Network Working Group                                            Y. Lee
Internet Draft                                                   Huawei
Intended status: Informational                             G. Bernstein
Expires: September 2012                               Grotto Networking
                                                                  D. Li
                                                             W. Imajuku

                                                          March 6, 2012

    Routing and Wavelength Assignment Information Model for Wavelength
                         Switched Optical Networks


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Copyright Notice

   Copyright (c) 2012 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
   ( in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with
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   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.


   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
      1.1. Revision History..........................................4
         1.1.1. Changes from 01......................................4
         1.1.2. Changes from 02......................................4
         1.1.3. Changes from 03......................................5
         1.1.4. Changes from 04......................................5
         1.1.5. Changes from 05......................................5
         1.1.6. Changes from 06......................................5
         1.1.7. Changes from 07......................................5
         1.1.8. Changes from 08......................................5
         1.1.9. Changes from 09......................................5
         1.1.10. Changes from 10.....................................6
         1.1.11. Changes from 11.....................................6
         1.1.12. Changes from 12.....................................6
         1.1.13. Changes from 13.....................................6
   2. Terminology....................................................6
   3. Routing and Wavelength Assignment Information Model............7
      3.1. Dynamic and Relatively Static Information.................7

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   4. Node Information (General).....................................8
      4.1. Connectivity Matrix.......................................8
      4.2. Shared Risk Node Group....................................9
   5. Node Information (WSON specific)...............................9
      5.1. Resource Accessibility/Availability......................11
      5.2. Resource Signal Constraints and Processing Capabilities..14
      5.3. Compatibility and Capability Details.....................15
         5.3.1. Shared Input or Output Indication...................15
         5.3.2. Modulation Type List................................15
         5.3.3. FEC Type List.......................................15
         5.3.4. Bit Rate Range List.................................15
         5.3.5. Acceptable Client Signal List.......................16
         5.3.6. Processing Capability List..........................16
   6. Link Information (General)....................................16
      6.1. Administrative Group.....................................17
      6.2. Interface Switching Capability Descriptor................17
      6.3. Link Protection Type (for this link).....................17
      6.4. Shared Risk Link Group Information.......................17
      6.5. Traffic Engineering Metric...............................17
      6.6. Port Label (Wavelength) Restrictions.....................18
         6.6.1. Port-Wavelength Exclusivity Example.................19
   7. Dynamic Components of the Information Model...................21
      7.1. Dynamic Link Information (General).......................21
      7.2. Dynamic Node Information (WSON Specific).................21
   8. Security Considerations.......................................22
   9. IANA Considerations...........................................22
   10. Acknowledgments..............................................22
   11. References...................................................23
      11.1. Normative References....................................23
      11.2. Informative References..................................24
   12. Contributors.................................................25
   Author's Addresses...............................................26
   Intellectual Property Statement..................................26
   Disclaimer of Validity...........................................27

1. Introduction

   The purpose of the following information model for WSONs 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

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   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.

   1.1. Revision History

   1.1.1. Changes from 01

   Added text on multiple fixed and switched connectivity matrices.

   Added text on the relationship between SRNG and SRLG and encoding

   Added clarifying text on the meaning and use of port/wavelength

   Added clarifying text on wavelength availability information and how
   to derive wavelengths currently in use.

   1.1.2. Changes from 02

   Integrated switched and fixed connectivity matrices into a single
   "connectivity matrix" model. Added numbering of matrices to allow
   for wavelength (time slot, label) dependence of the connectivity.
   Discussed general use of this node parameter beyond WSON.

   Integrated switched and fixed port wavelength restrictions into a
   single port wavelength restriction of which there can be more than
   one and added a reference to the corresponding connectivity matrix
   if there is one. Also took into account port wavelength restrictions
   in the case of symmetric switches, developed a uniform model and
   specified how general label restrictions could be taken into account
   with this model.

   Removed the Shared Risk Node Group parameter from the node info, but
   left explanation of how the same functionality can be achieved with
   existing GMPLS SRLG constructs.

