Network Working Group                                     H. Ould-Brahim
Request for Comments: 5543                               Nortel Networks
Category: Standards Track                                       D. Fedyk
                                                         Alcatel-Lucent
                                                             Y. Rekhter
                                                       Juniper Networks
                                                               May 2009


                  BGP Traffic Engineering Attribute

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) 2009 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 in effect on the date of
  publication of this document (http://trustee.ietf.org/license-info).
  Please review these documents carefully, as they describe your rights
  and restrictions with respect to this document.

Abstract

  This document defines a new BGP attribute, the Traffic Engineering
  attribute, that enables BGP to carry Traffic Engineering information.

  The scope and applicability of this attribute currently excludes its
  use for non-VPN reachability information.














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1.  Introduction

  In certain cases (e.g., Layer-1 VPNs (L1VPNs) [RFC5195]), it may be
  useful to augment the VPN reachability information carried in BGP
  with Traffic Engineering information.

  This document defines a new BGP attribute, the Traffic Engineering
  attribute, that enables BGP [RFC4271] to carry Traffic Engineering
  information.

  Section 4 of [RFC5195] describes one possible usage of this
  attribute.

  The scope and applicability of this attribute currently excludes its
  use for non-VPN reachability information.

  Procedures for modifying the Traffic Engineering attribute, when
  re-advertising a route that carries such an attribute, are outside
  the scope of this document.

2.  Specification of Requirements

  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 2119 [RFC2119].

3.  Traffic Engineering Attribute

  The Traffic Engineering attribute is an optional, non-transitive BGP
  attribute.

  The information carried in this attribute is identical to what is
  carried in the Interface Switching Capability Descriptor, as
  specified in [RFC4203] and [RFC5307].

  The attribute contains one or more of the following:















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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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Switching Cap |   Encoding    |           Reserved            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Max LSP Bandwidth at priority 0              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Max LSP Bandwidth at priority 1              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Max LSP Bandwidth at priority 2              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Max LSP Bandwidth at priority 3              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Max LSP Bandwidth at priority 4              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Max LSP Bandwidth at priority 5              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Max LSP Bandwidth at priority 6              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Max LSP Bandwidth at priority 7              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |             Switching Capability specific information         |
     |                           (variable)                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  The Switching Capability (Switching Cap) field contains one of the
  values specified in Section 3.1.1 of [RFC3471].

  The Encoding field contains one of the values specified in Section
  3.1.1 of [RFC3471].

  The Reserved field SHOULD be set to 0 on transmit and MUST be ignored
  on receive.

  Maximum LSP (Label Switched Path) Bandwidth is encoded as a list of
  eight 4-octet fields in the IEEE floating point format [IEEE], with
  priority 0 first and priority 7 last.  The units are bytes (not
  bits!)  per second.

  The content of the Switching Capability specific information field
  depends on the value of the Switching Capability field.

  When the Switching Capability field is PSC-1, PSC-2, PSC-3, or PSC-4,
  the Switching Capability specific information field includes Minimum
  LSP Bandwidth and Interface MTU.






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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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Minimum LSP Bandwidth                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           Interface MTU       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Minimum LSP Bandwidth is encoded in a 4-octet field in the IEEE
  floating point format.  The units are bytes (not bits!) per second.
  Interface MTU is encoded as a 2-octet integer.

  When the Switching Capability field is Layer-2 Switch Capable (L2SC),
  there is no Switching Capability specific information field present.

  When the Switching Capability field is Time-Division-Multiplex (TDM)
  capable, the Switching Capability specific information field includes
  Minimum LSP Bandwidth and an indication of whether the interface
  supports Standard or Arbitrary SONET/SDH (Synchronous Optical
  Network / Synchronous Digital Hierarchy).

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Minimum LSP Bandwidth                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Indication  |
     +-+-+-+-+-+-+-+-+

  Minimum LSP Bandwidth is encoded in a 4-octet field in the IEEE
  floating point format.  The units are bytes (not bits!) per second.
  The indication of whether the interface supports Standard or
  Arbitrary SONET/SDH is encoded as 1 octet.  The value of this octet
  is 0 if the interface supports Standard SONET/SDH, and 1 if the
  interface supports Arbitrary SONET/SDH.

  When the Switching Capability field is Lambda Switch Capable (LSC),
  there is no Switching Capability specific information field present.

4.  Implication on Aggregation

  Routes that carry the Traffic Engineering attribute have additional
  semantics that could affect traffic-forwarding behavior.  Therefore,
  such routes SHALL NOT be aggregated unless they share identical
  Traffic Engineering attributes.






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  Constructing the Traffic Engineering attribute when aggregating
  routes with identical Traffic Engineering attributes follows the
  procedure of [RFC4201].

5.  Implication on Scalability

  The use of the Traffic Engineering attribute does not increase the
  number of routes, but may increase the number of BGP Update messages
  required to distribute the routes, depending on whether or not these
  routes share the same BGP Traffic Engineering attribute (see below).

  When the routes differ other than in the Traffic Engineering
  attribute (e.g., differ in the set of Route Targets and/or NEXT_HOP),
  use of the Traffic Engineering attribute has no impact on the number
  of BGP Update messages required to carry the routes.  There is also
  no impact when routes share all other attribute information and have
  an aggregated or identical Traffic Engineering attribute.  When
  routes share all other attribute information and have different
  Traffic Engineering attributes, routes must be distributed in
  per-route BGP Update messages, rather than in a single message.

6.  IANA Considerations

  This document defines a new BGP attribute, Traffic Engineering.  This
  attribute is optional and non-transitive.

7.  Security Considerations

  This extension to BGP does not change the underlying security issues
  currently inherent in BGP.  BGP security considerations are discussed
  in RFC 4271.

8.  Acknowledgements

  The authors would like to thank John Scudder and Jeffrey Haas for
  their review and comments.

9.  References

9.1.  Normative References

  [IEEE]    IEEE, "IEEE Standard for Binary Floating-Point Arithmetic",
            Standard 754-1985, 1985 (ISBN 1-5593-7653-8).

  [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.





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  [RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label
            Switching (GMPLS) Signaling Functional Description", RFC
            3471, January 2003.

  [RFC4201] Kompella, K., Rekhter, Y., and L. Berger, "Link Bundling in
            MPLS Traffic Engineering (TE)", RFC 4201, October 2005.

  [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border
            Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006.

9.2.  Informative References

  [RFC4203] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions in
            Support of Generalized Multi-Protocol Label Switching
            (GMPLS)", RFC 4203, October 2005.

  [RFC5195] Ould-Brahim, H., Fedyk, D., and Y. Rekhter, "BGP-Based
            Auto-Discovery for Layer-1 VPNs", RFC 5195, June 2008.

  [RFC5307] Kompella, K., Ed., and Y. Rekhter, Ed., "IS-IS Extensions
            in Support of Generalized Multi-Protocol Label Switching
            (GMPLS)", RFC 5307, October 2008.

Authors' Addresses

  Hamid Ould-Brahim
  Nortel Networks
  EMail: [email protected]

  Don Fedyk
  Alcatel-Lucent
  EMail: [email protected]
  Phone: 978-467-5645

  Yakov Rekhter
  Juniper Networks, Inc.
  EMail: [email protected]














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