Network Working Group                                       Fatai Zhang
Internet Draft                                                   Huawei
Category: Standards Track                                  uoying Zhang
                                                                   CATR
                                                         Sergio Belotti
                                                         Alcatel-Lucent
                                                     Daniele Ceccarelli
                                                               Ericsson
Expires: March 2010                                  September 22, 2009




        Generalized Multi-Protocol Label Switching (GMPLS) Signaling
    Extensions for the evolving G.709 Optical Transport Networks Control


               draft-zhang-ccamp-gmpls-evolving-g709-02.txt


Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with
   the provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on March 22, 2010.



Abstract

   Recent progress in ITU-T Recommendation G.709 standardization has
   introduced new ODU containers (ODU0, ODU4, ODU2e, ODU3e1, ODU3e2 and
   ODUflex) and enhanced Optical Transport Networking (OTN) flexibility.



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   Several recent documents have proposed ways to modify GMPLS signaling
   protocols to support these new OTN features.

   It is important that a single solution is developed for use in GMPLS
   signaling and routing protocols. This solution must support ODUk
   multiplexing capabilities, address all of the new features, be
   acceptable to all equipment vendors, and be extensible considering
   continued OTN evolution.

   This document describes the extensions to the Generalized Multi-
   Protocol Label Switching (GMPLS) signaling to control the evolutive
   Optical Transport Networks (OTN) addressing ODUk multiplexing and new
   features including ODU0, ODU4, ODU2e, ODU3e1, ODU3e2 and ODUflex.

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 [RFC2119].

Table of Contents


   1. Introduction...................................................3
   2. Terminology....................................................4
   3. GMPLS Extensions for the Evolutive G.709 - Overview............4
      3.1. Extensions for Traffic Parameters for the Evolutive G.709 5
   4. Generalized Label..............................................7
      4.1. New definition of ODUk label..............................7
      4.2. Examples..................................................9
      4.3. Label Distribution Procedure.............................11
      4.4. Backward Compatibility Considerations....................11
         4.4.1. Control Plane Backward Compatibility Considerations.11
         4.4.2. Data Plane Backward Compatibility Considerations....13
      4.5. Collision management.....................................13
   5. Security Considerations.......................................14
   6. IANA Considerations...........................................14
   7. References....................................................14
      7.1. Normative References.....................................14
      7.2. Informative References...................................14
   8. Authors' Addresses............................................15
   Acknowledgment...................................................16







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1. Introduction

   Generalized Multi-Protocol Label Switching (GMPLS) [RFC3945] extends
   MPLS to include Layer-2 Switching (L2SC), Time-Division Multiplex
   (e.g., SONET/SDH, PDH, and ODU), Wavelength (OCh, Lambdas) Switching,
   and Spatial Switching (e.g., incoming port or fiber to outgoing
   port or fiber). [RFC3471] presents a functional description of the
   extensions to Multi-Protocol Label Switching (MPLS) signaling
   required to support Generalized MPLS.  RSVP-TE-specific formats and
   mechanisms and technology specific details are defined in [RFC3473].

   With the evolution and deployment of G.709 technology, it is
   necessary that appropriate enhanced control technology support be
   provided for G.709. [RFC4328] describes the control technology
   details that are specific to foundation G.709 Optical Transport
   Networks (OTN), as specified in the ITU-T G.709 recommendation [ITUT-
   G709], for ODUk deployments without multiplexing.

   In addition to increasing need to support ODUk multiplexing, the
   evolution of OTN has introduced additional containers and new
   flexibility. For example, ODU0, ODU2e, ODU4 containers as described
   in [G709-Amd3], ODU3e1, ODU3e2 described in [Gsup43], and ODUflex
   being developed in [G709draft-v3].

   In addition, the following issues require consideration:

        - Support for ODUflex resizing capabilities, potentially hitless
        (similar to LCAS, as defined in [VCAT-LCAS]), which is under
        discussion in ITU-T.

        - Support for Tributary Port Number. The Tributary Port Number
        has to be negotiated on each link for flexible assignment of
        tributary ports to tributary slots in case of LO-ODU over HO-ODU
        (e.g., ODU2 into ODU3). Alternatively, the nodes of the network
        are supposed to run AutoMSI mode.

