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Network Working Group                                          A. Retana
Internet-Draft                                                 A. Kapoor
Intended status: Informational                                  K. Patel
Expires: April 27, 2015                              Cisco Systems, Inc.
                                                        October 24, 2014


     Use of the Cost Community to carry the Accumulated IGP Metric
                draft-retana-idr-aigp-cost-community-01

Abstract

   This document explains the use of the Cost Community to flexibly
   carry the Accumulated IGP Metric.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on April 27, 2015.

Copyright Notice

   Copyright (c) 2014 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
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   described in the Simplified BSD License.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   2
   3.  Use of the Cost Community to carry the AIGP . . . . . . . . .   2
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   3
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   3
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   3
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   3

1.  Introduction

   The Accumulated IGP Metric (AIGP) Attribute [RFC7311] has been
   defined with the purpose of carrying an AIGP.  The attribute is used
   in the BGP selection process before the tie braking procedures
   [RFC4271], effectively after the LOCAL_PREF comparison.

   The Cost Community [I-D.ietf-idr-custom-decision] can provide a
   flexible mechanism to carry the AIGP.  It can se used both at a
   different point in the selection process, or as a direct replacement
   for the AIGP attribute in networks that don't fully support it.

2.  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 [RFC2119].

3.  Use of the Cost Community to carry the AIGP

   The applicability and procedures defined in [RFC7311] for originating
   and modifying the AIGP value are not changed in this document.  The
   value is used as the Cost of the Cost Community.

   The Point of Insertion (POI) can be set to any of the values defined
   in [I-D.ietf-idr-custom-decision].  Note that the use of the
   LOCAL_PREF POI is equivalent to using the AIGP Attribute in routers
   that don't support it.

   If the Cost Community is used to carry the AIGP value, then the AIGP
   Attribute SHOULD NOT be used.  If used, then the high-order bit of
   the Community-ID MUST be set in a Cost Community with a POI of AIGP
   to avoid an inconsistent selection process.  Note that this operation
   doesn't preclude using a Cost Community with a Cost of the AIGP at a
   different POI.



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4.  Security Considerations

   This document explains the use of the Cost Community to provide
   flexibility in the application of routing policy related to the
   accumulated IGP metric of a route.  As such, it does not introduce
   new security risks than the ones considered in
   [I-D.ietf-idr-custom-decision] or [RFC7311].

5.  IANA Considerations

   This document has no IANA actions.

6.  Acknowledgements

   TBD

7.  References

7.1.  Normative References

   [I-D.ietf-idr-custom-decision]
              Retana, A. and R. White, "BGP Custom Decision Process",
              draft-ietf-idr-custom-decision-05 (work in progress),
              October 2014.

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

   [RFC7311]  Mohapatra, P., Fernando, R., Rosen, E., and J. Uttaro,
              "The Accumulated IGP Metric Attribute for BGP", RFC 7311,
              August 2014.

7.2.  Informative References

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

Authors' Addresses

   Alvaro Retana
   Cisco Systems, Inc.
   7025 Kit Creek Rd.
   Research Triangle Park, NC  27709
   USA

   Email: aretana@cisco.com





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   Anoop Kapoor
   Cisco Systems, Inc.
   170 Tasman Drive
   San Jose, CA  95134
   USA

   Email: ankapoor@cisco.com


   Keyur Patel
   Cisco Systems, Inc.
   170 Tasman Drive
   San Jose, CA  95134
   USA

   Email: keyupate@cisco.com



































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