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rfc:rfc3468

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].

Andersson & Swallow Informational [Page 1] RFC 3468 Decision on MPLS Signaling Protocols February 2003

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].

Andersson & Swallow Informational [Page 2] RFC 3468 Decision on MPLS Signaling Protocols February 2003

    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:
  1. extensions to RSVP for setting up MPLS tunnels [RFC3209]
  1. 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

Andersson & Swallow Informational [Page 3] RFC 3468 Decision on MPLS Signaling Protocols February 2003

 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:
  1. 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
  1. 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

Andersson & Swallow Informational [Page 4] RFC 3468 Decision on MPLS Signaling Protocols February 2003

 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

Andersson & Swallow Informational [Page 5] RFC 3468 Decision on MPLS Signaling Protocols February 2003

 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:
  1. in MPLS WG
  2. - Multi Protocol Label Switching Label Distribution Protocol

Query Message Description

  1. - Improving Topology Data Base Accuracy with Label Switched Path
  2. - Feedback in Constraint Based Label Distribution Protocol
  3. - Signalling Unnumbered Links in CR-LDP
  4. - Fault Tolerance for the Label Distribution Protocol (LDP)
  5. in CCAMP WG
  6. - Generalized MPLS Signaling - CR-LDP Extensions
  7. - Generalized Multi-Protocol Label Switching Extensions for

SONET and SDH Control

  1. - Generalized MPLS Signalling Extensions for G.709 Optical

Transport Networks Control

  1. - 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.

Andersson & Swallow Informational [Page 6] RFC 3468 Decision on MPLS Signaling Protocols February 2003

5. MPLS Working Group consensus

 In a message to the working group (date) the working groups chairs
 stated that consensus had been reached on:
  1. that the MPLS WG needs to focus its efforts on RSVP-TE (RFC 3209)

as protocol for traffic engineering signalling.

  1. that the Working Group will undertake no new work related to

CR-LDP.

  1. that the WG charter should be updated to reflect this.
  1. that the WG will recommend that CR-LDP (RFC 3212) remain a

proposed standard.

  1. that the WG will recommend that RFCs 3213 and 3214, which are

closely related to CR-LDP, remain proposed standard.

  1. 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.
  1. that "the existing cr-ldp working group documents" are:
    1. - Multi Protocol Label Switching Label Distribution Protocol

Query Message Description

  1. - 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
  1. that the MPLS working group will take on no new Working Group

documents related to CR-LDP.

  1. that the MPLS working group will entertain no efforts to promote

CR-LDP beyond proposed standard.

  1. that individual contributions related to CR-LDP area are not

prohibited, but discouraged.

Andersson & Swallow Informational [Page 7] RFC 3468 Decision on MPLS Signaling Protocols February 2003

  1. 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:
  1. 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
  1. adopt as an IETF policy to refrain from entertaining work that

intends to progress RFC 3212 or related RFCs beyond proposed

       standard
  1. adopt as an IETF policy to refrain from entertaining new

working group documents that are extensions to RFC 3212

  1. review the IETF process with respect to management of documents

that needs to be moved from standards track to any other status

  1. 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.

Andersson & Swallow Informational [Page 8] RFC 3468 Decision on MPLS Signaling Protocols February 2003

 [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.

Andersson & Swallow Informational [Page 9] RFC 3468 Decision on MPLS Signaling Protocols February 2003

 [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

Andersson & Swallow Informational [Page 10] RFC 3468 Decision on MPLS Signaling Protocols February 2003

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.

Andersson & Swallow Informational [Page 11]

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