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Versions: (draft-ogrcetal-ccamp-flexi-grid-fwk) 00 01 02 03 04 05 06 07 RFC 7698

Network Working Group                           O. Gonzalez de Dios, Ed.
Internet-Draft                                            Telefonica I+D
Intended status: Standards Track                        R. Casellas, Ed.
Expires: August 18, 2014                                            CTTC
                                                                F. Zhang
                                                                  Huawei
                                                                   X. Fu
                                                                     ZTE
                                                           D. Ceccarelli
                                                                Ericsson
                                                              I. Hussain
                                                                Infinera
                                                       February 14, 2014


 Framework and Requirements for GMPLS based control of Flexi-grid DWDM
                                networks
                   draft-ietf-ccamp-flexi-grid-fwk-01

Abstract

   This document defines a framework and the associated control plane
   requirements for the GMPLS based control of flexi-grid DWDM networks.
   To allow efficient allocation of optical spectral bandwidth for high
   bit-rate systems, the International Telecommunication Union
   Telecommunication Standardization Sector (ITU-T) has extended the
   recommendations [G.694.1] and [G.872] to include the concept of
   flexible grid.  A new DWDM grid has been developed within the ITU-T
   Study Group 15 by defining a set of nominal central frequencies,
   channel spacings and the concept of "frequency slot".  In such
   environment, a data plane connection is switched based on allocated,
   variable-sized frequency ranges within the optical spectrum.

Status of This Memo

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

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   material or to cite them other than as "work in progress."




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   This Internet-Draft will expire on August 18, 2014.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   described in the Simplified BSD License.

Table of Contents

   1.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Acronyms  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Flexi-grid Networks . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Flexi-grid in the context of OTN  . . . . . . . . . . . .   4
     4.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   5
       4.2.1.  Frequency Slots . . . . . . . . . . . . . . . . . . .   5
       4.2.2.  Media Channels  . . . . . . . . . . . . . . . . . . .   7
       4.2.3.  Media Layer Elements  . . . . . . . . . . . . . . . .   7
       4.2.4.  Optical Tributary Signals . . . . . . . . . . . . . .   8
     4.3.  Flexi-grid layered network model  . . . . . . . . . . . .   8
       4.3.1.  Hierarchy in the Media Layer  . . . . . . . . . . . .   9
       4.3.2.  DWDM flexi-grid enabled network element models  . . .  10
   5.  GMPLS applicability . . . . . . . . . . . . . . . . . . . . .  11
     5.1.  General considerations  . . . . . . . . . . . . . . . . .  11
     5.2.  Considerations on TE Links  . . . . . . . . . . . . . . .  11
     5.3.  Considerations on Labeled Switched Path (LSP) in Flexi-
           grid  . . . . . . . . . . . . . . . . . . . . . . . . . .  14
     5.4.  Control Plane modeling of Network elements  . . . . . . .  18
     5.5.  Media Layer Resource Allocation considerations  . . . . .  19
     5.6.  Neighbor Discovery and Link Property Correlation  . . . .  23
     5.7.  Path Computation / Routing and Spectrum Assignment (RSA)   23
       5.7.1.  Architectural Approaches to RSA . . . . . . . . . . .  24
     5.8.  Routing / Topology dissemination  . . . . . . . . . . . .  24
       5.8.1.  Available Frequency Ranges/slots of DWDM Links  . . .  25
       5.8.2.  Available Slot Width Ranges of DWDM Links . . . . . .  25
       5.8.3.  Spectrum Management . . . . . . . . . . . . . . . . .  25
       5.8.4.  Information Model . . . . . . . . . . . . . . . . . .  26
   6.  Control Plane Requirements  . . . . . . . . . . . . . . . . .  27



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     6.1.  Support for Media Channels  . . . . . . . . . . . . . . .  27
     6.2.  Support for Media Channel Resizing  . . . . . . . . . . .  27
     6.3.  Support for Logical Associations of multiple media
           channels  . . . . . . . . . . . . . . . . . . . . . . . .  28
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  28
   8.  Contributing Authors  . . . . . . . . . . . . . . . . . . . .  28
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  30
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  30
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  30
     10.2.  Informative References . . . . . . . . . . . . . . . . .  32
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  32

1.  Requirements Language

   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].

2.  Introduction

   The term "Flexible grid" (flexi-grid for short) as defined by the
   International Telecommunication Union Telecommunication
   Standardization Sector (ITU-T) Study Group 15 in the latest version
   of [G.694.1], refers to the updated set of nominal central
   frequencies (a frequency grid), channel spacing and optical spectrum
   management/allocation considerations that have been defined in order
   to allow an efficient and flexible allocation and configuration of
   optical spectral bandwidth for high bit-rate systems.

   A key concept of flexi-grid is the "frequency slot"; a variable-sized
   optical frequency range that can be allocated to a data connection.
   As detailed later in the document, a frequency slot is characterized
   by its nominal central frequency and its slot width which, as per
   [G.694.1], is constrained to be a multiple of a given slot width
   granularity.

   Compared to a traditional fixed grid network, which uses fixed size
   optical spectrum frequency ranges or "frequency slots" with typical
   channel separations of 50 GHz, a flexible grid network can select its
   media channels with a more flexible choice of slot widths, allocating
   as much optical spectrum as required, allowing high bit rate signals
   (e.g., 400G, 1T or higher) that do not fit in the fixed grid.

   From a networking perspective, a flexible grid network is assumed to
   be a layered network [G.872][G.800] in which the media layer is the
   server layer and the optical signal layer is the client layer.  In
   the media layer, switching is based on a frequency slot, and the size
   of a media channel is given by the properties of the associated



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   frequency slot.  In this layered network, the media channel
   transports an Optical Tributary Signal.

   A Wavelength Switched Optical Network (WSON), addressed in [RFC6163],
   is a term commonly used to refer to the application/deployment of a
   Generalized Multi-Protocol Label Switching (GMPLS)-based control
   plane for the control (provisioning/recovery, etc) of a fixed grid
   WDM network in which media (spectrum) and signal are jointly
   considered

   This document defines the framework for a GMPLS-based control of
   flexi-grid enabled DWDM networks (in the scope defined by ITU-T
   layered Optical Transport Networks [G.872]), as well as a set of
   associated control plane requirements.  An important design
   consideration relates to the decoupling of the management of the
   optical spectrum resource and the client signals to be transported.

