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Versions: (draft-bernstein-ccamp-wson-info) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 RFC 7446

Network Working Group                                            Y. Lee
Internet Draft                                                   Huawei
Intended status: Informational                             G. Bernstein
Expires: June 2015                                    Grotto Networking
                                                                  D. Li
                                                                 Huawei
                                                             W. Imajuku
                                                                    NTT

                                                       December 4, 2014


    Routing and Wavelength Assignment Information Model for Wavelength
                         Switched Optical Networks


                     draft-ietf-ccamp-rwa-info-24.txt


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Copyright Notice



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



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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with
   respect to this document.  Code Components extracted from this
   document must include Simplified BSD License text as described in
   Section 4.e of the Trust Legal Provisions and are provided without
   warranty as described in the Simplified BSD License.

Abstract

   This document provides a model of information needed by the routing
   and wavelength assignment (RWA) process in wavelength switched
   optical networks (WSONs).  The purpose of the information described
   in this model is to facilitate constrained lightpath computation in
   WSONs. This model takes into account compatibility constraints
   between WSON signal attributes and network elements but does not
   include constraints due to optical impairments. Aspects of this
   information that may be of use to other technologies utilizing a
   GMPLS control plane are discussed.



Table of Contents


   1. Introduction...................................................3
   2. Terminology....................................................3
   3. Routing and Wavelength Assignment Information Model............4
      3.1. Dynamic and Relatively Static Information.................4
   4. Node Information (General).....................................5
      4.1. Connectivity Matrix.......................................5
   5. Node Information (WSON specific)...............................6
      5.1. Resource Accessibility/Availability.......................7
      5.2. Resource Signal Constraints and Processing Capabilities..11
      5.3. Compatibility and Capability Details.....................12
         5.3.1. Shared Input or Output Indication...................12
         5.3.2. Optical Interface Class List........................13
         5.3.3. Acceptable Client Signal List.......................13
         5.3.4. Processing Capability List..........................13
   6. Link Information (General)....................................14
      6.1. Administrative Group.....................................14
      6.2. Interface Switching Capability Descriptor................15
      6.3. Link Protection Type (for this link).....................15


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      6.4. Shared Risk Link Group Information.......................15
      6.5. Traffic Engineering Metric...............................15
      6.6. Port Label Restrictions..................................15
         6.6.1. Port-Wavelength Exclusivity Example.................18
   7. Dynamic Components of the Information Model...................19
      7.1. Dynamic Link Information (General).......................20
      7.2. Dynamic Node Information (WSON Specific).................20
   8. Security Considerations.......................................20
   9. IANA Considerations...........................................21
   10. Acknowledgments..............................................21
   11. References...................................................22
      11.1. Normative References....................................22
      11.2. Informative References..................................23
   12. Contributors.................................................24
   Authors' Addresses...............................................25
   Intellectual Property Statement..................................25
   Disclaimer of Validity...........................................26

1. Introduction

   The purpose of the WSONs information model described in this
   document is to facilitate constrained lightpath computation and as
   such is not a general purpose network management information model.
   This constraint is frequently referred to as the "wavelength
   continuity" constraint, and the corresponding constrained lightpath
   computation is known as the routing and wavelength assignment (RWA)
   problem. Hence the information model must provide sufficient
   topology and wavelength restriction and availability information to
   support this computation. More details on the RWA process and WSON
   subsystems and their properties can be found in [RFC6163]. The model
   defined here includes constraints between WSON signal attributes and
   network elements, but does not include optical impairments.

   In addition to presenting an information model suitable for path
   computation in WSON, this document also highlights model aspects
   that may have general applicability to other technologies utilizing
   a GMPLS control plane.  The portion of the information model
   applicable to other technologies beyond WSON is referred to as
   "general" to distinguish it from the "WSON-specific" portion that is
   applicable only to WSON technology.

2. Terminology

   Refer to [RFC6163] for Reconfigurable Optical Add/Drop Multiplexer
   (ROADM), RWA, Wavelength Conversion, Wavelength Division
   Multiplexing (WDM) and WSON.