   Therefore, it is clear that [RFC4328] has to be updated or replaced
   in order to support ODUk multiplexing, as well as other ODU
   enhancements introduced by evolution of OTN standards.

   This document updates RFC4328 extending the G.709 ODUk traffic
   parameters and also presents a new OTN label format which is very
   flexible and scalable.






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2. Terminology

   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 [RFC2119].

3. GMPLS Extensions for the Evolutive G.709 - Overview

   The new features for the evolutive OTN are described in the separate
   ITU-T documents, for example, ODU0, ODU2e,ODU4 are described in
   [G709-Amd3] and ODU3e1, ODU3e2 are described in [Gsup43] and ODUflex
   is being developed in [G709draft-v3].

   [Editors note] The signal types described in [Gsup43] (i.e., ODU3e1,
   ODU3e2) are non standard, should IETF address this kind of signals?

   The new signal types of digital wrapper layer for the evolutive OTN
   are listed as follows:

      - Optical Channel Transport Unit (OTUk):
         . OTU4
         . OTU2e
         . OTU3e1
         . OTU3e2
      - Optical Channel Data Unit (ODUk):
         . ODU0
         . ODU2e
         . ODU3e1
         . ODU3e2
         . ODU4
         . ODUflex

   A new Tributary Slot (TS) granularity (i.e., 1.25 Gbps) is introduced
   in [G709-Amd3]. At this point there are two TS granularities for the
   original ODU1, ODU2, ODU3. The TS granularity at 2.5 Gbps is used on
   legacy interfaces while the new 1.25 Gbps will be used for the new
   interfaces.

   New ITU-T documents not only introduce new signal types but also
   define the new multiplexing hierarchy for the evolutive OTN. In
   addition to the support of ODUk mapping into OTUk (k = 1, 2, 2e, 3,
   3e1, 3e2, 4), G.709 and its amendments, support ODUk multiplexing.
   For the evolutive OTN, the multiplexing of ODUj (j = 0, 1, 2, 2e, 3,
   flex) into an ODUk (k > j) signal can be depicted as follows:



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     -  ODU0 into ODU1 multiplexing (with 1,25Gbps TS granularity)

     -  ODU0, ODU1, ODUflex into ODU2 multiplexing (with 1.25Gbps
        TS granularity)

     -  ODU1 into ODU2 multiplexing (with 2.5Gbps TS granularity)

     -  ODU0, ODU1, ODU2, ODU2e and ODUflex into ODU3 multiplexing
        (with 1.25Gbps TS granularity)

     -  ODU1, ODU2 into ODU3 multiplexing (with 2.5Gbps TS granularity)

     -  ODU0, ODU1, ODU2, ODU2e, ODU3 and ODUflex into ODU4
        multiplexing (with 1.25Gbps TS granularity)

     - ODU2e into ODU3e1 multiplexing (with 2.5Gbps TS granularity)

     - ODU2e into ODU3e2 multiplexing (with 1.25Gbps TS granularity)

   [RFC4328] describes GMPLS signaling extensions to support the control
   for G.709 Optical Transport Networks (OTN) [ITUT-G709].However,
   [RFC4328] need to be updated because it does not provide the means to
   signal all the new signal types and related mapping and multiplexing
   functionalities. Moreover, it supports only the optional auto-MSI
   mode which assumes that the Tributary Port Number is automatically
   assigned in the transmit direction and not checked in the receive
   direction.

   This document extends the G.709 traffic parameters described in
   [RFC4328] and also presents a new OTN label format which is very
   flexible and scalable.

   [Editors note] There are several possibilities to include the
   Tributary Port Number information in the signaling. Note that ITU-T
   has not yet given a clear interpretation of the Tributary Port number
   information in case of bidirectional paths, so the adoption of any
   solution should be kept on hold until ITU-T provides an approved
   definition.

