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Network Working Group S. Bryant, Ed. Request for Comments: 5317 Cisco Systems Category: Informational L. Andersson, Ed.

                                                              Acreo AB
                                                         February 2009
                  Joint Working Team (JWT) Report
    on MPLS Architectural Considerations for a Transport Profile

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.

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 document authors.  All rights reserved.
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 Provisions Relating to IETF Documents (
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 This RFC archives the report of the IETF - ITU-T Joint Working Team
 (JWT) on the application of MPLS to transport networks.  The JWT
 recommended of Option 1: The IETF and the ITU-T jointly agree to work
 together and bring transport requirements into the IETF and extend
 IETF MPLS forwarding, OAM (Operations, Administration, and
 Management), survivability, network management and control plane
 protocols to meet those requirements through the IETF Standards
 Process.  This RFC is available in ASCII (which contains a summary of
 the slides) and in PDF (which contains the summary and a copy of the

Bryant & Andersson Informational [Page 1] RFC 5317 JWT MPLS-TP Report February 2009

Table of Contents

 1. Introduction ....................................................3
 2. Executive Summary ...............................................4
 3. Introduction and Background Material ............................6
 4. High-Level Architecture .........................................6
 5. OAM and Forwarding ..............................................6
 6. Control Plane ...................................................7
 7. Survivability ...................................................7
 8. Network Management ..............................................7
 9. Summary .........................................................7
 10. IANA Considerations ............................................8
 11. Security Considerations ........................................8
 12. The JWT Report .................................................8
 13. Informative References .........................................9

Bryant & Andersson Informational [Page 2] RFC 5317 JWT MPLS-TP Report February 2009

1. Introduction

 For a number of years, the ITU-T has been designing a connection-
 oriented packet switched technology to be used in Transport Networks.
 A Transport Network can be considered to be the network that provides
 wide area connectivity upon which other services, such as IP or the
 phone network, run.  The ITU-T chose to adapt the IETF's MPLS to this
 task, and introduced a protocol suite known as T-MPLS.
 Quite late in the ITU-T design and specification cycle, there were a
 number of liaison exchanges between the ITU-T and the IETF concerning
 this technology.  These liaisons can be found on the IETF Liaison
 Statement web page [LIAISON].  In addition, the chairs of the MPLS,
 PWE3, BFD, and CCAMP working groups as well as the Routing and
 Internet Area Directors attended a number of ITU-T meetings.  During
 this process, the IETF became increasingly concerned that the
 incompatibility of IETF MPLS and ITU-T T-MPLS would "represent a
 mutual danger to both the Internet and the Transport network".  These
 concerns led the chairs of the IESG and IAB to take the step of
 sending a liaison to the ITU-T, stating that either T-MPLS should
 become fully compliant MPLS protocol, standardized under the IETF
 process (the so-called "Option 1"), or it should become a completely
 disjoint protocol with a new name and completely new set of code
 points (the so-called "Option 2") [Ethertypes].
 Option 1 and Option 2 were discussed at an ITU-T meeting of Question
 12 Study Group 15 in Stuttgart [Stuttgart], where it was proposed
 that a Joint (ITU-T - IETF) Team should be formed to evaluate the
 issues, and make a recommendation to ITU-T management on the best way
 Following discussion between the management of the IETF and the
 ITU-T, a Joint Working Team (JWT) was established; this was supported
 by an IETF Design Team and an Ad Hoc Group on T-MPLS in the ITU-T
 [ahtmpls].  The first meeting of the Ad Hoc group occurred during the
 ITU-T Geneva Plenary in February 2008.  As a result of the work of
 the JWT and the resulting agreement on a way forward, the fears that
 a set of next-generation network transport specifications developed
 by ITU-T could cause interoperability problems were allayed.
 The JWT submitted their report to the ITU-T and IETF management in
 the form of a set of Power Point slides [MPLS-TP-22].  (See the PDF
 of this RFC.)  The ITU-T have accepted the JWT recommendations, as
 documented in [MPLS-TP].  This RFC archives the JWT report in a
 format that is accessible to the IETF.