   Removed Maximum bandwidth per channel parameter from link

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   1.1.3. Changes from 03

   Removed signal related text from section 3.2.4 as signal related
   information is deferred to a new signal compatibility draft.

   Removed encoding specific text from Section 3.3.1 of version 03.

   1.1.4. Changes from 04

   Removed encoding specific text from Section 4.1.

   Removed encoding specific text from Section 3.4.

   1.1.5. Changes from 05

   Renumbered sections for clarity.

   Updated abstract and introduction to encompass signal

   Generalized Section on wavelength converter pools to include electro
   optical subsystems in general.  This is where signal compatibility
   modeling was added.

   1.1.6. Changes from 06

   Simplified information model for WSON specifics, by combining
   similar fields and introducing simpler aggregate information

   1.1.7. Changes from 07

   Added shared fiber connectivity to resource pool modeling. This
   includes information for determining wavelength collision on an
   internal fiber providing access to resource blocks.

   1.1.8. Changes from 08

   Added PORT_WAVELENGTH_EXCLUSIVITY in the RestrictionType parameter.
   Added section 6.6.1 that has an example of the port wavelength
   exclusivity constraint.

   1.1.9. Changes from 09

   Section 5: clarified the way that the resource pool is modeled from
   blocks of identical resources.

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   Section 5.1: grammar fixes. Removed reference to "academic" modeling
   pre-print. Clarified RBNF resource pool model details.

   Section 5.2: Formatting fixes.

   1.1.10. Changes from 10

   Enhanced the explanation of shared fiber access to resources and
   updated Figure 2 to show a more general situation to be modeled.

   Removed all 1st person idioms.

   1.1.11. Changes from 11

   Replace all instances of "ingress" with "input" and all instances of
   "egress" with "output". Added clarifying text on relationship
   between resource block model and physical entities such as line

1.1.12. Changes from 12

   Section 5.2: Clarified RBNF optional elements for several

   Section 5.3.6: Clarified RBNF optional elements for

   Editorial changes for clarity.

   Update the contributor list.

1.1.13. Changes from 13

   Section 7.1: Clarified that this information model does not dictate
   placement of information elements in protocols. In particular, added
   a caveat that the available label information element may be placed
   within the ISCD information element in the case of OSPF.

2. Terminology

   CWDM: Coarse Wavelength Division Multiplexing.

   DWDM: Dense Wavelength Division Multiplexing.

   FOADM: Fixed Optical Add/Drop Multiplexer.

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   ROADM: Reconfigurable Optical Add/Drop Multiplexer. A reduced port
   count wavelength selective switching element featuring input and
   output line side ports as well as add/drop side ports.

   RWA: Routing and Wavelength Assignment.

   Wavelength Conversion. The process of converting an information
   bearing optical signal centered at a given wavelength to one with
   "equivalent" content centered at a different wavelength. Wavelength
   conversion can be implemented via an optical-electronic-optical
   (OEO) process or via a strictly optical process.

   WDM: Wavelength Division Multiplexing.

   Wavelength Switched Optical Network (WSON): A WDM based optical
   network in which switching is performed selectively based on the
   center wavelength of an optical signal.

3. Routing and Wavelength Assignment Information Model

   The following WSON RWA information model is grouped into four
   categories regardless of whether they stem from a switching
   subsystem or from a line subsystem:

   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

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   and that information that is relatively static on the time scales 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.

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.


   <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 inputinput ports and
   wavelengths could possibly be connected to a particular output port.

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   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 inputinput
   ports and N the number of outputoutput 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 [Encode].

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

   ConnectivityMatrix ::= <MatrixID> <ConnType> <Matrix>


   <MatrixID> is a unique identifier for the matrix.

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

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

   4.2. Shared Risk Node Group

   SRNG: Shared risk group for nodes. The concept of a shared risk link
   group was defined in [RFC4202]. This can be used to achieve a
   desired "amount" of link diversity. It is also desirable to have a
   similar capability to achieve various degrees of node diversity.
   This is explained in [G.7715]. Typical risk groupings for nodes can
   include those nodes in the same building, within the same city, or
   geographic region.