3.  Acronyms

   EFS: Effective Frequency Slot

   FS: Frequency Slot

   NCF: Nominal Central Frequency

   OCh: Optical Channel

   OCh-P: Optical Channel Payload

   OTS: Optical Tributary Signal

   OCC: Optical Channel Carrier

   SWG: Slot Width Granularity

4.  Flexi-grid Networks

4.1.  Flexi-grid in the context of OTN

   [G.872] describes from a network level the functional architecture of
   Optical Transport Networks (OTN).  The OTN is decomposed into
   independent layer networks with client/layer relationships among
   them.  A simplified view of the OTN layers is shown in Figure 1.








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                                 +----------------+
                                 | Digital Layer  |
                                 +----------------+
                                 | Signal Layer   |
                                 +----------------+
                                 |  Media Layer   |
                                 +----------------+

                      Figure 1: Generic OTN overview

   In the OTN layering context, the media layer is the server layer of
   the optical signal layer.  The optical signal is guided to its
   destination by the media layer by means of a network media channel.
   In the media layer, switching is based on a frequency slot, and the
   size of a media channel is given by the properties of the associated
   frequency slot.

   In this scope, this document uses the term flexi-grid enabled DWDM
   network to refer to a network in which switching is based on
   frequency slots defined using the flexible grid, and covers mainly
   the Media Layer as well as the required adaptations from the Signal
   layer.  The present document is thus focused on the control and
   management of the media layer.

4.2.  Terminology

   This section presents the definition of the terms used in flexi-grid
   networks.  These terms are included in the ITU-T recommendations
   [G.694.1], [G.872]), [G.870], [G.8080] and [G.959.1-2013].

   Where appropriate, this documents also uses terminology and
   lexicography from [RFC4397].

4.2.1.  Frequency Slots

   This subsection is focused on the frequency slot related terms.

   o  Frequency Slot [G.694.1]: The frequency range allocated to a slot
      within the flexible grid and unavailable to other slots.  A
      frequency slot is defined by its nominal central frequency and its
      slot width.

   Nominal Central Frequency: each of the allowed frequencies as per the
   definition of flexible DWDM grid in [G.694.1].  The set of nominal
   central frequencies can be built using the following expression f =
   193.1 THz + n x 0.00625 THz, where 193.1 THz is ITU-T ''anchor
   frequency'' for transmission over the C band, n is a positive or
   negative integer including 0.



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      -5 -4 -3 -2 -1  0  1  2  3  4  5     <- values of n
    ...+--+--+--+--+--+--+--+--+--+--+-
                      ^
                      193.1 THz <- anchor frequency

     Figure 2: Anchor frequency and set of nominal central frequencies

   Nominal Central Frequency Granularity: It is the spacing between
   allowed nominal central frequencies and it is set to 6.25 GHz (note:
   sometimes referred to as 0.00625 THz).

   Slot Width Granularity: 12.5 GHz, as defined in [G.694.1].

   Slot Width: The slot width determines the "amount" of optical
   spectrum regardless of its actual "position" in the frequency axis.
   A slot width is constrained to be m x SWG (that is, m x 12.5 GHz),
   where m is an integer greater than or equal to 1.


         Frequency Slot 1     Frequency Slot 2
          -------------     -------------------
          |           |     |                 |
      -3 -2 -1  0  1  2  3  4  5  6  7  8  9 10 11
   ..--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--...
          -------------     -------------------
                ^                    ^
        Central F = 193.1THz    Central F = 193.14375 THz
        Slot width = 25 GHz     Slot width = 37.5 GHz


                     Figure 3: Example Frequency slots

   o  The symbol '+' represents the allowed nominal central frequencies,
      the '--' represents the nominal central frequency granularity, and
      the '^' represents the slot nominal central frequency.  The number
      on the top of the '+' symbol represents the 'n' in the frequency
      calculation formula.  The nominal central frequency is 193.1 THz
      when n equals zero.

   Effective Frequency Slot: the effective frequency slot of a media
   channel is the common part of the frequency slots along the media
   channel through a particular path through the optical network.  It is
   a logical construct derived from the (intersection of) frequency
   slots allocated to each device in the path.  The effective frequency
   slot is an attribute of a media channel and, being a frequency slot,
   it is described by its nominal central frequency and slot width,
   according to the already described rules.




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                        Frequency Slot 1
                -------------
                |           |
      -3 -2 -1  0  1  2  3  4  5  6  7  8  9 10 11
      ..--+--+--+--+--X--+--+--+--+--+--+--+--+--+--+--+--...

             Frequency Slot 2
             -------------------
             |                 |
      -3 -2 -1  0  1  2  3  4  5  6  7  8  9 10 11
      ..--+--+--+--+--X--+--+--+--+--+--+--+--+--+--+--+--...

   ===============================================
           Effective Frequency Slot
                -------------
                |           |
      -3 -2 -1  0  1  2  3  4  5  6  7  8  9 10 11
      ..--+--+--+--+--X--+--+--+--+--+--+--+--+--+--+--+--...


                    Figure 4: Effective Frequency Slot

4.2.2.  Media Channels

   Media Channel: a media association that represents both the topology
   (i.e., path through the media) and the resource (frequency slot) that
   it occupies.  As a topological construct, it represents a (effective)
   frequency slot supported by a concatenation of media elements
   (fibers, amplifiers, filters, switching matrices...).  This term is
   used to identify the end-to-end physical layer entity with its
   corresponding (one or more) frequency slots local at each link
   filters.

   Network Media Channel: It is a media channel that transports an
   Optical Tributary Signal [Editor's note: this definition goes beyond
   current G.870 definition, which is still tightened to a particular
   case of OTS, the OCh-P]

4.2.3.  Media Layer Elements

   Media Element: a media element only directs the optical signal or
   affects the properties of an optical signal, it does not modify the
   properties of the information that has been modulated to produce the
   optical signal [G.870].  Examples of media elements include fibers,
   amplifiers, filters and switching matrices.

   Media Channel Matrixes: the media channel matrix provides flexible
   connectivity for the media channels.  That is, it represents a point



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   of flexibility where relationships between the media ports at the
   edge of a media channel matrix may be created and broken.  The
   relationship between these ports is called a matrix channel.
   (Network) Media Channels are switched in a Media Channel Matrix.

4.2.4.  Optical Tributary Signals

   Optical Tributary Signal [G.959.1-2013]: The optical signal that is
   placed within a network media channel for transport across the
   optical network.  This may consist of a single modulated optical
   carrier or a group of modulated optical carriers or subcarriers.  One
   particular example of Optical Tributary Signal is an Optical Channel
   Payload (OCh-P) [G.872].