3.1. Extensions for Traffic Parameters for the Evolutive G.709

   The traffic parameters for G.709 are defined in [RFC4328] as follows:




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      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Signal Type  |   Reserved    |              NMC              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |              NVC              |        Multiplier (MT)        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Reserved                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   [Editors note] NMC field in RFC4328 had the meaning to indicate how
   many labels have to be expected.  This information allows the
   protocol to operate without specific knowledge of the signal type.
   The same effect could be obtained either indicating the bit map
   length or indicating the number of labels.

   [Editors note] In the case ODUflex, Bit Rate and Bit Rate Tolerance
   (BR, BRT) should be indicated in the Traffic Parameters. For example,
   if an ODUflex connection with (2.5Gbps,+-20ppm) is requested, a HO
   OPU2 TS is a maximum of 1.249 494 145 Gbps, so the ODUflex GDPS 2.5G
   requires 3 TS in a HO OPU2. However, a HO OPU4 TS is a maximum of
   1.301 711 855 Gbps, so the ODUflex requires only 2 TS in a HO OPU4.
   Therefore, (BR, BRT) should be transmitted in the signaling End to
   End, and it will be reflected in the Traffic Parameters in the next
   version of this draft.

   It is obvious that the Signal Type should be extended to cover the
   new Signal Type introduced by the evolutive OTN. The new Signal Type
   is extended as follows:

      Value  Type

      -----  ----
      0      Not significant
      1      ODU1 (i.e., 2.5 Gbps)
      2      ODU2 (i.e., 10 Gbps)
      3      ODU3 (i.e., 40 Gbps)
      4      ODU4 (i.e., 100 Gbps)
      5      Reserved (for future use)
      6      OCh at 2.5 Gbps
      7      OCh at 10 Gbps
      8      OCh at 40 Gbps
      9      OCh at 100 Gbps
      10~19  Reserved (for future use)


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      20     ODU0 (i.e., 1.25 Gbps)
      21~30  Reserved (for future use)
      31     ODU2e (i.e., 10Gbps for FC1200 and GE LAN)
      32     ODU3e1
      33     ODU3e2
      34     ODUflex (i.e., 1.25*N Gbps)
      35~255 Reserved (for future use)

4. Generalized Label

   [RFC3471] has defined the Generalized Label which extends the
   traditional label by allowing the representation of not only labels
   which travel in-band with associated data packets, but also labels
   which identify time-slots, wavelengths, or space division multiplexed
   positions. The format of the corresponding RSVP-TE Generalized Label
   object is defined in the Section 2.3 of [RFC3473].

   However, for different technologies, we usually need use specific
   label rather than the Generalized Label. For example, the label
   format described in [RFC4606] could be used for SDH/SONET, the label
   format in [RFC4328] for G.709.

   According to the ODUk label format defined in [RFC4328], it could be
   updated to support new signal types defined in G.709 amendment 3 and
   G.sup43 but would hardly be further enhanced to support possible new
   signal types. Furthermore such label format can face big problems
   related to scalability matters due to the high number of labels
   needed. For example, when ODU3 is mapped into ODU4 with 1.25G
   tributary slots, it will need thirty-two labels (32*4*8=1024 bits) to
   be allocated for one ODU3 connection. If ODUflex into ODU4, it may
   need up to eighty labels (80*4*8=2560 bits) to be allocated for one
   ODUflex connection.

   In this document, a new ODUk label format is defined. The new ODUk
   label format is very flexible and scalable.

4.1. New definition of ODUk label

   In order to be compatible with new types of ODU signal and new types
   of tributary slot, the following new ODUk label format is defined:







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   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | ODUj  |OD(T)Uk| T | Reserved  |           Bit Map             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           .........                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   ODUj and OD(T)Uk (4 bits respectively): indicate that ODUj is
   multiplexed into ODUk(k>j), or ODUj is mapped into OTUk (j=k).

   ODUj field    Signal type

   ----------    -----------
      0          ODU0
      1          ODU1
      2          ODU2
      3          ODU3
      4          ODU4
      5          ODU2e
      6          ODUflex
      7-15       Reserved (for future use)


   OD(T)Uk field   Signal type

   ----------     -----------
      0           Reserved (for future use)
      1           ODU1/OTU1
      2           ODU2/OTU2
      3           ODU3/OTU3
      4           ODU4/OTU4
      5           OTU2e
      6           OTU3e1
      7           OTU3e2
      8-15        Reserved (for future use)


   T (2 bits): indicates the type of tributary slot of OD(T)Uk.
   Currently, two types of tributary slot are defined in [G.709], the
   1.25Gbps tributary slot and the 2.5Gbps tributary slot.





