Internet DRAFT - draft-many-mpls-multiple-gal
draft-many-mpls-multiple-gal
MPLS Working Group G. Mirsky
Internet-Draft ZTE Corp.
Updates: 5586 (if approved) H. van Helvoort
Intended status: Standards Track Individual Contributor
Expires: 30 October 2021 S. Bryant
Futurewei Technologies Inc.
A. Vainshtein
Ribbon Communications Inc.
I. Busi
Huawei
28 April 2021
Number of Generic Associated Channel Labels in the MPLS Label Stack
draft-many-mpls-multiple-gal-01
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.
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This Internet-Draft will expire on 30 October 2021.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
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 . . . . . . . . . . . . 3
4. Processing GAL when not at the Bottom of the Label Stack . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 4
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
8.1. Normative References . . . . . . . . . . . . . . . . . . 4
8.2. Informative References . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
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 times a GAL can appear in an MPLS
label stack to one time only. This document updates [RFC5586] by
removing that restriction for non-MPLS-TP networks.
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.
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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 the processing of OAM
packets and, as a result, improve the performance. An extension of
the MPLS Echo Request and Reply protocol [RFC8029] in such an
environment is discussed in [I-D.lm-mpls-sfc-path-verification].
Because it is expected that a general Service Function does not
support processing of MPLS echo request messages, a GAL being used
within a basic unit of MPLS label stack to indicate that the payload
is ACH-encapsulated OAM message. And in the label-stacking case,
multiple basic units on the MPLS label stack, and, consequently, GALs
could be placed in an MPLS label stack. 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:
Furthermore, in non-MPLS-TP networks, when present, the GAL MAY
appear more than once in the label stack.
[RFC5586] requires that when GAL is at the bottom of the label stack,
it is followed by an ACH:
Where the GAL is at the bottom of the label stack (i.e., S bit set
to 1), then it MUST always be followed by an ACH.
This document updates [RFC5586] by extending that requirement for
environments when GAL is not at the bottom of the label stack as
follows:
Where GAL is present in the label stack, the label element at the
bottom of the label stack (i.e., S bit set to 1) MUST always be
followed by an ACH.
4. Processing GAL when not at the Bottom of the Label Stack
[Ed.note: Describe GAL processing by transit and egress nodes.
Illustrate the transformation of the MPLS label stack as a packet
transits through the domain.]
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5. IANA Considerations
This document makes no request for IANA allocations. This section
should be removed before publication.
6. Security Considerations
There are no further security considerations than those in [RFC5586].
7. Acknowledgments
TBA
8. References
8.1. 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>.
8.2. Informative References
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[I-D.lm-mpls-sfc-path-verification]
Yao, L. and G. Mirsky, "MPLS-based Service Function
Path(SFP) Consistency Verification", Work in Progress,
Internet-Draft, draft-lm-mpls-sfc-path-verification-02, 21
February 2021, <https://tools.ietf.org/html/draft-lm-mpls-
sfc-path-verification-02>.
[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
Switched (MPLS) Data-Plane Failures", RFC 8029,
DOI 10.17487/RFC8029, March 2017,
<https://www.rfc-editor.org/info/rfc8029>.
Authors' Addresses
Greg Mirsky
ZTE Corp.
Email: gregimirsky@gmail.com, gregory.mirsky@ztetx.com
Huub van Helvoort
Individual Contributor
Email: huubatwork@gmail.com
Stewart Bryant
Futurewei Technologies Inc.
Email: sb@stewartbryant.com
Alexander Vainshtein
Ribbon Communications Inc.
Email: Alexander.Vainshtein@rbbn.com
Italo Busi
Huawei
Email: italo.busi@huawei.com
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