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3. Routing and Wavelength Assignment Information Model

   The WSON RWA information model in this document comprises four
   categories of information. The categories are independent of whether
   the information comes from a switching subsystem or from a line
   subsystem -- a switching subsystem refers to WSON nodes such as
   ROADM or Optical Add/Drop Multiplexer (OADM), and a line subsystem
   refers to devices such as WDM or Optical Amplifier. The categories
   are these:

   o  Node Information

   o  Link Information

   o  Dynamic Node Information

   o  Dynamic Link Information

   Note that this is roughly the categorization used in [G.7715]
   section 7.

   In the following, where applicable, the reduced Backus-Naur form
   (RBNF) syntax of [RBNF] is used to aid in defining the RWA
   information model.

   3.1. Dynamic and Relatively Static Information

   All the RWA information of concern in a WSON network is subject to
   change over time.  Equipment can be upgraded; links may be placed in
   or out of service and the like.  However, from the point of view of
   RWA computations there is a difference between information that can
   change with each successive connection establishment in the network
   and that information that is relatively static and independent of
   connection establishment. A key example of the former is link
   wavelength usage since this can change with connection
   setup/teardown and this information is a key input to the RWA
   process.  Examples of relatively static information are the
   potential port connectivity of a WDM ROADM, and the channel spacing
   on a WDM link.

   This document separates, where possible, dynamic and static
   information so that these can be kept separate in possible encodings
   and hence allowing for separate updates of these two types of
   information thereby reducing processing and traffic load caused by
   the timely distribution of the more dynamic RWA WSON information.



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4. Node Information (General)

   The node information described here contains the relatively static
   information related to a WSON node. This includes connectivity
   constraints amongst ports and wavelengths since WSON switches can
   exhibit asymmetric switching properties. Additional information
   could include properties of wavelength converters in the node if any
   are present. In [Switch] it was shown that the wavelength
   connectivity constraints for a large class of practical WSON devices
   can be modeled via switched and fixed connectivity matrices along
   with corresponding switched and fixed port constraints. These
   connectivity matrices are included with the node information while
   the switched and fixed port wavelength constraints are included with
   the link information.

   Formally,

   <Node_Information> ::= <Node_ID> [<ConnectivityMatrix>...]

   Where the Node_ID would be an appropriate identifier for the node
   within the WSON RWA context.

   Note that multiple connectivity matrices are allowed and hence can
   fully support the most general cases enumerated in [Switch].

   4.1. Connectivity Matrix

   The connectivity matrix (ConnectivityMatrix) represents either the
   potential connectivity matrix for asymmetric switches (e.g. ROADMs
   and such) or fixed connectivity for an asymmetric device such as a
   multiplexer. Note that this matrix does not represent any particular
   internal blocking behavior but indicates which input ports and
   wavelengths could possibly be connected to a particular output port.
   Representing internal state dependent blocking for a switch or ROADM
   is beyond the scope of this document and due to its highly
   implementation dependent nature would most likely not be subject to
   standardization in the future. The connectivity matrix is a
   conceptual M by N matrix representing the potential switched or
   fixed connectivity, where M represents the number of input ports and
   N the number of output ports. This is a "conceptual" matrix since
   the matrix tends to exhibit structure that allows for very compact
   representations that are useful for both transmission and path
   computation.

   Note that the connectivity matrix information element can be useful
   in any technology context where asymmetric switches are utilized.



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   <ConnectivityMatrix> ::= <MatrixID>

                            <ConnType>

                            <Matrix>

   Where

   <MatrixID> is a unique identifier for the matrix.

   <ConnType> can be either 0 or 1 depending upon whether the
   connectivity is either fixed or switched.

   <Matrix> represents the fixed or switched connectivity in that
   Matrix(i, j) = 0 or 1 depending on whether input port i can connect
   to output port j for one or more wavelengths.

5. Node Information (WSON specific)

   As discussed in [RFC6163] a WSON node may contain electro-optical
   subsystems such as regenerators, wavelength converters or entire
   switching subsystems. The model present here can be used in
   characterizing the accessibility and availability of limited
   resources such as regenerators or wavelength converters as well as
   WSON signal attribute constraints of electro-optical subsystems. As
   such this information element is fairly specific to WSON
   technologies.

   A WSON node may include regenerators or wavelength converters
   arranged in a shared pool. As discussed in [RFC6163] this can
   include OEO based WDM switches as well. There are a number of
   different approaches used in the design of WDM switches containing
   regenerator or converter pools. However, from the point of view of
   path computation the following need to be known:

   1. The nodes that support regeneration or wavelength conversion.

   2. The accessibility and availability of a wavelength converter to
      convert from a given input wavelength on a particular input port
      to a desired output wavelength on a particular output port.

