Use of Ethernet Control Word RECOMMENDED

Document Type Replaced Internet-Draft (pals WG)
Authors Stewart Bryant  , Andy Malis  , Ignas Bagdonas 
Last updated 2017-09-05 (latest revision 2017-08-02)
Replaced by RFC 8469
Stream IETF
Intended RFC status (None)
Expired & archived
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Stream WG state Adopted by a WG
Other - see Comment Log
Document shepherd Matthew Bocci
IESG IESG state Replaced by draft-ietf-pals-ethernet-cw
Consensus Boilerplate Unknown
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Responsible AD (None)
Send notices to Matthew Bocci <>

This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


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.


Stewart Bryant (
Andy Malis (
Ignas Bagdonas (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)