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Versions: 00 01 02 03 04 draft-ietf-ccamp-gmpls-vcat-lcas

CCAMP Working Group                                        G. Bernstein
Internet Draft                                        Grotto Networking
Updates: RFC 3946                                           D. Caviglia
Category: Standards Track                                      Ericsson
Expires: February 2007                                  R. Rabbat (ed.)
                                                         H. van Helvoort
                                                         August 4, 2006

       Operating Virtual Concatenation (VCAT) and the Link Capacity
      Adjustment Scheme (LCAS) with Generalized Multi-Protocol Label
                             Switching (GMPLS)

Status of this Memo

   By submitting this Internet-Draft, each author represents that
   any applicable patent or other IPR claims of which he or she is
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   This Internet-Draft will expire on February 4, 2007.


   This document describes requirements for, and use of, the Generalized
   Multi-Protocol Label Switching (GMPLS) control plane in conjunction

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   with the Virtual Concatenation (VCAT) layer 1 inverse multiplexing
   mechanism and its companion Link Capacity Adjustment Scheme (LCAS)
   which can be used for hitless dynamic resizing of the inverse
   multiplex group.  These techniques apply to the Optical Transport
   Network (OTN), Synchronous Optical Network (SONET), Synchronous
   Digital Hierarchy (SDH), and Plesiochronous Digital Hierarchy (PDH)

Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC-2119 [RFC2119].

Table of Contents

   1. Introduction...................................................3
   2. Changes from draft-bernstein-ccamp-gmpls-vcat-lcas-03..........3
   3. VCAT/LCAS Scenarios and Specific Requirements..................3
      3.1. Multiple VCAT Groups per GMPLS Endpoint...................3
      3.2. Component Signal Configuration Requirements...............4
      3.3. VCAT Operation With or Without LCAS.......................4
   4. GMPLS Mechanisms for Signaling VCAT/LCAS.......................4
      4.1. Co-Routed Signals.........................................5
         4.1.1. One-shot Setup of Co-Routed Signal...................5
         4.1.2. Incremental Setup of Co-Routed Signal................5
         4.1.3. Removing a Component Signal..........................6
         4.1.4. Removing Multiple Component Signals in One Shot......6
         4.1.5. Use of multiple LSPs for Co-Routed Signals...........7
         4.1.6. Teardown of Whole VCG................................7
      4.2. Diversely Routed Signals..................................7
         4.2.1. Associating Diversely Routed Signals.................7
         4.2.2. Procedures for VCG Setup Using Diversely Routed
         4.2.3. Procedures for VCG Reduction/Teardown Using Diversely
         Routed Components...........................................9
         4.2.4. Update of Already Established LSPs...................9
         4.2.5. One LSP per Circuit..................................9
   5. IANA Considerations...........................................10
   6. Security Considerations.......................................10
   7. Contributors..................................................11
   8. Acknowledgments...............................................11
   9. References....................................................12
      9.1. Normative References.....................................12
      9.2. Informative References...................................12
   Author's Addresses...............................................13

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   Intellectual Property Statement..................................14
   Disclaimer of Validity...........................................14
   Copyright Statement..............................................14

1. Introduction

   The Generalized Multi-Protocol Label Switching (GMPLS) suite of
   protocols allows the automated control of different switching
   technologies including SONET/SDH.

   This document describes extensions to RSVP-TE to support the Virtual
   Concatenation (VCAT) layer 1 inverse multiplexing mechanism and its
   companion Link Capacity Adjustment Scheme (LCAS).  These extensions
   enable the setup of diversely routed circuits that are members of the
   same VCAT group.

