Use of Ethernet Control Word RECOMMENDED
draft-ietf-pals-ethernet-cw-07

Document Type Active Internet-Draft (pals WG)
Last updated 2018-08-17 (latest revision 2018-07-02)
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: January 3, 2019                                         Equinix
                                                           July 02, 2018

                Use of Ethernet Control Word RECOMMENDED
                     draft-ietf-pals-ethernet-cw-07

Abstract

   The pseudowire (PW) encapsulation of Ethernet, as defined in RFC
   4448, 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 misordering
   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 RFC 4448.

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
   Task Force (IETF).  Note that other groups may also distribute
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   This Internet-Draft will expire on January 3, 2019.

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Copyright Notice

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   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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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 . . . . . . . . . . . . . . . . . . .   7
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   7
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     11.2.  Informative References . . . . . . . . . . . . . . . . .   8
   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 on 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 equal-cost-multi-path
   (ECMP) path based on the five-tuple.  This in turn may lead to the
   selection of the wrong ECMP path for the packet, leading in turn to
   the misordering of packets.  Further discussion of this topic is
   published in [RFC4928].

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