4.3.  Flexi-grid layered network model

   In the OTN layered network, the network media channel transports a
   single Optical Tributary Signal (see Figure 5)


     |                     Optical Tributary Signal                    |
     O - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - O
     |                                                                 |
     | Channel Port         Network Media Channel         Channel Port |
     O - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - O
     |                                                                 |
   +--------+                 +-----------+                   +--------+
   |  \ (1) |                 |    (1)    |                   | (1)  / |
   |   \----|-----------------|-----------|-------------------|-----/  |
   +--------+ Link Channel    +-----------+  Link Channel     +--------+
     Media Channel            Media Channel                Media Channel
     Matrix                   Matrix                       Matrix

   (1) - Matrix Channel

                Figure 5: Simplified Layered Network Model

   A particular example of Optical Tributary Signal is the OCh-P.
   Figure Figure 6 shows the example of the layered network model
   particularized for the OCH-P case, as defined in G.805.











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    OCh AP                     Trail (OCh)                    OCh AP
     O- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - O
     |                                                              |
    --- OCh-P                                                OCh-P ---
    \ / source                                               sink  \ /
     +                                                              +
     | OCh-P               OCh-P Network Connection           OCh-P |
     O TCP - - - - - - - - - - - - - - - - - - - - - - - - - - -TCP O
     |                                                              |
     |Channel Port          Network Media Channel      Channel Port |
     O - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  O
     |                                                              |
   +--------+                 +-----------+                 +---------+
   |  \ (1) |  OCh-P LC       |    (1)    |  OCh-P LC       |  (1)  / |
   |   \----|-----------------|-----------|-----------------|------/  |
   +--------+ Link Channel    +-----------+  Link Channel   +---------+
   Media Channel              Media Channel                Media Channel
     Matrix                     Matrix                        Matrix

   (1) - Matrix Channel

            Figure 6: Layered Network Model according to G.805

   By definition a network media channel only supports a single Optical
   Tributary signal.  How several Optical Tributary signals are bound
   together is out of the scope of the present document and is a matter
   of the signal layer.

4.3.1.  Hierarchy in the Media Layer

   In summary, the concept of frequency slot is a logical abstraction
   that represents a frequency range while the media layer represents
   the underlying media support.  Media Channels are media associations,
   characterized by their (effective) frequency slot, respectively; and
   media channels are switched in media channel matrixes.  From the
   control and management perspective, a media channel can be logically
   splited in other media channels.

   In Figure 7 , a Media Channel has been configured and dimensioned to
   support two network media channels, each of them carrying one optical
   tributary signal.










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                            Media Channel Frequency Slot
    +-------------------------------X------------------------------+
    |                                                              |
    |       Frequency Slot                  Frequency Slot         |
    |   +------------X-----------+      +----------X-----------+   |
    |   | Opt Tributary Signal  |       | Opt Tributary Signal |   |
    |   |           o           |       |          o           |   |
    |   |           |           |       |          |           |   |
   -4  -3  -2  -1   0   1   2   3   4   5   6   7  8   9  10  11  12
    +---+---+---+---+---+---+---+---+---+---+---+--+---+---+---+---+---

         <- Network Media Channel->     <- Network Media Channel->

     <------------------------ Media Channel ----------------------->

        X - Frequency Slot Central Frequency

        o - signal central frequency


      Figure 7: Example of Media Channel / Network Media Channels and
                        associated frequency slots

4.3.2.  DWDM flexi-grid enabled network element models

   Similar to fixed grid networks, a flexible grid network is also
   constructed from subsystems that include Wavelength Division
   Multiplexing (WDM) links, tunable transmitters and receivers, i.e,
   media elements including media layer switching elements (media
   matrices), as well as electro-optical network elements, all of them
   with flexible grid characteristics.

   As stated in [G.694.1] the flexible DWDM grid defined in Clause 7 has
   a nominal central frequency granularity of 6.25 GHz and a slot width
   granularity of 12.5 GHz.  However, devices or applications that make
   use of the flexible grid may not be capable of supporting every
   possible slot width or position.  In other words, applications may be
   defined where only a subset of the possible slot widths and positions
   are required to be supported.  For example, an application could be
   defined where the nominal central frequency granularity is 12.5 GHz
   (by only requiring values of n that are even) and that only requires
   slot widths as a multiple of 25 GHz (by only requiring values of m
   that are even).








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5.  GMPLS applicability

   The goal of this section is to provide an insight of the application
   of GMPLS to control flexi-grid networks, while specific requirements
   are covered in the next section.  The present framework is aimed at
   controlling the media layer within the Optical Transport Network
   (OTN) hierarchy and the required adaptations of the signal layer.
   This document also defines the term SSON (Spectrum-Switched Optical
   Network) to refer to a Flexi-grid enabled DWDM network that is
   controlled by a GMPLS/PCE control plane.

   This section provides a mapping of the ITU-T G.872 architectural
   aspects to GMPLS/Control plane terms, and considers the relationship
   between the architectural concept/construct of media channel and its
   control plane representations (e.g. as a TE link).

5.1.  General considerations

   The GMPLS control of the media layer deals with the establishment of
   media channels, which are switched in media channel matrixes.  GMPLS
   labels locally represent the media channel and its associated
   frequency slot.  Network media channels are considered a particular
   case of media channels when the end points are transceivers (that is,
   source and destination of an Optical Tributary Signal)

5.2.  Considerations on TE Links

   From a theoretical / abstract point of view, a fiber can be modeled
   has having a frequency slot that ranges from (-inf, +inf).  This
   representation helps understand the relationship between frequency
   slots / ranges.

   The frequency slot is a local concept that applies locally to a
   component / element.  When applied to a media channel, we are
   referring to its effective frequency slot as defined in [G.872].

   The association of a filter, a fiber and a filter is a media channel
   in its most basic form, which from the control plane perspective may
   modeled as a (physical) TE-link with a contiguous optical spectrum at
   start of day.  A means to represent this is that the portion of
   spectrum available at time t0 depends on which filters are placed at
   the ends of the fiber and how they have been configured.  Once
   filters are placed we have the one hop media channel.  In practical
   terms, associating a fiber with the terminating filters determines
   the usable optical spectrum.