2. Changes from draft-bernstein-ccamp-gmpls-vcat-lcas-03

   o  Dropped appendices

   o  Updated references

   o  Fixed error w/r to sessions. The LSPs belong to different sessions

   o  Many editorial changes throughout the document

   o  Rewrote the introduction

3. VCAT/LCAS Scenarios and Specific Requirements

   There are a number of specific requirements for the support of
   VCAT/LCAS in GMPLS that can be derived from the carriers'
   application-specific demands for the use of VCAT/LCAS and from the
   flexible nature of VCAT/LCAS.  These are set out in the following

3.1. Multiple VCAT Groups per GMPLS Endpoint

   In general, an LSR can be ingress/egress of one or more VCAT groups.
   VCAT and LCAS are interface capabilities.  An LSR may have, for
   example, VCAT-capable interfaces that are not LCAS-capable.  It may
   at the same time have interfaces that are neither VCAT nor LCAS-

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3.2. Component Signal Configuration Requirements

   We list in this section the different scenarios that SHOULD be
   supported.  Here we use the term "VCG" to refer to the entire VCAT
   group and the terminology "set" and "subset" to refer to the
   collection of potential VCAT group member signals.

   o  Fixed, co-routed: A fixed bandwidth VCG, transported over a co-
      routed set of member signals.  This is the case where the intended
      bandwidth of the VCG does not change and all member signals follow
      the same route and minimize differential delay.  The intent here
      is the capability to allocate an amount of bandwidth close to that
      required at the client layer.

   o  Fixed, diversely routed: A fixed bandwidth VCG, transported over
      at least two diversely routed subsets of member signals.  In this
      case, the subsets are link-disjoint over at least one link of the
      route.  The intent here is more efficient use of network resources
      (no unique route has the required bandwidth), and additional
      resilience and graceful degradation in the case of failure (note
      that differential delay may be a limiting factor).

   o  Dynamic, co-routed: A dynamic VCG (bandwidth can be increased or
      decreased via the addition or removal of member signals),
      transported over a co-routed set of members.  Intent here is
      dynamic sizing of bandwidth.

   o  Dynamic, diversely routed: A dynamic VCAT group, transported over
      at least two diversely routed subsets of member signals.  The
      intent here is dynamic resizing and resilience (but differential
      delay may be a limiting factor).

3.3. VCAT Operation With or Without LCAS

   VCAT capabilities may be present with or without the presence of
   LCAS.  The use of LCAS is beneficial to the provision of services,
   but in the absence of LCAS, VCAT is still a valid technique.
   Therefore GMPLS mechanisms for the operation of VCAT are REQUIRED for
   both the case where LCAS is available and the case where it is not
   available.  The GMPLS procedures for the two cases SHOULD be

4. GMPLS Mechanisms for Signaling VCAT/LCAS

   We describe in this section the signaling mechanisms that already
   exist in GMPLS using RSVP-TE [RFC3473] and the extensions needed, for
   diversely routed paths and in support of the LCAS procedure.

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   Section 4.1 is included for informational purposes only.  It
   describes existing procedures and makes no changes.

   Section 4.2 describes new procedures to support diversely routed VCAT
   groups.  Where possible it reuses applicable existing procedures from
   section 4.1.

4.1. Co-Routed Signals

   Note that this section is for informational purposes only.

   The existing signaling protocols support co-routed signal setup using
   the NVC field as explained in section 2.1 of [RFC3946bis].  In this
   case, one single LSP is set up in support of the VCAT group.

   There are two options for setting up the VCAT group, depending on
   hardware capability, or management preferences: one-shot setup and
   incremental setup.

   The following sections explain the procedure based on an example of
   setting up a VC4-7v SDH VCAT group (corresponding to an STS-3c-7v
   SONET VCAT group).

4.1.1. One-shot Setup of Co-Routed Signal

   An RSVP-TE Path message is used with the following parameters.

   With regards to the traffic parameters, the elementary signal is
   chosen (6 for VC-4/STS-3c_SPE).  The value of NVC is then set to 7.

   A Multiplier Transform greater than 1 (say N>1) is used if the
   operator wants to set up N VCAT groups that will belong to, and be
   assigned to, one LSP.

   SDH or SONET labels in turn have to be assigned for each member of
   the VCG and concatenated to form a single Generalized Label
   constructed as an ordered list of 32-bit timeslot identifiers of the
   same format as TDM labels.  [RFC3946bis] requires that the order of
   the labels reflect the order of the payloads to concatenate, and not
   the physical order of time-slots.