   3. Limitations on the types of signals that can be converted and the
      conversions that can be performed.

   Since resources tend to be packaged together in blocks of similar
   devices, e.g., on line cards or other types of modules, the
   fundamental unit of identifiable resource in this document is the


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   "resource block". A resource block may contain one or more
   resources. A resource is the smallest identifiable unit of
   processing allocation. One can group together resources into blocks
   if they have similar characteristics relevant to the optical system
   being modeled, e.g., processing properties, accessibility, etc.

   This leads to the following formal high level model:

   <Node_Information> ::= <Node_ID>

                          [<ConnectivityMatrix>...]

                          [<ResourcePool>]

   Where

   <ResourcePool> ::= <ResourceBlockInfo>...

                     [<ResourceAccessibility>...]

                     [<ResourceWaveConstraints>...]

                     [<RBPoolState>]



   First the accessibility of resource blocks is addressed then their
   properties are discussed.

   5.1. Resource Accessibility/Availability

   A similar technique as used to model ROADMs and optical switches can
   be used to model regenerator/converter accessibility. This technique
   was generally discussed in [RFC6163] and consisted of a matrix to
   indicate possible connectivity along with wavelength constraints for
   links/ports. Since regenerators or wavelength converters may be
   considered a scarce resource it is desirable that the model include,
   if desired, the usage state (availability) of individual
   regenerators or converters in the pool. Models that incorporate more
   state to further reveal blocking conditions on input or output to
   particular converters are for further study and not included here.

   The three stage model is shown schematically in Figure 1 and Figure
   2. The difference between the two figures is that Figure 1 assumes
   that each signal that can get to a resource block may do so, while
   in Figure 2 the access to sets of resource blocks is via a shared
   fiber which imposes its own wavelength collision constraint. The


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   representation of Figure 1 can have more than one input to each
   resource block since each input represents a single wavelength
   signal, while in Figure 2 shows a single multiplexed WDM input or
   output, e.g., a fiber, to/from each set of block.

   This model assumes N input ports (fibers), P resource blocks
   containing one or more identical resources (e.g. wavelength
   converters), and M output ports (fibers). Since not all input ports
   can necessarily reach each resource block, the model starts with a
   resource pool input matrix RI(i,p) = {0,1} whether input port i can
   potentially reach resource block p.

   Since not all wavelengths can necessarily reach all the resources or
   the resources may have limited input wavelength range the model has
   a set of relatively static input port constraints for each resource.
   In addition, if the access to a set of resource blocks is via a
   shared fiber (Figure 2) this would impose a dynamic wavelength
   availability constraint on that shared fiber. The resource block
   input port constraint is modeled via a static wavelength set
   mechanism and the case of shared access to a set of blocks is
   modeled via a dynamic wavelength set mechanism.

   Next a state vector RA(j) = {0,...,k} is used to track the number of
   resources in resource block j in use. This is the only state kept in
   the resource pool model. This state is not necessary for modeling
   "fixed" transponder system or full OEO switches with WDM interfaces,
   i.e., systems where there is no sharing.

   After that, a set of static resource output wavelength constraints
   and possibly dynamic shared output fiber constraints maybe used. The
   static constraints indicate what wavelengths a particular resource
   block can generate or are restricted to generating e.g., a fixed
   regenerator would be limited to a single lambda. The dynamic
   constraints would be used in the case where a single shared fiber is
   used to output the resource block (Figure 2).

   Finally, to complete the model, a resource pool output matrix
   RE(p,k) = {0,1} depending on whether the output from resource block
   p can reach output port k, may be used.










