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Protocol Independent Multicast Equal-Cost Multipath (ECMP) Redirect
RFC 6754

Internet Engineering Task Force (IETF)                            Y. Cai
Request for Comments: 6754                                     Microsoft
Category: Standards Track                                         L. Wei
ISSN: 2070-1721                                                    H. Ou
                                                     Cisco Systems, Inc.
                                                                 V. Arya
                                                             S. Jethwani
                                                            DIRECTV Inc.
                                                            October 2012

  Protocol Independent Multicast Equal-Cost Multipath (ECMP) Redirect

Abstract

   A Protocol Independent Multicast (PIM) router uses the Reverse Path
   Forwarding (RPF) procedure to select an upstream interface and router
   in order to build forwarding state.  When there are equal-cost
   multipaths (ECMPs), existing implementations often use hash
   algorithms to select a path.  Such algorithms do not allow the spread
   of traffic among the ECMPs according to administrative metrics.  This
   usually leads to inefficient or ineffective use of network resources.
   This document introduces the ECMP Redirect, a mechanism to improve
   the RPF procedure over ECMPs.  It allows ECMP selection to be based
   on administratively selected metrics, such as data transmission
   delays, path preferences, and routing metrics.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6754.

Cai, et al.                  Standards Track                    [Page 1]
RFC 6754                   PIMv2 ECMP Redirect              October 2012

Copyright Notice

   Copyright (c) 2012 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Applicability  . . . . . . . . . . . . . . . . . . . . . . . .  5
   5.  Protocol Specification . . . . . . . . . . . . . . . . . . . .  6
     5.1.  Sending ECMP Redirect  . . . . . . . . . . . . . . . . . .  6
     5.2.  Receiving ECMP Redirect  . . . . . . . . . . . . . . . . .  7
     5.3.  Transient State  . . . . . . . . . . . . . . . . . . . . .  7
     5.4.  Interoperability . . . . . . . . . . . . . . . . . . . . .  8
     5.5.  Packet Format  . . . . . . . . . . . . . . . . . . . . . .  8
       5.5.1.  PIM ECMP Redirect Hello Option . . . . . . . . . . . .  8
       5.5.2.  PIM ECMP Redirect Format . . . . . . . . . . . . . . .  9
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 11

Cai, et al.                  Standards Track                    [Page 2]
RFC 6754                   PIMv2 ECMP Redirect              October 2012

1.  Introduction

   A PIM router uses the RPF procedure to select an upstream interface
   and a PIM neighbor on that interface to build forwarding state.  When
   there are equal-cost multipaths (ECMPs) upstream, existing
   implementations often use hash algorithms to select a path.  Such
   algorithms do not allow the spread of traffic among the ECMP
   according to administrative metrics.  This usually leads to

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