BGP Link Bandwidth Extended Community
draft-ietf-idr-link-bandwidth-05

Network Working Group                                       P. Mohapatra
Internet-Draft                                               R. Fernando
Intended status: Standards Track                           Cisco Systems
Expires: May 9, 2013                                    November 5, 2012

                 BGP Link Bandwidth Extended Community
                  draft-ietf-idr-link-bandwidth-05.txt

Abstract

   This document describes an application of BGP extended communities
   that allows a router to perform unequal cost load balancing.

Status of this Memo

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   This Internet-Draft will expire on May 9, 2013.

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   10, 2008.  The person(s) controlling the copyright in some of this
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . . . 3
   2.  Link Bandwidth Extended Community . . . . . . . . . . . . . . . 3
   3.  Deployment Considerations . . . . . . . . . . . . . . . . . . . 3
   4.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   7.  Normative References  . . . . . . . . . . . . . . . . . . . . . 4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 5

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1.  Introduction

   When a BGP speaker receives multiple paths from its internal peers,
   it could select more than one path to send traffic to.  In doing so,
   it might be useful to provide the speaker with information that would
   help it distribute the traffic based on the bandwidth of the external
   (DMZ) link.  This document suggests that the external link bandwidth
   be carried in the network using a new extended community [RFC4360] -
   the link bandwidth extended community.

1.1.  Requirements Language

   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].

2.  Link Bandwidth Extended Community

   When a BGP speaker receives a route from an external neighbor and
   advertises this route (via IBGP) to internal neighbors, as part of
   this advertisement the router may carry the cost to reach the
   external neighbor.  The cost can be either configured per neighbor or
   derived from the bandwidth of the link that connects the router to a
   directly connected external neighbor.  This value is carried in the
   Link Bandwidth Extended Community.  No more than one link bandwidth
   extended community SHALL be attached to a route.  Additionally, if a
   route is received with link bandwidth extended community and the BGP
   speaker sets itself as next-hop while announcing that route to other
   peers, the link bandwidth extended community should be removed.

   The extended community is optional non-transitive.  The value of the
   high-order octet of the extended Type Field is 0x40.  The value of
   the low-order octet of the extended type field for this community is
   0x04.  The value of the Global Administrator subfield in the Value
   Field SHOULD represent the Autonomous System of the router that
   attaches the Link Bandwidth Community.  If four octet AS numbering
   scheme is used [RFC4893], AS_TRANS should be used in the Global
   Administrator subfield.  The bandwidth of the link is expressed as 4
   octets in IEEE floating point format, units being bytes (not bits!)
   per second.  It is carried in the Local Administrator subfield of the
   Value Field.

3.  Deployment Considerations

   The usage of this community is restricted to the cases where BGP
   multipath can be safely deployed.  In other words, the IGP distance

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   between the load balancing router and the exit points should be the
   same.  Alternatively, the path between the load sharing router and
   the exit points could be tunneled.  If there are multiple paths to
   reach a destination and if only some of them have link bandwidth
   community, the receiver should not perform unequal cost load
   balancing based on link bandwidths.

4.  Acknowledgments

   The authors would like to thank Yakov Rekhter, Srihari Sangli and Dan
   Tappan for proposing unequal cost load balancing as one possible
   application of the extended community attribute.

   The authors would like to thank Bruno Decraene, Robert Raszuk, Joel
   Halpern, Aleksi Suhonen, and Randy Bush for their useful comments and
   discussions.

5.  IANA Considerations

   This document defines a specific application of the two-octet AS
   specific extended community.  IANA is requested to assign a sub- type
   value of 0x04 for the link bandwidth extended community.

      Name                                           Value
      ----                                           -----
      non-transitive Link Bandwidth Ext. Community  0x4004

6.  Security Considerations

   There are no additional security risks introduced by this design.

7.  Normative References

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

   [RFC4360]  Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
              Communities Attribute", RFC 4360, February 2006.

   [RFC4893]  Vohra, Q. and E. Chen, "BGP Support for Four-octet AS
              Number Space", RFC 4893, May 2007.

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Authors' Addresses

   Pradosh Mohapatra
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Phone:
   Email: pmohapat@cisco.com

   Rex Fernando
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Phone:
   Email: rex@cisco.com

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