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      I1   +-------------+                       +-------------+ O1
     ----->|             |      +--------+       |             |----->
      I2   |             +------+ Rb #1  +-------+             | O2
     ----->|             |      +--------+       |             |----->
           |             |                       |             |
           | Resource    |      +--------+       |  Resource   |
           | Pool        +------+        +-------+  Pool       |
           |             |      + Rb #2  +       |             |
           | Input       +------+        +-------|  Output     |
           | Connection  |      +--------+       |  Connection |
           | Matrix      |           .           |  Matrix     |
           |             |           .           |             |
           |             |           .           |             |
      IN   |             |      +--------+       |             | OM
     ----->|             +------+ Rb #P  +-------+             |----->
           |             |      +--------+       |             |
           +-------------+   ^               ^   +-------------+
                             |               |
                             |               |
                             |               |
                             |               |

                    Input wavelength      Output wavelength
                    constraints for       constraints for
                    each resource         each resource

   Note: Rb is a Resource Block.


            Figure 1 Schematic diagram of resource pool model.
















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    I1   +-------------+                       +-------------+ O1
   ----->|             |      +--------+       |             |----->
    I2   |             +======+ Rb #1  +-+     |             | O2
   ----->|             |      +--------+ |     |             |----->
         |             |                 |=====|             |
         | Resource    |      +--------+ |     |  Resource   |
         | Pool        |    +-+ Rb #2  +-+     |  Pool       |
         |             |    | +--------+       |             |
         | Input       |====|                  |  Output     |
         | Connection  |    | +--------+       |  Connection |
         | Matrix      |    +-| Rb #3  |=======|  Matrix     |
         |             |      +--------+       |             |
         |             |           .           |             |
         |             |           .           |             |
         |             |           .           |             |
    IN   |             |      +--------+       |             | OM
   ----->|             +======+ Rb #P  +=======+             |----->
         |             |      +--------+       |             |
         +-------------+   ^               ^   +-------------+
                           |               |
                           |               |
                           |               |
               Single (shared) fibers for block input and output

                Input wavelength          Output wavelength
                availability for          availability for
                each block input fiber    each block output fiber

   Note: Rb is a Resource Block.


    Figure 2 Schematic diagram of resource pool model with shared block
                              accessibility.



   Formally the model can be specified as:

   <ResourceAccessibility> ::= <PoolInputMatrix>

                               <PoolOutputMatrix>







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   <ResourceWaveConstraints> ::= <InputWaveConstraints>

                                 <OutputOutputWaveConstraints>



   <RBSharedAccessWaveAvailability> ::= [<InAvailableWavelengths>]

                                        [<OutAvailableWavelengths>]



   <RBPoolState> ::=    <ResourceBlockID>

                        <NumResourcesInUse>

                        [<RBSharedAccessWaveAvailability>]

                        [<RBPoolState>]



   Note that except for <RBPoolState> all the other components of
   <ResourcePool> are relatively static. Also the
   <InAvailableWavelengths> and <OutAvailableWavelengths> are only used
   in the cases of shared input or output access to the particular
   block. See the resource block information in the next section to see
   how this is specified.



   5.2. Resource Signal Constraints and Processing Capabilities

   The wavelength conversion abilities of a resource (e.g. regenerator,
   wavelength converter) were modeled in the <OutputWaveConstraints>
   previously discussed. As discussed in [RFC6163] the constraints on
   an electro-optical resource can be modeled in terms of input
   constraints, processing capabilities, and output constraints:

   <ResourceBlockInfo> ::= <ResourceBlockSet>

                           [<InputConstraints>]

                           [<ProcessingCapabilities>]

                           [<OutputConstraints>]



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   Where  <ResourceBlockSet> is a list of resource block identifiers
   with the same characteristics. If this set is missing the
   constraints are applied to the entire network element.

   The <InputConstraints> are signal compatibility based constraints
   and/or shared access constraint indication. The details of these
   constraints are defined in section 5.3.

   <InputConstraints> ::= <SharedInput>

                          [<OpticalInterfaceClassList>]

                          [<ClientSignalList>]

   The <ProcessingCapabilities> are important operations that the
   resource (or network element) can perform on the signal. The details
   of these capabilities are defined in section 5.3.

   <ProcessingCapabilities> ::= [<NumResources>]

                                [<RegenerationCapabilities>]

                                [<FaultPerfMon>]

                                [<VendorSpecific>]

   The <OutputConstraints> are either restrictions on the properties of
   the signal leaving the block, options concerning the signal
   properties when leaving the resource or shared fiber output
   constraint indication.