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   -----------------+                             +-----------------+
                    |                             |
           +--------+                             +--------+
           |        |                             |        |  +---------
       ---o|        ===============================        o--|
           |        |             Fiber           |        |  | --\  /--
       ---o|        |                             |        o--|    \/
           |        |                             |        |  |    /\
       ---o|        ===============================        o--| --/  \--
           | Filter |                             | Filter |  |
           |        |                             |        |  +---------
           +--------+                             +--------+
                    |                             |
                 |------- Basic Media Channel  ---------|
   -----------------+                             +-----------------+


         --------+                                      +--------
                 |--------------------------------------|
          LSR    |               TE link                |  LSR
                 |--------------------------------------|
        +--------+                                      +--------


                Figure 8: (Basic) Media channel and TE link

   Additionally, when a cross-connect for a specific frequency slot is
   considered, the underlying media support is still a media channel,
   augmented, so to speak, with a bigger association of media elements
   and a resulting effective slot.  When this media channel is the
   result of the association of basic media channels and media layer
   matrix cross-connects, this architectural construct can be
   represented as / corresponds to a Label Switched Path (LSP) from a
   control plane perspective.  In other words, It is possible to
   "concatenate" several media channels (e.g.  Patch on intermediate
   nodes) to create a single media channel.















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   -----------+       +------------------------------+       +----------
              |       |                              |       |
       +------+       +------+                +------+       +------+
       |      |       |      |  +----------+  |      |       |      |
    --o|      =========      o--|          |--o      =========      o--
       |      | Fiber |      |  | --\  /-- |  |      | Fiber |      |
    --o|      |       |      o--|    \/    |--o      |       |      o--
       |      |       |      |  |    /\    |  |      |       |      |
    --o|      =========      o--***********|--o      =========      o--
       |Filter|       |Filter|  |          |  |Filter|       |Filter|
       |      |       |      |                |      |       |      |
       +------+       +------+                +------+       +------+
              |       |                              |       |
          <- Basic Media ->    <- Matrix ->       <- Basic Media->
              |Channel|           Channel            |Channel|
   -----------+       +------------------------------+       +----------

          <--------------------  Media Channel  ---------------->

     -----+                  +---------------+                  +-------
          |------------------|               |------------------|
     LSR  |       TE link    |       LSR     |   TE link        |   LSR
          |------------------|               |------------------|
     -----+                  +---------------+                  +-------


                     Figure 9: Extended Media Channel

   Additionally, if appropriate, it can also be represented as a TE link
   or Forwarding Adjacency (FA), augmenting the control plane network
   model.




















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   -----------+       +------------------------------+       +----------
              |       |                              |       |
       +------+       +------+                +------+       +------+
       |      |       |      |  +----------+  |      |       |      |
    --o|      =========      o--|          |--o      =========      o--
       |      | Fiber |      |  | --\  /-- |  |      | Fiber |      |
    --o|      |       |      o--|    \/    |--o      |       |      o--
       |      |       |      |  |    /\    |  |      |       |      |
    --o|      =========      o--***********|--o      =========      o--
       |Filter|       |Filter|  |          |  |Filter|       |Filter|
       |      |       |      |                |      |       |      |
       +------+       +------+                +------+       +------+
              |       |                              |       |
   -----------+       +------------------------------+       +----------

           <------------------------  Media Channel  ----------->

    +-----+                                                      +------
          |------------------------------------------------------|
    LSR   |                               TE link                |  LSR
          |------------------------------------------------------|
    +-----+                                                      +------


             Figure 10: Extended Media Channel / TE Link / FA

5.3.  Considerations on Labeled Switched Path (LSP) in Flexi-grid

   The flexi-grid LSP is seen as a control plane representation of a
   media channel.  Since network media channels are media channels, an
   LSP may also be the control plane representation of a network media
   channel, in a particular context.  From a control plane perspective,
   the main difference (regardless of the actual effective frequency
   slot which may be dimensioned arbitrarily) is that the LSP that
   represents a network media channel also includes the endpoints
   (transceivers) , including the cross-connects at the ingress / egress
   nodes.  The ports towards the client can still be represented as
   interfaces from the control plane perspective.

   Figure 11 describes an LSP routed along 3 nodes.  The LSP is
   terminated before the optical matrix of the ingress and egress nodes
   and can represent a Media Channel.  This case does NOT (and cannot)
   represent a network media channel as it does not include (and cannot
   include) the transceivers.







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   ----------+       +--------------------------------+       +---------
             |       |                                |       |
      +------+       +------+                  +------+       +------+
      |      |       |      |   +----------+   |      |       |      |
    -o|      =========      o---|          |---o      =========      o-
      |      | Fiber |      |   | --\  /-- |   |      | Fiber |      |
    -o|>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>o-
      |      |       |      |   |    /\    |   |      |       |      |
    -o|      =========      o---***********|---o      =========      o-
      |Filter|       |Filter|   |          |   |Filter|       |Filter|
      |      |       |      |                  |      |       |      |
      +------+       +------+                  +------+       +------+
             |       |                                |       |
   ----------+       +--------------------------------+       +---------

           >>>>>>>>>>>>>>>>>>>>>>>>>>>> LSP >>>>>>>>>>>>>>>>>>>>>>>>
      -----+                  +---------------+                +-----
           |------------------|               |----------------|
      LSR  |       TE link    |     LSR       |      TE link   | LSR
           |------------------|               |----------------|
      -----+                  +---------------+                +-----


   Figure 11: Flex-grid LSP representing a media channel that starts at
    the filter of the outgoing interface of the ingress LSR and ends at
          the filter of the incoming interface of the egress LSR

   In Figure 12 a Network Media Channel is represented as terminated at
   the DWDM side of the transponder, this is commonly named as OCh-trail
   connection.





















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   |--------------------- Network Media Channel ----------------------|

        +----------------------+           +----------------------+
        |                                  |                      |
        +------+        +------+           +------+        +------+
        |      | +----+ |      |           |      | +----+ |      |OCh-P
   OCh-P|      o-|    |-o      |  +-----+  |      o-|    |-o      |sink
    src |      | |    | |      ===+-+ +-+==|      | |    | |      O---|R
   T|***o******o********************************************************
        |      | |\  /| |         | | | |  |      | |\  /| |      |
        |      o-| \/ |-o      ===| | | |==|      o-| \/ |-o      |
        |      | | /\ | |      |  +-+ +-+  |      | | /\ | |      |
        |      o-|/  \|-o      |  |  \/ |  |      o-|/  \|-o      |
        |Filter| |    | |Filter|  |  /\ |  |Filter| |    | |Filter|
        +------+ |    | +------+  +-----+  +------+ |    | +------+
        |        |    |        |           |        |    |        |
        +----------------------+           +----------------------+
                                      LSP
   <------------------------------------------------------------------->

                                      LSP
    <------------------------------------------------------------------>
         +-----+                   +--------+                +-----+
    o--- |     |-------------------|        |----------------|     |---o
         | LSR |       TE link     |  LSR   |   TE link      | LSR |
         |     |-------------------|        |----------------|     |
         +-----+                   +--------+                +-----+


      Figure 12: LSP representing a network media channel (OCh-Trail)

   In a third case, a Network Media Channel terminated on the Filter
   ports of the Ingress and Egress nodes.  This is named in G.872 as
   OCh-NC (we need to discuss the implications, if any, once modeled at
   the control plane level of models B and C).
