4.1.2. Incremental Setup of Co-Routed Signal

   In some cases, it may be necessary or desirable to set up the VCG
   members individually, or to add group members to an existing group.

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   One example of this need is when the hardware that supports VCAT can
   only add VCAT elements one at a time or cannot automatically match
   the elements at the ingress and egress for the purposes of inverse
   multiplexing.  Serial or incremental setup solves this problem.

   In order to accomplish incremental setup an iterative process is used
   to add group members.  For each iteration, NVC is incremented up to
   the final value required.  The iteration consists of the successful
   completion of Path and Resv signaling.  At first, NVC = 1 and the
   label includes just one timeslot identifier

   At each of the next iterations, NVC is set to (NVC +1), one more
   timeslot identifier is added to the ordered list in the Generalized
   Label (in the Path or Resv message).  A node that receives a Path
   message that contains changed fields will process the full Path
   message and, based on the new value of NVC, it will add a component
   signal to the VCAT group, and switch the new timeslot based on the
   new label information.

   Following the addition of the new label to the LSP, LCAS may be used
   in-band to add the new label into the existing VCAT group.  LCAS
   signaling for this function is described in [ITU-T-G.7042].

4.1.3. Removing a Component Signal

   The procedure to remove a component signal is similar to that used to
   add components as described in Section 4.1.2.  The LCAS in-band
   signaling step is taken first to take the component out of the group.
   LCAS signaling is described in [ITU-T-G.7042].

   In this case, the NVC value is decremented by 1 and the timeslot
   identifier for the dropped component is removed from the ordered list
   in the Generalized Label.  This function is not supported without
   management intervention for VCAT-only interfaces as removing one
   component of the VCG will result in errors in the inverse-
   multiplexing procedure of VCAT and result in the teardown of the
   whole group.  So, this is a feature that only LCAS-capable VCAT
   interfaces can support without management intervention at the end

4.1.4. Removing Multiple Component Signals in One Shot

   The procedure is similar to 4.1.3.  In this case, the NVC value is
   changed to the new value and all relevant timeslot identifiers for
   the components to be torn down are removed from the ordered list in
   the Generalized Label.  This is also not supported for VCAT-only
   interfaces without management intervention as removing one component

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   of the VCG will tear down the whole group, but the use of LCAS can
   facilitate this procedure.

4.1.5. Use of multiple LSPs for Co-Routed Signals

   Co-routed signals may also be supported by distinct LSPs signaled
   separately using exactly the techniques described for diversely
   routed signals in Section 4.2.

4.1.6. Teardown of Whole VCG

   The entire LSP is deleted in a single step (i.e., all components are
   removed in one go) using deletion procedures of [RFC3473].

4.2. Diversely Routed Signals

   The initial GMPLS specification did not support diversely routed
   signals using the NVC construct.  In fact, [RFC3946bis] says:

         [...] The standard definition for virtual concatenation allows
         each virtual concatenation components to travel over diverse
         paths.  Within GMPLS, virtual concatenation components must
         travel over the same (component) link if they are part of the
         same LSP.  This is due to the way that labels are bound to a
         (component) link.  Note however, that the routing of components
         on different paths is indeed equivalent to establishing
         different LSPs, each one having its own route.  Several LSPs
         can be initiated and terminated between the same nodes and
         their corresponding components can then be associated together
         (i.e., virtually concatenated).

   Diverse routing of signals can be a useful capability but requires
   the extensions identified in this document.

4.2.1. Associating Diversely Routed Signals

   The feature that needs to be added is the functionality to associate
   the components of the same VCG.  For this purpose, we use the
   Association Object that was defined in [E2E-RECOVERY] to associate
   working and recovery LSPs.

