2.7.3 Multiprotocol Label Switching (mpls)

Last Modified: 2003-05-19

George Swallow <swallow@cisco.com>
Loa Andersson <loa@pi.se>
Sub-IP Area Director(s):
Bert Wijnen <bwijnen@lucent.com>
Alex Zinin <zinin@psg.com>
Sub-IP Area Advisor:
Alex Zinin <zinin@psg.com>
Mailing Lists:
General Discussion: mpls@uu.net
To Subscribe: mpls-request@uu.net
In Body: subscribe (unsubscribe)
Archive: http://cell.onecall.net/cell-relay/archives/mpls/mpls.index.html
Description of Working Group:
The MPLS working group has been responsible for standardizing a base
technology for using label switching and for the implementation of
label-switched paths over various link-level technologies, such as
Packet-over-Sonet, Frame Relay, ATM, and LAN technologies (e.g.  all
forms of Ethernet, Token Ring, etc.).  This includes procedures and
protocols for the distribution of labels between routers,
encapsulations and multicast considerations.

The initial goals of the working group have been largely completed. In
particular, it has produced a number of RFCs (see list below) that
define the base Label Distribution Protocol (LDP), the basic MPLS
architecture and encapsulations, and definitions for how MPLS runs over
ATM and Frame Relay links.

The Working Group chairs tracking of the working group documents can be
viewed at http://urax.utfors.net/~loa/MPLS_WG_Drafts.htm

The current goals of the working group are:

1. Complete outstanding items from the original MPLS effort:


    (6/12)  Applicability Statement for Extensions to RSVP for
    (8/08)  Applicability Statement for CR-LDP
    (6/12)  LDP State Machine


    (10/19/99)  MPLS Loop Prevention Mechanism

  Standards Track:

    (8/08)  Constraint-Based LSP Setup using LDP
    (2/07)  Carrying Label Information in BGP-4
    (8/29)  Extensions to RSVP for LSP Tunnels
    (8/29)  MPLS Support of Differentiated Services
    (6/27)  LSP Modification Using CR-LDP
    (9/01)  Definitions of Managed Objects for LDP
    (8/29)  MPLS Label Switch Router Management Information Base

2. Advance the Proposed Standards developed by the MPLS WG to Draft
  Standard.  This includes the LDP, CR-LDP, and RSVP-TE signaling
  specifications as well as the encapsulations.

3. Specify appropriate extensions to LDP and RSVP for authentication
  of LSP originators.

4. Complete work on the MPLS-TE MIB.

5. Specify improved fault tolerance mechanisms for LDP

6. Specify MPLS-specific recovery mechanisms to allow one
  path to be used as backup for a set of other label-switched paths,
  including cases which permit local repair. What constitutes the
  necessary set of MPLS-specific recovery mechanism should be
  ascertained through cooperation with the CCAMP and TE working

7. Document additional MPLS encapsulations to allow the operation of
  label-switched paths over additional lower-layer technologies, such
  as time-division (e.g. SONET ADMs), wavelength (optical lambdas)
  and spatial switching (e.g. incoming fiber to outgoing fiber).

