Network Working Group                           O. Gonzalez de Dios, Ed.
Internet-Draft                                            Telefonica I+D
Intended status: Standards Track                        R. Casellas, Ed.
Expires: February August 27, 2015                                            CTTC
                                                                F. Zhang
                                                                  Huawei
                                                                   X. Fu
                                                                     ZTE
                                                           D. Ceccarelli
                                                                Ericsson
                                                              I. Hussain
                                                                Infinera
                                                         August 26, 2014
                                                       February 23, 2015

 Framework and Requirements for GMPLS based GMPLS-based control of Flexi-grid DWDM
                                networks
                   draft-ietf-ccamp-flexi-grid-fwk-02
                   draft-ietf-ccamp-flexi-grid-fwk-03

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] its
   Recommendations G.694.1 and [G.872] G.872 to include the concept of
   flexible grid.  A a new DWDM dense wavelength
   division multiplexing (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 an environment, a data plane connection is switched
   based on allocated, variable-sized frequency ranges within the
   optical spectrum. spectrum creating what is known as a flexible grid (flexi-
   grid).

   This document defines a framework and the associated control plane
   requirements for the GMPLS-based control of flexi-grid DWDM networks.

Status of This Memo

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Table of Contents

   1.  Requirements Language  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Introduction  Terminology . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Acronyms .   4
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   4
     2.2.  Abbreviations . . . . . . . .   4
   4.  Flexi-grid Networks . . . . . . . . . . . . . .   4
   3.  Overview of Flexi-grid Networks . . . . . . . .   4
     4.1.  Flexi-grid in the context of OTN . . . . . . .   5
     3.1.  Flexi-grid in the Context of OTN  . . . . .   4
     4.2.  Terminology . . . . . . .   5
     3.2.  Flexi-grid Terminology  . . . . . . . . . . . . . . . .   5
       4.2.1. .   6
       3.2.1.  Frequency Slots . . . . . . . . . . . . . . . . . . .   5
       4.2.2.   6
       3.2.2.  Media Channels  . . . . . . . . . . . . . . . . . . .   7
       4.2.3.   8
       3.2.3.  Media Layer Elements  . . . . . . . . . . . . . . . .   7
       4.2.4.   8
       3.2.4.  Optical Tributary Signals . . . . . . . . . . . . . .   8
     4.3.  Flexi-grid layered network model   9
       3.2.5.  Composite Media Channels  . . . . . . . . . . . .   8
       4.3.1. . .   9
     3.3.  Hierarchy in the Media Layer  . . . . . . . . . . . .   9
       4.3.2.  DWDM flexi-grid enabled network element models  . . .  10
   5.  GMPLS applicability
     3.4.  Flexi-grid Layered Network Model  . . . . . . . . . . . .  10
       3.4.1.  DWDM Flexi-grid Enabled Network Element Models  . . .  12
   4.  GMPLS Applicability . . . . . .  11
     5.1.  General considerations . . . . . . . . . . . . . . .  12
     4.1.  General Considerations  . .  11
     5.2.  Considerations on TE Links . . . . . . . . . . . . . . .  11
     5.3.  Considerations on Labeled Switched Path (LSP) in Flexi-
           grid  12
     4.2.  Consideration of TE Links . . . . . . . . . . . . . . . .  13
     4.3.  Consideration of LSPs in Flexi-grid . . . . . . . . . . .  14
     5.4.  16
     4.4.  Control Plane modeling Modeling of Network elements Elements  . . . . . . .  18
     5.5.  21
     4.5.  Media Layer Resource Allocation considerations Considerations  . . . . .  19
     5.6.  21
     4.6.  Neighbor Discovery and Link Property Correlation  . . . .  23
     5.7.  25
     4.7.  Path Computation / Routing and Spectrum Assignment (RSA)   23
       5.7.1.   26
       4.7.1.  Architectural Approaches to RSA . . . . . . . . . . .  24
     5.8.  26
     4.8.  Routing / and Topology dissemination  . Dissemination  . . . . . . . . . . .  24
       5.8.1.  27
       4.8.1.  Available Frequency Ranges/slots Ranges/Slots of DWDM Links  . . .  25
       5.8.2.  28
       4.8.2.  Available Slot Width Ranges of DWDM Links . . . . . .  25
       5.8.3.  28
       4.8.3.  Spectrum Management . . . . . . . . . . . . . . . . .  25
       5.8.4.  28
       4.8.4.  Information Model . . . . . . . . . . . . . . . . . .  26
   6.  28
   5.  Control Plane Requirements  . . . . . . . . . . . . . . . . .  27
     6.1.  30
     5.1.  Support for Media Channels  . . . . . . . . . . . . . . .  27
     6.2.  Support for Media Channel Resizing  . . .  30
       5.1.1.  Signaling . . . . . . . .  27
     6.3.  Support for Logical Associations of multiple media
           channels . . . . . . . . . . . . . .  31
       5.1.2.  Routing . . . . . . . . . .  28
   7.  Security Considerations . . . . . . . . . . . . .  31
     5.2.  Support for Media Channel Resizing  . . . . . .  28 . . . . .  32
     5.3.  Support for Logical Associations of Multiple Media
           Channels  . . . . . . . . . . . . . . . . . . . . . . . .  32
     5.4.  Support for Composite Media Channels  . . . . . . . . . .  32
     5.5.  Support for Neighbor Discovery and Link Property
           Correlation . . . . . . . . . . . . . . . . . . . . . . .  32
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  33
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  33
   8.  Manageability Considerations  . . . . . . . . . . . . . . . .  33
   9.  Contributing Authors  . . . . . . . . . . . . . . . . . . . .  28
   9.  34
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  30
   10.  37
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  30
     10.1.  37
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  30
     10.2.  37
     11.2.  Informative References . . . . . . . . . . . . . . . . .  32  38
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  32  39

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" 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. required.

   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
   frequency slot.  In this layered network, the media channel
   transports an can
   transport more than one Optical Tributary Signal. Signals.

