Dear All,
Stewart, Adrian, Italo, Huub, and I had discussed the question of multiple
GALs in an MPLS label stack after the IETF-110. The question is directly
related to the mechanism proposed in draft-lm-mpls-sfc-path-verification
<https://datatracker.ietf.org/doc/draft-lm-mpls-sfc-path-verification/>.
I've put together a short draft (attached). It appears, that this issue may
fit in the scope of the work of the MPLS Open DT. Appreciate your thoughts
on whether it can be discussed at one of the Open DT meetings. Also,
welcome your comments, suggestion on the attached draft.
Regards,
Greg (on behalf of the group)
MPLS Working Group G. Mirsky
Internet-Draft ZTE Corp.
Updates: 5586 (if approved) 11 March 2021
Intended status: Standards Track
Expires: 12 September 2021
Number of Generic Associated Channel Labels in the MPLS Label Stack
draft-many-mpls-multiple-gal-00
Abstract
This document describes the requirements for using multiple Generic
Associated Channel Labels (GALs) in an MPLS label stack. As a
result, the document updates RFC 5586 by removing the restriction
imposed on the usage of GAL that limits the number of GAL in the MPLS
label stack to one.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 12 September 2021.
Copyright Notice
Copyright (c) 2021 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
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
3. Number of GAL in the MPLS Label Stack . . . . . . . . . . . . 2
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
5. Security Considerations . . . . . . . . . . . . . . . . . . . 3
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 3
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 3
7.1. Normative References . . . . . . . . . . . . . . . . . . 3
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 3
1. Introduction
[RFC5085] defined the associated channel mechanism and the Associated
Channel Header (ACH) for exchange of control, management, and
Operations, Administration, and Maintenance (OAM) messages in
Pseudowires (PWs). [RFC5586] generalized that associated channel
mechanism and the ACH for use in Sections, Label Switched Paths
(LSPs), and PWs as the Generic Associated Channel (G-ACh) and
introduced the generalized label-based exception mechanism using the
Generic Associated Channel Label (GAL).
[RFC5586] restricted the number of GAL labels present in the MPLS
label stack to not more than one appearance. This document updates
[RFC5586] by removing that restriction.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Number of GAL in the MPLS Label Stack
[RFC5586] has limited the number of GALs in an MPLS label stack:
Furthermore, when present, the GAL MUST NOT appear more than once
in the label stack.
In some MPLS networks, e.g., when realizing Service Function Chaining
with MPLS-based forwarding plane [RFC8595], putting more than a
single GAL in the MPLS label stack can simplify processing of OAM
control packets and, as a result, improve the performance. Thus,
this document removes the limit on the number of GALs present in an
MPLS label stack by changing the statement in [RFC5586] as follows:
Mirsky Expires 12 September 2021 [Page 2]
Internet-Draft Multiple GAL March 2021
Furthermore, when present, the GAL MAY appear more than once in
the label stack.
4. IANA Considerations
This document has not requests for IAN and this section can be
removed before the publication.
5. Security Considerations
There are no further security considerations than those in [RFC5586].
6. Acknowledgments
TBA
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5085] Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual
Circuit Connectivity Verification (VCCV): A Control
Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085,
December 2007, <https://www.rfc-editor.org/info/rfc5085>.
[RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
"MPLS Generic Associated Channel", RFC 5586,
DOI 10.17487/RFC5586, June 2009,
<https://www.rfc-editor.org/info/rfc5586>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8595] Farrel, A., Bryant, S., and J. Drake, "An MPLS-Based
Forwarding Plane for Service Function Chaining", RFC 8595,
DOI 10.17487/RFC8595, June 2019,
<https://www.rfc-editor.org/info/rfc8595>.
Author's Address
Mirsky Expires 12 September 2021 [Page 3]
Internet-Draft Multiple GAL March 2021
Greg Mirsky
ZTE Corp.
Email: gregory.mir...@ztetx.com, gregimir...@gmail.com
Mirsky Expires 12 September 2021 [Page 4]
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