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     |---------------------  Network Media Channel --------------------|

     +------------------------+               +------------------------+
     +------+        +------+                 +------+          +------+
     |      | +----+ |      |                 |      | +----+ |      |
     |      o-|    |-o      |    +------+     |      o-|    |-o      |
     |      | |    | |      =====+-+  +-+=====|      | |    | |      |
   T-o******o********************************************************O-R
     |      | |\  /| |           | |  | |     |      | |\  /| |      |
     |      o-| \/ |-o      =====| |  | |=====|      o-| \/ |-o      |
     |      | | /\ | |      |    +-+  +-+     |      | | /\ | |      |
     |      o-|/  \|-o      |    |  \/  |     |      o-|/  \|-o      |
     |Filter| |    | |Filter|    |  /\  |     |Filter| |    | |Filter|
     +------+ |    | +------+    +------+     +------+ |    | +------+
     |        |    |        |                 |        |    |        |
     +----------------------+                 +----------------------+
     <----------------------------------------------------------------->
                                    LSP

                                     LSP
     <-------------------------------------------------------------->
      +-----+                    +--------+                   +-----+
   o--|     |--------------------|        |-------------------|     |--o
      | LSR |       TE link      |  LSR   |      TE link      | LSR |
      |     |--------------------|        |-------------------|     |
      +-----+                    +--------+                   +-----+


      Figure 13: LSP representing a network media channel (OCh-P NC)

   [Note: not clear the difference, from a control plane perspective, of
   figs Figure 12 and Figure 13.]

   Applying the notion of hierarchy at the media layer, by using the LSP
   as a FA, the media channel created can support multiple (sub) media
   channels.  [Editot note : a specific behavior related to Hierarchies
   will be verified at a later point in time].














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   +--------------+                      +--------------+
   |    OCh-P     |           TE         |     OCh-P    |  Virtual TE
   |              |          link        |              |    link
   |    Matrix    |o- - - - - - - - - - o|    Matrix    |o- - - - - -
   +--------------+                      +--------------+
                  |     +---------+      |
                  |     |  Media  |      |
                  |o----| Channel |-----o|
                        |         |
                        | Matrix  |
                        +---------+


            Figure 14: MRN/MLN topology view with TE link / FA

   Note that there is only one media layer switch matrix (one
   implementation is FlexGrid ROADM) in SSON, while "signal layer LSP is
   mainly for the purpose of management and control of individual
   optical signal".  Signal layer LSPs (OChs) with the same attributions
   (such as source and destination) could be grouped into one media-
   layer LSP (media channel), which has advantages in spectral
   efficiency (reduce guard band between adjacent OChs in one FSC) and
   LSP management.  However, assuming some network elements indeed
   perform signal layer switch in SSON, there must be enough guard band
   between adjacent OChs in one media channel, in order to compensate
   filter concatenation effect and other effects caused by signal layer
   switching elements.  In such condition, the separation of signal
   layer from media layer cannot bring any benefit in spectral
   efficiency and in other aspects, but make the network switch and
   control more complex.  If two OChs must switch to different ports, it
   is better to carry them by diferent FSCs and the media layer switch
   is enough in this scenario.

5.4.  Control Plane modeling of Network elements

   Optical transmitters/receivers may have different tunability
   constraints, and media channel matrixes may have switching
   restrictions.  Additionally, a key feature of their implementation is
   their highly asymmetric switching capability which is described in
   [RFC6163] in detail.  Media matrices include line side ports which
   are connected to DWDM links and tributary side input/output ports
   which can be connected to transmitters/receivers.

   A set of common constraints can be defined:

   o  The minimum and maximum slot width.





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   o  Granularity: the optical hardware may not be able to select
      parameters with the lowest granularity (e.g. 6.25 GHz for nominal
      central frequencies or 12.5 GHz for slot width granularity).

   o  Available frequency ranges: the set or union of frequency ranges
      that are not allocated (i.e. available).  The relative grouping
      and distribution of available frequency ranges in a fiber is
      usually referred to as ''fragmentation''.

   o  Available slot width ranges: the set or union of slot width ranges
      supported by media matrices.  It includes the following
      information.

      *  Slot width threshold: the minimum and maximum Slot Width
         supported by the media matrix.  For example, the slot width can
         be from 50GHz to 200GHz.

      *  Step granularity: the minimum step by which the optical filter
         bandwidth of the media matrix can be increased or decreased.
         This parameter is typically equal to slot width granularity
         (i.e. 12.5GHz) or integer multiples of 12.5GHz.

   [Editor's note: different configurations such as C/CD/CDC will be
   added later.  This section should state specifics to media channel
   matrices, ROADM models need to be moved to an appendix].

5.5.  Media Layer Resource Allocation considerations

   A media channel has an associated effective frequency slot.  From the
   perspective of network control and management, this effective slot is
   seen as the "usable" frequency slot end to end.  The establishment of
   an LSP related the establishment of the media channel and effective
   frequency slot.

   In this context, when used unqualified, the frequency slot is a local
   term, which applies at each hop.  An effective frequency slot applies
   at the media chall (LSP) level

   A "service" request is characterized as a minimum, by its required
   effective slot width.  This does not preclude that the request may
   add additional constraints such as imposing also the nominal central
   frequency.  A given frequency slot is requested for the media channel
   say, with the Path message.  Regardless of the actual encoding, the
   Path message sender descriptor sender_tspec shall specify a minimum
   frequency slot width that needs to be fulfilled.

   In order to allocate a proper effective frequency slot for a LSP, the
   signaling should specify its required slot width.



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   An effective frequency slot must equally be described in terms of a
   central nominal frequency and its slot width (in terms of usable
   spectrum of the effective frequency slot).  That is, one must be able
   to obtain an end-to-end equivalent n and m parameters.  We refer to
   this as the "effective frequency slot of the media channel/LSP must
   be valid".

   In GMPLS the requested effective frequency slot is represented to the
   TSpec and the effective frequency slot is mapped to the FlowSpec.