   <OutputConstraints> := <SharedOutput>

                          [<OpticalInterfaceClassList>]

                          [<ClientSignalList>]



   5.3. Compatibility and Capability Details

   5.3.1. Shared Input or Output Indication

   As discussed in the previous section and shown in Figure 2 the input
   or output access to a resource block may be via a shared fiber. The
   <SharedInput> and <SharedOutput> elements are indicators for this
   condition with respect to the block being described.


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      5.3.2. Optical Interface Class List

          <OpticalInterfaceClassList> ::= <OpticalInterfaceClass> ...

      The Optical Interface Class is a unique number that identifies
      all information related to optical characteristics of a physical
      interface.  The class may include other optical parameters
      related to other interface properties.  A class always includes
      signal compatibility information.

      The content of each class is out of the scope of this document
      and can be defined by other entities (e.g.  ITU, optical
      equipment vendors, etc.).

      Since even current implementation of physical interfaces may
      support different optical characteristics, a single interface may
      support multiple interface classes.  Which optical interface
      class is used among all the ones available for an interface is
      out of the scope of this document but is an output of the RWA
      process.

      5.3.3. Acceptable Client Signal List

      The list is simply:

      <ClientSignalList>::=[<G-PID>]...

      Where the Generalized Protocol Identifiers (G-PID) object
      represents one of the IETF standardized G-PID values as defined
      in [RFC3471] and [RFC4328].

      5.3.4. Processing Capability List

     The ProcessingCapabilities were defined in Section 5.2.

     The processing capability list sub-TLV is a list of processing
     functions that the WSON network element (NE) can perform on the
     signal including:

        1. Number of Resources within the block

        2. Regeneration capability

        3. Fault and performance monitoring

        4. Vendor Specific capability



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     Note that the code points for Fault and performance monitoring and
     vendor specific capability are subject to further study.



6. Link Information (General)

   MPLS-TE routing protocol extensions for OSPF and IS-IS [RFC3630],
   [RFC5305] along with GMPLS routing protocol extensions for OSPF and
   IS-IS [RFC4203, RFC5307] provide the bulk of the relatively static
   link information needed by the RWA process. However, WSON networks
   bring in additional link related constraints. These stem from WDM
   line system characterization, laser transmitter tuning restrictions,
   and switching subsystem port wavelength constraints, e.g., colored
   ROADM drop ports.

   In the following summarize both information from existing GMPLS
   route protocols and new information that maybe needed by the RWA
   process.

   <LinkInfo> ::=  <LinkID>

                   [<AdministrativeGroup>]

                   [<InterfaceCapDesc>]

                   [<Protection>]

                   [<SRLG>...]

                   [<TrafficEngineeringMetric>]

                   [<PortLabelRestriction>...]

   Note that these additional link characteristics only applies to line
   side ports of WDM system or add/drop ports pertaining to Resource
   Pool (e.g., Regenerator or Wavelength Converter Pool). The
   advertisement of input/output tributary ports is not intended here.

   6.1. Administrative Group

   Administrative Group: Defined in [RFC3630] and extended for MPLS-TE
   [RFC7308]. Each set bit corresponds to one administrative group
   assigned to the interface.  A link may belong to multiple groups.
   This is a configured quantity and can be used to influence routing
   decisions.



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   6.2. Interface Switching Capability Descriptor

   InterfaceSwCapDesc: Defined in [RFC4202], lets us know the different
   switching capabilities on this GMPLS interface. In both [RFC4203]
   and [RFC5307] this information gets combined with the maximum LSP
   bandwidth that can be used on this link at eight different priority
   levels.

   6.3. Link Protection Type (for this link)

   Protection: Defined in [RFC4202] and implemented in [RFC4203,
   RFC5307]. Used to indicate what protection, if any, is guarding this
   link.

   6.4. Shared Risk Link Group Information

   SRLG: Defined in [RFC4202] and implemented in [RFC4203, RFC5307].
   This allows for the grouping of links into shared risk groups, i.e.,
   those links that are likely, for some reason, to fail at the same
   time.

   6.5. Traffic Engineering Metric

   TrafficEngineeringMetric: Defined in [RFC3630] and [RFC5305].  This
   allows for the identification of a data channel link metric value
   for traffic engineering that is separate from the metric used for
   path cost computation of the control plane.

   Note that multiple "link metric values" could find use in optical
   networks, however it would be more useful to the RWA process to
   assign these specific meanings such as link mile metric, or
   probability of failure metric, etc...

