



Internet Engineering Task Force (IETF)                       Y. Lee, Ed.
Request for Comments: 8780                           Samsung Electronics
Category: Standards Track                               R. Casellas, Ed.
ISSN: 2070-1721                                                     CTTC
                                                               July 2020


The Path Computation Element Communication Protocol (PCEP) Extension for
   Wavelength Switched Optical Network (WSON) Routing and Wavelength
                            Assignment (RWA)

Abstract

   This document provides Path Computation Element Communication
   Protocol (PCEP) extensions for the support of Routing and Wavelength
   Assignment (RWA) in Wavelength Switched Optical Networks (WSONs).
   Path provisioning in WSONs requires an RWA process.  From a path
   computation perspective, wavelength assignment is the process of
   determining which wavelength can be used on each hop of a path and
   forms an additional routing constraint to optical path computation.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8780.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://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.

Table of Contents

   1.  Introduction
   2.  Terminology
   3.  Requirements Language
   4.  Encoding of an RWA Path Request
     4.1.  Wavelength Assignment (WA) Object
     4.2.  Wavelength Selection TLV
     4.3.  Wavelength Restriction TLV
       4.3.1.  Link Identifier Field
       4.3.2.  Wavelength Constraint Field
     4.4.  Signal Processing Capability Restrictions
       4.4.1.  Signal Processing Exclusion
       4.4.2.  Signal Processing Inclusion
   5.  Encoding of an RWA Path Reply
     5.1.  Wavelength Allocation TLV
     5.2.  Error Indicator
     5.3.  NO-PATH Indicator
   6.  Manageability Considerations
     6.1.  Control of Function and Policy
     6.2.  Liveness Detection and Monitoring
     6.3.  Verifying Correct Operation
     6.4.  Requirements on Other Protocols and Functional Components
     6.5.  Impact on Network Operation
   7.  Security Considerations
   8.  IANA Considerations
     8.1.  New PCEP Object: Wavelength Assignment Object
     8.2.  WA Object Flag Field
     8.3.  New PCEP TLV: Wavelength Selection TLV
     8.4.  New PCEP TLV: Wavelength Restriction TLV
     8.5.  Wavelength Restriction TLV Action Values
     8.6.  New PCEP TLV: Wavelength Allocation TLV
     8.7.  Wavelength Allocation TLV Flag Field
     8.8.  New PCEP TLV: Optical Interface Class List TLV
     8.9.  New PCEP TLV: Client Signal Information TLV
     8.10. New Bit Flag for NO-PATH-VECTOR TLV
     8.11. New Error-Types and Error-Values
     8.12. New Subobjects for the Exclude Route Object
     8.13. New Subobjects for the Include Route Object
     8.14. Request for Updated Note for LMP TE Link Object Class Type
   9.  References
     9.1.  Normative References
     9.2.  Informative References
   Acknowledgments
   Contributors
   Authors' Addresses

1.  Introduction

   [RFC5440] specifies the Path Computation Element Communication
   Protocol (PCEP) for communications between a Path Computation Client
   (PCC) and a PCE, or between two PCEs.  Such interactions include Path
   Computation Requests (PCReqs) and Path Computation Replies (PCReps)
   as well as notifications of specific states related to the use of a
   PCE in the context of Multiprotocol Label Switching (MPLS) and
   Generalized MPLS (GMPLS) Traffic Engineering (TE).

   A PCC is said to be any network component that makes such a request
   and may be, for instance, an optical switching element within a
   Wavelength Division Multiplexing (WDM) network.  The PCE, itself, can
   be located anywhere within the network and may be within an optical
   switching element, a Network Management System (NMS), or an
   Operational Support System (OSS), or it may be an independent network
   server.

   This document provides the PCEP extensions for the support of Routing
   and Wavelength Assignment (RWA) in Wavelength Switched Optical
   Networks (WSONs) based on the requirements specified in [RFC6163] and
   [RFC7449].

   WSON refers to WDM-based optical networks in which switching is
   performed selectively based on the wavelength of an optical signal.
   The devices used in WSONs that are able to switch signals based on
   signal wavelength are known as Lambda Switch Capable (LSC).  WSONs
   can be transparent or translucent.  A transparent optical network is
   made up of optical devices that can switch but not convert from one
   wavelength to another, all within the optical domain.  On the other
   hand, translucent networks include 3R regenerators (reamplification,
   reshaping, and retiming) that are sparsely placed.  The main function
   of the 3R regenerators is to convert one optical wavelength to
   another.