   The switched element corresponds in GMPLS to the 'label'.  As in
   flexi-grid the switched element is a frequency slot, the label
   represents a frequency slot.  Consequently, the label in flexi-grid
   must convey the necessary information to obtain the frequency slot
   characteristics (i.e, center and width, the n and m parameters).  The
   frequency slot is locally identified by the label

   The local frequency slot may change at each hop, typically given
   hardware constraints (e.g. a given node cannot support the finest
   granularity).  Locally n and m may change.  As long as a given
   downstream node allocates enough optical spectrum, m can be different
   along the path.  This covers the issue where concrete media matrices
   can have different slot width granularities.  Such "local" m will
   appear in the allocated label that encodes the frequency slot as well
   as the flow descriptor flowspec.

   Different modes are considered: RSA with explicit label control, and
   for R+DSA, the GMPLS signaling procedure is similar to the one
   described in section 4.1.3 of [RFC6163] except that the label set
   should specify the available nominal central frequencies that meet
   the slot width requirement of the LSP.  The intermediate nodes can
   collect the acceptable central frequencies that meet the slot width
   requirement hop by hop.  The tail-end node also needs to know the
   slot width of a LSP to assign the proper frequency resource.
   Compared with [RFC6163], except identifying the resource (i.e., fixed
   wavelength for WSON and frequency resource for flexible grids), the
   other signaling requirements (e.g., unidirectional or bidirectional,
   with or without converters) are the same as WSON described in the
   section 6.1 of [RFC6163].

   Regarding how a GMPLS control plane can assign n and m, different
   cases can apply:

      a) n and m can both change.  It is the effective slot what
      matters.  Some entity needs to make sure the effective frequency
      slot remains valid.





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      b) m can change; n needs to be the same along the path.  This
      ensures that the nominal central frequency stays the same.

      c) n and m need to be the same.

      d)n can change, m needs to be the same.

   In consequence, an entity such as a PCE can make sure that the n and
   m stay the same along the path.  Any constraint (including frequency
   slot and width granularities) is taken into account during path
   computation.  alternatively, A PCE (or a source node) can compute a
   path and the actual frequency slot assignment is done, for example,
   with a distributed (signaling) procedure:

      Each downstream node ensures that m is >= requested_m.

      Since a downstream node cannot foresee what an upstream node will
      allocate in turn, a way we can ensure that the effective frequency
      slot is valid is then by ensuring that the same "n" is allocated.
      By forcing the same n, we avoid cases where the effective
      frequency slot of the media channel is invalid (that is, the
      resulting frequency slot cannot be described by its n and m
      parameters).

      Maybe this is a too hard restriction, since a node (or even a
      centralized/combined RSA entity) can make sure that the resulting
      end to end (effective) frequency slot is valid, even if n is
      different locally.  That means, the effective (end to end)
      frequency slot that characterizes the media channel is one and
      determined by its n and m, but are logical, in the sense that they
      are the result of the intersection of local (filters) freq slots
      which may have different freq. slots

   For Figure Figure 15 the effective slot is valid by ensuring that the
   minimum m is greater than the requested m.  The effective slot
   (intersection) is the lowest m (bottleneck).

   For Figure Figure 16 the effective slot is valid by ensuring that it
   is valid at each hop in the upstream direction.  The intersection
   needs to be computed.  Invalid slots could result otherwise.











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             |Path(m_req)   |                ^                |
             |--------->    |                #                |
             |              |                #                ^
            -^--------------^----------------#----------------#--
   Effective #              #                #                #
   FS n, m   # . . . . . . .#. . . . . . . . # . . . . . . . .# <-fixed
             #              #                #                #   n
            -v--------------v----------------#----------------#---
             |              |                #                v
             |              |                #          Resv  |
             |              |                v        <------ |
             |              |                |flowspec(n, m_a)|
             |              |       <--------|                |
             |              |  flowspec (n,  |
                   <--------|      min(m_a, m_b))
             flowspec (n,  |
               min(m_a, m_b, m_c))


       Figure 15: Distributed allocation with different m and same n


             |Path(m_req)  ^                |
             |--------->   #                |                 |
             |             #                ^                 ^
            -^-------------#----------------#-----------------#--------
   Effective #             #                #                 #
   FS n, m   #             #                #                 #
             #             #                #                 #
            -v-------------v----------------#-----------------#--------
             |             |                #                 v
             |             |                #           Resv  |
             |             |                v         <------ |
             |             |                |flowspec(n_a, m_a)
             |             |       <--------|                 |
             |             |  flowspec (FSb [intersect] FSa)
                  <--------|
            flowspec ([intersect] FSa,FSb,FSc)


    Figure 16: Distributed allocation with different m and different n

   Note, when a media channel is bound to one OCh-P (i.e is a Network
   media channel), the EFS must be the one of the Och-P. The media
   channel setup by the LSP may contains the EFS of the network media
   channel EFS.  This is an endpoint property, the egress and ingress
   SHOULD constrain the EFS to Och-P EFS .




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5.6.  Neighbor Discovery and Link Property Correlation

   Potential interworking problems between fixed-grid DWDM and flexible-
   grid DWDM nodes, may appear.  Additionally, even two flexible-grid
   optical nodes may have different grid properties, leading to link
   property conflict.

   Devices or applications that make use of the flexible-grid may not be
   able to support every possible slot width.  In other words,
   applications may be defined where different grid granularity can be
   supported.  Taking node F as an example, an application could be
   defined where the nominal central frequency granularity is 12.5 GHz
   requiring slot widths being multiple of 25 GHz.  Therefore the link
   between two optical nodes with different grid granularity must be
   configured to align with the larger of both granularities.  Besides,
   different nodes may have different slot width tuning ranges.

   In summary, in a DWDM Link between two nodes, at least the following
   properties should be negotiated:

      Grid capability (channel spacing) - Between fixed-grid and
      flexible-grid nodes.

      Grid granularity - Between two flexible-grid nodes.

      Slot width tuning range - Between two flexible-grid nodes.

5.7.  Path Computation / Routing and Spectrum Assignment (RSA)

   Much like in WSON, in which if there is no (available) wavelength
   converters in an optical network, an LSP is subject to the
   ''wavelength continuity constraint'' (see section 4 of [RFC6163]), if
   the capability of shifting or converting an allocated frequency slot,
   the LSP is subject to the Optical ''Spectrum Continuity Constraint''.

   Because of the limited availability of wavelength/spectrum converters
   (sparse translucent optical network) the wavelength/spectrum
   continuity constraint should always be considered.  When available,
   information regarding spectrum conversion capabilities at the optical
   nodes may be used by RSA (Routing and Spectrum Assignment)
   mechanisms.