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   T field      TS type
   -------      -------
     0          1.25Gbps TS granularity
     1          2.5Gbps TS granularity
     2-3        Reserved (for future use)


   Bit Map (variable): indicates which tributary slots in ODUk that the
   ODUj will be multiplexed into. The sequence of the Bit Map is
   consistent with the sequence of the tributary slots in ODUk. Each bit
   in the bit map represents the corresponding tributary slot in ODUk
   with a value of 1 or 0 indicating whether the tributary slot will be
   used by ODUj or not.

   The size of the bit map equals to the total number of the tributary
   slots of ODUk.

   Padded bits are added behind the Bit Map to make the whole label a
   multiple of four bytes if necessary. Padded bit MUST be set to 0 and
   MUST be ignored.

   In case of an ODUk mapped into OTUk, it's no need to indicate which
   tributary slots will be used by ODUk, so the size of Bit Map is 0.

   [Editors note] Tributary Port Number information to be inserted as
   soon as clarification from ITU has been provided.

4.2. Examples

   The following examples are given in order to illustrate the label
   format described in the previous sections of this document.

   (1) ODUk in OTUk mapping:

   In such conditions, the downstream node along an LSP returns a label
   indicating that the ODU1 (ODU2 or ODU3 or ODU4) is directly mapped
   into the corresponding OTU1 (OTU2 or OTU3 or ODU4). The following
   example label indicates an ODU1 mapped into OTU1 with 2.5Gbps TS
   granularity.

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 1|0 0 0 1|0 1| Reserved  |        Padded Bits (0)        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




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   (2) ODUj into ODUk multiplexing:

   In such conditions, this label indicates that an ODUj is multiplexed
   into several tributary slots of OPUk and then mapped into OTUk. Some
   instances are shown as follow:

   - ODU0 into ODU2 Multiplexing:

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0|0 0 1 0|0 0| Reserved  |0 1 0 0 0 0 0 0|Padded Bits (0)|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   This above label indicates an ODU0 multiplexed into the second
   tributary slot of ODU2, wherein the type of the tributary slot is
   1.25Gbps.

   - ODU1 into ODU2 Multiplexing with 1.25Gbps TS granularity:

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 1|0 0 1 0|0 0| Reserved  |0 1 0 1 0 0 0 0|Padded Bits (0)|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   This above label indicates an ODU1 multiplexed into the 2nd, 4th
   tributary slot of ODU2, wherein the type of the tributary slot is
   1.25Gbps.

   - ODU2 into ODU3 Multiplexing with 2.5Gbps TS granularity:

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 1 0|0 0 1 1|0 1| Reserved  |0 1 1 0 1 0 1 0 0 0 0 0 0 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   This above label indicates an ODU2 multiplexed into the 2nd, 3rd, 5th
   and 7th tributary slot of ODU3, wherein the type of the tributary
   slot is 2.5Gbps.





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4.3. Label Distribution Procedure

   This document does not change the existing label distribution
   procedures [RFC4328] for GMPLS except that the new ODUk label should
   be processed as follows.

   When a node receives a generalized label request for setting up an
   ODUj LSP from its upstream node, the node should generate an ODU
   label according to the signal type of the requested LSP and the free
   resources (i.e., free tributary slots of ODUk) that will be reserved
   for the LSP, and send the label to its upstream node. Note that these
   labels can also be specified by the source node of the connection.

   In case of ODUj to ODUk multiplexing, the node should firstly
   determine the size of the Bit Map field according to the signal type
   and the tributary slot type of ODUk, and then set the bits to 1 in
   the Bit Map field corresponding to the reserved tributary slots.

   In case of ODUk to OTUk mapping, the node only needs to fill the ODUj
   and the ODUk fields with corresponding values in the label. Other
   bits are reserved and MUST be set to 0.

