OSPF Extensions for Routing Constraint Encoding in Flexible-Grid Networks
draft-wangl-ccamp-ospf-ext-constraint-flexi-grid-00

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Network Working Group                                            L. Wang
Internet-Draft                                                     Y. Li
Intended status: Standards Track                                     ZTE
Expires: August 18, 2012                               February 15, 2012

    OSPF Extensions for Routing Constraint Encoding in Flexible-Grid
                                Networks
          draft-wangl-ccamp-ospf-ext-constraint-flexi-grid-00

Abstract

   In Flexible-Grid networks, network elements and links may impose
   additional routing constraints, which cannot be ignored in Routing
   and Spectrum Assignment (RSA) process.  This document describes the
   requirements of such constraints, and then provides efficient
   encodings to specify how the information is carried.

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   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   the Trust Legal Provisions and are provided without warranty as

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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  3
   3.  Terminologies  . . . . . . . . . . . . . . . . . . . . . . . .  3
   4.  Requirements of Routing Constraint for RSA in
       Flexible-Grid Networks . . . . . . . . . . . . . . . . . . . .  4
     4.1.  Label set  . . . . . . . . . . . . . . . . . . . . . . . .  7
     4.2.  Port Flexible-Grid Supporting Ability Constraint . . . . .  7
     4.3.  Optical Signal Compatibility Constraint  . . . . . . . . .  8
   5.  Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     5.1.  Label Set  . . . . . . . . . . . . . . . . . . . . . . . .  9
     5.2.  Port Flexible-Grid Supporting Ability Constraint . . . . . 13
     5.3.  Optical Signal Compatibility Constraint  . . . . . . . . . 15
   6.  Encoding Example . . . . . . . . . . . . . . . . . . . . . . . 16
     6.1.  Example of Label Set Encoding  . . . . . . . . . . . . . . 16
     6.2.  Example of Port Flexible-Grid Supporting Ability
           Constraint Encoding  . . . . . . . . . . . . . . . . . . . 19
     6.3.  Example of Signal Compatibility Encoding . . . . . . . . . 19
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 20
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 20
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 20
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 20
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21

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1.  Introduction

   Flexible-Grid technique breaks the rigid nature of traditional DWDM
   wavelength Grid, and enables flexible allocation of optical spectrum
   resources to accommodate ultra-high data rate traffic.  Currently,
   there are several IETF draft addressing GMPLS routing and signaling
   extension to support Flexible-Grid DWDM Networks, such as
   [I-D.farrkingel-ccamp-flexigrid-lambda-label][I-D.li-ccamp-flexible-g
   rid-label][I-D.zhang-ccamp-flexible-grid-requirements][I-D.zhang-ccam
   p-flexible-grid-rsvp-te-ext][I-D.zhang-ccamp-flexible-grid-ospf-ext][
   I-D.hussain-ccamp-super-channel-label][I-D.dhillon-ccamp-super-channe
   l-ospfte-ext][I-D.zhangj-ccamp-flexi-grid-ospf-te-ext].  However, all
   these documents mainly focus on Label/Label-set extensions and
   spectrum consecutiveness/continuity constraints in Flexible-Grid
   Networks, but ignore other aspects of RSA problem.  In fact, Network
   elements (such as nodes and Optical-to-Electronic/
   Electronic-to-Optical sub-systems) and links may impose additional
   routing constraints such as flexible-grid ability/range limitations
   on ports, asymmetric switch connectivity, and signal processing
   limitations of each OE/EO system.  Without considering these
   constraints, it cannot be guaranteed to obtain available results in
   RSA process especially for network scenarios with various Flexible-
   Grid and Fixed-Grid elements, which leads to inefficient routing and
   high blocking probability of end-to-end paths.

   This document describes and encodes the constraints imposed by
   network elements and links, which could be carried in OSPF Messages
   to flood to each node for efficient RSA.  In addition, such
   information could be conveyed by other mechanisms to a Path
   Computation Element (PCE).  Note that, impairment-related constraints
   are not considered here.