   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
   GMPLS-based control plane for the control (provisioning/recovery, etc)
   etc.) of a fixed grid
   WDM wavelength division multiplexing (WDM) network
   in which media (spectrum) and signal are jointly
   considered considered.

   This document defines the framework for a GMPLS-based control of
   flexi-grid enabled DWDM dense wavelength division multiplexing (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:

2.  Terminology

   Further terminology specific to flexi-grid networks can be found in
   Section 3.2.

2.1.  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].

2.2.  Abbreviations

   EFS: Effective Frequency Slot

   FS: Frequency Slot

   FSC: Fiber-Switch Capable

   LSR: Label Switching Router

   NCF: Nominal Central Frequency

   OCh: Optical Channel

   OCh-P: Optical Channel Payload
   OTSi: Optical Tributary Signal

   OTSiG: OTSi Group is the set of OTSi signals

   OCC: Optical Channel Carrier

   PCE: Path Computation Element

   ROADM: Reconfigurable Optical Add-Drop Multiplexer

   SSON: Spectrum-Switched Optical Network

   SWG: Slot Width Granularity

4.

3.  Overview of Flexi-grid Networks

4.1.

3.1.  Flexi-grid in the context Context of OTN

   [G.872] describes describes, from a network level 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.

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

                      Figure 1: Generic OTN overview 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.

3.2.  Flexi-grid Terminology

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

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

4.2.1.

3.2.1.  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.

   o  Effective Frequency Slot [G.870]: The effective frequency slot of
      a media channel is that part of the frequency slots of the filters
      along the media channel that is common to all of the filters'
      frequency slots.  Note that both the Frequency Slot and Effective
      Frequency Slot are both local terms.

   o  Nominal Central Frequency: each 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, THz

      where 193.1 THz is ITU-T ''anchor
   frequency'' "anchor frequency" for transmission over
      the C band, and n is a positive or negative integer including 0.

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

     Figure 2: Anchor frequency Frequency and set Set of nominal central frequencies Nominal Central Frequencies

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

   o  Slot Width Granularity: Granularity (SWG): 12.5 GHz, as defined in [G.694.1].

   o  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 Slots

      *  The symbol '+' represents the allowed nominal central frequencies,
      the
         frequencies

      *  The '--' represents the nominal central frequency granularity, and
      the granularity

      *  The '^' represents the slot nominal central frequency. 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.

   o  Effective Frequency Slot: the 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.

                        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.

3.2.2.  Media Channels

   This section defines concepts such as (Network) Media Channel; the
   mapping to GMPLS constructs (i.e., LSP) is detailed in Section 4.

   o  Media Channel: a 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 (an 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.

   o  Network Media Channel: It is a [G.870] defines the Network Media Channel
      in terms of the media channel that transports an
   Optical Tributary Signal [Editor's note: this the OTSi.  This
      document broadens the definition goes beyond
   current G.870 definition, which is still tightened to cover any OTSi so that a particular
   case of OTS, the OCh-P]

4.2.3.
      Network Media Channel is a media channel that transports an OTSi.

3.2.3.  Media Layer Elements

   o  Media Element: a A media element only directs the an optical signal or
      affects the properties of an optical signal, it 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 filters, and switching matrices.

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

3.2.4.  Optical Tributary Signals

   o  Optical Tributary Signal (OTSi) [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  To provide a connection between the OTSi source and
      the OTSi sink the optical signal must be assigned to a network
      media channel.

   o  OTSi Group (OTSiG): The set of Optical Tributary Signal OTSi signals that are carried by a
      group of network media channels.  Each OTSi is carried by one
      network media channel.  From a management perspective it should be
      possible to manage both the OTSiG and a group of Network Media
      Channels as single entities.

3.2.5.  Composite Media Channels

   o  It is possible to construct an Optical Channel
   Payload (OCh-P) [G.872].

4.3.  Flexi-grid layered end-to-end media channel as a
      composite of more than one network model media channels.  A composite
      media channel carries a group of OTSi (i.e., OTSiG).  Each OTSi is
      carried by one network media channel.  This group of OTSi should
      be carried over a single fibre.

   o  In this case, the OTN layered network, effective frequency slots may be contiguous
      (i.e., there is no spectrum between them that can be used for
      other media channels) or non-contiguous.

   o  It is not currently envisaged that such composite media channels
      may be constructed from slots carried on different fibers whether
      those fibers traverse the same hop-by-hop path through the network
      or not.

   o  Furthermore, it is not considered likely that a media channel transports may
      be constructed from a
   single Optical Tributary Signal (see Figure 5)

     |                     Optical Tributary Signal                    |
     O - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - O different variation of slot composition on
      each hop.  That is, the slot composition must be the same from one
      end to the other of the media channel even if the specific slots
      and their spacing may vary hop by hop.

   o  How the signal is carried across such groups of network media
      channels is out of scope for this document.

3.3.  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
   split into network media channels.

   In Figure 5, a media channel has been configured and dimensioned to
   support two network media channels, each of them carrying one optical
   tributary signal.

                             Media Channel Frequency Slot
     +-------------------------------X------------------------------+
     |                                                              |
     | Channel Port         Network Media Channel         Channel Port       Frequency Slot                  Frequency Slot         |
     O - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - O
     |   +------------X-----------+      +----------X-----------+   |
   +--------+                 +-----------+                   +--------+
     |  \ (1)   | Opt Tributary Signal  |       |    (1) Opt Tributary Signal |   | (1)  /
     |   |   \----|-----------------|-----------|-------------------|-----/           o           |
   +--------+ Link Channel    +-----------+  Link Channel     +--------+
     Media Channel       |          o           |   |
     |   |           |           |       |          |           |   |
    -4  -3  -2  -1   0   1   2   3   4   5   6   7  8   9  10  11  12
   --+---+---+---+---+---+---+---+---+---+---+---+--+---+---+---+---+--

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

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

         X - Frequency Slot Central Frequency

         o - signal central frequency

      Figure 5: Example of Media Channel / Network Media Channels and
                        Associated Frequency Slots

3.4.  Flexi-grid Layered Network Model

   In the OTN layered network, the network media channel transports a
   single Optical Tributary Signal (see Figure 6)
     |                     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

   The symbol (1) - indicates a Matrix Channel

                Figure 5: 6: Simplified Layered Network Model

   A particular example of Optical Tributary Signal is the OCh-P.
   Figure Figure 6 7 shows the this specific example of the layered network model
   particularized for the OCH-P case, as defined in G.805. G.805 [G.805].

