One document matched: draft-ietf-idr-link-bandwidth-00.txt

Network Working Group                                       P. Mohapatra
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                             R. Fernando
Expires: October 23, 2009                               Juniper Networks
                                                          April 21, 2009


                 BGP Link Bandwidth Extended Community
                  draft-ietf-idr-link-bandwidth-00.txt

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   Copyright (c) 2009 IETF Trust and the persons identified as the
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   This document is subject to BCP 78 and the IETF Trust's Legal
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Abstract

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


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . . . 3
   2.  Link Bandwidth Extended Community . . . . . . . . . . . . . . . 3
   3.  Deployment Considerations . . . . . . . . . . . . . . . . . . . 4
   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 unequally based on the cost 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 a directly connected
   external neighbor (the external neighbor that is one IP hop away) and
   advertises this route (via IBGP) to internal neighbors, as part of
   this advertisement the router may carry the bandwidth of the link
   that connects the router with the external neighbor.  The bandwidth
   of such a link is carried in the Link Bandwidth Community.  The
   community is optional non-transitive.  A border router MUST strip the
   link bandwidth community from a route when it advertises the route to
   an external neighbor.

   It is noteworthy that the bandwidth carried in the Link Bandwidth
   extended community is the configured bandwidth of the EBGP link.  It
   does not depend on the amount of traffic transiting that link.

   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 per second.  It is carried in the
   Local Administrator subfield of the Value Field.





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3.  Deployment Considerations

   This document proposes to use the Link Bandwidth extended community
   for the purpose of load balancing in the following two scenarios.
   The first scenario is when the candidate paths are identical until
   and including the IGP distance step in the BGP decision process.  The
   second scenario is when the traffic goes via a tunneled network, in
   which case the candidate paths are identical for all steps before the
   IGP distance step in the BGP decision process.  Use of this community
   for other scenarios is outside the scope of this document.

   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.


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.



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


Authors' Addresses

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

   Phone:
   Email: pmohapat@cisco.com


   Rex Fernando
   Juniper Networks
   1194 N. Mathilda Ave
   Sunnyvale, CA  94089
   USA

   Phone:
   Email: rex@juniper.net



























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