2.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

3.  Terminologies

   GMPLS: Generalized Multi-Protocol Label Switching

   LSP: Label Switched Path

   ROADM: Reconfigurable Optical Add-Drop Multiplexer

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   RSA: Routing and spectrum assignment

   Slice: the basic slot unit, and the slot width of one slice is equal
   to slot width granularity

   WSON: Wavelength Switched Optical Networks [RFC6163]

   WSS: Wavelength Selective Switch

4.  Requirements of Routing Constraint for RSA in Flexible-Grid Networks

   In Flexible-Grid network, there is one key problem: how to route and
   allocate spectrum resources for each end-to end optical channel, so
   to fulfill their requirements in an efficient way?  To address this
   problem, some constraints must be taken into consideration, which are
   listed as follows.

   -Spectrum availability constraint.

   -Flexible-Grid supporting ability constraint.

   -Asymmetric switch connectivity constraint.

   -Optical signal compatibility constraint.

   -Other constraints.

   The asymmetric switch connectivity constraint in Flexible-Grid
   network could be well addressed by Connectivity matrix sub-TLV used
   in Wavelength Switched Optical Networks (WSON)
   [I-D.ietf-ccamp-general-constraint-encode].  The spectrum
   availability constraint is studied in several drafts, and could be
   represented by Label-set extensions of
   [I-D.li-ccamp-flexible-grid-label][I-D.zhang-ccamp-flexible-grid-ospf
   -ext][I-D.dhillon-ccamp-super-channel-ospfte-ext].  However, these
   extensions are not complete, so we reorganize the Flexible-Grid
   label-set according to WSON definition.  In addition, this document
   also takes the constraints imposed by network ports and OE/EO
   subsystems into consideration.

   Here a general use scenario of Flexible-Grid Network is given to
   illustrate these requirements.

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                 +----+A-E2    B-I1+----+B-E2    C-I1+----+
                 | A  |----------->| B  |----------->| C  |
                 |    |<-----------|    |<-----------|    |
                 +----+A-I2    B-E1+----+B-I2    C-E1+----+
                   O|                O|                O|
               A-I1||A-E1        B-I3||B-E3        C-I2||C-E2
                   ||                ||                ||
                   ||                ||                ||
                   ||                ||                ||
                   ||                ||                ||
               D-E1||D-I1        E-E3||E-I3        F-E2||F-I2
                   |O                |O                |O
                 +----+D-E2    E-I1+----+E-E2    F-I1+----+
                 | D  |----------->| E  |----------->| F  |
                 |    |<-----------|    |<-----------|    |
                 +----+D-I2    E-E1+----+E-I2    F-E1+----+

     Figure 1. A sample network with both Fixed-Grid and Flexible-Grid
                                 elements

         Tributary Side:        E5 I5 E6 I6
                                O |   O |
                                | |   | |
                                | O   | O
                         +-----------------------+
                         |+-----+         +-----+|
         Line side-1 --->||Split|         |WSS-2||---> Line side-2
         Input (I1)      |+-----+         +-----+|     Output (E2)
         Line side-1 <---||WSS-1|         |Split||<--- Line side-2
         Output  (E1)    |+-----+         +-----+|     Input (I2)
                         |         ROADM         |
                         |+-----+         +-----+|
         Line side-3 --->||Split|         |WSS-4||---> Line side-4
         Input (I3)      |+-----+         +-----+|     Output (E4)
         Line side-3 <---||WSS-3|         |Split||<--- Line side-4
         Output (E3)     |+-----+         +-----+|     Input (I4)
                         +-----------------------+
                                | O   | O
                                | |   | |
                                O |   O |
         Tributary Side:        E7 I7 E8 I8

        Figure 2. A ROADM Composed of WSSs and splitters (Internal
                      connections are not presented)

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   Figure 1 shows the network topology, while Figure 2 shows the
   architecture of nodes.  The ROADM of Figure 2 is composed of WSSs and
   splitters.  I1~4/E1~4 are line-side input/output ports, while I5~8/
   E5~8 are tributary-side add/drop ports to/from line-side 1~4
   respectively.  The configuration of each line-side output port is
   shown as follows:

       +----+---------+-----+------+-----------+---------+---------+
       |Node|Node-Type|Ports| Type |Granularity|Min width|Max width|
       +----+---------+-----+------+-----------+---------+---------+
       |    |         |A-E1 | Flex |    25GHz  |  50GHz  | 300GHz  |
       | A  |  Flex   |-----+------+-----------+---------+---------+
       |    |         |A-E2 | Flex |  12.5GHz  |  50GHz  | 300GHz  |
       +----+---------+-----+------+-----------+---------+---------+
       |    |         |B-E1 | Flex |  12.5GHz  |  50GHz  | 200GHz  |
       |    |         |-----+------+-----------+---------+---------+
       | B  |  Mixed  |B-E2 | Fixed|    50GHz  |  50GHz  |  50GHz  |
       |    |         |-----+------+-----------+---------+---------+
       |    |         |B-E3 | Flex |  12.5GHz  |  50GHz  | 200GHz  |
       +----+---------+-----+------+-----------+---------+---------+
       |    |         |C-E1 | Fixed|    50GHz  |  50GHz  |  50GHz  |
       | C  |  Fixed  |-----+------+-----------+---------+---------+
       |    |         |C-E2 | Fixed|    50GHz  |  50GHz  |  50GHz  |
       +----+---------+-----+------+-----------+---------+---------+
       |    |         |D-E1 | Flex |    25GHz  |  50GHz  | 300GHz  |
       | D  |  Flex   |-----+------+-----------+---------+---------+
       |    |         |D-E2 | Flex |    25GHz  |  50GHz  | 300GHz  |
       +----+---------+-----+------+-----------+---------+---------+
       |    |         |E-E1 | Flex |    25GHz  |  50GHz  | 300GHz  |
       |    |         |-----+------+-----------+---------+---------+
       | E  |  Flex   |E-E2 | Flex |  12.5Ghz  |  50GHz  | 200GHz  |
       |    |         |-----+------+-----------+---------+---------+
       |    |         |E-E3 | Flex |  12.5GHz  |  50GHz  | 200GHz  |
       +----+---------+-----+------+-----------+---------+---------+
       |    |         |F-E1 | Flex |  12.5GHz  |  50GHz  | 200GHz  |
       | F  |  Mixed  |-----+------+-----------+---------+---------+
       |    |         |F-E2 | Fixed|    50GHz  |  50GHz  |  50GHz  |
       +----+---------+-----+------+-----------+---------+---------+

   The granularity denotes the slot width granularity.  The Min-width
   and Max-width denote the slot width range.  There are three types of
   nodes: Node A, node D and node E are Flexible-Grid ROADMs, which only
   consist of Flexible-Grid elements; Node C is a Fixed-Grid ROADM,
   which only consists of Fixed-Grid elements; Node B and Node F are
   Mixed-Grid ROADMs, which consist of both Flexible-Grid and Fixed-Grid
   Elements.  Both Flexible-Grid ROADM and Mixed-Grid ROADM can support

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   Flexible-Grid LSPs to accommodate ultra-high data rate traffic such
   as beyond 100G. In addition, the Fixed-Grid ROADM can be smoothly
   updated to Mixed-Grid ROADM by adding Flexible-Grid ports.  With
   appropriate RSA, the network is able to support both Fixed-Grid
   services and Flexible-Grid services in an efficient way.

4.1.  Label set

   In Flexible-Grid networks, the spectrum assignment is not a local
   matter due to spectral consecutiveness and continuity constraints, so
   it is needed to get the information of which slice may or may not be
   used on each link and node port along the path in RSA process.  For
   example, in the network of Figure 1, when a LSP request from node A
   to node E with 50GHz slot width and route A->B->E arrives, the label
   restriction of input port A-I6, output port E-E7, switch port A-E2,
   B-I1, B-E3, E-I3 and spectrum availability of link AB, BE must be got
   for the spectrum assignment.  All the information is described by the
   label set objects which is decided by the label format.  The
   generalized label for the flexible grid can be referred to
   [I-D.farrkingel-ccamp-flexigrid-lambda-label] including central
   frequency and slot width information.