   6.6. Port Label Restrictions

   Port label restrictions could be applied generally to any label
   types in GMPLS by adding new kinds of restrictions. Wavelength is a
   type of label.

   Port label (wavelength) restrictions (PortLabelRestriction) model
   the label (wavelength) restrictions that the link and various
   optical devices such as OXCs, ROADMs, and waveband multiplexers may
   impose on a port. These restrictions tell us what wavelength may or
   may not be used on a link and are relatively static. This plays an
   important role in fully characterizing a WSON switching device
   [Switch]. Port wavelength restrictions are specified relative to the


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   port in general or to a specific connectivity matrix (section 4.1.
   Reference [Switch] gives an example where both switch and fixed
   connectivity matrices are used and both types of constraints occur
   on the same port.


   <PortLabelRestriction> ::= <MatrixID>

                              <RestrictionType>

                              <Restriction parameters list>


   <Restriction parameters list> ::=

                        <Simple label restriction parameters> |

                        <Channel count restriction parameters> |

                        <Label range restriction parameters> |

                        <Simple+channel restriction parameters> |

                        <Exclusive label restriction parameters>


   <Simple label restriction parameters> ::= <LabelSet> ...


   <Channel count restriction parameters> ::= <MaxNumChannels>


   <Label range restriction parameters> ::= <MaxLabelRange>

                                            (<LabelSet> ...)


   <Simple+channel restriction parameters> ::= <MaxNumChannels>

                                               (<LabelSet> ...)



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   <Exclusive label restriction parameters> ::= <LabelSet> ...


   Where

   MatrixID is the ID of the corresponding connectivity matrix (section
   4.1.

   The RestrictionType parameter is used to specify general port
   restrictions and matrix specific restrictions. It can take the
   following values and meanings:

   SIMPLE_LABEL:   Simple label (wavelength) set restriction; The label
   set parameter is required.

   CHANNEL_COUNT: The number of channels is restricted to be less than
   or equal to the Max number of channels parameter (which is
   required).

   LABEL_RANGE:  Used to indicate a restriction on a range of labels
   that can be switched.  For example, a waveband device with a tunable
   center frequency and passband. This constraint is characterized by
   the MaxLabelRange parameter which indicates the maximum range of the
   labels, e.g., which may represent a waveband in terms of channels.
   Note that an additional parameter can be used to indicate the
   overall tuning range. Specific center frequency tuning information
   can be obtained from dynamic channel in use information. It is
   assumed that both center frequency and bandwidth (Q) tuning can be
   done without causing faults in existing signals.

   SIMPLE LABEL & CHANNEL COUNT: In this case, the accompanying label
   set and MaxNumChannels indicate labels permitted on the port and the
   maximum number of labels that can be simultaneously used on the
   port.

   LINK LABEL_EXCLUSIVITY: A label (wavelength) can be used at most
   once among a given set of ports. The set of ports is specified as a
   parameter to this constraint.

   Restriction specific parameters are used with one or more of the
   previously listed restriction types. The currently defined
   parameters are:

     LabelSet is a conceptual set of labels (wavelengths).


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     MaxNumChannels is the maximum number of channels that can be
     simultaneously used (relative to either a port or a matrix).

     LinkSet is a conceptual set of ports.

   MaxLabelRange indicates the maximum range of the labels. For
   example, if the port is a "colored" drop port of a ROADM then there
   are two restrictions: (a) CHANNEL_COUNT, with MaxNumChannels = 1,
   and (b) SIMPLE_WAVELENGTH, with the wavelength set consisting of a
   single member corresponding to the frequency of the permitted
   wavelength. See [Switch] for a complete waveband example.

   This information model for port wavelength (label) restrictions is
   fairly general in that it can be applied to ports that have label
   restrictions only or to ports that are part of an asymmetric switch
   and have label restrictions. In addition, the types of label
   restrictions that can be supported are extensible.