    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

    The symbol (1) - indicates a Matrix Channel

            Figure 6: 7: Layered Network Model according According to G.805

   By definition definition, a network media channel only supports only a single Optical
   Tributary signal.  How several Optical Tributary signals are bound
   together Signal.

3.4.1.  DWDM Flexi-grid Enabled Network Element Models

   A flexible grid network is out of the scope of the present document constructed from subsystems that include
   WDM links, tunable transmitters, and receivers, (i.e, media elements
   including media layer switching elements that are media matrices) as
   well as electro-optical network elements.  This is a matter
   of just 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 same as
   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.

                            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 except 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 each element has flexible grid
   characteristics.

   As stated in Clause 7 of [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 might 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).

5.

4.  GMPLS applicability Applicability

   The goal of this section is to provide an insight of into the
   application of GMPLS to as a control mechanism in flexi-grid networks, while specific networks.
   Specific control plane requirements for the support of flexi-grid
   networks are covered in the next section.  The present Section 5.  This framework is aimed at
   controlling the media layer within the Optical Transport Network
   (OTN) hierarchy OTN hierarchy, and controlling
   the required adaptations of the signal layer.  This document also
   defines the term SSON (Spectrum-Switched Spectrum-Switched Optical
   Network) Network (SSON) 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. (e.g., as a TE link).

5.1.

4.1.  General considerations Considerations

   The GMPLS control of the media layer deals with the establishment of
   media channels, which channels that are switched in media channel matrixes. matrices.  GMPLS
   labels are used to 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

4.2.  Consideration of TE Links

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

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

   The association of the three components a filter, a fiber fiber, and a filter
   filter, is a media channel in its most basic form, which from form.  From the control
   plane perspective this may modeled as a (physical) TE-link with a
   contiguous optical spectrum at
   start of day.  A means to represent this is spectrum.  This can be represented by saying 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 a one-hop media channel.
   In practical terms, associating a fiber with the terminating filters
   determines the usable optical spectrum.

   -----------------+

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

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

                Figure 8: (Basic) Media channel Channel and TE link 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 / (i.e., corresponds to to) a Label Switched Path (LSP)
   from a control plane perspective.  In other words, It is possible to
   "concatenate" several media channels (e.g. (e.g., Patch on intermediate
   nodes) to create a single media channel.

   -----------+

   ----------+       +------------------------------+       +----------       +---------
             |       |                              |       |
      +------+       +------+                +------+       +------+
      |      |       |      |  +----------+  |      |       |      |
   --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,

   Furthermore, if appropriate, it the media channel can also be
   represented as a TE link or Forwarding Adjacency (FA), (FA) [RFC4206],
   augmenting the control plane network model.

   -----------+

   ----------+       +------------------------------+       +----------       +---------
             |       |                              |       |
      +------+       +------+                +------+       +------+
      |      |       |      |  +----------+  |      |       |      |
   --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)

4.3.  Consideration of LSPs 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. channel
   (without considering the adaptation functions).  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) ,
   (transceivers), including the cross-connects at the ingress / and
   egress nodes.  The ports towards the client can still be represented
   as interfaces from the control plane perspective.

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

   ----------+

   ---------+       +--------------------------------+       +---------       +--------
            |       |                                |       |
     +------+       +------+                  +------+       +------+
     |      |       |      |   +----------+   |      |       |      |
   -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 Representing a media channel Media Channel that starts Starts at
    the filter Filter of the outgoing interface Outgoing Interface of the ingress Ingress LSR and ends at
          the filter Filter of the incoming interface Incoming Interface of the egress Egress LSR

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

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

        +----------------------+           +----------------------+
        |                                  |                      |
        +------+        +------+           +------+        +------+
        |      | +----+ |      |           |      | +----+ |      |OCh-P
   OCh-P|      |OTSi
    OTSi|      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 Representing a network media channel (OCh-Trail) Network Media Channel (OTSi Trail)

   In a third case, a Network Media Channel is terminated on the Filter
   ports of the Ingress and Egress nodes.  This is named in G.872 as
   OCh-NC (we need
   OTSi Network Connection.  As can be seen from the figures, there is
   no difference from a GMPLS modelling perspective between these cases,
   but they are shown as distinct examples to discuss highlight the implications, if any, once modeled at differences
   in the control plane level of models B and C). data plane.

     |---------------------  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 Representing a control plane perspective, of
   figs Figure 12 and Figure 13.] Network Media Channel (OTSi Network
                                Connection)

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

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

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

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

5.4.

   As discussed in Section 3.2.5, a media channel may be constructed
   from a compsite of network media channels.  This may be achieved in
   two ways using LSPs.  These mechanisms may be compared to the
   techniques used in GMPLS to support inverse multiplexing in Time
   Division Multiplexing (TDM) networks and in OTN [RFC4606], [RFC6344],
   and [RFC7139].

   o  In the first case, a single LSP may be established in the control
      plane.  The signaling messages include information for all of the
      component network media channels that make up the composite media
      channel.

   o  In the second case, each component network media channel is
      established using a separate control plane LSP, and these LSPs are
      associated within the control plane so that the end points may see
      them as a single media channel.

4.4.  Control Plane modeling Modeling of Network elements Elements

   Optical transmitters/receivers transmitters and 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]
   detail in detail. [RFC6163].  Media matrices include line side ports which that are
   connected to DWDM links links, and tributary side input/output ports
   which that
   can be connected to transmitters/receivers.

   A set of common constraints can be defined:

   o  Slot widths: The minimum and maximum slot width.

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

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

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

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

      *  Step granularity: the 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.
         (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.

