Mechanisms for Optimizing Link Aggregation Group (LAG) and Equal-Cost Multipath (ECMP) Component Link Utilization in Networks
RFC 7424

Document Type RFC - Informational (January 2015; No errata)
Last updated 2015-10-14
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Document shepherd Warren Kumari
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IESG IESG state RFC 7424 (Informational)
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Responsible AD Benoit Claise
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Internet Engineering Task Force (IETF)                       R. Krishnan
Request for Comments: 7424                        Brocade Communications
Category: Informational                                          L. Yong
ISSN: 2070-1721                                               Huawei USA
                                                             A. Ghanwani
                                                                    Dell
                                                                   N. So
                                                           Vinci Systems
                                                           B. Khasnabish
                                                         ZTE Corporation
                                                            January 2015

       Mechanisms for Optimizing Link Aggregation Group (LAG) and
   Equal-Cost Multipath (ECMP) Component Link Utilization in Networks

Abstract

   Demands on networking infrastructure are growing exponentially due to
   bandwidth-hungry applications such as rich media applications and
   inter-data-center communications.  In this context, it is important
   to optimally use the bandwidth in wired networks that extensively use
   link aggregation groups and equal-cost multipaths as techniques for
   bandwidth scaling.  This document explores some of the mechanisms
   useful for achieving this.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see 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/rfc7424.

Krishnan, et al.              Informational                     [Page 1]
RFC 7424       Optimizing Load Distribution over LAG/ECMP   January 2015

Copyright Notice

   Copyright (c) 2015 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.

Krishnan, et al.              Informational                     [Page 2]
RFC 7424       Optimizing Load Distribution over LAG/ECMP   January 2015

Table of Contents

   1. Introduction ....................................................4
      1.1. Acronyms ...................................................4
      1.2. Terminology ................................................5
   2. Flow Categorization .............................................6
   3. Hash-Based Load Distribution in LAG/ECMP ........................6
   4. Mechanisms for Optimizing LAG/ECMP Component Link Utilization ...8
      4.1. Differences in LAG vs. ECMP ................................9
      4.2. Operational Overview ......................................10
      4.3. Large Flow Recognition ....................................11
           4.3.1. Flow Identification ................................11
           4.3.2. Criteria and Techniques for Large Flow
                  Recognition ........................................12
           4.3.3. Sampling Techniques ................................12
           4.3.4. Inline Data Path Measurement .......................14
           4.3.5. Use of Multiple Methods for Large Flow
                  Recognition ........................................15
      4.4. Options for Load Rebalancing ..............................15
           4.4.1. Alternative Placement of Large Flows ...............15
           4.4.2. Redistributing Small Flows .........................16
           4.4.3. Component Link Protection Considerations ...........16
           4.4.4. Algorithms for Load Rebalancing ....................17
           4.4.5. Example of Load Rebalancing ........................17
   5. Information Model for Flow Rebalancing .........................18
      5.1. Configuration Parameters for Flow Rebalancing .............18
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