CCAMP Working Group                                  G. Bernstein (ed.)
Internet Draft                                        Grotto Networking
Updates: RFC 3946                                           D. Caviglia
Category: Standards Track                                      Ericsson
Expires: September 2007                                       R. Rabbat
                                                                 Google
                                                        H. van Helvoort
                                                                 Huawei
                                                         March 30, 2007



       Operating Virtual Concatenation (VCAT) and the Link Capacity
      Adjustment Scheme (LCAS) with Generalized Multi-Protocol Label
                             Switching (GMPLS)
                  draft-ietf-ccamp-gmpls-vcat-lcas-02.txt


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Abstract

   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)
   signals.

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 RFC-2119 [RFC2119].

Table of Contents


   1. Introduction...................................................3
   2. Revision History...............................................3
      2.1. Changes from draft-ieft-ccamp-gmpls-vcat-lcas-01..........3
      2.2. Changes from draft-ietf-ccamp-gmpls-vcat-lcas-00..........4
   3. VCAT/LCAS Scenarios and Specific Requirements..................4
      3.1. VCAT/LCAS Interface Capabilities..........................4
      3.2. Member Signal Configuration Scenarios.....................4
      3.3. VCAT Operation With or Without LCAS.......................5
   4. GMPLS Mechanisms in Support of VCGs............................6
      4.1. VCGs Composed of a Single Co-Signaled Member Set..........7
         4.1.1. One-shot VCG Setup with Co-Signaled Members..........7
         4.1.2. Incremental VCG Setup with Co-Signaled Members.......7
         4.1.3. Procedure for VCG Reduction by Removing a Member.....8
         4.1.4. Removing Multiple VCG Members in One Shot............8
         4.1.5. Teardown of Whole VCG................................9
      4.2. VCGs Composed of Multiple Co-Signaled Member Sets.........9
         4.2.1. Signaled VCG Layer Information.......................9
         4.2.2. Procedures for VCG Control with Multiple Co-signaled
         Member Sets................................................10
      4.3. Member Sharing -- Multiple VCGs per Call.................11
   5. IANA Considerations...........................................12
   6. Security Considerations.......................................12
   7. Contributors..................................................13
   8. Acknowledgments...............................................13
   9. References....................................................14
      9.1. Normative References.....................................14
      9.2. Informative References...................................14
   Author's Addresses...............................................15
   Intellectual Property Statement..................................15
   Disclaimer of Validity...........................................16


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   Copyright Statement..............................................16
   Acknowledgment...................................................16

1. Introduction

   The Generalized Multi-Protocol Label Switching (GMPLS) suite of
   protocols allows the automated control of different switching
   technologies including SONET/SDH and OTN. This document describes
   extensions to RSVP-TE to support the Virtual Concatenation (VCAT)
   layer 1 inverse multiplexing mechanism that has been standardized for
   SONET, SDH, OTN and PDH technologies along with its companion Link
   Capacity Adjustment Scheme (LCAS).

   VCAT is a TDM oriented byte striping inverse multiplexing method that
   works with a wide range of existing and emerging TDM framed signals,
   including very high bit rate OTN and SDH/SONET signals. Other than
   member signal skew compensation layer 1 inverse multiplexing
   mechanism add minimal additional signal delay. VCAT permits the
   selection of an optimal signals size, extracting bandwidth from mesh
   networks and when combined with LCAS hitless dynamic resizing of
   bandwidth and fast graceful degradation in the presence of network
   faults. To take full advantage of VCAT/LCAS functionality extensions
   to GMPLS signaling are given that enable the setup of diversely
   routed circuits that are members of the same VCAT group.

2. Revision History

2.1. Changes from draft-ieft-ccamp-gmpls-vcat-lcas-01

   o  Changed section 3.1 from "Multiple VCAT Groups per GMPLS endpoint"
      to "Multiple VCAT Groups per Interface" to improve clarity.

   o  Changed terminology from "component" signal to "member" signal
      where possible (not quoted text) to avoid confusion with link
      bundle components.

   o  Added "Dynamic, member sharing" scenario.

   o  Clarified requirements with respect to scenarios and the LCAS and
      non-LCAS cases.

   o  Added text describing needed signaling information between the
      VCAT endpoints to support required scenarios.

   o  Added text to describe: co-signaled, co-routed, data plane LSP,
      control plane LSP and their relationship to the VCAT/LCAS
      application.