4.5.  Media Layer Resource Allocation considerations 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" end-to-end frequency slot end to end. slot.  The establishment of
   an LSP is related to 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
   configuration of the effective frequency slot applies
   at the media chall (LSP) level slot.

   A "service" request "service request" is characterized as (at a minimum, minimum) by its required
   effective frequency slot width.  This does not preclude that the
   request may add additional constraints such as imposing also imposing the
   nominal central frequency.  A given effective frequency slot is may be
   requested for the media channel
   say, with the Path message.  Regardless of the actual encoding, in the
   Path message sender descriptor sender_tspec shall specify control plane LSP setup
   messages, and a minimum specific frequency slot can be requeste on any
   specific hop of the LSP setup.  Regardless of the actual encoding,
   the LSP setup message specifies a minimum frequency slot width that
   needs to be fulfilled.

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

   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 it must be able
   possible to obtain an determine the end-to-end equivalent values of the n and m
   parameters.  We refer to this as by saying that the "effective frequency
   slot of the media channel/LSP must be valid".

   In GMPLS the requested effective frequency slot is represented to the
   TSpec present in the Path message, and the effective frequency slot
   is mapped to the FlowSpec.

   The FlowSpec carried in the Resv message.

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

   The local frequency slot may change at each hop, typically given hardware
   constraints (e.g. and capabilities (e.g., a given node cannot might not support
   the finest granularity).  Locally  This means that the values of n and m may change.
   change at each hop.  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" variations in the local value of m will appear
   in the allocated label that encodes the frequency slot as well as the flow descriptor flowspec.
   in the FlowSpec that describes the flow.

   Different operational modes are considered: RSA can be considered.  For Routing and
   Spectrum Assignment (RSA) with explicit label control, and for R+DSA,
   Routing and Distributed Spectrum Assignment (R+DSA), the GMPLS
   signaling procedure is procedures are similar to the one those described in section 4.1.3
   of [RFC6163] except for Routing and Wavelength Assignment (RWA) and for
   Routing and Distributed Wavelength Assignment (R+DWA).  The main
   difference is that the label set
   should specify specifies the available nominal
   central frequencies that meet the slot width requirement requirements of the LSP.

   The intermediate nodes can use the control plane to 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
   an LSP to assign the proper frequency resource.
   Compared with [RFC6163], except  Except for
   identifying the resource (i.e., fixed wavelength for WSON WSON, and
   frequency resource for flexible grids), the other signaling
   requirements (e.g., unidirectional or bidirectional, with or without
   converters) are the same as for WSON as described in the section 6.1 of
   [RFC6163].

   Regarding how a GMPLS control plane can assign n and m, m hop-by-hop
   along the path of an LSP, different cases can apply:

      a)

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

      b) path.

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

      c) n and m need to be same,
       but the same.

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

   In consequence, an entity such as a PCE slot can make sure vary along the path.  Again, the
       important thing is that the effective frequency slot remains
       valid and satisfies the requested parameters along the whole path
       of the LSP.

   c.  n and m stay the same need to be unchanging along the path.  Any constraint (including  This ensures that
       the frequency slot is well-known end-to-end, and width granularities) is taken into account during a simple way
       to ensure that the effective frequency slot remains valid for the
       whole LSP.

   d.  n can change, but m needs to remain the same along the path.
       This ensures that the effective frequency slot remains valid, but
       allows the frequency slot to be moved within the spectrum from
       hop to hop.

   The selection of a path that ensures n and m continuity can be
   delegated to a dedicated entity such as a Path Computation Element
   (PCE).  Any constraint (including frequency slot and width
   granularities) can be taken into account during path computation.  alternatively,
   Alternatively, A PCE (or a source node) can compute a path and leaving the actual frequency
   slot assignment is to be done, for example, with a distributed
   (signaling) procedure:

   o  Each downstream node ensures that m is >= requested_m.

      Since a

   o  A downstream node cannot foresee what an upstream node will
      allocate in turn, a
      allocate.  A way we can to ensure that the effective frequency slot is
      valid along the length of the LSP is then by ensuring to ensure that the same "n" value
      of n is allocated. allocated at each hop.  By forcing the same n, value of 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

   o  This may be too hard restriction, restrictive, since a node (or even a
      centralized/combined centralized/
      combined RSA entity) can make sure may be able ensure that the resulting end-to-
      end to end (effective) effective frequency slot is valid, valid even if n is
      different varies locally.
      That means, the effective (end to end) frequency slot that characterizes the
      media channel from end to end is one consistent and is determined by
      its n and m, m values, but that the effective frequency slot and
      those values are logical, logical (i.e., do not map direct to the
      physically assigned spectrum) in the sense that they are the
      result of the intersection of local (filters) freq locally-assigned frequency slots
      applicable at local components (such as filters) each of which may
      have assigned different freq. slots frequency slots.

   For Figure Figure 15 the effective slot is made 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 made valid by ensuring that it is
   valid at each hop in the upstream direction.  The intersection needs
   to be computed.  Invalid computed because invalid slots could result otherwise.

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

       Figure 15: Distributed allocation Allocation with different Different m and same Same n
             |Path(m_req)  ^                |
             |--------->   #                |                 |
             |             #                ^                 ^
            -^-------------#----------------#-----------------#--------
   Effective #             #                #                 #
   FS n, m   #             #                #                 #
             #             #                #                 #
            -v-------------v----------------#-----------------#--------
             |             |                #                 v
             |             |                #           Resv  |
             |             |                v         <------ |
             |             |                |flowspec(n_a,                |FlowSpec(n_a, m_a)
             |             |       <--------|                 |
             |             |  flowspec  FlowSpec (FSb [intersect] FSa)
                  <--------|
            flowspec
            FlowSpec ([intersect] FSa,FSb,FSc)

    Figure 16: Distributed allocation Allocation with different Different m and different Different n

   Note, when a media channel is bound to one OCh-P (i.e OTSi (i.e., is a network
   media channel), the EFS must be the one of the OTSi.  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
   have to constrain the EFS to be the OTSi EFS.

