for
   advertisement and discovery.  Future OSPF features could also
   use this mechanism for advertisement and discovery.

2. OSPF Router Information (RI) Opaque LSA

   OSPF routers will optionally advertise their optional capabilities
   in an area-scoped, local scope, or AS-scoped Opaque-LSA [2].
   If a router does not advertise this LSA, it does not imply that the
   router does not support one or more of the defined capabilities.
   For existing OSPF capabilities, this advertisement will be used
   primarily for informational purposes.  For MPLS TE features,
   it is used for advertisement and discovery.  Future OSPF features
   could also use this mechanism for advertisement and discovery.
   The RI opaque LSA will be originated when one of the advertised
   capabilities is configured or changed.

   The Router Information LSA will have 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            |
   |                                                               |
   +-                            TLV's                            -+
   |                             ...                               |

             Figure 2. OSPF Router Information LSA
    The format of the TLV's within the body of a router information LSA
    is the same as the format used by the Traffic Engineering
    Extensions to OSPF [4].  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...                           |

             Figure 3. 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 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
    TLV's are also 32-bit aligned.  For example, a one byte value
    would have the length field set to 1, and three bytes of padding
    would be added to the end of the value portion of the TLV.
    Unrecognized types are ignored.

2.1 OSPF Router Capabilities TLV

   The first defined TLV in the body of a RI opaque LSA is
   the Router Capabilities TLV.  A router advertising a RI opaque LSA
   SHOULD include the Router Capabilities TLV and SHOULD correctly
   identify the status of the capabilities defined in section 2.2.

   The format of the Router 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            |
   |             Capabilities                                      |

                Figure 4. OSPF Router Capabilities TLV
   Type        A 16 bit field set to 1.
   Length      A 16 bit field that indicates the length of the value
               portion in bytes.  Its set to N x 4 octets.  N starts
               from 1 and can be increased when there is a need.  Each 4
               octets are referred to as a capability flag.
   Value       This comprises one or more capability flags.  For each 4
               octets, the bits are indexed from the most significant
               to the least significant, where each bit represents one
               router capability.  When the first 32 capabilities are
               defined, a new capability flag will be used to
               accommodate the next capability.

   The Router Capabilities TLV MAY be followed by optional TLV's that
   further specify a capability.

2.2 Reserved OSPF Router Capability Bits

   The following bits in the first capability flag have been

   Bit       Capabilities

   0-3       Reserved
   4         OSPF graceful restart capable [5]
   5         OSPF graceful restart helper  [5]
   6         Stub Router support [6]
   7         Traffic Engineering support [4]
   8         OSPF point-to-point over LAN [9]
   9         OSPF Path Computation Server discovery [7, 8]
   10-31     Future assignments

2.3 Flooding Scope of the Router Information LSA

   The flooding scope of the Router Information opaque LSA is determined
   by the LSA type.  A type 9 (link-scope), type 10 (area-scoped), or a
   type 11 (AS-scoped) opaque LSA may be used.  If a type 11 opaque LSA
   is chosen, the originating router should also advertise type 10
   LSA(s) into any attached NSSA/stub area(s).  An OSPF router MAY
   advertise different values in advertised NSSA/stub area type 10
   LSA(s) and its AS scoped type 11 opaque LSA.  The choice of
   flooding scope is made by the advertising router and is a matter of
   local policy.  The originating router MAY advertise multiple Router
   Information LSAs as long as the flooding scope differs.  TLV
   flooding scope rules will be specified on a per-TLV basis.

3. Security Consideration

   This memo does not create any new security issues for the OSPF
   protocol.  Security considerations for the base OSPF protocol are
   covered in [1].

4. 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 early versions of the draft.

   Funding for the RFC Editor function is currently provided by the
   Internet Society.

5. IANA Considerations

   A new opaque LSA type will need to be assigned by IANA.
   Additionally, IANA will need to have registries for the Router
   Information opaque LSA TLV's.  The TLV assignee will be responsible
   for allocation of any sub-TLV's for the IANA assigned TLV.  All
   TLV's and sub-TLV's will be subject to OSPF WG review.

6. References

Normative References

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

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

   [3]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Level", BCP 14, RFC 2119, March 1997.

Informative References

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

   [5]  Moy, J., P. Pillay-Esnault and A. Lindem, "OSPF Graceful
        OSPF Restart", Internet Draft, work in
        progress. RFC 3623, November 2003.

   [6]  Retana, A., et al, "OSPF Stub Router Advertisement",
        RFC 3137, June 2001.

   [7]  Vasseur, J., P. Psenak, "Traffic Engineering Capability TLV
        for OSPF", Internet Draft, work in progress.

   [8]  Vasseur  Vasseur, J., et al, "RSVP Path computation request and reply
        messages", draft-vasseur-mpls-computation-rsvp-te-03.txt,
        work in progress

   [9]  N. Shen, et al, "Point-to-point operation over LAN in
        link-state-routing protocols", Internet Draft, work in

9. Author Information

Acee Lindem
Redback Networks
350 Holger Way
San Jose, CA 95134

Naiming Shen
Redback Networks
350 Holger Way
San Jose, CA 95134

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

Scott Shaffer
Level 3 Communications

JP Vasseur
Cisco Systems, Inc.
300 Apollo Drive
Chelmsford, MA 01824

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