   6.6.1. Port-Wavelength Exclusivity Example

   Although there can be many different ROADM or switch architectures
   that can lead to the constraint where a lambda (label) maybe used at
   most once on a set of ports Figure 3 shows a ROADM architecture
   based on components known as a Wavelength Selective Switch
   (WSS)[OFC08]. This ROADM is composed of splitters, combiners, and
   WSSes. This ROADM has 11 output ports, which are numbered in the
   diagram. Output ports 1-8 are known as drop ports and are intended
   to support a single wavelength. Drop ports 1-4 output from WSS #2,
   which is fed from WSS #1 via a single fiber. Due to this internal
   structure a constraint is placed on the output ports 1-4 that a
   lambda can be only used once over the group of ports (assuming uni-
   cast and not multi-cast operation). Similarly the output ports 5-8
   have a similar constraint due to the internal structure.
















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                               |               A
                               v            10 |
                           +-------+        +-------+
                           | Split |        |WSS  6 |
                           +-------+        +-------+
        +----+              | | | |          | | | |
        | W  |              | | | |          | | | +-------+   +----+
        | S  |--------------+ | | |    +-----+ | +----+    |   | S  |
      9 | S  |----------------|---|----|-------|------|----|---| p  |
     <--|    |----------------|---|----|-------|----+ |    +---| l  |<
        | 5  |--------------+ |   |    | +-----+    | |     +--| i  |
        +----+              | |   |    | |   +------|-|-----|--| t  |
                   +--------|-+   +----|-|---|------|----+  |  +----+
        +----+     |        |          | |   |      | |  |  |
        | S  |-----|--------|----------+ |   |      | |  |  |  +----+
        | p  |-----|--------|------------|---|------|----|--|--| W  |
     -->| l  |-----|-----+  | +----------+   |      | |  +--|--| S  |11
        | i  |---+ |     |  | | +------------|------|-------|--| S  |->
        | t  |   | |     |  | | |            |      | | +---|--|    |
        +----+   | | +---|--|-|-|------------|------|-|-|---+  | 7  |
                 | | |   +--|-|-|--------+ | |      | | |      +----+
                 | | |      | | |        | | |      | | |
                +------+   +------+     +------+   +------+
                | WSS 1|   | Split|     | WSS 3|   | Split|
                +--+---+   +--+---+     +--+---+   +--+---+
                   |          A            |          A
                   v          |            v          |
                +-------+  +--+----+    +-------+  +--+----+
                | WSS 2 |  | Comb. |    | WSS 4 |  | Comb. |
                +-------+  +-------+    +-------+  +-------+
                1|2|3|4|    A A A A     5|6|7|8|    A A A A
                 v v v v    | | | |      v v v v    | | | |

       Figure 3 A ROADM composed from splitter, combiners, and WSSs.

7. Dynamic Components of the Information Model

   In the previously presented information model there are a limited
   number of information elements that are dynamic, i.e., subject to
   change with subsequent establishment and teardown of connections.
   Depending on the protocol used to convey this overall information
   model it may be possible to send this dynamic information separate
   from the relatively larger amount of static information needed to
   characterize WSON's and their network elements.





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   7.1. Dynamic Link Information (General)

   For WSON links wavelength availability and wavelengths in use for
   shared backup purposes can be considered dynamic information and
   hence are grouped with the dynamic information in the following set:

   <DynamicLinkInfo> ::=  <LinkID>

                          <AvailableLabels>

                          [<SharedBackupLabels>]

   AvailableLabels is a set of labels (wavelengths) currently available
   on the link. Given this information and the port wavelength
   restrictions one can also determine which wavelengths are currently
   in use. This parameter could potential be used with other
   technologies that GMPLS currently covers or may cover in the future.

   SharedBackupLabels is a set of labels (wavelengths) currently used
   for shared backup protection on the link. An example usage of this
   information in a WSON setting is given in [Shared]. This parameter
   could potential be used with other technologies that GMPLS currently
   covers or may cover in the future.

   Note that the above does not dictate a particular encoding or
   placement for available label information. In some routing protocols
   it may be advantageous or required to place this information within
   another information element such as the interface switching
   capability descriptor (ISCD). Consult routing protocol specific
   extensions for details of placement of information elements.

   7.2. Dynamic Node Information (WSON Specific)

   Currently the only node information that can be considered dynamic
   is the resource pool state and can be isolated into a dynamic node
   information element as follows:

   <DynamicNodeInfo> ::=  <NodeID> [<ResourcePool>]



8. Security Considerations

   This document discussed an information model for RWA computation in
   WSONs. Such a model is very similar from a security standpoint of
   the information that can be currently conveyed via GMPLS routing
   protocols.  Such information includes network topology, link state


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   and current utilization, and well as the capabilities of switches
   and routers within the network.  As such this information should be
   protected from disclosure to unintended recipients.  In addition,
   the intentional modification of this information can significantly
   affect network operations, particularly due to the large capacity of
   the optical infrastructure to be controlled. A general discussion on
   security in GMPLS networks can be found in [RFC5920].