4.6.  Neighbor Discovery and Link Property Correlation

   There are potential interworking problems between fixed-grid DWDM and
   flexi-grid DWDM nodes.  Additionally, even two flexi-grid nodes may
   have different grid properties, leading to link property conflict
   with resulting limited interworking.

   Devices or applications that make use of the flexi-grid might not be
   able to support every possible slot width.  In other words, different
   applications may be defined where each supports a different grid
   granularity.  Consider a node with an application where the nominal
   central frequency granularity is 12.5 GHz and where slot widths are
   multiples of 25 GHz.  In this case the link between two optical nodes
   with different grid granularities must be configured to align with
   the larger of both granularities.  Furthermore, different nodes may
   have different slot-width tuning ranges.

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

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

   o  Grid granularity - Between two flexi-grid nodes.

   o  Slot width tuning range - Between two flexi-grid nodes.

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

   In WSON, if there is no (available) wavelength converter in an
   optical network, an LSP is subject to the "wavelength continuity
   constraint" (see section 4 of [RFC6163]).  Similarly in flexi-grid,
   if the capability to shift or convert an allocated frequency slot is
   absent, the LSP is subject to the "Spectrum Continuity Constraint".

   Because of the limited availability of wavelength/spectrum converters
   (in what is called a "sparse translucent optical network") the
   wavelength/spectrum continuity constraint always has to be
   considered.  When available, information regarding spectrum
   conversion capabilities at the optical nodes may be used by RSA
   mechanisms.

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

4.7.1.  Architectural Approaches to RSA

   Similar to RWA for fixed grids [RFC6163], 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.

   Note that all of these models allow the concept of a composite media
   channel supported by a single control plane LSP or by a set of
   associated LSPs.

4.7.1.1.  Combined RSA (R&SA)

   In this case, a computation entity performs both routing and
   frequency slot assignment.  The computation entity needs access to
   detailed network information, e.g., the connectivity topology of the
   nodes and links, the available frequency ranges on each link, the
   node capabilities, etc.

   The computation entity could reside on a dedicated PCE server, in the
   provisioning application that requests the service, or on the ingress
   node.

4.7.1.2.  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 needs the connectivity topology to compute the
   proper routes.  The second entity needs information about the
   available frequency ranges of the links and the capabilities of the
   nodes in order to assign the spectrum.

4.7.1.3.  Routing and Distributed SA (R+DSA)

   In this case an 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 need to be collected hop-by-hop along the
   route.  This procedure can be implemented by the GMPLS signaling
   protocol.

4.8.  Routing and Topology Dissemination

   In the case of the combined RSA architecture, the computation entity
   needs 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, while spectrum assignment is performed based on
   the available frequency ranges of the links.  The computation entity
   may get the detailed network information via the GMPLS routing
   protocol.

   For WSON, the connectivity topology and node capabilities can be
   advertised by the GMPLS routing protocol (refer to section 6.2 of
   [RFC6163].  Except for wavelength-specific availability information,
   the information for flexi-grid is the same as for WSON and can
   equally be distributed by the GMPLS routing protocol.

   This section analyses the necessary changes on link information
   brought by flexible grids.

4.8.1.  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 need to be
   advertised.

4.8.2.  Available Slot Width Ranges of DWDM Links

   The available slot width ranges need to be advertised in combination
   with the available frequency ranges, in order that the computing
   entity can verify whether an LSP with a given slot width can be set
   up or not.  This 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.

4.8.3.  Spectrum Management

   The total available spectrum on a fiber can be described as a
   resource that can be partitioned.  For example, a Network
   media channel), part of the EFS must
   spectrum could be the one assigned to a third party to manage, or parts of
   the Och-P.  The media
   channel setup spectrum could be assigned by the LSP may contains the EFS operator for different classes
   of the network media
   channel EFS. traffic.  This is an endpoint property, the egress and ingress
   SHOULD constrain partitioning creates the EFS to Och-P EFS .

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 impression that make use spectrum
   is a hierarchy in view 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 Management and Control Plane: each
   partition could be
   defined where itself be partitioned.  However, the nominal central frequency granularity hierarchy is 12.5 GHz
   requiring slot widths being multiple
   created purely within a management system: it defines a hierarchy of 25 GHz.  Therefore
   access or management rights, but there is no corresponding resource
   hierarchy within the fiber.

   The end of fiber is a link
   between two optical nodes with different grid granularity must be
   configured to align with the larger end and presents a fiber port which
   represents all of both granularities.  Besides,
   different nodes may have different spectrum available on the fiber.  Each spectrum
   allocation appears as Link Channel Port (i.e., frequency slot width tuning ranges.

   In summary, in port)
   within fiber.  Thus, while there is a DWDM Link between two nodes, at least the following
   properties should be negotiated:

      Grid capability (channel spacing) - Between fixed-grid hierarchy of ownership (the
   Link Channel Port 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 corresponding LSP are located on a fiber and Spectrum Assignment (RSA)

   Much like in WSON, in which if so
   associated with a fiber port) 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 continued nesting hierarchy
   of shifting or converting an allocated frequency slot, slots within larger frequency slots.  In its way, this
   mirrors the LSP fixed grid behavior where a wavelength is subject to the Optical ''Spectrum Continuity Constraint''.

   Because associated with
   a port/fiber, but cannot be subdivided even though it is a partition
   of the limited availability of wavelength/spectrum converters
   (sparse translucent optical network) total spectrum available on the wavelength/spectrum
   continuity constraint should always be considered.  When available, fiber.

4.8.4.  Information Model

   This section defines an information regarding spectrum conversion capabilities at model to describe the optical
   nodes may be used by RSA (Routing data that
   represents the capabilities and Spectrum Assignment)
   mechanisms.

   The RSA process determines resources available in an flexi-grid
   network.  It is not a route data model and frequency slot for a LSP.
   Hence, when a route is computed the spectrum assignment process (SA)
   should determine not intended to limit any
   protocol solution such as an encoding for an IGP.  For example,
   information required for routing/path selection may be the set of
   available nominal central frequencies from which a frequency and slot of
   the required width based on can be allocated.  A convenient encoding for this
   information is for further study in an IGP encoding document.