8. Complete work in progress for specifying the framework for IP
  multicast over label switched paths.
Goals and Milestones:
Done  Submit documents from original MPLS effort to IESG
Jan 01  Shepherd completed MPLS specifications through IESG review and RFC editor processing
Feb 01  MPLS-TE MIB ready for advancement to Proposed Standard
Mar 01  Framework for IP multicast over label-switched paths ready for advancement.
Jun 01  LDP fault tolerance specification ready for advancement to Proposed Standard.
Aug 01  Specification for MPLS-specific recovery ready for advancement.
Nov 01  Base MPLS Proposed Standard RFCs ready for advancement to Draft Standard.
Dec 01  LDP end-to-end LSP authentication ready for advancement to Proposed Standard.
  • - draft-ietf-mpls-ldp-mib-13.txt
  • - draft-ietf-mpls-te-mib-12.txt
  • - draft-ietf-mpls-lsr-mib-12.txt
  • - draft-ietf-mpls-te-feed-06.txt
  • - draft-ietf-mpls-lsp-hierarchy-08.txt
  • - draft-ietf-mpls-ftn-mib-08.txt
  • - draft-ietf-mpls-lsp-query-09.txt
  • - draft-ietf-mpls-tc-mib-09.txt
  • - draft-ietf-mpls-bundle-04.txt
  • - draft-ietf-mpls-mgmt-overview-08.txt
  • - draft-ietf-mpls-bgp-mpls-restart-02.txt
  • - draft-ietf-mpls-rsvp-lsp-fastreroute-03.txt
  • - draft-ietf-mpls-lsp-ping-03.txt
  • - draft-ietf-mpls-fastreroute-mib-01.txt
  • - draft-ietf-mpls-ldp-mtu-extensions-01.txt
  • - draft-ietf-mpls-in-ip-or-gre-02.txt
  • - draft-ietf-mpls-ldp-restart-applic-01.txt
  • - draft-ietf-mpls-ldp-dod-restart-00.txt
  • - draft-ietf-mpls-nodeid-subobject-01.txt
  • - draft-ietf-mpls-oam-requirements-01.txt
  • - draft-ietf-mpls-soft-preemption-00.txt
  • - draft-ietf-mpls-telink-mib-03.txt
  • Request For Comments:
    Requirements for Traffic Engineering Over MPLS (RFC 2702) (68386 bytes)
    Multiprotocol Label Switching Architecture (RFC 3031) (147175 bytes)
    MPLS Label Stack Encoding (RFC 3032) (48314 bytes)
    Use of Label Switching on Frame Relay Networks Specification (RFC 3034) (53176 bytes)
    MPLS using LDP and ATM VC Switching (RFC 3035) (46463 bytes)
    LDP Specification (RFC 3036) (274855 bytes)
    LDP Applicability (RFC 3037) (13601 bytes)
    VCID Notification over ATM link for LDP (RFC 3038) (39134 bytes)
    The Assignment of the Information Field and Protocol Identifier in the Q.2941 Generic Identifier and Q.2957 User-to-user Signaling for the Internet Protocol (RFC 3033) (52188 bytes)
    MPLS Loop Prevention Mechanism (RFC 3063) (93523 bytes)
    Carrying Label Information in BGP-4 (RFC 3107) (16442 bytes)
    RSVP-TE: Extensions to RSVP for LSP Tunnels (RFC 3209) (132264 bytes)
    Applicability Statement for Extensions to RSVP for LSP-Tunnels (RFC 3210) (17691 bytes)
    Constraint-Based LSP Setup using LDP (RFC 3212) (87591 bytes)
    Applicability Statement for CR-LDP (RFC 3213) (14489 bytes)
    LSP Modification Using CR-LDP (RFC 3214) (25453 bytes)
    LDP State Machine (RFC 3215) (117278 bytes)
    MPLS Support of Differentiated Services (RFC 3270) (137960 bytes)
    Framework for IP Multicast in MPLS (RFC 3353) (65860 bytes)
    Time to Live (TTL) Processing in MPLS Networks (Updates RFC 3032) (RFC 3443) (18749 bytes)
    Signalling Unnumbered Links in Resource ReSerVation Protocol - Traffic Engineering (RSVP-TE) (RFC 3477) (19899 bytes)
    Framework for MPLS-based Recovery (RFC 3469) (89331 bytes)
    Graceful Restart Mechanism for Label Distribution Protocol (RFC 3478) (29248 bytes)
    Fault Tolerance for the Label Distribution Protocol (LDP) (RFC 3479) (115778 bytes)
    Signalling Unnumbered Links in CR-LDP (Constraint-Routing Label Distribution Protocol) (RFC 3480) (17076 bytes)