   An LSC Label Switched Path (LSP) may span one or several transparent
   segments, which are delimited by 3R regenerators typically with
   electronic regenerator and optional wavelength conversion.  Each
   transparent segment or path in WSON is referred to as an optical
   path.  An optical path may span multiple fiber links, and the path
   should be assigned the same wavelength for each link.  In a case, the
   optical path is said to satisfy the wavelength-continuity constraint.
   Figure 1 illustrates the relationship between an LSC LSP and
   transparent segments (optical paths).

   +---+       +-----+       +-----+      +-----+         +-----+
   |   |I1     |     |       |     |      |     |       I2|     |
   |   |o------|     |-------[(3R) ]------|     |--------o|     |
   |   |       |     |       |     |      |     |         |     |
   +---+       +-----+       +-----+      +-----+         +-----+
       (X  LSC)     (LSC  LSC)    (LSC  LSC)     (LSC  X)
        <------->   <------->       <----->     <------->
        <-----------------------><---------------------->
         Transparent Segment         Transparent Segment
       <------------------------------------------------->
                              LSC LSP

       Figure 1: Illustration of an LSC LSP and Transparent Segments

   Note that two transparent segments within a WSON LSP do not need to
   operate on the same wavelength (due to wavelength conversion
   capabilities).  Two optical channels that share a common fiber link
   cannot be assigned the same wavelength; otherwise, the two signals
   would interfere with each other.  Note that advanced additional
   multiplexing techniques such as polarization-based multiplexing are
   not addressed in this document since the physical-layer aspects are
   not currently standardized.  Therefore, assigning the proper
   wavelength on a path is an essential requirement in the optical path
   computation process.

   When a switching node has the ability to perform wavelength
   conversion, the wavelength-continuity constraint can be relaxed, and
   an LSP may use different wavelengths on different links along its
   route from origin to destination.  It is, however, to be noted that
   wavelength converters may be limited due to their relatively high
   cost, while the number of WDM channels that can be supported in a
   fiber is also limited.  As a WSON can be composed of network nodes
   that cannot perform wavelength conversion, nodes with limited
   wavelength conversion, and nodes with full wavelength conversion
   abilities, wavelength assignment is an additional routing constraint
   to be considered in all optical path computation.

   For example (see Figure 1), within a translucent WSON, an LSC LSP may
   be established between interfaces I1 and I2, spanning two transparent
   segments (optical paths) where the wavelength continuity constraint
   applies (i.e., the same unique wavelength must be assigned to the LSP
   at each TE link of the segment).  If the LSC LSP induced a Forwarding
   Adjacency / TE link, the switching capabilities of the TE link would
   be (X X), where X refers to the switching capability of I1 and I2.
   For example, X can be Packet Switch Capable (PSC), Time-Division
   Multiplexing (TDM), etc.

   This document aligns with [RFC8779] for generic properties such as
   label, label set, and label assignment, noting that a wavelength is a
   type of label.  Wavelength restrictions and constraints are also
   formulated in terms of labels per [RFC7579].

   The optical modulation properties, which are also referred to as
   signal compatibility, are already considered in the signaling in
   [RFC7581] and [RFC7688].  In order to improve the signal quality and
   limit some optical effects, several advanced modulation processing
   capabilities are used by the mechanisms specified in this document.
   These modulation capabilities not only contribute to optical signal
   quality checks but also constrain the selection of sender and
   receiver, as they should have matching signal processing
   capabilities.  This document includes signal compatibility
   constraints as part of RWA path computation.  That is, the signal
   processing capabilities (e.g., modulation and Forward Error
   Correction (FEC)) indicated by means of the Optical Interface Class
   (OIC) must be compatible between the sender and the receiver of the
   optical path across all optical elements.

   This document, however, does not address optical impairments as part
   of RWA path computation.  See [RFC6566] for the framework for optical
   impairments.

2.  Terminology

   This document uses the terminology defined in [RFC4655] and
   [RFC5440].