   Fixed DWDM 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 and available or central frequencies information of the
   transmitter and receiver, and the available frequency ranges
   information and available slot width ranges of the links that position.  Thus, the
   route traverses.

5.7.1.  Architectural Approaches to RSA

   Similar
   information model needs to RWA for fixed grids, different ways enable:

      exchange of performing information to enable RSA in
   conjunction with the control plane can be considered.  The approaches
   included a flexi-grid network

      representation of a fixed grid device participating 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 flexi-
      grid network

      full interworking of fixed and
   frequency slot assignment.  The computation entity should have flexible grid devices within the
   detailed
      same network information, e.g.  connectivity topology constructed
   by nodes/links information, available

      interworking of flexgrid devices with different capabilities.

   The information model is represented using Routing Backus-Naur Format
   (RBNF) as defined in [RFC5511].

   <Available Spectrum in Fiber for frequency ranges on each link,
   node capabilities, etc. 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> ::= (2^n) x 6.25GHz
     where n is positive integer, giving rise to granularities
     such as 6.25GHz, 12.5GHz, 25GHz, 50GHz, and 100GHz

   <Available Slot Width Granularity> ::= (2^m) x 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

5.  Control Plane Requirements

   The computation entity could reside either on control of a PCE or flexi-grid networks places additional requirements
   on the ingress
   node.

5.7.1.2.  Separated RSA (R+SA)

   In this case, routing computation GMPLS protocols.  This section summarizes those requirements
   for signaling and frequency slot assignment are
   performed by different entities. routing.

5.1.  Support for Media Channels

   The first entity computes the
   routes and provides them control plane SHALL be able to the second entity; the second entity
   assigns the support Media Channels,
   characterized by a single frequency slot.  The first entity should get representation of the connectivity topology to compute
   Media Channel in the
   proper routes; GMPLS control plane is the second entity should get so-called flexi-grid
   LSP.  Since network media channels are media channels, an LSP may
   also be the available frequency
   ranges control plane representation of a network media channel.
   Consequently, the links and nodes' capabilities information control plane will also be able to assign support Network
   Media Channels.

5.1.1.  Signaling

   The signaling procedure SHALL be able to configure the
   spectrum.

5.7.1.3.  Routing and Distributed SA (R+DSA)

   In this case, one entity computes nominal
   central frequency (n) of a flexi-grid LSP.

   The signaling procedure SHALL allow a flexible range of values for
   the route but frequency slot width (m) parameter.  Specifically, the control
   plane SHALL allow setting up a media channel with frequency slot
   assignment is performed hop-by-hop in
   width (m) ranging from a distributed way along minimum of m=1 (12.5GHz) to a maximum of the
   route.
   entire C-band with a slot width granularity of 12.5GHz.

   The available central frequencies which meet the spectrum
   continuity constraint should signaling procedure SHALL be collected hop by hop along able to configure the minimum width
   (m) of a flexi-grid LSP.  In addition, the route.
   This signaling procedure can SHALL
   be implemented by the GMPLS signaling protocol.

5.8.  Routing / Topology dissemination

   In able to configure local frequency slots.

   The control plane architecture SHOULD allow for the case support of combined RSA architecture, the computation entity
   needs L-band
   and S-band.

   The signalling process SHALL be able to get collect the detailed network information, i.e. connectivity
   topology, node capabilities and available local frequency ranges of
   slot assigned at each link along the
   links.  Route computation is performed based on path.

   The signaling procedures SHALL support all of the connectivity
   topology RSA architectural
   models (R&SA, R+SA, and node capabilities; spectrum assignment is performed
   based R+DSA) within a single set of protocol
   objects although some objects may only be applicable within on the available frequency ranges of the links.
   models.

5.1.2.  Routing

   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 protocol will support all functions as WSON, which can be advertised by GMPLS described in
   [RFC4202] and extend them to a flexi-grid data plane.

   The routing protocol (refer SHALL distribute sufficient information to section 6.2 of [RFC6163].
   compute paths to enable the signaling procedure to establish LSPs as
   described in the previous sections.  This section
   analyses includes, at a minimum the necessary changes on link information brought
   data described by
   flexible grids.

5.8.1.  Available Frequency Ranges/slots of DWDM Links

   In the case Information Model in Figure 17.

   The routing protocol SHALL update its advertisements of flexible grids, channel central frequencies span from
   193.1 THz towards both ends available
   resources and capabilities as the usage of resources in the C band spectrum network
   varies with 6.25 GHz
   granularity.  Different LSPs could make use the establishment or tear-down of LSPs.  These updates
   SHOULD be amenable to damping and thresholds as in other traffic
   engineering routing advertisements.

   The routing protocol SHALL support all of different slot widths
   on the same link.  Hence, RSA architectural
   models (R&SA, R+SA, and R+DSA) without any configuration or change of
   behavior.  Thus, the available frequency ranges should routing protocols SHALL be
   advertised.

5.8.2.  Available Slot Width Ranges of DWDM Links

   The available slot width ranges needs agnostic to be advertised, in
   combination with the Available frequency ranges,
   computation and signaling model that is in order to verify
   whether a LSP with a given slot width can be set up use.

5.2.  Support for Media Channel Resizing

   The signaling procedures SHALL allow resizing (grow or not; this is
   is constrained by shrink) the available
   frequency slot width ranges of the a 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: channel/network media channel.  The
   resizing MAY imply resizing the part on local frequency slots along the hierarchy path
   of the optical spectrum
   could be confusing, we can discuss it]. flexi-grid LSP.

   The total routing protocol SHALL update its advertisements of available spectrum
   on a fiber could be described
   resources and capabilities as a resource that can be divided by a
   media device into a set the usage of Frequency Slots.  In terms resources in the network
   varies with the resizing of managing
   spectrum, it is necessary to LSP.  These updates SHOULD be able amenable to speak about different
   granularities
   damping and thresholds as in other traffic engineering routing
   advertisements.