   As specified in [I-D.li-ccamp-flexible-grid-label] in section 4.1,
   this kind of label format is backward compatible to support the
   traditional 5 ways of wavelength label set encoding
   [I-D.ietf-ccamp-general-constraint-encode].

   o  1.  Inclusive list

   o  2.  Exclusive list

   o  3.  Inclusive range

   o  4.  Exclusive range

   o  5.  Bitmap set

   It can be seen that these 5 types of representations can be easily
   inherited by incorporating the new flexible label into the object.
   Note that in the procedure of flooding, any combination of the 5
   types of label sets is feasible.

4.2.  Port Flexible-Grid Supporting Ability Constraint

   Flexible-Grid supporting ability may include the type (Fixed-Grid or
   Flexible-Grid), center frequency granularity and slot width range.
   This information can be seen as the attribution of network ports with
   relations to links or nodes.  The RSA requirements of such fields are

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   listed as follows:

   Firstly, Flexible-Grid WSSs of different companies or product-types
   may have different slot width granularity and range, which may be a
   subset of possible values specified by ITU-T [G.694.1], so it should
   be taken into consideration in RSA process to avoid invalid route
   selection.  For example, in the network of Figure 1, when a LSP
   request from node A to node E with 250GHz slot width arrives, only
   the optical channel with a route A->D->E is able to carry the traffic
   due to the slot width range limitations on other ports.

   Secondly, Fixed-Grid ports/links cannot support Flexible-Grid LSPs
   with high slot width requirements, so it is necessary to distinguish
   Fixed-Grid ports/links from Flexible-Grid ports/links.  For example,
   in the network of Figure 1, when a LSP request from node B to Node F
   with 150GHz slot width arrives, the route B->C->F may be selected
   without considering Flexible-Grid Supporting Ability constraints.
   Even if there are free consecutive and continuous spectrum resources
   along the route, the optical channel cannot be setup successfully due
   to the limitation of Fixed-Grid ports/links.

   Thirdly, Although Flexible-Grid technology may offer full backwards
   compatibility with the standard ITU-T DWDM grids, it is a cost-
   efficient way to consider port Flexible-Grid Supporting Ability
   constraints in RSA process for Fixed-Grid requirements.  For example,
   in the network of figure 1, when a LSP request from node B to node F
   with 50GHz slot width arrives, it is a better route of B->C->F than
   the route B->E->F, because that flexible-Grid WSSs are more expensive
   than fixed-grid ones, and routing fixed-Grid requests on fixed-Grid
   elements could leave the Flexible-Grid elements and related spectrum
   resources to subsequent high data rate traffic.

4.3.  Optical Signal Compatibility Constraint

   Optical Signal Compatibility Constraint includes the signal
   processing ability (for example, data rate, FEC and modulation
   format) and modulation-related minimum slot width for each Optical-
   to-Electronic (OE)/Electronic-to-Optical (EO) subsystem.  The RSA
   requirements of such fields are listed as follows:

   Firstly, as described in [I-D.ietf-ccamp-rwa-wson-encode], OE/EO
   subsystems may be limited to process only certain types of optical
   signal in WSON or Flexible-Grid networks, so it is needed to get
   sufficient information characterizing OE/EO elements in RSA process
   to determine the signal compatibility along the path.  Examples of
   such subsystems include transponders, regenerators and so on.

   Secondly, for each Label Switch Path, the required slot width is

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   determined by the attribution of optical signal.  Generally, a client
   requests "data rate" as its traffic parameter but not "slot width",
   so it is needed to establish the mapping relations between data-rate/
   modulation-format and slot width, which should be reflected in
   optical signal compatibility constraint.  For example, in the network
   of Figure 1, when a LSP request from node A to Node E with 100Gbit/s
   data rate arrives, and both the transmitter of node A and the
   responder of node E support optical tributary signal class DP-QPSK
   100G with the same FEC and corresponding slot width 50GHz, the
   minimum slot width required by this connection should be 50GHz
   (without the consideration of impairments and regeneration).

5.  Encoding

5.1.  Label Set

   The general format for a label set is in accordance with that in
   [I-D.ietf-ccamp-general-constraint-encode],with a new flag G (1bit)
   representing the grid type of label sets(1~Flexible-Grid DWDM;
   0~Fixed-Grid DWDM):

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |G| Act.|    Num Labels         |          Length               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         start Label                           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         start Label(continue)                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     :     Additional fields as necessary per action                 :
     :                                                               :
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   the label format is in accordance with that in
   [I-D.farrkingel-ccamp-flexigrid-lambda-label].

