Network Working Group L. Andersson
Request for Comments: 3468 Consultant
Category: Informational G. Swallow
Cisco Systems
February 2003
The Multiprotocol Label Switching (MPLS) Working Group
decision on MPLS signaling protocols
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document documents the consensus reached by the Multiprotocol
Label Switching (MPLS) Working Group within the IETF to focus its
efforts on "Resource Reservation Protocol (RSVP)-TE: Extensions to
RSVP for Label-Switched Paths (LSP) Tunnels" (RFC 3209) as the MPLS
signalling protocol for traffic engineering applications and to
undertake no new efforts relating to "Constraint-Based LSP Setup
using Label Distribution Protocol (LDP)" (RFC 3212). The
recommendations of section 6 have been accepted by the IESG.
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119
[RFC2119].
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Table of Contents
1. Introduction ................................................. 2
1.1 Objectives of document ................................. 2
1.2 Nomenclature ........................................... 2
2. Background ................................................... 3
3. CCAMP implementation study ................................... 4
4. MPLS Working Group discussion ................................ 4
4.1 Phase 1 ................................................ 4
4.2 IETF process ........................................... 5
4.3 Relationship to other standards organizations .......... 5
4.4 Phase 2 ................................................ 5
5. MPLS Working Group consensus ................................. 7
6. Recommendation to the IESG ................................... 8
7. Security Considerations ...................................... 8
8. IANA Considerations .......................................... 8
9. References ................................................... 8
9.1 Normative .............................................. 8
9.2 Informative ............................................ 9
10. Authors' Addresses ...........................................10
11. Full Copyright Statement .....................................11
1. Introduction
1.1 Objectives of document
This document documents the MPLS Working group consensus to continue
to develop RFC 3209 [RFC3209] as the signalling protocol for MPLS
signaling for Traffic Engineering applications.
This document also documents the MPLS working group consensus to not
undertake any new work related to RFC 3212 [RFC3212], e.g., there are
no plans to progress RFC 3212 beyond proposed standard. No other
actions are taken relative the document status of RFC 3212 [RFC3212]
or RFCs that specify extensions to RFC 3212.
Section 6 summarizes the consensus of the MPLS working group on this
issue. This consensus has been accepted by the IESG. All other
sections are documentation of the consensus process.
1.2 Nomenclature
This document uses the term "CR-LDP related working group drafts" to
refer to a group of Internet Drafts that specify changes or
extensions to [RFC3212] and the term "CR-LDP related RFCs" to discuss
the group of RFCs that specify the protocol and the applicability of
[RFC3212].
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The CR-LDP related working group drafts are:
"Multi Protocol Label Switching Label Distribution Protocol
Query Message Description" [QUERY]
"Improving Topology Data Base Accuracy with Label Switched
Path Feedback in Constraint Based Label Distribution
Protocol [FEED]
"Signalling Unnumbered Links in CR-LDP" [UNNUM]
"Fault Tolerance for the Label Distribution Protocol
(LDP)" [FT]
"Generalized MPLS Signaling - CR-LDP Extensions" [RFC3472]
"Generalized Multi-Protocol Label Switching Extensions for
SONET and SDH Control" [SONET]
"Generalized MPLS Signalling Extensions for G.709 Optical
Transport Networks Control" [G709]
"Generalized Multiprotocol Label Switching Extensions to
Control Non-Standard SONET and SDH Features" [SDH]
CR-LDP related RFCs
The CR-LDP related RFCs are:
RFC 3212, "Constraint-Based LSP Setup using LDP"
RFC 3213, "Applicability Statement for CR-LDP"
RFC 3214, "LSP Modification Using CR-LDP"
No further updates of the CR-LDP related RFCs, beyond their current
statuses are planned within the MPLS Working Group.
2. Background
Very early (1997) in the MPLS standardization it was clear that a
protocol would be needed that would enable providers to setup LSPs
that took other information (e.g., various QoS parameters) into
account.
Development of this type of signalling protocol took two different
tracks:
- extensions to RSVP for setting up MPLS tunnels [RFC3209]
- extensions to LDP for setting constraint based LSPs [RFC3212]
The motivation for the choice of protocol in both cases was
straightforward. Extending RSVP-TE to do in an MPLS environment what
it already was doing (handling QoS information and reserving
resources) in an IP environment is comprehensible; you only have to
add the label distribution capability. Extending a native MPLS
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protocol like LDP, which was designed to do label distribution, to
handle some extra TLVs with QoS information is also not
revolutionary.
The MPLS group never reached a consensus on which way to go. Both
protocols were progressed to proposed standard.
3. CCAMP implementation study
An implementation survey of GMPLS implementations was published in
June 2002 [GMPLS]. The survey includes responses from 22 different
implementers. Twenty-one of 22 implementations include the GMPLS
signalling based on [RFC3209], while only 3 include signalling based
on [RFC3212].