5.3.  Support for Logical Associations of managed spectrum.  For example, a part Multiple Media Channels

   A set of the
   spectrum could media channels can be assigned used to transport signals that have a third party to manage.  This need
   logical association between them.  The control plane architecture
   SHOULD allow multiple media channels to
   partition creates be logically associated.  The
   control plane SHOULD allow the impression co-routing of a set of media channels
   that spectrum is a hierarchy are logically associated.

5.4.  Support for Composite Media Channels

   As described in view
   of Management Section 3.2.5 and Control Plane.  The hierarchy is created within Section 4.3, a
   management system, and it is an access right hierarchy only.  It is media channel may be
   composed of multiple network media channels.

   The signaling procedures SHOULD include support for signaling a
   management hierarchy without any actual resource hierarchy within
   fiber.
   single control plane LSP that includes information about multiple
   network media channels that will comprise the single compound media
   channel.

   The end of fiber is signaling procedures SHOULD include a link mechanism to associate
   separately signaled control plane LSPs so that the end and presents points may
   correlate them into a fiber port
   which represents all of spectrum available on single compound media channel.

   The signaling procedures MAY include a mechanism to dynamically vary
   the fiber.  Each
   spectrum allocation appears as Link Channel Port (i.e., frequency
   slot port) within fiber.

5.8.4.  Information Model

   Fixed DM grids can also be described via suitable choices composition of slots in a flexible DWDM grid.  However, devices or applications that make use
   of the flexible grid may not composite media channel by allowing network
   media channels to be capable of supporting every possible
   slot width added to or central frequency position.  Following is removed from the
   definition of information model, not intended to limit any IGP
   encoding implementation.  For example, whole.

   The routing protocols MUST provide sufficient information required for
   routing/path selection may be the set
   computation of available nominal central
   frequencies from which a frequency slot paths and slots for composite media channels using any
   of the required width can be
   allocated.  A convenient encoding three RSA architectural models (R&SA, R+SA, and R+DSA).

5.5.  Support for this information (may Neighbor Discovery and Link Property Correlation

   The control plane MAY include support for neighbor discovery such
   that an flexi-grid network can be as constructed in a
   frequency slot or sets "plug-and-play"
   manner.

   The control plane SHOULD allow the nodes at opposite ends 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 a link
   to correlate the properties that they will apply to the link.  Such
   correlation SHOULD include at least the identities of contiguous slices>

   <Available Central Frequency Granularity> ::= n A&#151; 6.25GHz,
     where n is positive integer, the node and
   the identities they apply to the link.  Other properties 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 the
   link characteristics described for the routing information model in
   Figure 17 SHOULD also be correlated.

   Such neighbor discovery and link property correlation, if provided,
   MUST be able to operate in both an out-of-band and an out-of-fiber
   control channel.

6.  Control Plane Requirements  IANA Considerations

   This framework document makes no requests for IANA action.

7.  Security Considerations

   The GMPLS based control plane and data plane aspects of a flexi-grid networks provides
   aditional requirements system are
   fundamentally the same as a fixed grid system and there is no
   substantial reason to GMPLS.  In this section expect the features security considerations to be
   covered by GMPLS signaling any
   different.

   A good overview of the security considerations for a GMPLS-based
   control plane can be found in [RFC5920].

   [RFC6163] includes a section describing security considerations for
   WSON, and it is reasonable to infer that these considerations apply
   and may be exacerbated in a flexi-grid are identified.  [Editor's
   note: Only discussed requirements are included at this stage.
   Routing requirements will come SSON system.  In particular,
   the detailed and granular information describing a flexi- grid
   network and the capabilities of nodes in that network could put
   stress on the next version]

6.1.  Support for Media Channels

   The routing protocol or the out-of-band control plane SHALL channel
   used by the protocol.  An attacker might be able to support Media Channels,
   characterized cause small
   variations in the use of the network or the available resources
   (perhaps by a single frequency slot.  The representation modifying the environment of a fiber) and so trigger the
   Media Channel
   routing protocol to make new flooding announcements.  This situation
   is explicitly mitigated in the GMPLS Control plane requirements for the routing protocol
   extensions where it is noted that the so-called flexi-grid
   LSP.  Since network media channels are media channels, an LSP may
   also be protocol must include damping
   and configurable thresholds as already exist in the control plane representation of core GMPLS
   routing protocols.

8.  Manageability Considerations

   GMPLS systems already contain a network media channel.
   Consequently, number of management tools.

   o  MIB modules exist to model the control plane SHALL be able protocols and the
      network elements [RFC4802], [RFC4803], and there is early work to support Network
   Media Channels.
      provide similar access through YANG.  The signaling procedure SHALL be able features described in
      these models are currently designed to configure represent fixed-label
      technologies such as optical networks using the nominal
   central fixed grid:
      extensions may be needed in order to represent bandwidth,
      frequency (n) of a flexi-grid LSP.

   The control plane protocols SHALL allow flexible range of values for
   the slots, and effective frequency slot width (m) parameter.  Specifically, the slots in flexi- grid
      networks.

   o  There are protocol extensions within GMPLS signaling to allow
      control plane SHALL allow setting up a media channel with frequency slot
   width (m) ranging from a minimum of m=1 (12.5GHz) systems to a maximum report the presence of faults that affect
      LSPs [RFC4783], although it must be carefully noted that these
      mechanisms do not constitute an alarm mechanism that could be used
      to rapidly propagate information about faults in a way that would
      allow the
   entire C-band data plane to perform protection switching.  These
      mechanisms could easily be enhanced with a slot width granularity the addition of 12.5GHz.
      technology-specific reasons codes if any are needed.

   o  The signaling procedure of GMPLS protocols, themselves, already include fault detection
      and recovery mechanisms (such as the PathErr and Notify messages
      in RSVP-TE signaling as used by GMPLS control plane SHALL [RFC3473].  It is not
      anticipated that these mechanisms will need enhancement to support
      flexi-grid although additional reason codes may be able needed to
   configure the minimum width (m) of
      describe technology-specific error cases.