   The RSA process determines a route and frequency slot for a LSP.
   Hence, when a route is computed the spectrum assignment process (SA)
   should determine the central frequency and slot width based on the
   slot width and available central frequencies information of the
   transmitter and receiver, and the available frequency ranges




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   information and available slot width ranges of the links that the
   route traverses.

5.7.1.  Architectural Approaches to RSA

   Similar to RWA for fixed grids, different ways of performing RSA in
   conjunction with the control plane can be considered.  The approaches
   included in this document are provided for reference purposes only;
   other possible options could also be deployed.

5.7.1.1.  Combined RSA (R&SA)

   In this case, a computation entity performs both routing and
   frequency slot assignment.  The computation entity should have the
   detailed network information, e.g.  connectivity topology constructed
   by nodes/links information, available frequency ranges on each link,
   node capabilities, etc.

   The computation entity could reside either on a PCE or the ingress
   node.

5.7.1.2.  Separated RSA (R+SA)

   In this case, routing computation and frequency slot assignment are
   performed by different entities.  The first entity computes the
   routes and provides them to the second entity; the second entity
   assigns the frequency slot.

   The first entity should get the connectivity topology to compute the
   proper routes; the second entity should get the available frequency
   ranges of the links and nodes' capabilities information to assign the
   spectrum.

5.7.1.3.  Routing and Distributed SA (R+DSA)

   In this case, one entity computes the route but the frequency slot
   assignment is performed hop-by-hop in a distributed way along the
   route.  The available central frequencies which meet the spectrum
   continuity constraint should be collected hop by hop along the route.
   This procedure can be implemented by the GMPLS signaling protocol.

5.8.  Routing / Topology dissemination

   In the case of combined RSA architecture, the computation entity
   needs to get the detailed network information, i.e. connectivity
   topology, node capabilities and available frequency ranges of the
   links.  Route computation is performed based on the connectivity
   topology and node capabilities; spectrum assignment is performed



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   based on the available frequency ranges of the links.  The
   computation entity may get the detailed network information by the
   GMPLS routing protocol.  Compared with [RFC6163], except wavelength-
   specific availability information, the connectivity topology and node
   capabilities are the same as WSON, which can be advertised by GMPLS
   routing protocol (refer to section 6.2 of [RFC6163].  This section
   analyses the necessary changes on link information brought by
   flexible grids.

5.8.1.  Available Frequency Ranges/slots of DWDM Links

   In the case of flexible grids, channel central frequencies span from
   193.1 THz towards both ends of the C band spectrum with 6.25 GHz
   granularity.  Different LSPs could make use of different slot widths
   on the same link.  Hence, the available frequency ranges should be
   advertised.

5.8.2.  Available Slot Width Ranges of DWDM Links

   The available slot width ranges needs to be advertised, in
   combination with the Available frequency ranges, in order to verify
   whether a LSP with a given slot width can be set up or not; this is
   is constrained by the available slot width ranges of the media matrix
   Depending on the availability of the slot width ranges, it is
   possible to allocate more spectrum than strictly needed by the LSP.

5.8.3.  Spectrum Management

   [Editors' note: the part on the hierarchy of the optical spectrum
   could be confusing, we can discuss it].  The total available spectrum
   on a fiber could be described as a resource that can be divided by a
   media device into a set of Frequency Slots.  In terms of managing
   spectrum, it is necessary to be able to speak about different
   granularities of managed spectrum.  For example, a part of the
   spectrum could be assigned to a third party to manage.  This need to
   partition creates the impression that spectrum is a hierarchy in view
   of Management and Control Plane.  The hierarchy is created within a
   management system, and it is an access right hierarchy only.  It is a
   management hierarchy without any actual resource hierarchy within
   fiber.  The end of fiber is a link end and presents a fiber port
   which represents all of spectrum available on the fiber.  Each
   spectrum allocation appears as Link Channel Port (i.e., frequency
   slot port) within fiber.








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5.8.4.  Information Model

   Fixed DM grids can also be described via suitable choices of slots in
   a flexible DWDM grid.  However, devices or applications that make use
   of the flexible grid may not be capable of supporting every possible
   slot width or central frequency position.  Following is the
   definition of information model, not intended to limit any IGP
   encoding implementation.  For example, information required for
   routing/path selection may be the set of available nominal central
   frequencies from which a frequency slot of the required width can be
   allocated.  A convenient encoding for this information (may be as a
   frequency slot or sets of contiguous slices) is further study in IGP
   encoding document.

   <Available Spectrum in Fiber for frequency slot> ::=
       <Available Frequency Range-List>
       <Available Central Frequency Granularity >
       <Available Slot Width Granularity>
       <Minimal Slot Width>
       <Maximal Slot Width>

   <Available Frequency Range-List> ::=
       <Available Frequency Range >[< Available Frequency Range-List>]

   <Available Frequency Range >::=
     <Start Spectrum Position><End Spectrum Position> |
     <Sets of contiguous slices>

   <Available Central Frequency Granularity> ::= n A&#151; 6.25GHz,
     where n is positive integer, such as 6.25GHz, 12.5GHz, 25GHz, 50GHz
     or 100GHz

   <Available Slot Width Granularity> ::= m A&#151; 12.5GHz,
     where m is positive integer

   <Minimal Slot Width> ::= j x 12.5GHz,
     j is a positive integer

   <Maximal Slot Width> ::= k x 12.5GHz,
       k is a positive integer (k >= j)


                   Figure 17: Routing Information model








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6.  Control Plane Requirements

   The GMPLS based control plane of a flexi-grid networks provides
   aditional requirements to GMPLS.  In this section the features to be
   covered by GMPLS signaling for flexi-grid are identified.  [Editor's
   note: Only discussed requirements are included at this stage.
   Routing requirements will come in the next version]

6.1.  Support for Media Channels

   The control plane SHALL be able to support Media Channels,
   characterized by a single frequency slot.  The representation of the
   Media Channel in the GMPLS Control plane is the so-called flexi-grid
   LSP.  Since network media channels are media channels, an LSP may
   also be the control plane representation of a network media channel.
   Consequently, the control plane SHALL be able to support Network
   Media Channels.

   The signaling procedure SHALL be able to configure the nominal
   central frequency (n) of a flexi-grid LSP.

   The control plane protocols SHALL allow flexible range of values for
   the frequency slot width (m) parameter.  Specifically, the control
   plane SHALL allow setting up a media channel with frequency slot
   width (m) ranging from a minimum of m=1 (12.5GHz) to a maximum of the
   entire C-band with a slot width granularity of 12.5GHz.