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   o  Change implementation mechanism from one based on the Association
      object to one based on "Call concepts" utilizing the Notify
      message.

2.2. Changes from draft-ietf-ccamp-gmpls-vcat-lcas-00

   o  Updated reference from RFC3946bis to issued RFC4606

   o  Updated section 3.2 based on discussions on the mailing list

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
   section.



3.1. VCAT/LCAS Interface Capabilities

   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-
   capable.

3.2. Member Signal Configuration Scenarios

   We list in this section the different scenarios.  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).


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   o  Fixed, member sharing: A fixed bandwidth VCG, transported over a
      set of member signals that are allocated from a common pool of
      available member signals without requiring member connection
      teardown and setup.

   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.  The intent here is
      dynamic resizing and resilience of bandwidth.

   o  Dynamic, diversely routed: A dynamic VCG (bandwidth can be
      increased or decreased via the addition or removal of member
      signals), transported over at least two diversely routed subsets
      of member signals.  The intent here is efficient use of network
      resources, dynamic resizing and resilience of bandwidth.

   o  Dynamic, member sharing: A dynamic bandwidth VCG, transported over
      a set of member signals that are allocated from a common pool of
      available member signals without requiring member connection
      teardown and setup.

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
   identical.

   o  GMPLS signaling for LCAS-capable interfaces MUST support all
      scenarios of section 3.2. with no loss of traffic.

   o  GMPLS signaling for non-LCAS-capable interfaces MUST support only
      the "fixed" scenarios of section 3.2.

   To provide for these requirements GMPLS signaling MUST carry the
   following information on behalf of the VCAT endpoints:

   o  The type of the member signal that the VCG will contain, e.g., VC-
      3, VC-4, etc.







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   o  The total number of member to be in the VCG. This provides the
      endpoints in both the LCAS and non-LCAS case with information on
      which to accept or reject the request, and in the non-LCAS case
      will let the receiving endpoint know when all members of the VCG
      have been established.

   o  Identification of the VCG and its associated members. This
      provides information that allows the endpoints to differentiate
      multiple VCGs and to tell what members (LSPs) to associate with a
      particular VCG.

4. GMPLS Mechanisms in Support of VCGs

   We describe in this section the signaling mechanisms that already
   exist in GMPLS using RSVP-TE [RFC3473] and the extensions needed to
   completely support the requirements of section 3.

   When utilizing GMPLS with VCAT/LCAS we utilize a number of control
   and data plane concepts that we describe below.

  1. VCG member -- This is an individual data plane signal of one of the
     permitted SDH, SONET, OTN or PDH signal types.

  2. Co-signaled member set -- One or more VCG members (or potential
     members) set up via the same control plane signaling exchange. Note
     that all members in a co-signaled set follow the same route.

  3. Co-routed member set - One or more VCG members that follow the same
     route. Although VCG members may follow the same path, this does not
     imply that they we co-signaled.

  4. Data plane LSP -- for our purposes here this is equivalent to an
     individual VCG member.

  5. Control plane LSP -- A control plane entity that can control
     multiple data plane LSPs. For our purposes here this is equivalent
     to our co-signaled member set.


   Section 4.1 is included for informational purposes only.  It
   describes existing GMPLS procedures that support a single VCG
   composed of a single co-signaled member set.

   Section 4.2 describes new procedures to support VCGs composed of more
   that one co-signaled member sets. This includes the important
   application of a VCG composed of diversely routed members.  Where
   possible it reuses applicable existing procedures from section 4.1.


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4.1. VCGs Composed of a Single Co-Signaled Member Set

   Note that this section is for informational purposes only.

   The existing signaling GMPLS signaling protocols support a VCG
   composed of a single co-signaled member set. Setup using the NVC
   field as explained in section 2.1 of [RFC4606].  In this case, one
   single control plane LSP is used in support of the VCG.

   There are two options for setting up the VCG, 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 VC-4-7v SDH VCAT group (corresponding to an STS-3c-7v
   SONET VCAT group).