   o  [RFC7260] describes a flexi-grid LSP.  In adition, framework for the control and configuration
      of data plane SHALL Operations, Administration, and Management (OAM).
      It would not be able appropriate for the IETF to configure local frecuency slots,

   The control define or describe
      data plane architecture SHOULD allow OAM for optical systems, but the support of L-band
   and S-band

   The signalling process of the control plane SHALL allow framework described in
      RFC 7260 could be used (with minor protocol extensions) to collect enable
      data plane OAM that has been defined by the local frequency slot asigned at each link along originators of the path

6.2.  Support for Media Channel Resizing

   The control
      flexi-grid data plane SHALL technology (the ITU-T).

   o  The Link Management Protocol [RFC4204] is designed to allow resizing (grow or shrink) the frequency
   slot width
      two ends of a media channel/network media channel.  The resizing
   MAY imply resizing network link to coordinate and confirm the local frequency slots along
      configuration and capabilities that they will apply to the path of link.
      This protocol is particularly applicable to optical links where
      the
   flexi-grid LSP.

6.3.  Support for Logical Associations characteristics of multiple media channels

   A set the network devices may considerably affect
      how the link is used and where misconfiguration of media channels can mis-fibering
      could make physical interoperability impossible.  LMP could easily
      be used extended to transport signals that have a
   logical association collect and report information between them.  The control plane architecture
   SHOULD allow multiple media channels to be logically associated.  The
   control plane SHOULD allow the co-routing end
      points of links in a set of media channels
   logically associated

7.  Security Considerations

   TBD

8. flexi-grid network.

9.  Contributing Authors

      Adrian Farrel
      Old Dog Consulting
      adrian@olddog.co.uk

      Daniel King
      Old Dog Consulting
      daniel@olddog.co.uk

      Xian Zhang
      Huawei
      zhang.xian@huawei.com

      Cyril Margaria
      Juniper Networks
      cmargaria@juniper.net

      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
      Juniper Networks
      cmargaria@juniper.net

      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

      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
      U.C.  Davis, USA
      leiliu@ucdavis.edu

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

      Young Lee
      Huawei

      Jianrui Han
      Huawei

      Sharfuddin Syed
      Infinera

      Rajan Rao
      Infinera

      Marco Sosa
      Infinera

      Biao Lu
      Infinera

      Abinder Dhillon
      Infinera

      Felipe Jimenez Arribas
      TelefA^3nica
      Telefonica I+D

      Andrew G.  Malis
      Verizon

      Adrian Farrel
      Old Dog Consulting

      Daniel King
      Old Dog Consulting
      Huawei
      agmalis@gmail.com

      Huub van Helvoort

9.
      Hai Gaoming BV
      The Neterlands
      huubatwork@gmail.com

10.  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.

11.  References

10.1.

11.1.  Normative References

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

   [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

   [RFC4202]  Kompella, K. and Y. Rekhter, "Routing Extensions in
              Support of Generalized Multi-Protocol Label Switching
              (GMPLS) Architecture",
              (GMPLS)", RFC 3945, 4202, October 2004. 2005.

   [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,

   [RFC5511]  Farrel, A., Kompella, K., Vasseur, JP., "Routing Backus-Naur Form (RBNF): A Syntax
              Used to Form Encoding Rules in Various Routing Protocol
              Specifications", RFC 5511, April 2009.

11.2.  Informative References

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

   [RFC4204]  Lang, J., "Link Management Protocol (LMP)", RFC 4204,
              October 2005.

   [RFC4397]  Bryskin, I. and A. Farrel,
              "Label Switched Path Stitching with "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.

   [RFC4606]  Mannie, E. and D. Papadimitriou, "Generalized Multi-
              Protocol Label Switching (GMPLS) Extensions for
              Synchronous Optical Network (SONET) and Synchronous
              Digital Hierarchy (SDH) Control", RFC 4606, August 2006.

   [RFC4783]  Berger, L., "GMPLS - Communication of Alarm Information",
              RFC 4783, December 2006.

   [RFC4802]  Nadeau, T. and A. Farrel, "Generalized Multiprotocol Label
              Switching (GMPLS) Traffic Engineering (GMPLS
              TE)", Management
              Information Base", RFC 4802, February 2007.

   [RFC4803]  Nadeau, T. and A. Farrel, "Generalized Multiprotocol Label
              Switching (GMPLS) Label Switching Router (LSR) Management
              Information Base", RFC 5150, 4803, February 2008. 2007.

   [RFC5920]  Fang, L., "Security Framework for MPLS and GMPLS
              Networks", RFC 5920, July 2010.

   [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.

10.2.  Informative References

   [RFC4397]  Bryskin, I.

   [RFC6344]  Bernstein, G., Caviglia, D., Rabbat, R., and H. van
              Helvoort, "Operating Virtual Concatenation (VCAT) and A. Farrel, "A Lexicography for the
              Interpretation of
              Link Capacity Adjustment Scheme (LCAS) with Generalized Multiprotocol
              Multi-Protocol Label Switching (GMPLS) Terminology within the Context (GMPLS)", RFC 6344, August
              2011.

   [RFC7139]  Zhang, F., Zhang, G., Belotti, S., Ceccarelli, D., and K.
              Pithewan, "GMPLS Signaling Extensions for Control of the
              ITU-T's Automatically Switched
              Evolving G.709 Optical Network (ASON)
              Architecture", Transport Networks", RFC 4397, February 2006. 7139,
              March 2014.

   [RFC7260]  Takacs, A., Fedyk, D., and J. He, "GMPLS RSVP-TE
              Extensions for Operations, Administration, and Maintenance
              (OAM) Configuration", RFC 7260, June 2014.

Authors' Addresses

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

   Phone: +34913128832
   Email: oscar.gonzalezdedios@telefonica.com
   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
   ZTE Plaza,No.10,Tangyan South Road, Gaoxin District
   Xi'An
   China

   Email: fu.xihua@zte.com.cn

   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