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Versions: (draft-bernstein-ccamp-gmpls-vcat-lcas) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 RFC 6344

CCAMP Working Group                                  G. Bernstein (ed.)
Internet Draft                                        Grotto Networking
Updates: RFC 3946                                           D. Caviglia
Category: Standards Track                                      Ericsson
Expires: May 2009                                             R. Rabbat
                                                                 Google
                                                        H. van Helvoort
                                                                 Huawei
                                                      November 17, 2008


       Operating Virtual Concatenation (VCAT) and the Link Capacity
      Adjustment Scheme (LCAS) with Generalized Multi-Protocol Label
                             Switching (GMPLS)
                  draft-ietf-ccamp-gmpls-vcat-lcas-06.txt





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   This Internet-Draft will expire on January 17, 2009.








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Abstract

   This document describes requirements for, and use of, the Generalized
   Multi-Protocol Label Switching (GMPLS) control plane in conjunction
   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 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-ietf-ccamp-gmpls-vcat-lcas-05..........3
      2.2. Changes from draft-ietf-ccamp-gmpls-vcat-lcas-04..........4
      2.3. Changes from draft-ietf-ccamp-gmpls-vcat-lcas-03..........4
      2.4. Changes from draft-ietf-ccamp-gmpls-vcat-lcas-02..........4
      2.5. Changes from draft-ieft-ccamp-gmpls-vcat-lcas-01..........4
      2.6. Changes from draft-ietf-ccamp-gmpls-vcat-lcas-00..........5
   3. VCAT/LCAS Scenarios and Specific Requirements..................5
      3.1. VCAT/LCAS Interface Capabilities..........................5
      3.2. Member Signal Configuration Scenarios.....................5
      3.3. VCAT Operation With or Without LCAS.......................6
      3.4. VCGs and VCG Members......................................7
   4. GMPLS Mechanisms in Support of VCGs............................7
      4.1. VCGs Composed of a Single Co-Signaled Member Set..........8
         4.1.1. One-shot VCG Setup with Co-Signaled Members..........8
         4.1.2. Incremental VCG Setup with Co-Signaled Members.......9
         4.1.3. Procedure for VCG Reduction by Removing a Member.....9
         4.1.4. Removing Multiple VCG Members in One Shot...........10
         4.1.5. Teardown of Whole VCG...............................10
      4.2. VCGs Composed of Multiple Co-Signaled Member Sets........10
         4.2.1. Signaled VCG Layer Information......................11
      4.3. Use of the CALL_ATTRIBUTES Object........................11
      4.4. VCAT CALL_ATTRIBUTES TLV Object..........................12
      4.5. Procedures for Multiple Co-signaled Member Sets..........13
         4.5.1. Setting up a VCAT call and VCG......................15
         4.5.2. Setting up a VCAT call + LSPs with no VCG...........15


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         4.5.3. Associating an existing VCAT call with a VCG........15
         4.5.4. Removing the association between a call and VCG.....16
   5. Error Conditions and Codes....................................16
   6. IANA Considerations...........................................16
   7. Security Considerations.......................................17
   8. Contributors..................................................17
   9. Acknowledgments...............................................17
   10. References...................................................19
      10.1. Normative References....................................19
      10.2. Informative References..................................19
   Author's Addresses...............................................20
   Intellectual Property Statement..................................21
   Disclaimer of Validity...........................................21
   Copyright Statement..............................................21
   Acknowledgment...................................................21

1. Introduction

   The Generalized Multi-Protocol Label Switching (GMPLS) suite of
   protocols allows for the automated control of different switching
   technologies including Synchronous Optical Network (SONET),
   Synchronous Digital Hierarchy (SDH), Optical Transport Network (OTN)
   and Plesiochronous Digital Hierarchy (PDH). 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 this layer 1 inverse multiplexing
   mechanism adds minimal additional signal delay. VCAT enables the
   selection of an optimal signal bandwidth (size), extraction of
   bandwidth from a mesh network, 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-ietf-ccamp-gmpls-vcat-lcas-05

   Used the CALL_ATTRIBUTES Object from [MLN-Ext] rather than defining a
   new CALL_DATA object.