3.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

4.  Encoding of an RWA Path Request

   Figure 2 shows one typical PCE-based implementation, which is
   referred to as the Combined Process (R&WA).  With this architecture,
   the two processes of routing and wavelength assignment are accessed
   via a single PCE.  This architecture is the base architecture
   specified in [RFC6163], and the PCEP extensions that are specified in
   this document are based on this architecture.

                          +----------------------------+
            +-----+       |     +-------+     +--+     |
            |     |       |     |Routing|     |WA|     |
            | PCC |<----->|     +-------+     +--+     |
            |     |       |                            |
            +-----+       |             PCE            |
                          +----------------------------+

               Figure 2: Combined Process (R&WA) Architecture

4.1.  Wavelength Assignment (WA) Object

   Wavelength allocation can be performed by the PCE by means of:

   (a)  Explicit Label Control [RFC3471] where the PCE allocates which
        label to use for each interface/node along the path.  The
        allocated labels MAY appear after an interface route subobject.

   (b)  A Label Set where the PCE provides a range of potential labels
        to be allocated by each node along the path.

   Option (b) allows distributed label allocation (performed during
   signaling) to complete wavelength assignment.

   Additionally, given a range of potential labels to allocate, a PCReq
   SHOULD convey the heuristic or mechanism used for the allocation.

   Per [RFC5440], the format of a PCReq message after incorporating the
   Wavelength Assignment (WA) object is as follows:

   <PCReq Message> ::= <Common Header>

                          [<svec-list>]

                          <request-list>

   Where:

         <request-list>::=<request>[<request-list>]

         <request>::= <RP>
                      <END-POINTS>

                      <WA>

                      [other optional objects...]

   If the WA object is present in the request, it MUST be encoded after
   the END-POINTS object as defined in [RFC8779].  The WA object is
   mandatory in this document.  Orderings for the other optional objects
   are irrelevant.

   For the WA object, the Object-Class is 42, and the Object-Type is 1.

   The format of the WA object body is 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Reserved             |            Flags            |M|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                            TLVs                             //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                            Figure 3: WA Object

   Reserved (16 bits):  Reserved for future use and SHOULD be zeroed and
      ignored on receipt.

   Flags field (16 bits):  One flag bit is allocated as follows:

      M (1 bit):  Wavelength Allocation Mode.  The M bit is used to
         indicate the mode of wavelength assignment.  When the M bit is
         set to 1, this indicates that the label assigned by the PCE
         must be explicit.  That is, the selected way to convey the
         allocated wavelength is by means of Explicit Label Control for
         each hop of a computed LSP.  Otherwise (M bit is set to 0), the
         label assigned by the PCE need not be explicit (i.e., it can be
         suggested in the form of Label Set objects in the corresponding
         response, to allow distributed WA.  If M is 0, the PCE MUST
         return a Label Set Field as described in Section 2.6 of
         [RFC7579] in the response.  See Section 5 of this document for
         the encoding discussion of a Label Set Field in a PCRep
         message.

      All unused flags SHOULD be zeroed.  IANA has created a new
      registry to manage the Flags field of the WA object.

   TLVs (variable):  In the TLVs field, the following two TLVs are
      defined.  At least one TLV MUST be present.

      Wavelength Selection TLV:  The type of this TLV is 8, and it has a
         fixed length of 32 bits.  This TLV indicates the wavelength
         selection.  See Section 4.2 for details.

      Wavelength Restriction TLV:  The type of this TLV is 9, and it has
         a variable length.  This TLV indicates wavelength restrictions.
         See Section 4.3 for details.

4.2.  Wavelength Selection TLV

   The Wavelength Selection TLV is used to indicate the wavelength
   selection constraint in regard to the order of wavelength assignment
   to be returned by the PCE.  This TLV is only applied when the M bit
   is set in the WA object specified in Section 4.1.  This TLV MUST NOT
   be used when the M bit is cleared.

   The encoding of this TLV is specified as the WavelengthSelection sub-
   TLV in Section 4.2.2 of [RFC7689].  IANA has allocated a new TLV type
   for the Wavelength Selection TLV (Type 8).

