BGP Traffic Engineering Attribute

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


                   <span class="h1">BGP Traffic Engineering Attribute</span>

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 <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a> and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (<a href="http://trustee.ietf.org/license-info">http://trustee.ietf.org/license-info</a>).
   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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<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>.  Introduction</span>

   In certain cases (e.g., Layer-1 VPNs (L1VPNs) [<a href="./rfc5195" title=""BGP-Based Auto-Discovery for Layer-1 VPNs"">RFC5195</a>]), 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 [<a href="./rfc4271" title=""A Border Gateway Protocol 4 (BGP-4)"">RFC4271</a>] to carry Traffic Engineering
   information.

   <a href="./rfc5195#section-4">Section 4 of [RFC5195]</a> 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.

<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>.  Specification of Requirements</span>

   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 <a href="./rfc2119">RFC 2119</a> [<a href="./rfc2119" title=""Key words for use in RFCs to Indicate Requirement Levels"">RFC2119</a>].

<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>.  Traffic Engineering Attribute</span>

   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 [<a href="./rfc4203" title=""OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)"">RFC4203</a>] and [<a href="./rfc5307" title=""IS-IS Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)"">RFC5307</a>].

   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 <a href="./rfc3471#section-3.1.1">Section 3.1.1 of [RFC3471]</a>.

   The Encoding field contains one of the values specified in <a href="./rfc3471#section-3.1.1">Section</a>
   <a href="./rfc3471#section-3.1.1">3.1.1 of [RFC3471]</a>.

   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 [<a href="#ref-IEEE" title=""IEEE Standard for Binary Floating-Point Arithmetic"">IEEE</a>], 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.

<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>.  Implication on Aggregation</span>

   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 [<a href="./rfc4201" title=""Link Bundling in MPLS Traffic Engineering (TE)"">RFC4201</a>].

<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>.  Implication on Scalability</span>

   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.

<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>.  IANA Considerations</span>

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

<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>.  Security Considerations</span>

   This extension to BGP does not change the underlying security issues
   currently inherent in BGP.  BGP security considerations are discussed
   in <a href="./rfc4271">RFC 4271</a>.

<span class="h2"><a class="selflink" id="section-8" href="#section-8">8</a>.  Acknowledgements</span>

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

<span class="h2"><a class="selflink" id="section-9" href="#section-9">9</a>.  References</span>

<span class="h3"><a class="selflink" id="section-9.1" href="#section-9.1">9.1</a>.  Normative References</span>

   [<a id="ref-IEEE">IEEE</a>]    IEEE, "IEEE Standard for Binary Floating-Point Arithmetic",
             Standard 754-1985, 1985 (ISBN 1-5593-7653-8).

   [<a id="ref-RFC2119">RFC2119</a>] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", <a href="https://www.rfc-editor.org/bcp/bcp14">BCP 14</a>, <a href="./rfc2119">RFC 2119</a>, March 1997.





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   [<a id="ref-RFC3471">RFC3471</a>] Berger, L., Ed., "Generalized Multi-Protocol Label
             Switching (GMPLS) Signaling Functional Description", <a href="./rfc3471">RFC</a>
             <a href="./rfc3471">3471</a>, January 2003.

   [<a id="ref-RFC4201">RFC4201</a>] Kompella, K., Rekhter, Y., and L. Berger, "Link Bundling in
             MPLS Traffic Engineering (TE)", <a href="./rfc4201">RFC 4201</a>, October 2005.

   [<a id="ref-RFC4271">RFC4271</a>] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border
             Gateway Protocol 4 (BGP-4)", <a href="./rfc4271">RFC 4271</a>, January 2006.

<span class="h3"><a class="selflink" id="section-9.2" href="#section-9.2">9.2</a>.  Informative References</span>

   [<a id="ref-RFC4203">RFC4203</a>] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions in
             Support of Generalized Multi-Protocol Label Switching
             (GMPLS)", <a href="./rfc4203">RFC 4203</a>, October 2005.

   [<a id="ref-RFC5195">RFC5195</a>] Ould-Brahim, H., Fedyk, D., and Y. Rekhter, "BGP-Based
             Auto-Discovery for Layer-1 VPNs", <a href="./rfc5195">RFC 5195</a>, June 2008.

   [<a id="ref-RFC5307">RFC5307</a>] Kompella, K., Ed., and Y. Rekhter, Ed., "IS-IS Extensions
             in Support of Generalized Multi-Protocol Label Switching
             (GMPLS)", <a href="./rfc5307">RFC 5307</a>, 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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