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rfc:rfc4970

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)).

Lindem, et al. Standards Track [Page 1] RFC 4970 OSPF Capability Extensions July 2007

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

Lindem, et al. Standards Track [Page 2] RFC 4970 OSPF Capability Extensions July 2007

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.

Lindem, et al. Standards Track [Page 3] RFC 4970 OSPF Capability Extensions July 2007

     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.

Lindem, et al. Standards Track [Page 4] RFC 4970 OSPF Capability Extensions July 2007

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.

Lindem, et al. Standards Track [Page 5] RFC 4970 OSPF Capability Extensions July 2007

 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

Lindem, et al. Standards Track [Page 6] RFC 4970 OSPF Capability Extensions July 2007

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].

Lindem, et al. Standards Track [Page 7] RFC 4970 OSPF Capability Extensions July 2007

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.

Lindem, et al. Standards Track [Page 8] RFC 4970 OSPF Capability Extensions July 2007

  • 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.

Lindem, et al. Standards Track [Page 9] RFC 4970 OSPF Capability Extensions July 2007

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.

Lindem, et al. Standards Track [Page 10] RFC 4970 OSPF Capability Extensions July 2007

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.

Lindem, et al. Standards Track [Page 11] RFC 4970 OSPF Capability Extensions July 2007

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

Lindem, et al. Standards Track [Page 12] RFC 4970 OSPF Capability Extensions July 2007

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Lindem, et al. Standards Track [Page 13]

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