   Since the failure of a node implies the failure of all links
   associated with that node a sufficiently general shared risk link
   group (SRLG) encoding, such as that used in GMPLS routing extensions
   can explicitly incorporate SRNG information.

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

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   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

   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 inputinput wavelength on a particular
      inputinput port to a desired outputoutput wavelength on a
      particular outputoutput 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
   "resource block". A resource block may contain one or more
   resources. As resources are the smallest identifiable unit of
   processing resource, 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> ::= <ResourceBlockInfo>...
   [<ResourceAccessibility>...] [<ResourceWaveConstraints>...]

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

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   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
   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 inputinput
   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
   reach 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.

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   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.

      I1   +-------------+                       +-------------+ E1
     ----->|             |      +--------+       |             |----->
      I2   |             +------+ Rb #1  +-------+             | E2
     ----->|             |      +--------+       |             |----->
           |             |                       |             |
           | Resource    |      +--------+       |  Resource   |
           | Pool        +------+        +-------+  Pool       |
           |             |      + Rb #2  +       |             |
           | Input       +------+        +-------|  Output     |
           | Connection  |      +--------+       |  Connection |
           | Matrix      |           .           |  Matrix     |
           |             |           .           |             |
           |             |           .           |             |
      IN   |             |      +--------+       |             | EM
     ----->|             +------+ Rb #P  +-------+             |----->
           |             |      +--------+       |             |
           +-------------+   ^               ^   +-------------+
                             |               |
                             |               |
                             |               |
                             |               |

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

            Figure 1 Schematic diagram of resource pool model.

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    I1   +-------------+                       +-------------+ E1
   ----->|             |      +--------+       |             |----->
    I2   |             +======+ Rb #1  +-+     +             | E2
   ----->|             |      +--------+ |     |             |----->
         |             |                 |=====|             |
         | Resource    |      +--------+ |     |  Resource   |
         | Pool        |    +-+ Rb #2  +-+     |  Pool       |
         |             |    | +--------+       +             |
         | Input       |====|                  |  Output     |
         | Connection  |    | +--------+       |  Connection |
         | Matrix      |    +-| Rb #3  |=======|  Matrix     |
         |             |      +--------+       |             |
         |             |           .           |             |
         |             |           .           |             |
         |             |           .           |             |
    IN   |             |      +--------+       |             | EM
   ----->|             +======+ 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

    Figure 2 Schematic diagram of resource pool model with shared block

   Formally the model can be specified as:

   <ResourceAccessibility ::= <PoolInputMatrix> <PoolOutputMatrix>

   <ResourceWaveConstraints> ::= <InputWaveConstraints>


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   Note that except for <ResourcePoolState> 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> ::= ([<ResourceSet>] <InputConstraints>
   [<ProcessingCapabilities>] <OutputConstraints>)*

   Where  <ResourceSet> 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> [<ModulationTypeList>]
   [<FECTypeList>] [<BitRateRange>] [<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> [<ModulationTypeList>]

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   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.

      5.3.2. Modulation Type List

      Modulation type, also known as optical tributary signal class,
      comes in two distinct flavors: (i) ITU-T standardized types; (ii)
      vendor specific types. The permitted modulation type list can
      include any mixture of standardized and vendor specific types.


      Where the STANDARD_MODULATION object just represents one of the
      ITU-T standardized optical tributary signal class and the
      VENDOR_MODULATION object identifies one vendor specific
      modulation type.

      5.3.3. FEC Type List

      Some devices can handle more than one FEC type and hence a list
      is needed.

      <fec-list>::= [<FEC>]

      Where the FEC object represents one of the ITU-T standardized
      FECs defined in [G.709], [G.707], [G.975.1] or a vendor-specific

      5.3.4. Bit Rate Range List

      Some devices can handle more than one particular bit rate range
      and hence a list is needed.