4.3.  Wavelength Restriction TLV

   For any request that contains a wavelength assignment, the requester
   (PCC) MUST specify a restriction on the wavelengths to be used.  This
   restriction is to be interpreted by the PCE as a constraint on the
   tuning ability of the origination laser transmitter or on any other
   maintenance-related constraints.  Note that if the LSC LSP spans
   different segments, the PCE must have mechanisms to know the
   tunability restrictions of the involved wavelength converters/
   regenerators, e.g., by means of the Traffic Engineering Database
   (TED) via either IGP or NMS.  Even if the PCE knows the tunability of
   the transmitter, the PCC must be able to apply additional constraints
   to the request.

   The format of the Wavelength Restriction TLV is as follows:

   <Wavelength Restriction> ::=

                  (<Action> <Count> <Reserved>

                  <Link Identifiers> <Wavelength Constraint>)...

   Where:

   <Link Identifiers> ::= <Link Identifier> [<Link Identifiers>]

   See Section 4.3.1 for the encoding of the Link Identifier field.

   These fields (i.e., <Action>, <Link Identifiers>, and <Wavelength
   Constraint>, etc.)  MAY appear together more than once to be able to
   specify multiple actions and their restrictions.

   IANA has allocated a new TLV type for the Wavelength Restriction TLV
   (Type 9).

   The TLV data is defined 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Action        |    Count      |           Reserved            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Link Identifiers                         |
   //                          . . .                              //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Wavelength Constraint                      |
   //                        . . . .                              //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                         . . . .                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Action        |    Count      |           Reserved            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Link Identifiers                         |
   //                          . . .                              //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Wavelength Constraint                      |
   //                        . . . .                              //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 4: Wavelength Restriction TLV Encoding

   Action (8 bits):
      0:  Inclusive List.  Indicates that one or more link identifiers
         are included in the Link Set. Each identifies a separate link
         that is part of the set.

      1:  Inclusive Range.  Indicates that the Link Set defines a range
         of links.  It contains two link identifiers.  The first
         identifier indicates the start of the range (inclusive).  The
         second identifier indicates the end of the range (inclusive).
         All links with numeric values between the bounds are considered
         to be part of the set.  A value of zero in either position
         indicates that there is no bound on the corresponding portion
         of the range.

      2-255:  Unassigned.

      IANA has created a new registry to manage the Action values of the
      Wavelength Restriction TLV.

      If a PCE receives an unrecognized Action value, the PCE MUST send
      a PCEP Error (PCErr) message with a PCEP-ERROR object with Error-
      Type=27 and an Error-value=3.  See Section 5.2 for details.

      Note that "links" are assumed to be bidirectional.

   Count (8 bits):
      The number of the link identifiers.

      Note that a PCC MAY add a Wavelength restriction that applies to
      all links by setting the Count field to zero and specifying just a
      set of wavelengths.

      Note that all link identifiers in the same list MUST be of the
      same type.

   Reserved (16 bits):
      Reserved for future use and SHOULD be zeroed and ignored on
      receipt.

   Link Identifiers:
      Identifies each link ID for which restriction is applied.  The
      length is dependent on the link format and the Count field.  See
      Section 4.3.1 for encoding of the Link Identifier field.

   Wavelength Constraint:
      See Section 4.3.2 for the encoding of the Wavelength Constraint
      field.

   Various encoding errors are possible with this TLV (e.g., not exactly
   two link identifiers with the range case, unknown identifier types,
   no matching link for a given identifier, etc.).  To indicate errors
   associated with this encoding, a PCEP speaker MUST send a PCErr
   message with Error-Type=27 and Error-value=3.  See Section 5.2 for
   details.

4.3.1.  Link Identifier Field

   The Link Identifier field can be an IPv4 [RFC3630], IPv6 [RFC5329],
   or unnumbered interface ID [RFC4203].

   <Link Identifier> ::=

               <IPv4 Address> | <IPv6 Address> | <Unnumbered IF ID>

   The encoding of each case is 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Type = 1     |    Reserved  (24 bits)                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | IPv4 address (4 bytes)                                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Figure 5: IPv4 Address Field

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Type = 2     |    Reserved  (24 bits)                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | IPv6 address (16 bytes)                                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | IPv6 address (continued)                                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | IPv6 address (continued)                                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | IPv6 address (continued)                                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Figure 6: IPv6 Address Field

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Type = 3     |    Reserved (24 bits)                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        TE Node ID (32 bits)                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Interface ID (32 bits)                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 7: Unnumbered Interface ID Address Field

   Type (8 bits):  Indicates the type of the link identifier.

