Use of Ethernet Control Word RECOMMENDED
draft-ietf-pals-ethernet-cw-00

Document Type Active Internet-Draft (pals WG)
Last updated 2017-09-18
Replaces draft-bryant-pals-ethernet-cw
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PALS Working Group                                             S. Bryant
Internet-Draft                                                  A. Malis
Updates: 4448 (if approved)                                       Huawei
Intended status: Standards Track                             I. Bagdonas
Expires: March 22, 2018                                          Equinix
                                                      September 18, 2017

                Use of Ethernet Control Word RECOMMENDED
                     draft-ietf-pals-ethernet-cw-00

Abstract

   The pseudowire (PW) encapsulation of Ethernet, as defined in RFC4448,
   specifies that the use of the control word (CW) is optional.  In the
   absence of the CW an Ethernet pseudowire packet can be misidentified
   as an IP packet by a label switching router (LSR).  This in turn may
   lead to the selection of the wrong equal-cost-multi-path (ECMP) path
   for the packet, leading in turn to the mis-ordering of packets.  This
   problem has become more serious due to the deployment of equipment
   with Ethernet MAC addresses that start with 0x4 or 0x6.  The use of
   the Ethernet PW CW addresses this problem.  This document recommends
   the use of the Ethernet pseudowire control word in all but
   exceptional circumstances.

   This document updates RFC4448.

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 March 22, 2018.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Specification of Requirements . . . . . . . . . . . . . . . .   3
   3.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Recommendation  . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Equal Cost Multi-path (ECMP)  . . . . . . . . . . . . . . . .   5
   6.  Mitigations . . . . . . . . . . . . . . . . . . . . . . . . .   6
   7.  Operational Considerations  . . . . . . . . . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     11.2.  Informative References . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   The pseudowire(PW) encapsulation of Ethernet, as defined in RFC4448,
   specifies that the use of the control word (CW) is optional.  It is
   common for label switching routers (LSRs) to search past the end of
   the label stack to determine whether the payload is an IP packet, and
   if the payload is an IP packet, to select the next hop based of the
   so called "five-tuple" (IP source address, IP destination address,
   protocol/next-header, transport layer source port and transport layer
   destination port).  In the absence of a PW CW an Ethernet pseudowire
   packet can be misidentified as an IP packet by a label switching
   router (LSR) selecting the ECMP path based on the five-tuple.  This
   in turn may lead to the selection of the wrong equal-cost-multi-path
   (ECMP) path for the packet, leading in turn to the mis-ordering of
   packets.  Further discussion of this topic is published in [RFC4928].

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