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2.2. Changes from draft-ietf-ccamp-gmpls-vcat-lcas-04

   Fixed text in section 4.1.3 on VCG Reduction to more accurately
   describe LCAS and non-LCAS cases.



2.3. Changes from draft-ietf-ccamp-gmpls-vcat-lcas-03

   Added requirements on pre-existing members.

   Slightly modified solution for member sharing to constrain calls to a
      maximum of one VCG.

   Introduced the CALL_DATA object.

   Detailed coding of new TLV for VCAT to be included in the CALL_DATA
      object.

   Modified and expanded procedures to deal with new requirements and
      modified solution methodology.

   Added a list of error conditions.

2.4. Changes from draft-ietf-ccamp-gmpls-vcat-lcas-02

   Grammar and punctuation fixes. Updated references with newly
      published RFCs.

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

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

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

   Added "Dynamic, member sharing" scenario.

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

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




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

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

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

   Updated reference from RFC3946bis to issued RFC4606

   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.

   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 to minimize differential delay.  The intent here is
      the capability to allocate an amount of bandwidth close to that
      required at the client layer.




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   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, e.g., no unique route has the required bandwidth.

   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.

   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.

   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.

   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.

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

   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:




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

   The total number of members 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.

   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.

3.4. VCGs and VCG Members

   VCG members (server layer connections) may be set up prior to their
      use in a VCG.

   VCG members (server layer connections) may exist after their
      corresponding VCG has been removed.

   The signaling solution SHOULD provide a mechanism to support the
   previous scenarios. However, it is not required that arbitrarily
   created server layer connections be supported in the above scenarios.

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 [RFC4328], 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.

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

  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.

  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 were co-signaled.



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

  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
   than 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.

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

   Note that this section is for informational purposes only.

   The existing GMPLS signaling protocols support a VCG composed of a
   single co-signaled member set. Setup using the NVC field is 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


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   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
   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

   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


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   whole group.  So, this is a feature that only LCAS-capable VCAT
   interfaces can support without management intervention at the end
   points.

   Note also that a VCG member can be temporary removed from the VCG due
   to a failure of the component signal. The LCAS in-band signaling will
   take appropriate actions to adjust the VCG as described in [ITU-T-
   G.7042].

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.

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


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   and exchange information pertaining to the VCG as a whole. This is
   very similar to the "Call" concept described in [RFC4974]. 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 are
   incorporated into the Notify message as it is described for use in
   call signaling in [RFC4974].

   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)

     4. VCG Identifier - Used to identify a particular VCG separately
        from the call ID so that call members can be reused with
        different VCGs per the requirements for member sharing and the
        requirements of section 3.4.

4.3. Use of the CALL_ATTRIBUTES Object

   In RFC4974 the general mechanism for communicating call information
   via Notify messages is given. In [MLN-Ext] the CALL_ATTRIBUTES object
   is introduce for the conveyance of call related information during
   call establishment and updates. We define a new






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4.4. VCAT CALL_ATTRIBUTES TLV Object

   For use in the CALL_ATTRIBUTES object in Notify messages we define
   the following VCAT related TLV:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        Type = TBD             |     Length = 12               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Signal Type                   |      Number of Members        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | LCAS Req      |  Action       |            VCG ID             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Where Type is TBD, and the Length = 12 bytes.

   Signal Type can take the following values and MUST never change over
   the lifetime of a VCG:

      Value  Type (Elementary Signal)
      -----  ------------------------
        1     VT1.5  SPE / VC-11
        2     VT2    SPE / VC-12
        3     STS-1  SPE / VC-3
        4     STS-3c SPE / VC-4
       11     OPU1 (i.e., 2.5 Gbit/s
       12     OPU2 (i.e., 10  Gbit/s)
       13     OPU3 (i.e., 40  Gbit/s)
       21     T1   (i.e., 1.544 Mbps)
       22     E1   (i.e., 2.048 Mbps)
       23     E3   (i.e., 34.368 Mbps)
       24     T3   (i.e., 44.736 Mbps)


   Number of Members is a non-negative integer that indicates the total
   number of members in the VCG (not just the call)and MUST be changed
   over the life of the VCG to indicate the current number of members.