4.1.1. One-shot VCG Setup with Co-Signaled Members

   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.  [RFC4606] 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 VCG Setup with Co-Signaled Members

   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.

   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


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   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. Procedure for VCG Reduction by Removing a Member

   A VCG member can be permanently removed from the VCG either as the
   result of a management command or following a temporary removal (due
   to a failure).

   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 service
   from 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.

   Note that for interfaces that are not LCAS-capable, 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
   points.

4.1.4. Removing Multiple VCG Members 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 procedure is also not supported for
   VCAT-only interfaces without management intervention as removing one
   or more components of the VCG will tear down the whole group.



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4.1.5. 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. VCGs Composed of Multiple Co-Signaled Member Sets

   The motivation for VCGs composed of multiple co-signaled member sets
   comes from the requirement to support VCGs with diversely routed
   members. The initial GMPLS specification did not support diversely
   routed signals using the NVC construct.  In fact, [RFC4606] 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).

   The setup of diversely routed VCG members requires multiple co-
   signaled VCG member sets, i.e., multiple control plane LSPs.

   To support a VCG with multiple co-signaled VCG members sets requires
   being able to identify separate control plane LSPs with a single VCG
   and exchange information pertaining to the VCG as a whole. This is
   very similar to the "Call" concept described in [CallDraft]. We can
   think of our VCAT/LCAS connection, e.g., our VCG, as a higher layer
   service that makes use of multiple lower layer (server) connections
   that are controlled by one or more control plane LSPs.

4.2.1. Signaled VCG Layer Information

   When a VCG is composed of multiple co-signaled member sets, none of
   the control plane LSP's signaling information can contain information
   pertinent to the entire VCG. In this section we give a list of
   information that should be communicated at what we define as the VCG
   Call layer, i.e., between the VCG signaling endpoints.  To
   accommodate this information additional objects or TLVs would need to
   be incorporated into the Notify message as it is described for use in
   call signaling in [CallDraft].




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   VCG Call setup information signaled via the Notify message with the
   Call management bit (C-bit) set:

     1. Signal Type

     2. Number of VCG Members

     3. LCAS requirements:

          a.  LCAS required

          b. LCAS desired

          c. LCAS not desired (but acceptable)

          d. LCAS not acceptable

     4. Maximum Number of VCGs per Call-- This is a hook to support the
        member sharing scenario. In the non-member sharing case the
        value is one.

4.2.2. Procedures for VCG Control with Multiple Co-signaled Member Sets

   This section deals only with the case of one VCG per (VCG) Call. To
   establish a VCG, the information of section 4.2.1. is exchanged and
   agreed upon with the corresponding VCG signaling endpoint. Since only
   one VCG is being signaled by this call, all control plane LSPs used
   with this call establish members for this VCG and there is no
   ambiguity as to which VCG a potential member belongs. Procedures for
   addition and removal of bandwidth are the same as the single co-
   signaled case except that a VCG Call layer message should precede any
   of those changes and indicate the new total number of VCG members.

   In general the following order is used to establish and increase the
   bandwidth in a VCG:

     1. VCG Call layer information is conveyed. Note that during a
        "bandwidth" change only the total number of VCG members is
        allowed to change.

     2. Control Plane LSPs are used to add data plane LSPs (members) to
        the VCG.

     3. If LCAS is supported on this VCG call it should be instructed by
        the endpoints to "activate" the member.




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   In general the following order is used when decreasing the bandwidth
   in a VCG:

     1. VCG Call layer information is conveyed concerning the decreased
        number of VCG members.

     2. If LCAS is supported on this VCG call it should be instructed by
        the endpoints to "deactivate" the members to be removed.

     3. Existing control plane LSPs are used to remove the data plane
        LSPs (members).

   Note that when LCAS is not used or unavailable the VCG will be in an
   unknown state between the time the VCG call level information is
   updated and the actual data plane LSPs are added or removed.

4.3. Member Sharing -- Multiple VCGs per Call

   To support the member sharing scenario of section 3.2. we allow
   multiple VCGs within the context of the VCG Call defined here. This
   is partially due to the requirement in reference [CallDraft] that
   LSPs are associated with a single call over their lifetime. Hence we
   propose using the VCG Call mechanism previously described to
   establish the common member pool for all the VCGs to be included in
   the scope of this particular VCG Call. Note that the maximum number
   of VCGs per call is a key parameter to call acceptance or rejection
   since VCAT equipment typically puts limits on the total number of
   VCGs that can be simultaneously supported.

