Recommendation to Use the Ethernet Control Word
RFC 8469
| Document | Type |
RFC - Proposed Standard
(November 2018; Errata)
Updates RFC 4448
|
|
|---|---|---|---|
| Last updated | 2020-04-11 | ||
| Replaces | draft-bryant-pals-ethernet-cw | ||
| Stream | IETF | ||
| Formats | plain text html pdf htmlized bibtex | ||
| Reviews | |||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Matthew Bocci | ||
| Shepherd write-up | Show (last changed 2018-05-10) | ||
| IESG | IESG state | RFC 8469 (Proposed Standard) | |
| Consensus Boilerplate | Yes | ||
| Telechat date | |||
| Responsible AD | Deborah Brungard | ||
| Send notices to | Matthew Bocci <matthew.bocci@nokia.com> | ||
| IANA | IANA review state | IANA OK - No Actions Needed | |
| IANA action state | No IANA Actions | ||
Internet Engineering Task Force (IETF) S. Bryant
Request for Comments: 8469 A. Malis
Updates: 4448 Huawei
Category: Standards Track I. Bagdonas
ISSN: 2070-1721 Equinix
November 2018
Recommendation to Use the Ethernet Control Word
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 PW packet can be
misidentified as an IP packet by a label switching router (LSR).
This may lead to the selection of the wrong equal-cost multipath
(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 Media Access Control (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 PW CW in
all but exceptional circumstances.
This document updates RFC 4448.
Status of This Memo
This is an Internet Standards Track document.
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). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8469.
Bryant, et al. Standards Track [Page 1]
RFC 8469 Ethernet CW Recommendation November 2018
Copyright Notice
Copyright (c) 2018 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
(https://trustee.ietf.org/license-info) in effect on the date of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................3
2. Specification of Requirements ...................................3
3. Background ......................................................4
4. Recommendation ..................................................5
5. Equal-Cost Multipath (ECMP) .....................................5
6. Mitigations .....................................................6
7. Operational Considerations ......................................6
8. Security Considerations .........................................7
9. IANA Considerations .............................................7
10. References .....................................................7
10.1. Normative References ......................................7
10.2. Informative References ....................................8
Acknowledgments ....................................................9
Authors' Addresses .................................................9
Bryant, et al. Standards Track [Page 2]
RFC 8469 Ethernet CW Recommendation November 2018
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 then, if it is, 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 PW
packet can be misidentified as an IP packet by a label switching
router (LSR) selecting the ECMP path based on the five-tuple. This
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].
Flow misordering can also happen in a single-path scenario when
traffic classification and differential forwarding treatment
mechanisms are in use. These errors occur when a forwarder
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