9. IANA Considerations

   This informational document does not make any requests for IANA
   action.

10. Acknowledgments

   This document was prepared using 2-Word-v2.0.template.dot.































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11. References

   11.1. Normative References



   [G.7715] ITU-T Recommendation G.7715, Architecture and requirements
             for routing in the automatically switched optical
             networks, June 2002.

   [RBNF]   A. Farrel, "Reduced Backus-Naur Form (RBNF) A Syntax Used
             in Various Protocol Specifications", RFC 5511, April 2009.

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

   [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
             (TE) Extensions to OSPF Version 2", RFC 3630, September
             2003.

   [RFC5305] T. Li, and H. SMIT, "Intermediate System to Intermediate
             System (IS-IS) Extensions for Traffic Engineering (TE)",
             RFC 5305, October 2008.

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

   [RFC4203] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions
             in Support of Generalized Multi-Protocol Label Switching
             (GMPLS)", RFC 4203, October 2005.

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

   [RFC5307] Kompella, K., Ed., and Y. Rekhter, Ed., "IS-IS Extensions
             in Support of Generalized Multi-Protocol Label Switching
             (GMPLS)", RFC 5307, October 2008.

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



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   [RFC7308] E. Osborne, "Extended Administrative Groups in MPLS
             Traffic Engineering (MPLS-TE)", RFC 7308, July 2014.




   11.2. Informative References

   [OFC08]  P. Roorda and B. Collings, "Evolution to Colorless and
             Directionless ROADM Architectures," Optical Fiber
             communication/National Fiber Optic Engineers Conference,
             2008. OFC/NFOEC 2008. Conference on, 2008, pp. 1-3.

   [Shared] G. Bernstein, Y. Lee, "Shared Backup Mesh Protection in
             PCE-based WSON Networks", iPOP 2008.

   [Switch] G. Bernstein, Y. Lee, A. Gavler, J. Martensson, "Modeling
             WDM Wavelength Switching Systems for Use in GMPLS and
             Automated Path Computation", Journal of Optical
             Communications and Networking, vol. 1, June, 2009, pp.
             187-195.

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























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12. Contributors

   Diego Caviglia
   Ericsson
   Via A. Negrone 1/A 16153
   Genoa Italy

   Phone: +39 010 600 3736
   Email: diego.caviglia@(marconi.com, ericsson.com)

   Anders Gavler
   Acreo AB
   Electrum 236
   SE - 164 40 Kista Sweden

   Email: Anders.Gavler@acreo.se

   Jonas Martensson
   Acreo AB
   Electrum 236
   SE - 164 40 Kista, Sweden

   Email: Jonas.Martensson@acreo.se

   Itaru Nishioka
   NEC Corp.
   1753 Simonumabe, Nakahara-ku, Kawasaki, Kanagawa 211-8666
   Japan

   Phone: +81 44 396 3287
   Email: i-nishioka@cb.jp.nec.com

   Lyndon Ong
   Ciena
   Email: lyong@ciena.com


   Cyril Margaria
   Email: cyril.margaria@gmail.com










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Authors' Addresses

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

   Phone: (510) 573-2237
   Email: gregb@grotto-networking.com


   Young Lee (ed.)
   Huawei Technologies
   5369 Legacy Drive, Building 3
   Plano, TX 75023
   USA

   Phone: (469) 277-5838
   Email: leeyoung@huawei.com


   Dan Li
   Huawei Technologies Co., Ltd.
   F3-5-B R&D Center, Huawei Base,
   Bantian, Longgang District
   Shenzhen 518129 P.R.China

   Phone: +86-755-28973237
   Email: danli@huawei.com

   Wataru Imajuku
   NTT Network Innovation Labs
   1-1 Hikari-no-oka, Yokosuka, Kanagawa
   Japan

   Phone: +81-(46) 859-4315
   Email: imajuku.wataru@lab.ntt.co.jp



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