   LCAS Required can take the following values and MUST NOT change over
   the life of a VCG:





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      Value                Meaning
      -----    ---------------------------------
      0        LCAS required
      1        LCAS desired
      2        LCAS not desired (but acceptable)

   Action is used to indicate the relationship between the call and the
   VCG and takes the following values.

      Value                Meaning
      -----    ---------------------------------
      0        No VCG ID (set up call prior to VCG creation)
      1        New VCG for Call
      2        No Change in VCG ID (number of members may have changed)
      3        Remove VCG from Call


   VCG ID: A 16 bit non-negative integer used to identify a particular
   VCG within a session. This number MUST NOT change over the lifetime
   of a VCG but can change over the lifetime of a call. To support the
   member sharing scenario of section 3.2. and the requirements of
   section 3.4. we allow the VCG Identifier within a call to be changed.
   In this way the connections associated with a call can be dedicated
   to a new VCG (allowing for a priori connection establishment and
   connection persistence after a VCG has been removed).



4.5. Procedures for Multiple Co-signaled Member Sets

   To establish a VCG a CALL_DATA object containing a VCAT TLV is
   exchanged as part of call establishment or update. A VCG can be
   established at the same time as a new call or associated with an
   existing call that currently has no VCG association. When modifying
   the bandwidth of a VCG a CALL_DATA object containing a VCAT TLV MUST
   precede any of those changes and indicate the new total number of VCG
   members.

   The following mechanisms can be used to increase the bandwidth of a
   VCG.

   LSPs are added to a VCAT Call associated with a VCG (Action = 2).

   A VCG is associated with an existing VCAT call containing LSPs
      (Action = 1).



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   The following internal ordering is used when increasing the bandwidth
   of a VCG in a hitless fashion when LCAS is supported:

   A CALL_DATA Object containing a VCAT TLV indicating the new number of
      members after the proposed increase is sent. If an error is
      returned from the receiver the VCG state remains the same prior to
      the attempted increase.

   Either: (a) New LSPs are set up within a call associated with the
      VCG, or (b) LSPs in an existing call are now associated with the
      VCG.

   The internal LCAS entity is instructed by the endpoints to "activate"
      the new VCG member(s).

   The following mechanisms can be used to decrease the bandwidth of a
   VCG.

   LSPs are removed from a VCAT Call associated with a VCG (Action = 2).

   A VCG association is removed from existing VCAT call containing LSPs
      (Action = 3).

   In general the following internal ordering is used when decreasing
   the bandwidth of a VCG in a hitless fashion when LCAS is supported:

   1. A CALL_DATA Object containing a VCAT TLV indicating the new number
      of members after the proposed decrease is sent. If an error is
      returned from the receiver the VCG state remains the same prior to
      the attempted decrease.

   2. The LCAS entity is instructed by the endpoints to "deactivate" the
      members to be removed from the VCG.

   3. Either: (a) An LSP is removed from a call associated with a VCG;
      or (b) All the LSPs of a call are removed from the VCG when the
      association between the VCG and VCAT call is removed.

   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. Note
   that the incremental setup procedure of section 4.1.2. can be applied
   to any of the above procedures.






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4.5.1. Setting up a VCAT call and VCG

   Arguably the most common operation will be simultaneously setting up
   a VCAT call and its associated VCG at the same time. To do this when
   one sets up a new VCAT call in the VCAT TLV one sets Action = 1
   indicating that this is a new VCG for this call.  LSPs would then be
   added to the call until the number of members reaches the number
   specified in the VCAT TLV.

   Note that any other bandwidth modifications to the VCG whether up or
   down will require a new VCAT call message with an appropriately
   modified TLV reflecting the new number of members.

4.5.2. Setting up a VCAT call + LSPs with no VCG

   To provide for pre-establishment of the server layer connections for
   a VCG one can establish a VCAT call without an associated VCG. In
   addition, to provide for member sharing a pool of calls with
   connections can be established, then one or more of these calls (with
   accompanying connections) can be associated with a particular VCG
   (via the VCG ID). Note that multiple calls can be associated with a
   single VCG but that no call contains members used in more than one
   VCG.

