Internet Engineering Task Force (IETF) L. Jin, Ed.
Request for Comments: 6723 ZTE
Updates: 4447, 6073 R. Key, Ed.
Category: Standards Track Huawei
ISSN: 2070-1721 S. Delord
Alcatel-Lucent
T. Nadeau
Juniper
S. Boutros
Cisco Systems, Inc.
September 2012
Update of the Pseudowire Control-Word Negotiation Mechanism
Abstract
The control-word negotiation mechanism specified in RFC 4447 has a
problem when a PE (Provider Edge) changes the preference for the use
of the control word from NOT PREFERRED to PREFERRED. This document
updates RFC 4447 and RFC 6073 by adding the Label Request message to
resolve this control-word negotiation issue for single-segment and
multi-segment pseudowires.
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 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6723.
Jin, et al. Standards Track [Page 1]RFC 6723 Update of PW C-Bit Negotiation September 2012Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . . 3
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . . 3
4. Control-Word Renegotiation by Label Request Message . . . . . . 4
4.1. Control-Word Renegotiation for Multi-Segment PW . . . . . . 5
4.2. Control-Word Renegotiation Use Case . . . . . . . . . . . . 5
5. Backward Compatibility . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 7
9. Normative References . . . . . . . . . . . . . . . . . . . . . 7
Appendix A. Updated Diagram of C-Bit Handling Procedures . . . . . 8
1. Introduction
The control-word negotiation mechanism specified in [RFC4447],
Section 6.2, encounters a problem when a PE changes the preference
for the use of the control word from NOT PREFERRED to PREFERRED.
[RFC4447] specifies that if both endpoints prefer the use of the
control word, then the pseudowire control word should be used.
However, in the case where a PE changes its preference from NOT
PREFERRED to PREFERRED and both ends of the PW (pseudowire) PE have
the use of control word set as PREFERRED, an incorrect negotiated
result of the control word as "not used" occurs. This document
updates the control-word negotiation mechanism in [RFC4447] by adding
a Label Request message to resolve this negotiation issue for single-
segment PW. Multi-segment PW in [RFC6073] inherits the control-word
negotiation mechanism in [RFC4447], and this document updates
[RFC6073] by adding the processing of Label Request message on the
Jin, et al. Standards Track [Page 2]RFC 6723 Update of PW C-Bit Negotiation September 2012
S-PE (Switching Provider Edge). When the PE changes the preference
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