4. MPLS Working Group discussion
4.1 Phase 1
The GMPLS implementation report prompted questions asking if it was
reasonable to have two different protocols for the same thing. The
discussion was brought to the MPLS Working Group at the meeting in
Yokohama in July 2002. After discussion at the meeting it was
decided to "bring this to the list" and also invite comments from the
other Sub-IP Area Working Groups.
The following question sent to the mailing lists:
"As there are issues with having two similar standards (potentially
diverging), and it generates duplicate work in several IETF working
groups, the question was asked whether we should make CR-LDP
informational (which still make it available and possible to work
with) and progress only RSVP-TE on the standards track."
The response to this question was largely positive, but some problems
were immediately pointed out:
- there are non-IETF standards which reference RFC 3212. Taking
CR-LDP off the standards track would cause un-necessary problems
for those organizations and should be done only after co-
ordinating with those organizations
- there is, e.g., in RFC 2026 [RFC2026], no documented process
according to which a document on the standards track may be move
to a status that is non-standards track
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Each of these arguments is by themselves strong and would have led to
some reformulation of the proposal to move CR-LDP to informational.
Moreover, in combination it was clear that the original proposal was
not viable.
On the other hand the support for doing additional development of
CR-LDP as an IETF standards track alternative to RSVP-TE was
extremely small.
4.2 IETF process
The current IETF process for managing changes in RFC status does not
include any information on how to move an existing standard track RFC
to a non-standard track status, nor does it include a prohibition of
such an action. It has been shown that such actions have been
previously taken e.g., RFCs 2673 and 2874 were moved from Proposed
Standard to Experimental. Though the cases are not exactly parallel
to the MPLS signalling case it shows that the IETF and IESG are
prepared to take such decisions given that the arguments are
sufficiently strong.
4.3 Relationship to other standards organizations
The relationship with other standard organizations is an important
part of IETF work. We are dependent on their work and they make use
of our technology; each organization has their own area of expertise.
It is therefore necessary that both sides handle their standards
documentation in such a way that no unnecessary updates or revisions
are introduced simply by sloppy handling of documents.
Consequently we need to keep CR-LDP referenceable, i.e., on the
standards track, for the foreseeable future. The implication of this
is not that we need to progress it further, or need to undertake
further work in the area. One implication however is that standards
organizations which reference the document, need to be notified of
our decision so that they (at their own pace) can change their
references to more appropriate documents. It is also expected that
they will notify us when they no longer have a need to normative
reference to CR-LDP.
4.4 Phase 2
Based on the feed back from this first discussion the question to the
working group were reformulated as:
"Should the MPLS WG focus its efforts on a signalling protocol for
traffic engineering applications on RSVP-TE, and hence the WG effort
with CR-LDP be discontinued? This would not involve any change in
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document status for CR-LDP, nor would it hinder continued individual
contributions in the CR-LDP space. It would involve a change in the
MPLS WG charter to reflect this."
It was pointed out that "nor would it hinder continued individual
contributions" is too weak. We actually discourage, while it is not
prohibited, continued work in the CR-LDP area. That is the whole
point with taking this decision.
It was also pointed out that while it is quite acceptable to not
accept further working group documents, it would also be appropriate
to take the existing CR-LDP related working group Internet Drafts
through the process to proposed standard or informational as
intended. This is applicable to the following documents, since much
of the work has already been completed on them:
- in MPLS WG
-- Multi Protocol Label Switching Label Distribution Protocol
Query Message Description
-- Improving Topology Data Base Accuracy with Label Switched Path
-- Feedback in Constraint Based Label Distribution Protocol
-- Signalling Unnumbered Links in CR-LDP
-- Fault Tolerance for the Label Distribution Protocol (LDP)
- in CCAMP WG
-- Generalized MPLS Signaling - CR-LDP Extensions
-- Generalized Multi-Protocol Label Switching Extensions for
SONET and SDH Control
-- Generalized MPLS Signalling Extensions for G.709 Optical
Transport Networks Control
-- Generalized Multiprotocol Label Switching Extensions to
Control Non-Standard SONET and SDH Features
Some of the documents listed above are not in themselves extensions
to CR-LDP, but in one way or another are deemed to be "equally
applicable to CR-LDP". For those documents it will be fully
appropriate to progress them beyond proposed standard in the future
if they meet the requirements.
RFCs that are extensions to CR-LDP, e.g., RFCs 3213 and 3214, will
remain proposed standard documents.
After this compromise was proposed a good consensus quickly formed
supporting the proposal. Close to 90% of the people participating
discussion said that they support or at least accept this outcome of
the working group discussion.
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5. MPLS Working Group consensus
In a message to the working group (date) the working groups chairs
stated that consensus had been reached on:
- that the MPLS WG needs to focus its efforts on RSVP-TE (RFC 3209)
as protocol for traffic engineering signalling.
- that the Working Group will undertake no new work related to
CR-LDP.
- that the WG charter should be updated to reflect this.
- that the WG will recommend that CR-LDP (RFC 3212) remain a
proposed standard.