   To establish a VCAT call with no VCG association when one sets up a
   new VCAT call in the VCAT TLV one sets Action = 0 indicating that
   this is a VCAT call without an associated VCG.  LSPs can then be
   added to the call. The number of members parameter in the VCAT TLV
   has no meaning at this point since it reflects the intended number of
   members in a VCG and not in a call.  A call will know via the
   containment hierarchy about its associated data plane LSPs. However,
   the signal type does matter since signal types can never be mixed in
   a VCG and hence a VCAT call should only contain one signal type.



4.5.3. Associating an existing VCAT call with a VCG

   Given a VCAT call without an associated VCG such as that set up in
   section 4.5.2. one associates it with a VCG as follows. In the VCAT
   call a new notify message is sent with a CALL_DATA object with a VCAT
   TLV with Action = 1, a VCG ID, and the correct number of VCG members
   specified based on adding all of the calls data plane LSPs to the VCG
   as members.

   Note that the total number of VCGs supported by a piece of equipment
   may be limited and hence on reception of any message with a change of


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   VCG ID this limit should be checked. Likewise the sender of a message
   with a change in VCG ID should be prepared to receive an error
   response. To take a particular VCG out of service, rather than just
   removing all its member, a special flag element is included.



4.5.4. Removing the association between a call and VCG

   To reuse the server layer connections in a call in another VCG one
   first needs to remove the current association between the call and a
   VCG.  To do this, in the VCAT call a new notify message is sent with
   a CALL_DATA object with a VCAT TLV with Action = 3, a VCG ID, and the
   correct number of VCG members specified based on removing all of the
   calls data plane LSPs from the VCG as members. When the association
   between a VCG and all existing calls has been removed then the VCG is
   considered torn down.

5. Error Conditions and Codes

   VCAT Call and member LSP setup can be denied for various reasons.
   Below is a list of error conditions that can be encountered during
   these procedures.  These fall under RSVP error code TBD.

   These can occur when setting up a VCAT call or associating a VCG with
   a VCAT call.

   Error                                  Subcode
   ------------------------------------   --------
   VCG signal type not Supported             1
   LCAS option not supported                 2
   Max number of VCGs exceeded               3
   Max number of VCG members exceeded        4
   LSP Type incompatible with VCAT call      5


6. IANA Considerations

   This document requests from IANA the assignment of a new TLV for the
   CALL_ATTRIBUTES Object from [MLN-Ext]. Within this VCAT TLV are a set
   of code points for permissible signal types. In addition, we request
   a new RSVP error code for use with VCAT call and define a number of
   corresponding error sub-codes.






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7. Security Considerations

   This document introduces a specific use of the Notify message and
   admin status object for GMPLS signaling as originally specified in
   [RFC4974].  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
   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.

8. 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


9. Acknowledgments

   The authors would like to thank Adrian Farrel, Maarten Vissers,
   Trevor Wilson, Evelyne Roch, Vijay Pandian, Fred Gruman, Dan Li,


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   Stephen Shew, Jonathan Saddler and Dieter Beller for extensive
   reviews and contributions to this draft.















































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10. References

10.1. Normative References

   [MLN-Ext]      Papadimitriou, D., Vigoureux M., Shiomoto, K.
                  Brungard, D., Le Roux, JL., "Generalized Multi-
                  Protocol Label Switching (GMPLS) Protocol Extensions
                  for Multi-Layer and Multi-Region Networks (MLN/MRN)",
                  work in progress: draft-ietf-ccamp-gmpls-mln-
                  extensions-03.txt, October, 2008.

   [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.

   [RFC4328]      Papadimitriou, D., Ed., "Generalized Multi-Protocol
                  Label Switching (GMPLS) Signaling Extensions for G.709
                  Optical Transport Networks Control", RFC 4328, January
                  2006.

   [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.

   [RFC4974]      Papadimitriou, D. and A. Farrel, "Generalized MPLS
                  (GMPLS) RSVP-TE Signaling Extensions in Support of
                  Calls", RFC 4974, August 2007.

10.2. 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.





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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
                  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.

Author's Addresses

   Greg M. Bernstein (ed.)
   Grotto Networking
   Fremont California, USA

   Phone: (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, Inc.
   1600 Amphitheatre Parkway
   Mountain View, CA 94043, USA

   Email: rabbat@alum.mit.edu


   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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