   In the case of Inclusive/Exclusive label lists (0/1), the label set
   format is given as follows:

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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1| 0or1| Num Labels (not used) |          Length               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         First Label                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         First Label(continue)                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      :                                                               :
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Last  Label                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Last  Label(continue)                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Note that one label set may contain multiple labels.  The lowest/
   highest frequency of the K-th label is calculated as follows:

   Lowest frequency_k = (central frequency_k) - (slot width_k)/2

   = (193.1 + n_k * C.S.) - (2 * C.S. * m_k)/2

   = (193.1 + (n_k - m_k) * C.S.) THz;

   Highest frequency_k = Lowest frequency_k + slot width_k

   = (193.1 + (n_k + m_k) * C.S.) THz;

   In the case of Inclusive/Exclusive label ranges (2/3), the label set
   format is given as follows:

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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1| 2or3| Num Labels(not used)  |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Start Label #1                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Start Label #1(continue)                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     End Label #1                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     End Label #1(continue)                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      :                                                               :
      :                                                               :
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Start Label #n                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Start Label #n(continue)                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     End Label #n                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     End Label #n(continue)                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Note that one label set may contain multiple label ranges.  The value
   of m in start/end label has no effect on the label set, however, in
   order to keep the integrity of labels and avoid misunderstanding, it
   is set to default value: m = (slot width granularity)/12.5GHz.

   The lowest/highest frequency of the K-th label range is calculated as
   follows:

   Lowest frequency_k = (central frequency_kstart) - (slot width
   granularity)/2

   = (193.1 + n_kstart * C.S.) - C.S.

   = (193.1 + (n_kstart - 1) * C.S.) THz;

   Highest frequency_k = (central frequency_kend) + (slot width
   granularity)/2

   = (193.1 + n_kend * C.S.) + C.S.

   = (193.1 + (n_kend + 1) * C.S.) THz;

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   In the case of bitmap (4), the label set format is given as follows:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |1|  4  |   Num Labels          |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         Start Label                           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         Start Label(continue)                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    Bit Map Word #1 (Lowest numerical labels)                  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     :                                                               :
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    Bit Map Word #N (Highest numerical labels)                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Based on [I-D.ietf-ccamp-general-constraint-encode], Num labels
   denote the number of slices represented by the bit map; where the
   slice denotes the basic slot unit, and the slot width of one slice is
   equal to the slot width granularity.  As there may exist some
   situations that the unused bandwidth between two occupied bandwidth
   is odd times of the central frequency granularity (not integral times
   of the slot with granularity), two bits are needed to represent a
   single slice.  Each bit in the bit map represents a particular label
   of half a slice with a value of 1/0 indicating whether the part is in
   the set or not.  Bit position zero and one represent the lowest slice
   and corresponds to the start label.  The lowest/highest frequency of
   label range represented by bit position K is calculated as follows:

   Lowest frequency_k = (central frequency_start) + (K - 1) * (slot
   width granularity)/2

   = (193.1 + n_start * C.S.) + (K - 1) * C.S.

   = 193.1 + (n_start + K -1) * C.S.;

   Highest frequency_k = Low frequency_k + C.S.

   = 193.1 + (n_start + K) * C.S.

   The size of the bit map is (2 * Num Label) bits, but the bit map is
   padded out to a full multiple of 32 bits so that the TLV is a
   multiple of four bytes.  "Bits that do not represent labels (i.e.,
   those in positions) and beyond SHOULD be set to zero and MUST be

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   ignored" [I-D.ietf-ccamp-general-constraint-encode].