    Current Meeting Report

    MPLS WG, Tuesday July 15 at 9am
     Scribes / Dave Allan and Tove Madsen
     Agenda bashing
     - no comments
     - blue sheets
     - note takers
     ITU Liaison/Jun Kyun Choi
     Mobile IP over MPLS 11/13
       (see slides)
     - overview of features
     - scope and "out of scope"
     - reference architecture
     - service scenarios (tunneling, route optimization, binding update,
       hierarchical tunneling)
     - overview of other aspects
     - status in SG13 (consent in Geneva next week)
     Comment from George Swallow : on the status of progressing RSVP over CR-LDP.
     Clarification from George: on binding, we will have one solution.
     Monique Morrow: What considerations to OAM have you thought about?
     A: No inclusion of diagnostics in the document at this time.
     Rahual Aggarwal: Not clear to me what kind of feedback you are looking for.
     Not clear what has to be done here.
     A: Work to be done to bind mobile IP network to the MPLS network.
     George: Is there a specific item of work you are looking for, what kind of
     response? Is this informational?
     A: Mainly informational, this work is kept in the ITU. Would like to
     Alex: If you want collaboration, you should publish as one or more drafts
     and solicit feedback from the list.
     MIB Discussion
     Loa : Since Atlanta we've been driving the MIB authors quite hard. I'd like
     to thank those working hard on this. The work is late and this has been a
     source of frustration. We are not finished but are pretty close. Send for
     IESG review before end of summer.
     Bert: The most important thing is the discussion between the authors and the
     AD (acting as MIB doctor). Things needed fixing and there were items where
     the approach was questioned. Over the last few weeks we've had good
     discussion. Meeting all AD/doctor requirements are not completely necessary,
     WG consensus is key due to implementation experience etc.
     (see Tom Nadeau's slides).
     - general updates applied to all MIBs
     - overview of changes to individual MIBs
     Bert:  Adrian had a list of some 65 nits on the TE MIB and hasn't been able
     to check if all of these have been addressed. I've posted compile comments
     last night and this morning. Is the plan to recycle a few MIBs?
     Tom: I think we'll have to in a few cases. Some comments were too nitty.
     of the comments are adressed.
     Bert: Would like to see that signed off, chairs need to establish consensus.
     Loa: Consensus is problematic. There is a huge consensus in the room, on the
     list etc. to get this done now. Not ready to take the MIBs and send to the
     IESG. When Adrian/etc. etc satisfied that we've addressed the comments then
     I'd like to go. We're 99% ready, lets do the last little bit.
     Adrian: Looking to do a point by point review of the emails and finish them
     off this week.
     Tom: On setting a final deadline, a week, two weeks.
     Loa: Don't want shorter than required, what about two weeks? Lets set Aug 1
     as the deadline.
     Loa: FRR MIB not complete. Pretty much stable. Would like to do a last call
     coming out of this meeting.
     Tom: There are three implementations of the existing MIB. Have a look on
     before last call.
     Loa: You want to do a pass before last call.
     Tom: Probably a good idea.
     Adrian: Hold up the overview until the new MIBs done?
     Loa: Need a respin.
     Tom: Purpose was the base 5 MIBs.
     LDP Requirements/ Wai Sum Lai        draft-lai-mpls-mib-rqmts-00
     (see slides)
     focus on LDP MIBs,
     - pm requirements
     - fm requirements
     Information that would help them engineer resource usage etc. Help with
     trouble shooting. Get good linkages with I/F MIB.
     Propose meeting requirements be delegated to the MIB authors.
     Tom Nadeau: Bunch of points (already discussed on the list). Want to hear
     from other operators. IMHO requires protocol changes so needs consensus.
     Some points were added to current MIB. Vast majority not addressed in the
     absence of other operator feedback.
     Loa: These are going into mailing list and has no effect on current MIBs.
     we have to see imapct on future MIBs.
     Lots of impedance. (Mainly Kireeti, Rahul and Yakov). Centered around MPLS
     PID in general.
     Discussion points:
     - Is reserved labels and ECMP an issue (to be taken to the list)?
     - Is the PW PID applicable to MPLS?
     - Effect on whats out there now? (George Swallow)
     - Backward copatability? (Thomas Nadeau)
     - What processing power do I need? (G.Swallow)
     - Where are the changes suggested? In PWE3 or MPLS? (Loa)
     - Is IP ok? (G.Swallow) Yes (D. Allan)
     - Will rename the MPLS PID to PWE3 PID (Stewart Bryant)
     Dave to post a problem statement to the list for discussion.
     Draft-swallow-lsr-self-test-00/George Swallow
     George walked through the ECMP example of how it gets combinatorial.
     Outlined LSR self test as a means of an LSR instigating tests of its own
     forwarding table. An extension of LSP Ping.
     Adrian: Applicability to RSVP-TE (draft focuses on LDP)?
     G.Swallow: yes.
     Dave Allan: Concern with requirement to generate a ping transaction per ILM
     entry in each LSR.
     George: You're making assumptions as to the frequency.
     Dave: no.
     Jun Kyun Choi: end to end but no hierarchy?
     G.Swallow: Hop by Hop.
     Tom Nadeau: Recycles existing forwarding behavior. Already optimized on my
     Loa: Need to go on. Show of hands for making this a WG document. Sufficient
     interest to take this to the list.
     Multicast Seisho Yasukawa & Rahul Aggarwal
     Outline of deltas between IP multicast and expectations that can only be met
     with addition of QoS.
     Overview of joint requirements draft. A short history of this multicast work
     was presented.
     Establishing P2MP MPLS TE LSPs draft-raggarwa-mpls-p2mp-te-00
     Overview of the proposed mechanisms for setup of P2MP LSPs.
     - P2MP session object
     - Rpe discovery (application dependent)
     - Make before break...
     - Some FRR applicability
     Alex: IPR notification in the draft needs to be sent on to IETF secretary.
     "Other proposal" (Allan Kullberg)
     Draft summary presented
     Goal is to reconcile approaches, provide a common requirements and problem
     statement draft. Targeted for next IETF.
     Need WG to confirm inclusion in charter and determine next steps.
     Loa: Like the time schedule. Need a short problem statement and milestones
     to take to the IESG.
     Rahul: I'll send a mail to the mailing list.
     Loa: I'll add milestone to charter.
     Dimitri: Do you want to see the spectrum of solutions discussed?
     George: only want crisp requirements, not a framework document.
     RRO Node-ID Subobject; draft ietf mpls nodeid subobject/ JP Vasseur
     Quick overview.
     Ongoing implementations and several planned deployments, proposal to move
     the I-D to last call.
     George: take it to the list.
     Dimitri: Is it really necessary to use an RRO subobject
     flag to implement this feature since this i-d takes the use of the
     RRO subobject flag up to all but two bits used ?
     Draft vasseur-mpls-loose-path-reopt-02/JP Vasseur
     Conclusion, draft proposes mechanisms that are identified as required in the
     TEWG inter-AS requirements document.
     George: How to proceed simply needs a discussion between Alex, Kireeti
     and charis.
     LDP MTU Discovery/Kireeti
     - provided some new definitions (hop MTU)
     - egress MTU is broken
     - transit node decides what downstream MTU is.
     - Handling U/F when not supported.
     - Revise according to last round of comments, post to last call.
     Luca: Please make sure you agree on what MTU is. DO not want more arguments
     between Cisco and Juniper.
     Kireeti: Definition is in the draft. Needs to be compatible with RSVP.
     Please read the definition.
     I've also posted a new version of LSP PING, please comment, if we get no
     comments I'll go to last call. (George indicated some comments, short issues
     Draft-ietf-mpls-LSP-query-09/Dave Allan
     Overview of changes as a result of IESG review, including changes (query
     payload TLV) that necessitate a WG last call.
     George: We'll post it to the list.
     Alex: Implementation status?
     Dave: We've done some prototyping, but not of the new TLV.
     WG Status:/Loa
     We did a start of re-chartering the working group after Atlanta.
     Coincided with the discussion/decission on splitting the
     Sub-IP Area. Since the charter criteria are (marginally)
     different between areas it had to wait. Will restart the process
     Meeting concluded.


    None received.