Skip to main content

Use of Ethernet Control Word RECOMMENDED

Document Type Replaced Internet-Draft (pals WG)
Expired & archived
Authors Stewart Bryant , Andrew G. Malis , Ignas Bagdonas
Last updated 2017-09-05 (Latest revision 2017-08-02)
Replaced by draft-ietf-pals-ethernet-cw
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status (None)
Additional resources Mailing list discussion
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
Telechat date (None)
Responsible AD (None)
Send notices to Matthew Bocci <>

This Internet-Draft is no longer active. A copy of the expired Internet-Draft is available in these formats:


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
Andrew G. Malis
Ignas Bagdonas

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