5.2.  Port Flexible-Grid Supporting Ability Constraint

   To accommodate the feature of port Flexible-Grid Supporting Ability
   constraint, we extend the Port Label Restriction sub-TLV defined in
   [I-D.ietf-ccamp-general-constraint-encode] for Flexible-Grid
   networks:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | MatrixID      | RstType = 5   |        Reserved               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |Grid | C.S.  |    Reserved     |   Min-Width   |   Max-Width   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   In WSON network, Matrix ID is used to represent "either the value in
   the corresponding Connectivity Matrix sub-TLV or takes the value OxFF
   to indicate the restriction applies to the port regardless of any
   Connectivity Matrix"[I-D.ietf-ccamp-general-constraint-encode].
   RstType is used to represent the restriction type.  This document
   defines a new RstType value to express the port Flexible-Grid
   Supporting Ability constraint in Flexible-Grid networks:

   5: PORT_ATTRIBUTION.

   The meaning of Grid and C.S. is defined in
   [I-D.farrkingel-ccamp-flexigrid-lambda-label], which is shown as
   follows:

                         +---------------+-------+
                         | Grid          | Value |
                         +---------------+-------+
                         | Reserved      |   0   |
                         +---------------+-------+
                         | ITU-T DWDM    |   1   |
                         +---------------+-------+
                         | ITU-T CWDM    |   2   |
                         +---------------+-------+
                         | Flexible DWDM |   3   |
                         +---------------+-------+
                         | Any           | 4(TBA)|
                         +---------------+-------+
                         | Future use    |  5-7  |

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

                         +-------------+---------+
                         |C.S. (GHz)   |  Value  |
                         +-------------+---------+
                         | Reserved    |    0    |
                         +-------------+---------+
                         |    100      |    1    |
                         +-------------+---------+
                         |    50       |    2    |
                         +-------------+---------+
                         |    25       |    3    |
                         +-------------+---------+
                         |    12.5     |    4    |
                         +-------------+---------+
                         |    6.25     | 5 (TBA) |
                         +-------------+---------+
                         |Future use   | 6 ~ 15  |
                         +-------------+---------+

   A new Grid type "Any" is defined.

   "Within the fixed grid network, the C.S. value is used to represent
   the channel spacing, as the spacing between adjacent channels is
   constant.  While for flexible grid situation, this field should be
   used to represent central frequency
   granularity."[I-D.farrkingel-ccamp-flexigrid-lambda-label]
   Accordingly the slot width granularity is twice of the C.S..

   Min-Width/Max-Width: 8bits, unsigned integer.  Min-Width/Max-Width
   denotes the minimum/maximum slot width that the port supports, which
   is an inherent attribution of the network elements.  The formula is
   shown as follows:

   Minimum Slot Width (GHz) = 12.5GHz * Min-Width;

   Maximum Slot Width (GHz) = 12.5GHz * Max-Width;

   For flexible-Grid ports (Grid = 3), the possible values of slot width
   are within the range [Minimum Slot Width, Maximum Slot Width] and
   with the slot width granularity of 2 * C.S.; for Fixed-Grid ports
   (Grid = 1 or 2), Min-Width/Max-Width is meaningless and padded with
   0.  For any port with Grid type "any", it means that the port support
   any Grid type, any slot width granularity and any slot width range,

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   so C.S. and Min-Width/Max-Width are meaningless and padded with 0..
   One example of such port is A-I1, which is comprised of optical
   splitter.

   Note that, the similar field of Min-Width/Max-Width is also included
   in object "BW sub-TLV" proposed by
   [I-D.dhillon-ccamp-super-channel-ospfte-ext].  However, BW sub-TLV is
   mainly used to present the available label set, so it belongs to
   dynamic information according to [RFC6163] and should be flooded
   frequently whenever the link state changes (for example, after the
   setup/teardown of the path traversing the link).  In this document,
   the Port Label Restriction sub-TLV with PORT_ATTRIBUTION type is
   regarded as relatively static information, as changes to these
   properties such as Grid, C.S. and Min-Width/Max-Width require
   hardware upgrades.  It is more suitable to carry such information
   separated from available label set in order to alleviate unnecessary
   flooding.

   Other port label restrictions have no difference with that in
   [I-D.ietf-ccamp-general-constraint-encode].

5.3.  Optical Signal Compatibility Constraint

   To accommodate the feature of Optical Signal Compatibility
   Constraint, we extend the Modulation Type sub-TLV defined in
   [I-D.ietf-ccamp-rwa-wson-encode] for Fixed-Grid networks:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |S|I|        Modulation ID         |          Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       m       |   Possible additional modulation parameters   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      :   the modulation ID                                           :
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The meaning of S, I and Modulation ID is in accordance with that of
   [I-D.ietf-ccamp-rwa-wson-encode].