   The signaling procedure of the GMPLS control plane SHALL be able to
   configure the minimum width (m) of a flexi-grid LSP.  In adition, the
   control plane SHALL be able to configure local frecuency slots,

   The control plane architecture SHOULD allow for the support of L-band
   and S-band

   The signalling process of the control plane SHALL allow to collect
   the local frequency slot asigned at each link along the path

6.2.  Support for Media Channel Resizing

   The control plane SHALL allow resizing (grow or shrink) the frequency
   slot width of a media channel/network media channel.  The resizing
   MAY imply resizing the local frequency slots along the path of the
   flexi-grid LSP.








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6.3.  Support for Logical Associations of multiple media channels

   A set of media channels can be used to transport signals that have a
   logical association between them.  The control plane architecture
   SHOULD allow multiple media channels to be logically associated.  The
   control plane SHOULD allow the co-routing of a set of media channels
   logically associated

7.  Security Considerations

   TBD

8.  Contributing Authors

      Qilei Wang
      ZTE
      Ruanjian Avenue, Nanjing, China
      wang.qilei@zte.com.cn


      Malcolm Betts
      ZTE
      malcolm.betts@zte.com.cn


      Xian Zhang
      Huawei
      zhang.xian@huawei.com


      Cyril Margaria
      Nokia Siemens Networks
      St Martin Strasse 76, Munich, 81541, Germany
      +49 89 5159 16934
      cyril.margaria@nsn.com


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


      Yao Li
      Nanjing University
      wsliguotou@hotmail.com



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      Fei Zhang
      ZTE
      Zijinghua Road, Nanjing, China
      zhang.fei3@zte.com.cn


      Lei Wang
      ZTE
      East Huayuan Road, Haidian district, Beijing, China
      wang.lei131@zte.com.cn


      Guoying Zhang
      China Academy of Telecom Research
      No.52 Huayuan Bei Road, Beijing, China
      zhangguoying@ritt.cn


      Takehiro Tsuritani
      KDDI R&D Laboratories Inc.
      2-1-15 Ohara, Fujimino, Saitama, Japan
      tsuri@kddilabs.jp


      Lei Liu
      KDDI R&D Laboratories Inc.
      2-1-15 Ohara, Fujimino, Saitama, Japan
      le-liu@kddilabs.jp


      Eve Varma
      Alcatel-Lucent
      +1 732 239 7656
      eve.varma@alcatel-lucent.com


      Young Lee
      Huawei


      Jianrui Han
      Huawei


      Sharfuddin Syed
      Infinera





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      Rajan Rao
      Infinera


      Marco Sosa
      Infinera


      Biao Lu
      Infinera


      Abinder Dhillon
      Infinera


      Felipe Jimenez Arribas
      TelefA^3nica I+D


      Andrew G. Malis
      Verizon


      Adrian Farrel
      Old Dog Consulting


      Daniel King
      Old Dog Consulting


      Huub van Helvoort


9.  Acknowledgments

   The authors would like to thank Pete Anslow for his insights and
   clarifications.  This work was supported in part by the FP-7 IDEALIST
   project under grant agreement number 317999.

10.  References

10.1.  Normative References

   [G.694.1]  International Telecomunications Union, "ITU-T
              Recommendation G.694.1, Spectral grids for WDM
              applications: DWDM frequency grid", November 2012.



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   [G.709]    International Telecomunications Union, "ITU-T
              Recommendation G.709, Interfaces for the Optical Transport
              Network (OTN).", March 2009.

   [G.800]    International Telecomunications Union, "ITU-T
              Recommendation G.800, Unified functional architecture of
              transport networks.", February 2012.

   [G.805]    International Telecomunications Union, "ITU-T
              Recommendation G.805, Generic functional architecture of
              transport networks.", March 2000.

   [G.8080]   International Telecomunications Union, "ITU-T
              Recommendation G.8080/Y.1304, Architecture for the
              automatically switched optical network", 2012.

   [G.870]    International Telecomunications Union, "ITU-T
              Recommendation G.870/Y.1352, Terms and definitions for
              optical transport networks", November 2012.

   [G.872]    International Telecomunications Union, "ITU-T
              Recommendation G.872, Architecture of optical transport
              networks, draft v0.16 2012/09 (for discussion)", 2012.

   [G.959.1-2013]
              International Telecomunications Union, "Update of ITU-T
              Recommendation G.959.1, Optical transport network physical
              layer interfaces (to appear in July 2013)", 2013.

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

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

   [RFC4206]  Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
              Hierarchy with Generalized Multi-Protocol Label Switching
              (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005.

   [RFC5150]  Ayyangar, A., Kompella, K., Vasseur, JP., and A. Farrel,
              "Label Switched Path Stitching with Generalized
              Multiprotocol Label Switching Traffic Engineering (GMPLS
              TE)", RFC 5150, February 2008.

   [RFC6163]  Lee, Y., Bernstein, G., and W. Imajuku, "Framework for
              GMPLS and Path Computation Element (PCE) Control of
              Wavelength Switched Optical Networks (WSONs)", RFC 6163,
              April 2011.



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10.2.  Informative References

   [RFC4397]  Bryskin, I. and A. Farrel, "A Lexicography for the
              Interpretation of Generalized Multiprotocol Label
              Switching (GMPLS) Terminology within the Context of the
              ITU-T's Automatically Switched Optical Network (ASON)
              Architecture", RFC 4397, February 2006.

Authors' Addresses

   Oscar Gonzalez de Dios (editor)
   Telefonica I+D
   Don Ramon de la Cruz 82-84
   Madrid  28045
   Spain

   Phone: +34913128832
   Email: ogondio@tid.es


   Ramon Casellas (editor)
   CTTC
   Av. Carl Friedrich Gauss n.7
   Castelldefels  Barcelona
   Spain

   Phone: +34 93 645 29 00
   Email: ramon.casellas@cttc.es


   Fatai Zhang
   Huawei
   Huawei Base, Bantian, Longgang District
   Shenzhen  518129
   China

   Phone: +86-755-28972912
   Email: zhangfatai@huawei.com


   Xihua Fu
   ZTE
   Ruanjian Avenue
   Nanjing
   China

   Email: fu.xihua@zte.com.cn




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   Daniele Ceccarelli
   Ericsson
   Via Calda 5
   Genova
   Italy

   Phone: +39 010 600 2512
   Email: daniele.ceccarelli@ericsson.com


   Iftekhar Hussain
   Infinera
   140 Caspian Ct.
   Sunnyvale  94089
   USA

   Phone: 408-572-5233
   Email: ihussain@infinera.com

































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