- that the WG will recommend that RFCs 3213 and 3214, which are
closely related to CR-LDP, remain proposed standard.
- that existing Working Group drafts related to or updating/changing
CR-LDP will be progressed through the standards process to
proposed standard or informational RFCs as appropriate.
- that "the existing cr-ldp working group documents" are:
-- Multi Protocol Label Switching Label Distribution Protocol
Query Message Description
-- Improving Topology Data Base Accuracy with Label Switched Path
Feedback in Constraint Based Label Distribution Protocol
Signalling Unnumbered Links in CR-LDP
-- Fault Tolerance for the Label Distribution Protocol (LDP)
-- Generalized MPLS Signaling - CR-LDP Extensions
-- Generalized Multi-Protocol Label Switching Extensions for SONET
and SDH Control
-- Generalized MPLS Signalling Extensions for G.709 Optical
Transport Networks Control
-- Generalized Multiprotocol Label Switching Extensions to Control
Non-Standard SONET and SDH Features
- that the MPLS working group will take on no new Working Group
documents related to CR-LDP.
- that the MPLS working group will entertain no efforts to promote
CR-LDP beyond proposed standard.
- that individual contributions related to CR-LDP area are not
prohibited, but discouraged.
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- that a message will be sent to the relevant standards
organizations notifying them of this change of focus on MPLS
signalling protocols.
6. Recommendation to the IESG
Based on the consensus in the MPLS working group we recommend the
IESG to:
- confirm the MPLS Working Group consensus to undertake no new
work on CR-LDP and focus on RSVP-TE as signalling protocol for
traffic engineering applications for MPLS, as described in this
document
- adopt as an IETF policy to refrain from entertaining work that
intends to progress RFC 3212 or related RFCs beyond proposed
standard
- adopt as an IETF policy to refrain from entertaining new
working group documents that are extensions to RFC 3212
- review the IETF process with respect to management of documents
that needs to be moved from standards track to any other status
- publish this document as Informational RFC
7. Security Considerations
This document only discusses a refocusing of the MPLS Working Group
work and consequently brings no new security considerations.
8. IANA Considerations
This document brings no IANA considerations.
9. References
9.1 Normative
[RFC2026] Bradner, S. "The Internet Standards Process -- Revision 3",
BCP 9, RFC 2026, October 1996.
[RFC2119] Bradner, S. "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC3212] Jamoussi, B., Ed., Andersson, R., Callon, R., Dantu, R.,
Wu, L., Doolan, P., Worster, T., Feldman, N., Fredette, A.,
Girish, M., Gray, E., Heinanen, J., Kitly, T. and A. Malis,
"Constraint-Based LSP Setup using LDP", RFC 3212, January
2002.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
9.2 Informative
[RFC3213] Jamoussi, B., Ash, J., Girish, M., Gray, B. and G. Wright,
"Applicability Statement for CR-LDP", RFC 3213, January
2002.
[RFC3214] Jamoussi, B., Ash, J., Lee, Y., Ashwood-Smith, P., Fedyk,
D., Shalecki, D. and L. Li, "LSP Modification Using CR-LDP"
RFC 3214, January 2002.
[RFC3472] Ashwood-Smith, P. and L. Berger, Eds., "Generalized Multi-
Protocol Label Switching (GMPLS) Signaling Constraint-based
Routed Label Distribution Protocol (CR-LDP) Extensions",
RFC 3472, January 2003.
[GMPLS] Rekhther, Y. and L. Berger, "Generalized MPLS
Signaling - Implementation Survey",
http://www.ietf.org/IESG/Implementations/
MPLS-SIGNALING-Implementation.txt, June 2002.
[QUERY] Ashwood-Smith P. and A. Paraschiv, "Multi Protocol Label
Switching Label Distribution Protocol Query Message
Description", Work in Progress.
[FEED] Jamoussi, B., et al., "Improving Topology Data Base
Accuracy with LSP Feedback in CR-LDP", Work in Progress.
[RFC3480] Kompella, K., Rekhter, Y. and A. Kullberg, "Signalling
Unnumbered Links in CR-LDP (Constraint-Routing Label
Distribution Protocol)", RFC 3480, February 2003.
[RFC3479] Farrel, A., Ed., "Fault Tolerance for the Label
Distribution Protocol (LDP)", RFC 3479, February 2003.
[SONET] Mannie, E. and D. Papadimitriou, "Generalized Multiprotocol
Label Switching Extensions for SONET and SDH Control", Work
in Progress.
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[G709] Papadimitriou, D., Ed., "Generalized MPLS Signalling
Extensions for G.709 Optical Transport Networks Control",
Work in Progress.
[SDH] "Generalized Multiprotocol Label Switching Extensions to
Control Non-Standard SONET and SDH Features" Work in
Progress.
10. Authors' Addresses
Loa Andersson
EMail: loa@pi.se
George Swallow
Cisco Systems, Inc.
250 Apollo Drive
Chelmsford, MA 01824
EMail: swallow@cisco.com
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11. Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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