   This document adds a new field "m" (8bit) to represent the minimum
   slot width requirement for corresponding Modulation ID:

   Minimum Slot Width = 12.5GHz * m.

   Note that the modulation type sub-TLV may contain multiple modulation

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   IDs, which means the transmitter/responder/transponder support
   multiple data rate/modulation format.

   This sub-TLV establishes mapping relations between data rate/
   modulation format (Modulation ID) and slot width.  In addition, it
   also provides the signal processing ability for each OE/EO element in
   the network.  However, FEC may impact the value of m, but it is not
   discussed here and leaved for further study.  New values of
   Modulation ID should be defined for ultra-high speed transmission,
   but it depends on transmission technique and not specified in this
   document.

   Other signal compatibility constraints have no difference with that
   in [I-D.ietf-ccamp-rwa-wson-encode].

6.  Encoding Example

6.1.  Example of Label Set Encoding

   Taking the network of figure 1 as an example, the available spectral
   resource of link AB is shown in figure 3.

               #1    Lowest    #2  Highest               #3
             |-|-|   |---------|---------|       |-------|-------|
               |               |Center Freq.             |       ^
             |1 1 0 0 1 1 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 1 1 1 1|
           __|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|__
         n= -16 -14 -12 -10 -8  -6  -4  -2   0   2   4   6   8   10
               |                                             |___|
             |_|_|                                          12.5GHz
               |
             slice

               Figure 3. Spectral resource state of link AB

   In figure 3, the spectral resource is from 193.1THz - 16 * 6.25GHz to
   193.1THz + 10 * 6.25GHz.  For label list type, the label set format
   is given as followsGBPo

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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1|  0  | Num Labels(not used)  |             Length(28)        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  3  |C.S.(5)|    Identifier   |              n(-15)           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       m(1)    |                  Reserved                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  3  |C.S.(5)|    Identifier   |              n(-7)            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       m(5)    |                  Reserved                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  3  |C.S.(5)|    Identifier   |              n(6)             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       m(4)    |                  Reserved                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   For label range type, the label set format is given as followsGBPo

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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1|  2  | Num Labels(not used)  |             Length(52)        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  3  |C.S.(5)|    Identifier   |              n(-15)           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       m(1)    |                  Reserved                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  3  |C.S.(5)|    Identifier   |              n(-15)           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       m(1)    |                  Reserved                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  3  |C.S.(5)|    Identifier   |              n(-11)           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       m(1)    |                  Reserved                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  3  |C.S.(5)|    Identifier   |              n(-3)            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       m(1)    |                  Reserved                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  3  |C.S.(5)|    Identifier   |              n(3)             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       m(1)    |                  Reserved                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  3  |C.S.(5)|    Identifier   |              n(9)             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       m(1)    |                  Reserved                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   For bitmap type, the label set format is given as followsGBPo

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1|  4  | Num Labels(26)        |             Length(16)        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  3  |C.S.(5)|    Identifier   |              n(-15)           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       m(1)    |                  Reserved                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1|1|0|0|1|1|1|1|1|1|1|1|1|1|0|0|0|0|1|1|1|1|1|1|1|1|0|0|0|0|0|0|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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6.2.  Example of Port Flexible-Grid Supporting Ability Constraint
      Encoding

   Taking the network of figure 1 as an example, the port Flexible-Grid
   supporting ability constraint of A-E1 can be encoded as follows:

        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | MatrixID(0xff)| RstType(5)    |        Reserved               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  3  |C.S.(5)|    Reserved     |  Min-Width(4) | Max-Width(16) |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The port port Flexible-Grid supporting ability constraint of A-E2 can
   be encoded as follows:

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | MatrixID(0xff)| RstType(5)    |        Reserved               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  3  |C.S.(4)|    Reserved     |  Min-Width(4) | Max-Width(24) |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The port Flexible-Grid supporting ability constraint of B-E2 can be
   encoded as follows:

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | MatrixID(0xff)| RstType(5)    |        Reserved               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  1  |C.S.(2)|    Reserved     |  Min-Width(0) | Max-Width(0)  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

6.3.  Example of Signal Compatibility Encoding

   Assuming an optical transmitter can support the following modulation
   typesGBPooptical tributary signal class DP-QPSK 100G (minimum slot
   width: 50GHz); optical tributary signal class DP-BPSK 100G (minimum
   slot width: 100GHz).  The Modulation Type sub-TLV is given as
   follows:

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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1|0|       DP-QPSK 100G        |             Length(8)         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      m(4)     |   Possible additional modulation parameters   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1|0|       DP-BPSK 100G        |             Length(8)         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      m(8)     |   Possible additional modulation parameters   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

7.  Security Considerations

8.  IANA Considerations

   TBD.

9.  References

9.1.  Normative References

   [G.694.1]  ITU-T Recommendation G.694.1, "Spectral grids for WDM
              apllications: DWDM frequency grid", November 2011.

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

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

9.2.  Informative References

   [I-D.dhillon-ccamp-super-channel-ospfte-ext]
              Dhillon, A., Hussain, I., Rao, RJ., and M. Sosa, "OSPFTE
              extension to support GMPLS for Flex Grid", October 2011.

   [I-D.farrkingel-ccamp-flexigrid-lambda-label]
              Farrel, A., King, D., Li, Y., Zhang, F., and R. Casellas,
              "Generalized Labels for the Flexi-Grid in Lambda-Switch-
              Capable (LSC) Label Switching Routers", October 2011.

   [I-D.hussain-ccamp-super-channel-label]

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              Hussain, I., Dhillon, A., Pan, Z., Sosa, M., Basch, B.,
              Liu, S., and A-G. Malis, "Generalized Label for Super-
              Channel Assignment on Flexible Grid", October 2011.

   [I-D.ietf-ccamp-general-constraint-encode]
              Bernstein, G., Lee, Y., Li, D., Imajuku, W., and JR. Han,
              "General Network Element Constraint Encoding for GMPLS
              Controlled Networks", May 2011.

   [I-D.ietf-ccamp-rwa-wson-encode]
              Bernstein, G., Lee, Y., Li, D., Imajuku, W., and JR. Han,
              "Routing and Wavelength Assignment Information Encoding
              for Wavelength Switched Optical Networks", October 2011.

   [I-D.li-ccamp-flexible-grid-label]
              Li, Y., Zhang, F., and R. Casellas, "Flexible Grid Label
              Format in Wavelength Switched Optical Network", July 2011.

   [I-D.zhang-ccamp-flexible-grid-ospf-ext]
              Zhang, FT., Zi, XB., Casellas, R., Gonzales-de-Dios, O.,
              and D. Ceccarelli, "GMPLS OSPF-TE Extensions in support of
              Flexible-Grid in DWDM Networks", October 2011.

   [I-D.zhang-ccamp-flexible-grid-requirements]
              Zhang, FT., Zi, XB., Gonzales-de-Dios, O., and R.
              Casellas, "Requirements for GMPLS Control of Flexible
              Grids", October 2011.

   [I-D.zhang-ccamp-flexible-grid-rsvp-te-ext]
              Zhang, FT., Gonzales-de-Dios, O., and D. Ceccarelli,
              "RSVP-TE Signaling Extensions in support of Flexible
              Grid", October 2011.

   [I-D.zhangj-ccamp-flexi-grid-ospf-te-ext]
              Zhang, J., Zhao, YL., and ZY. Yu, "OSPF-TE Protocol
              Extension for Constraint-aware RSA in Flexi-Grid
              Networks", October 2011.

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Authors' Addresses

   Lei Wang
   ZTE
   No.19, Huayuan East Road, Haidian District
   Beijing  100191
   P.R.China

   Phone: +86 13811440067
   Email: wang.lei131@zte.com.cn (hechen0001@gmail.com)
   URI:   http://www.zte.com.cn/

   Yao Li
   ZTE
   P.R.China

   Phone: +86 025 52871109
   Email: li.yao3@zte.com.cn
   URI:   http://www.zte.com.cn/

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