   When receiving an ODU label from its downstream node, the node should
   learn which ODU signal type is multiplexed or mapped into which ODU
   signal type by analyzing the ODUj and the ODUk fields.

   In case of ODUj to ODUk multiplexing, the node should firstly
   determine the size of the Bit Map field according to the signal type
   and the tributary slot type of ODUk, and then obtain which tributary
   slots in ODUk are reserved by its downstream node according to the
   position of the bits that are set to 1 in the Bit Map field, so that
   the node can multiplex the ODUj into the reserved tributary slots of
   ODUk after the LSP is established.

   In case of ODUk to OTUk mapping, the size of Bit Map field is 0 and
   no additional procedure is needed.

4.4. Backward Compatibility Considerations

4.4.1. Control Plane Backward Compatibility Considerations

   Since the [RFC4328] has been deployed in the network for the nodes
   which support the [ITUT-G709] (herein we call them "old nodes"), the
   backward compatibility SHOULD be take into consideration when the new
   nodes (i.e., nodes that support the [G709-Amd3] or [Gsup43] or
   [G709draft-v3]) and the old nodes are interworking.



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   For backward compatibility consideration, the new node SHOULD have
   the ability to generate and parse old labels.

   -  For the old node, it always generates and sends old label to its
      upstream node, no matter the upstream node is new or old, as
      described in [RFC4328].

   -  For the new node, it will generate and send old label if its
      upstream node is an old one, and generate and send new label if
      its upstream node is a new one.

   One backward compatibility example is shown below:

            Path          Path          Path          Path
    +-----+ ----> +-----+ ----> +-----+ ----> +-----+ ----> +-----+
    |     |       |     |       |     |       |     |       |     |
    |  A  +-------+  B  +-------+  C  +-------+  D  +-------+  E  |
    |(new)|       |(new)|       |(old)|       |(old)|       |(new)|
    +-----+ <---- +-----+ <---- +-----+ <---- +-----+ <---- +-----+
             Resv          Resv          Resv          Resv
          (new label)   (old label)   (old label)   (old label)


   As described above, for backward compatibility considerations, it is
   necessary for a new node to know whether the neighbor node is new or
   old.

   One optional method is manual configuration. But it is recommended to
   use LMP to discover the capability of the neighbor node automatically,
   as described in [OTN-LMP].

   When performing the HO ODU link capability negotiation:

   o  If the neighbor node only support the 2.5Gbps TS and only support
      ODU1/ODU2/ODU3, the neighbor node should be treated as an old node.

   o  If the neighbor node can support the 1.25Gbps TS, or can support
      other LO ODU types defined in [G709-Amd3] or [Gsup43] or
      [G709draft-v3]), the neighbor node should be treated as new node.

   o  If the neighbor node returns a LinkSummaryNack message including
      an ERROR_CODE indicating nonsupport of HO ODU link capability
      negotiation, the neighbor node should be treated as an old node.






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4.4.2. Data Plane Backward Compatibility Considerations

   As described in chapter 3.1 and 4.1 of [OTN-LMP], the node supporting
   1.25Gbps TS can interwork with the other nodes that supporting
   2.5Gbps TS by combining Specific TSs together in data plane. The
   control plane MUST support this TS combination.

   Take the following figure as an example. Assume that there is an ODU2
   link between node A and B, where node A only supports the 2.5Gbps TS
   while node B supports the 1.25Gbps TS. In this case, the TS#i and
   TS#i+4 (where i<=4) of node B are combined together. When creating an
   ODU1 service in this ODU2 link, node B reserves the TS#i and TS#i+4
   with the granularity of 1.25Gbps. But in the label sent from B to A,
   it is indicated that the TS#i with the granularity of 2.5Gbps is
   reserved.

                             Path
         +----------+   ------------>    +----------+
         |     TS1==|===========\--------+--TS1     |
         |     TS2==|=========\--\-------+--TS2     |
         |     TS3==|=======\--\--\------+--TS3     |
         |     TS4==|=====\--\--\--\-----+--TS4     |
         |          |      \  \  \  \----+--TS5     |
         |          |       \  \  \------+--TS6     |
         |          |        \  \--------+--TS7     |
         |          |         \----------+--TS8     |
         +----------+   <------------    +----------+
            node A           Resv           node B

   In the contrary direction, when receiving a label from node A
   indicating that the TS#i with the granularity of 2.5Gbps is reserved,
   node B will reserved the TS#i and TS#i+4 with the granularity of
   1.25Gbps in its control plane.