Bryant & Andersson Informational [Page 3] RFC 5317 JWT MPLS-TP Report February 2009

 This RFC is available in ASCII (which contains a summary of the
 slides) and in PDF (which contains the summary and a copy of the
 slides).  In the case of a conflict between the summary and the
 slides, the slides take precedence.  Since those slides were the
 basis of an important agreement between the IETF and the ITU-T, it
 should further be noted that in the event that the PDF version of the
 slides differs from those emailed to ITU-T and IETF management on 18
 April 2008 by the co-chairs of the JWT, the emailed slides take

2. Executive Summary

 Slides 4 to 10 provide an executive summary of the JWT Report.  The
 following is a summary of those slides:
 The JWT achieved consensus on the recommendation of Option 1: to
 jointly agree to work together and bring transport requirements into
 the IETF and extend IETF MPLS forwarding, OAM, survivability, network
 management, and control plane protocols to meet those requirements
 through the IETF Standards Process.  The Joint Working Team believed
 that this would fulfill the mutual goals of improving the
 functionality of the transport networks and the Internet and
 guaranteeing complete interoperability and architectural soundness.
 This technology would be referred to as the Transport Profile for
 The JWT recommended that future work should focus on:
 In the IETF:
    Definition of the MPLS "Transport Profile" (MPLS-TP).
 In the ITU-T:
    Integration of MPLS-TP into the transport network,
    Alignment of the current T-MPLS ITU-T Recommendations with MPLS-TP
    Termination of the work on current T-MPLS.
 The technical feasibility analysis concluded there were no "show
 stopper" issues in the recommendation of Option 1 and that the IETF
 MPLS and Pseudowire architecture could be extended to support
 transport functional requirements.  Therefore, the team believed that
 there was no need for the analysis of any other option.

Bryant & Andersson Informational [Page 4] RFC 5317 JWT MPLS-TP Report February 2009

 The JWT proposed that the MPLS Interoperability Design Team (MEAD
 Team), JWT, and Ad Hoc T-MPLS groups continue as described in SG15
 TD515/PLEN [JWTcreation] with the following roles:
    Facilitate the rapid exchange of information between the IETF and
    Ensure that the work is progressing with a consistent set of
    Identify gaps/inconsistencies in the solutions under development,
    Propose solutions for consideration by the appropriate WG/
    Provide guidance when work on a topic is stalled or a technical
    decision must be mediated.
 None of these groups would have the authority to create or modify
 IETF RFCs or ITU-T Recommendations.  Any such work would be
 progressed via the normal process of the respective standards body.
 Direct participation in the work by experts from the IETF and ITU-T
 would be required.
 The JWT recommended that the normative definition of the MPLS-TP that
 supports the ITU-T transport network requirements be captured in IETF
 RFCs.  It proposed that the ITU-T should:
    Develop ITU-T Recommendations to allow MPLS-TP to be integrated
    with current transport equipment and networks, including in
    agreement with the IETF, the definition of any ITU-T-specific
    functionality within the MPLS-TP architecture via the MPLS change
    process [RFC4929],
    Revise existing ITU-T Recommendations to align with MPLS-TP,
    ITU-T Recommendations will make normative references to the
    appropriate RFCs.
 The executive summary contains a number of detailed JWT
 recommendations to both IETF and ITU-T management together with
 proposed document structure and timetable.
 These JWT recommendations were accepted by ITU-T management

Bryant & Andersson Informational [Page 5] RFC 5317 JWT MPLS-TP Report February 2009

3. Introduction and Background Material

 Slides 11 to 22 provide introductory and background material.
 The starting point of the analysis was to attempt to satisfy Option 1
 by showing the high-level architecture, any show stoppers, and the
 design points that would need to be addressed after the decision had
 been made to work together.  Option 1 was stated as preferred by the
 IETF and because Option 1 was shown to be feasible, Option 2 was not
 The work was segmented into five groups looking at: Forwarding, OAM,
 Protection, Control Plane, and Network Management.  The outcome of
 each review was reported in the following sections and is summarized
 There follows a detailed description of the overall requirements and
 architectural assumptions that would be used in the remainder of the

4. High-Level Architecture

 Slides 23 to 28 provide a high-level architectural view of the
 proposed design.
 The spectrum of services that the MPLS-TP needs to address and the
 wider MPLS context is described, together with the provisioning
 issues.  Some basic terminology needed in order to understand the
 MPLS-TP is defined and some context examples are provided.

5. OAM and Forwarding

 Slides 29 to 32 describe the OAM requirements and talk about segment
 recovery and node identification.
 Slides 33 to 38 introduce OAM hierarchy and describe Label Switched
 Path (LSP) monitoring, the Maintenance End Point (MEP) and
 Maintenance Intermediate Point (MIP) relationship and the LSP and
 pseudowire (PW) monitoring relationship.
 Sides 39 to 46 introduce the Associated Channel Header (ACH) and its
 generalization to carry the OAM over LSPs through the use of the
 "Label for You" (LFU).

Bryant & Andersson Informational [Page 6] RFC 5317 JWT MPLS-TP Report February 2009

 Slides 47 to 48 provide a description of how the forwarding and the
 ACH OAM mechanism work in detail.  A significant number of scenarios
 are described to work through the operation on a case-by-case basis.
 These slides introduce a new textual notation to simplify the
 description of complex MPLS stacks.
 Note that the MPLS forwarding, as specified by IETF RFCs, requires no
 changes to support MPLS-TP.