   A diversely routed VCG uses a number of routes R <= VCG size, as some
   routes may be the same for several components.  A number of LSPs, L
   (VCG >= L >= R) are used with each LSP establishing at least one
   component of the VCG, and at most all of the co-routed members of the
   group.  For a set of c components using the same route, we set up the
   LSP with NVC = c exactly as explained in section 4.1.1.  Therefore,

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   the association of group members or of sub-groups to form the VCG
   requires the association of the LSPs used to establish the group

   To be able to distinguish the LSPs in the VCG each must have a unique
   identifier. LSPs are identified by the combination of Session and
   Sender Template fields.  It is common practice when make-before-break
   [RFC3209] is supported to allow LSPs with the same Session, but
   different Sender Templates (specifically with different LSP IDs) to
   share resources.  Since resource sharing between VCG members must not
   be allowed (because we want each LSP to contribute capacity to the
   VCG), but since we want to continue to support make-before-break for
   each group member, it is necessary to distinguish the LSPs in the VCG
   by varying the fields in the Session object.  Specifically, a
   different Tunnel ID is used to identify each LSP in the VCG.

   Thus, VCG members cannot be associated through the Session object,
   and the Association object is used instead.

   The assignment of the Association ID is outside the scope of GMPLS
   but MUST be unique for each VCAT group.

   Note that the use of the Association object to associate members of a
   VCG does not preclude the use of another instance of the object with
   a different Association ID to indicate the association of working and
   recovery LSPs, as [E2E-RECOVERY] allows the use of multiple
   Association objects.  We differentiate between the Association
   objects used for the VCAT group and other Association objects through
   the definition of a new association type to indicate that this is a
   VCG association.

   Association Type: 16 bits

               Value       Type
               -----       ----

                 3         VCAT group

   See [E2E-RECOVERY] for the definition of other fields and values of
   the Association object.

4.2.2. Procedures for VCG Setup Using Diversely Routed Components

   For every route R, use the procedure outlined in section 4.1.1 or
   4.1.2 depending on the capability of the equipment or local policy.
   The Path message MUST include the Association object with type set to
   3, and each Path message MUST use the same Association ID.

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   Following the addition of each new LSP (i.e., once the RESV message
   has been received by the ingress LSR), LCAS signaling is used in-band
   to hitlessly add the new label into the existing group [ITU-T-

4.2.3. Procedures for VCG Reduction/Teardown Using Diversely Routed

   To remove the component circuits on any route, LCAS signaling is used
   in-band to remove the labels associated with the LSP from the group.
   LCAS signaling is defined in [ITU-T-G.7042].

   In addition, the procedures outlined in section 4.1.3 or 4.1.4 are
   used to tear down the unwanted LSP.

   Again, this can only be done on LCAS-capable interfaces.  If the
   procedure is attempted on VCAT-only interfaces, then the whole VCG is
   torn down (this is not a graceful teardown so ingress/egress initiate
   a Path Tear/Resv Tear) on all routes.

4.2.4. Update of Already Established LSPs

   Established co-routed VCAT groups currently do not support the
   Association object.  If a co-routed VCAT Group size is to be
   increased with new diversely routed members, we use the LSP
   modification procedure described in [RFC2205].  An Association object
   is added to the Path message for the existing LSP(s).  That
   Association object can then be used to set up new diversely routed
   group members.

   The same applies to SONET/SDH LSPs.  An operator may decide to use an
   already cross-connected SONET/SDH LSP for diversely-routed VCAT.  In
   this case the modification procedure described in [RFC2205] is used
   as well.

4.2.5. One LSP per Circuit

   These procedures can support the use of as many LSPs as there are
   circuits in the VCG.  This can be done when each circuit is
   separately routed, or when some of the circuits are co-routed, and
   each LSP will be used to set up one element of the VCG.  The
   Association object is used to indicate the VCG association.

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5. IANA Considerations

   This document requests from IANA the assignment of a new Association
   Type within the Association object.  This object was defined in [E2E-

   The value 3 "VCAT group" is suggested in section 4.2.1.

6. Security Considerations

   This document introduces a new use of the Association object for
   GMPLS signaling [RFC3473] to associate diversely routed VCAT group
   members.  It does not introduce any new signaling messages, nor
   change the relationship between LSRs that are adjacent in the control
   plane.  This association information in the event of an interception
   may indicate that there are members of the same VCAT group that take
   a different route and may indicate to an interceptor that the network
   may be more robust.