4.5. Collision management

   [Editors note] This chapter should indicate the procedure in case of
   collision between Tributary Port Numbers and/or Tributary Slots e.g.
   two different LSP setups may choose a disjoint set of Tributary Slots
   but they may request the same Tributary Port Number value (same MSI
   in G.709 OPUk field).

   In this case the first signaling should be successful and the second
   one must fail.




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5. Security Considerations

   TBD.

6. IANA Considerations

   TBD.

7. References

7.1. Normative References

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

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

   [RFC3471] Berger, L., Editor, "Generalized Multi-Protocol Label
             Switching (GMPLS) Signaling Functional Description",
             RFC 3471, January 2003.

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

   [RFC3945] Mannie, E., "Generalized Multi-Protocol Label Switching
             (GMPLS) Architecture", RFC 3945, October 2004.

   [VCAT-LCAS] G. Bernstein, Ed., "Operating Virtual Concatenation (VCAT)
             and the Link Capacity Adjustment Scheme (LCAS) with
             Generalized Multi-Protocol Label Switching (GMPLS)", draft-
             bernstein-ccamp-gmpls-vcat-lcas, July 29, 2009.

   [OTN-LMP] Fatai Zhang, Ed., "Link Management Protocol (LMP)
             extensions for G.709 Optical Transport Networks", draft-
             zhang-ccamp-gmpls-g.709-lmp-discovery-00.txt, Sep 19, 2009.

7.2. Informative References

[ITUT-G709] ITU-T, "Interface for the Optical Transport Network (OTN),"
G.709 Recommendation (and Amendment 1), February 2001 (October 2001).

[G709-Amd3] ITU-T, "Interface for the Optical Transport Network (OTN),"
G.709 Recommendation Amendment3), December 2008.



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   [Gsup43]  ITU-T, " Proposed revision of G.sup43 (for agreement),",
             December 2008.

   [G709draft-v3] ITU-T, "Draft revised G.709, version 3,", May 2009.



8. Authors' Addresses

   Fatai Zhang
   Huawei Technologies
   F3-5-B R&D Center, Huawei Base
   Bantian, Longgang District
   Shenzhen 518129 P.R.China
   Phone: +86-755-28972912
   Email: zhangfatai@huawei.com


   Guoying Zhang
   China Academy of Telecommunication Research of MII
   11 Yue Tan Nan Jie Beijing, P.R.China
   Phone: +86-10-68094272
   Email: zhangguoying@mail.ritt.com.cn


   Sergio Belotti
   Alcatel-Lucent
   Optics CTO
   Via Trento 30 20059 Vimercate (Milano) Italy
   +39 039 6863033
   Email: sergio.belotti@alcatel-lucent.it


   Daniele Ceccarelli
   Ericsson
   Via A. Negrone 1/A
   Genova - Sestri Ponente
   Italy
   Email: daniele.ceccarelli@ericsson.com


   Yi Lin
   Huawei Technologies
   F3-5-B R&D Center, Huawei Base



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   Bantian, Longgang District
   Shenzhen 518129 P.R.China
   Phone: +86-755-28972914
   Email: linyi_hw@huawei.com


   Yunbin Xu
   China Academy of Telecommunication Research of MII
   11 Yue Tan Nan Jie Beijing, P.R.China
   Phone: +86-10-68094134
   Email: xuyunbin@mail.ritt.com.cn


   Pietro Grandi
   Alcatel-Lucent
   Optics CTO
   Via Trento 30 20059 Vimercate (Milano) Italy
   +39 039 6864930
   Email: pietro_vittorio.grandi@alcatel-lucent.it


   Diego Caviglia
   Ericsson
   Via A. Negrone 1/A
   Genova - Sestri Ponente
   Italy
   Email: diego.caviglia@ericsson.com



Acknowledgment

   TBD.



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