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The Use of Entropy Labels in MPLS Forwarding
RFC 6790

Internet Engineering Task Force (IETF)                       K. Kompella
Request for Comments: 6790                                      J. Drake
Updates: 3031, 3107, 3209, 5036                         Juniper Networks
Category: Standards Track                                      S. Amante
ISSN: 2070-1721                             Level 3 Communications, Inc.
                                                           W. Henderickx
                                                          Alcatel-Lucent
                                                                 L. Yong
                                                              Huawei USA
                                                           November 2012

              The Use of Entropy Labels in MPLS Forwarding

Abstract

   Load balancing is a powerful tool for engineering traffic across a
   network.  This memo suggests ways of improving load balancing across
   MPLS networks using the concept of "entropy labels".  It defines the
   concept, describes why entropy labels are useful, enumerates
   properties of entropy labels that allow maximal benefit, and shows
   how they can be signaled and used for various applications.  This
   document updates RFCs 3031, 3107, 3209, and 5036.

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/rfc6790.

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

Kompella, et al.             Standards Track                    [Page 1]
RFC 6790                   MPLS Entropy Labels             November 2012

   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
      1.1. Conventions Used ...........................................4
      1.2. Motivation .................................................6
   2. Approaches ......................................................7
   3. Entropy Labels and Their Structure ..............................8
   4. Data Plane Processing of Entropy Labels .........................9
      4.1. Egress LSR .................................................9
      4.2. Ingress LSR ...............................................10
      4.3. Transit LSR ...............................................11
      4.4. Penultimate Hop LSR .......................................12
   5. Signaling for Entropy Labels ...................................12
      5.1. LDP Signaling .............................................12
           5.1.1. Processing the ELC TLV .............................13
      5.2. BGP Signaling .............................................13
      5.3. RSVP-TE Signaling .........................................14
      5.4. Multicast LSPs and Entropy Labels .........................15
   6. Operations, Administration, and Maintenance (OAM) and
      Entropy Labels .................................................15
   7. MPLS-TP and Entropy Labels .....................................16
   8. Entropy Labels in Various Scenarios ............................16
      8.1. LDP Tunnel ................................................17
      8.2. LDP over RSVP-TE ..........................................20
      8.3. MPLS Applications .........................................20
   9. Security Considerations ........................................20
   10. IANA Considerations ...........................................21
      10.1. Reserved Label for ELI ...................................21
      10.2. LDP Entropy Label Capability TLV .........................21
      10.3. BGP Entropy Label Capability Attribute ...................21
      10.4. RSVP-TE Entropy Label Capability Flag ....................22
   11. Acknowledgments ...............................................22

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