6. Control Plane

 Sides 79 to 83 discuss various aspects of the control plane design.
 Control plane sub-team stated that existing IETF protocols can be
 used to provide required functions for transport network operation
 and for data-communications-network/switched-circuit-network
 operation.  IETF GMPLS protocols have already applied to Automatic
 Switched Optical Network (ASON) architecture, and the JWT considered
 that any protocol extensions needed will be easy to make.  The slides
 provide a number of scenarios to demonstrate this conclusion.

7. Survivability

 The survivability considerations are provided in slides 95 to 104.
 The survivability sub-team did not find any issues that prevented the
 creation of an MPLS-TP, and therefore recommended that Option 1 be
 selected.  Three potential solutions were identified.  Each solution
 has different attributes and advantages, and it was thought that
 further work in the design phase should eliminate one or more of
 these options and/or provide an applicability statement.
 After some clarifications and discussion, there follow in the slide
 set a number of linear and ring protection scenarios with examples of
 how they might be addressed.

8. Network Management

 Slide 106 states the conclusion of the Network Management sub-team :
 that it found no issues that prevent the creation of an MPLS-TP and
 hence Option 1 can be selected.

9. Summary

 Slide 113 provides a summary of the JWT report.

Bryant & Andersson Informational [Page 7] RFC 5317 JWT MPLS-TP Report February 2009

 The JWT found no show stoppers and unanimously agreed that they had
 identified a viable solution.  They therefore recommend Option 1.
 They stated that in their view, it is technically feasible that the
 existing MPLS architecture can be extended to meet the requirements
 of a Transport profile, and that the architecture allows for a single
 OAM technology for LSPs, PWs, and a deeply nested network.  From
 probing various ITU-T Study Groups and IETF Working Groups it appears
 that MPLS reserved label 14 has had wide enough implementation and
 deployment that the solution may have to use a different reserved
 label (e.g., Label 13).  The JWT recommended that extensions to Label
 14 should cease.
 The JWT further recommended that this architecture appeared to
 subsume Y.1711, since the requirements can be met by the mechanism
 proposed in their report.

10. IANA Considerations

 There are no IANA considerations that arise from this document.
 Any IANA allocations needed to implement the JWT recommendation will
 be requested in the Standards-Track RFCs that define the MPLS-TP

11. Security Considerations

 The only security consideration that arises as a result of this
 document is the need to ensure that this is a faithful representation
 of the JWT report.
 The protocol work that arises from this agreement will have technical
 security requirements that will be identified in the RFCs that define

12. The JWT Report

 In the PDF of this RFC, there follows the JWT report as a set of

Bryant & Andersson Informational [Page 8] RFC 5317 JWT MPLS-TP Report February 2009

13. Informative References

 [Ethertypes]   IESG and IAB, "T-MPLS use of the MPLS Ethertypes",
                2006, <
 [JWTcreation]  Chairman, ITU-T SG 15, "Proposal to establish an Ad
                Hoc group on T-MPLS", 2008, <
 [LIAISON]      Liaison statements to and from the IETF can be found
                at: <>.
 [MPLS-TP]      "IETF and ITU-T cooperation on extensions to MPLS for
                transport network functionality", May 2008,
 [MPLS-TP-22]   IETF - ITU-T Joint Working Team, "MPLS Architectural
                Considerations for a Transport Profile", April 2008,
 [MPLS-TP1]     "IETF and ITU-T cooperation on extensions to MPLS for
                transport network functionality", ITU-T SG15,
                May 2008, <
 [RFC4929]      Andersson, L. and A. Farrel, "Change Process for
                Multiprotocol Label Switching (MPLS) and Generalized
                MPLS (GMPLS) Protocols and Procedures", BCP 129,
                RFC 4929, June 2007.
 [Stuttgart]    IETF - IESG and IAB Chairs, "Report of interim meeting
                of Q.12 on T-MPLS", Stuttgart, Germany, Annex 4, 12-14
                September 2007, 2008, <
                T-MPLS/wdt03_rapporteur_report-final.doc>.  This
                document is available on request from the ITU-T.
 [ahtmpls]      "Ad Hoc group on T-MPLS", 2008, <

Bryant & Andersson Informational [Page 9] RFC 5317 JWT MPLS-TP Report February 2009

Editors' Addresses

 Stewart Bryant (editor)
 Cisco Systems
 250, Longwater, Green Park,
 Reading  RG2 6GB
 Loa Andersson (editor)
 Acreo AB
 Isafjordsgatan 22

Bryant & Andersson Informational [Page 10]

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