   To assign a data plane LSP to be a member of a particular VCG or to
   remove a data plane LSP from being a member of a particular VCG,
   requires additional VCG layer communications. LCAS [ITU-T-G.7042]
   cannot provide such signaling since it does not to provide a way to
   indicate which VCG out of multiple between a source and destination a
   member should belong. In particular, although, it seems that LCAS'
   Group Identification (GID) bit should be useful for this purpose
   reference [ITU-T-G.7042] specifically states:

          "The GID provides the receiver with a means of
          verifying that all the arriving members originated
          from one transmitter. The contents are pseudo-
          random, but the receiver is not required to
          synchronize with the incoming stream."





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   In the following we sketch the outline of such a high level VCG layer
   signaling procedure that could make use of the Notify message as in
   reference [CallDraft].

   After the VCG call has been established, a signaling endpoint of the
   VCG call for would then:

     1. Choose an identifier for each VCG that will use member signals
        from the common pool. Note that these identifiers only need to
        be unique with in the context of the VCG Call.

     2. Assign member signals from the common pool to each of the VCG
        utilizing the previously defined VCG IDs.  Member signals are
        identified by their tunnel id, LSP id, and label ordinal (labels
        for control plane LSPs with multiple members are strictly
        ordered so we can specify an individual signal from its label
        order). Similarly for removing a member signal from a VCG and
        returning it to the common pool.

     3. Coordinate with LCAS in that a member signal is first added to a
        VCG from the pool before LCAS is notified to "activate" that
        signal in the VCG. Similarly LCAS is notified to "deactivate" a
        member signal prior to removing it from the VCG and returning it
        to the pool.

     4. Note that before any LSPs or members of an LSP can be removed
        from the (overall) VCG Call, the originator must ensure that
        signals have been removed from any of the VCGs. This is the
        situation where the entire pool size is lowered.

   The exact objects and formats to carry this information is to be
   determined. Once again the Notify mechanism would be appropriate
   since this is information to be transferred between the VCG Call
   endpoints and is not relevant to the intermediate switches.

5. IANA Considerations

   This document requests from IANA the assignment of ... (Don't know
   yet what we may want)

6. Security Considerations

   This document introduces a specific use of the Notify message and
   admin status object for GMPLS signaling as originally specified in
   [CallDraft].  It does not introduce any new signaling messages, nor
   change the relationship between LSRs that are adjacent in the control
   plane.  The call information associated with diversely routed control


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   plane LSPs, 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 VCG call desires increased
   reliability.

   Otherwise, this document does not introduce any additional security
   considerations.

7. Contributors

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

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

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

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

   Lyndon Ong
   Ciena
   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 Adrian Farrel, Maarten Vissers,
   Trevor Wilson, Evelyne Roch, Vijay Pandian, Fred Gruman, Dan Li,
   Stephen Shew, Jonathan Saddler and Dieter Beller 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.

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

   [RFC4606]      Mannie, E. and D. Papadimitriou, "Generalized Multi-
                  Protocol Label Switching (GMPLS) Extensions for
                  Synchronous Optical Network (SONET) and Synchronous
                  Digital Hierarchy (SDH) Control", RFC 4606, December
                  2005.

   [CallDraft]    D. Papadimitriou and A. Farrel, "Generalized MPLS
                  (GMPLS) RSVP-TE Signaling Extensions in support of
                  Calls", draft-ietf-ccamp-gmpls-rsvp-te-call-04.txt,
                  January, 2007.

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, March 2006.

   [ITU-T-G.7043] International Telecommunications Union, "Virtual
                  Concatenation of Plesiochronous Digital Hierarchy
                  (PDH) Signals", ITU-T Recommendation G.7043, July
                  2004.

   [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.



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Author's Addresses

   Greg Bernstein
   Grotto Networking

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


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

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


   Richard Rabbat
   Google

   Email: richard.rabbat@gmail.com


   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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   specification can be obtained from the IETF on-line IPR repository at
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