   Otherwise, this document does not introduce any additional security

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7. Contributors

   Wataru Imajuku (NTT)
   1-1 Hikari-no-oka Yokosuka Kanagawa 239-0847

   Phone +81-46-859-4315
   Email: imajuku.wataru@lab.ntt.co.jp

   Julien Meuric
   France Telecom
   2, avenue Pierre Marzin
   22307 Lannion Cedex

   Phone: + 33 2 96 05 28 28
   Email: julien.meuric@orange-ft.com

   Lyndon Ong
   PO Box 308
   Cupertino, CA 95015
   United States of America

   Phone: +1 408 705 2978
   Email: lyong@ciena.com

8. Acknowledgments

   The authors would like to thank Maarten Vissers and Adrian Farrel for
   extensive reviews and contributions to this draft.

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9. References

9.1. Normative References

   [RFC2119]      Bradner, S., "Key words for use in RFCs to Indicate
                  Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2205]      Braden, R., Zhang, L., Berson, S., Herzog, S. and S.
                  Jamin, "Resource ReSerVation Protocol (RSVP) --
                  Version 1, Functional Specification", RFC 2205,
                  September 1997.

   [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.

   [RFC3473]      Berger, L., "Generalized Multi-Protocol Label
                  Switching (GMPLS) Signaling Resource ReserVation
                  Protocol-Traffic Engineering (RSVP-TE) Extensions",
                  RFC 3473, January 2003.

   [RFC3946bis]   Mannie, E. and D. Papadimitriou, "Generalized Multi-
                  Protocol Label Switching (GMPLS) Extensions for
                  Synchronous Optical Network (SONET) and Synchronous
                  Digital Hierarchy (SDH) Control", IETF draft, work in
                  progress, December 2005.

   [E2E-RECOVERY] Lang, J.P., Rekhter, Y., and D. Papadimitriou (eds.),
                  "RSVP-TE Extensions in support of End-to-End
                  Generalized Multi-Protocol Label Switching (GMPLS)-
                  based Recovery", IETF draft, work in progress, April

9.2. Informative References

   [ANSI-T1.105]  American National Standards Institute, "Synchronous
                  Optical Network (SONET) - Basic Description including
                  Multiplex Structure, Rates, and Formats", ANSI T1.105-
                  2001, May 2001.

   [ITU-T-G.7042] International Telecommunications Union, "Link Capacity
                  Adjustment Scheme (LCAS) for Virtual Concatenated
                  Signals", ITU-T Recommendation G.7042, February 2004.

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   [ITU-T-G.7043] International Telecommunications Union, "Virtual
                  Concatenation of Plesiochronous Digital Hierarchy
                  (PDH) Signals", ITU-T Recommendation G.7043, July

   [ITU-T-G.707]  International Telecommunications Union, "Network Node
                  Interface for the Synchronous Digital Hierarchy
                  (SDH)", ITU-T Recommendation G.707, December 2003.

   [ITU-T-G.709]  International Telecommunications Union, "Interfaces
                  for the Optical Transport Network (OTN)", ITU-T
                  Recommendation G.709, March 2003.

Author's Addresses

   Greg Bernstein
   Grotto Networking

   Phone: +1-510-573-2237
   Email: gregb@grotto-networking.com

   Diego Caviglia
   Via A. Negrone 1/A 16153
   Genoa Italy

   Phone: +39 010 600 3736
   Email: diego.caviglia@(marconi.com, ericsson.com)

   Richard Rabbat
   Fujitsu Laboratories of America
   1240 East Arques Ave, MS 345
   Sunnyvale, CA 94085
   United States of America

   Phone: +1 408-530-4537
   Email: richard@us.fujitsu.com

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   Huub van Helvoort
   Huawei Technologies, Ltd.
   Kolkgriend 38, 1356 BC Almere
   The Netherlands

   Phone:   +31 36 5315076
   Email:   hhelvoort@huawei.com

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Copyright Statement

   Copyright (C) The Internet Society (2006).

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   This document is subject to the rights, licenses and restrictions
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