      <rate-range-list>::= [<rate-range>]...


      Where the START_RATE object represents the lower end of the range
      and the END_RATE object represents the higher end of the range.

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      5.3.5. Acceptable Client Signal List

      The list is simply:


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

      5.3.6. Processing Capability List

     The ProcessingCapabilities were defined in Section 5.2 as follows:

     <ProcessingCapabilities> ::= [<NumResources>]
     [<RegenerationCapabilities>] [<FaultPerfMon>] [<VendorSpecific>]

     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

     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.

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

   <LinkInfo> ::=  <LinkID> [<AdministrativeGroup>]
   [<InterfaceCapDesc>] [<Protection>] [<SRLG>]...
   [<TrafficEngineeringMetric>] [<PortLabelRestriction>]

   6.1. Administrative Group

   AdministrativeGroup: Defined in [RFC3630]. 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.

   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

   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

   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

   6.5. Traffic Engineering Metric

   TrafficEngineeringMetric: Defined in [RFC3630].  This allows for the
   definition of one additional link metric value for traffic
   engineering separate from the IP link state routing protocols link
   metric. 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...

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   6.6. Port Label (Wavelength) Restrictions

   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
   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. Such restrictions could be applied generally to
   other label types in GMPLS by adding new kinds of restrictions.

   <PortLabelRestriction> ::= [<GeneralPortRestrictions>...]

   <GeneralPortRestrictions> ::= <RestrictionType>

   <MatrixSpecificRestriction> ::= <MatrixID> <RestrictionType>

   <RestrictionParameters> ::= [<LabelSet>...] [<MaxNumChannels>]


   MatrixID is the ID of the corresponding connectivity matrix (section

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

   SIMPLE_WAVELENGTH:   Simple wavelength set restriction; The
   wavelength 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

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   PORT_WAVELENGTH_EXCLUSIVITY: A 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.

   WAVEBAND1:   Waveband device with a tunable center frequency and
   passband. This constraint is characterized by the MaxWaveBandWidth
   parameters which indicates the maximum width of the waveband in
   terms of channels. Note that an additional wavelength set 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.

   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).

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

     MaxWaveBandWidth is the maximum width of a tunable waveband
     switching device.

     PortSet is a conceptual set of ports.

   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

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   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.

                               |               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.

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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.

   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>

   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> [<ResourcePoolState>]

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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
   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.

9. IANA Considerations

   This informational document does not make any requests for IANA

10. Acknowledgments

   This document was prepared using

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11. References

   11.1. Normative References

   [Encode] G. Bernstein, Y. Lee, D. Li, W. Imajuku, "Routing and
             Wavelength Assignment Information Encoding for Wavelength
             Switched Optical Networks", work in progress: draft-ietf-

   [G.707] ITU-T Recommendation G.707, Network node interface for the
             synchronous digital hierarchy (SDH), January 2007.

   [G.709] ITU-T Recommendation G.709, Interfaces for the Optical
             Transport Network(OTN), March 2003.

   [G.975.1] ITU-T Recommendation G.975.1, Forward error correction for
             high bit-rate DWDM submarine systems, February 2004.

   [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

   [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.

   [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
             Engineering", RFC 5305, October 2008.

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

   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, http://www.grotto-

   [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.

   [G.Sup39] ITU-T Series G Supplement 39, Optical system design and
             engineering considerations, February 2006.

   [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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12. Contributors

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

   Phone: +39 010 600 3736
   Email: diego.caviglia@(,

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


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


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

   Phone: +81 44 396 3287

   Lyndon Ong

   Cyril Margaria
   Nokia Siemens Networks
   St Martin Strasse 76
   Munich,   81541
   Phone: +49 89 5159 16934

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Author's Addresses

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

   Phone: (510) 573-2237

   Young Lee (ed.)
   Huawei Technologies
   1700 Alma Drive, Suite 100
   Plano, TX 75075

   Phone: (972) 509-5599 (x2240)

   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

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

   Phone: +81-(46) 859-4315

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