   Reserved (24 bits):  Reserved for future use and SHOULD be zeroed and
      ignored on receipt.

   Link Identifier:  When the Type field is 1, a 4-byte IPv4 address is
      encoded; when the Type field is 2, a 16-byte IPv6 address is
      encoded; and when the Type field is 3, a tuple of a 4-byte TE node
      ID and a 4-byte interface ID is encoded.

   The Type field is extensible and matches the "TE_LINK Object Class
   type name space (Value 11)" registry created for the Link Management
   Protocol (LMP) [RFC4204] (see [LMP-PARAM]).  IANA has added an
   introductory note before the aforementioned registry stating that the
   values have additional usage for the Link Identifier Type field.  See
   Section 8.14.

4.3.2.  Wavelength Constraint Field

   The Wavelength Constraint field of the Wavelength Restriction TLV is
   encoded as a Label Set Field as specified in Section 2.6 of [RFC7579]
   with the base label encoded as a 32-bit LSC label, as defined in
   [RFC6205].  The Label Set format is repeated here for convenience,
   with the base label internal structure included.  See [RFC6205] for a
   description of Grid, Channel Spacing (C.S.), Identifier, and n, and
   see [RFC7579] for the details of each action.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Action|    Num Labels         |          Length               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Grid | C.S.  |    Identifier   |              n                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Additional fields as necessary per action                 |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 8: Wavelength Constraint Field

   Action (4 bits):
      0:  Inclusive List

      1:  Exclusive List

      2:  Inclusive Range

      3:  Exclusive Range

      4:  Bitmap Set

   Num Labels (12 bits):
      It is generally the number of labels.  It has a specific meaning
      depending on the action value.

   Length (16 bits):
      It is the length in bytes of the entire Wavelength Constraint
      field.

   Identifier (9 bits):
      The Identifier is always set to 0.  If PCC receives the value of
      the identifier other than 0, it will ignore.

   See Sections 2.6.1-2.6.3 of [RFC7579] for details on additional field
   discussion for each action.

4.4.  Signal Processing Capability Restrictions

   Path computation for WSON includes the checking of signal processing
   capabilities at each interface against requested capability; the PCE
   MUST have mechanisms to know the signal processing capabilities at
   each interface, e.g., by means of (TED) via either IGP or NMS.
   Moreover, a PCC should be able to indicate additional restrictions to
   signal processing compatibility, on either the endpoint or any given
   link.

   The supported signal processing capabilities considered in the RWA
   Information Model [RFC7446] are:

   *  Optical Interface Class List

   *  Bit Rate

   *  Client Signal

   The bit rate restriction is already expressed in the BANDWIDTH object
   in [RFC8779].

   In order to support the optical interface class information and the
   client signal information, new TLVs are introduced as endpoint
   restrictions in the END-POINTS type Generalized Endpoint:

   *  Client Signal Information TLV

   *  Optical Interface Class List TLV

   The END-POINTS type Generalized Endpoint is extended as follows:

   <endpoint-restriction> ::=
                         <LABEL-REQUEST> <label-restriction-list>

   <label-restriction-list> ::= <label-restriction>
                                [<label-restriction-list>]

   <label-restriction> ::= (<LABEL-SET>|
                           [<Wavelength Restriction>]
                           [<signal-compatibility-restriction>])

   Where:

   <signal-compatibility-restriction> ::=
       [<Optical Interface Class List>] [<Client Signal Information>]

   The Wavelength Restriction TLV is defined in Section 4.3.

   A new Optical Interface Class List TLV (Type 11) is defined; the
   encoding of the value part of this TLV is described in Section 4.1 of
   [RFC7581].

   A new Client Signal Information TLV (Type 12) is defined; the
   encoding of the value part of this TLV is described in Section 4.2 of
   [RFC7581].

4.4.1.  Signal Processing Exclusion

   The PCC/PCE should be able to exclude particular types of signal
   processing along the path in order to handle client restriction or
   multi-domain path computation.  [RFC5521] defines how the Exclude
   Route Object (XRO) subobject is used.  In this document, we add two
   new XRO Signal Processing Exclusion subobjects.

   The first XRO subobject type (8) is the Optical Interface Class List,
   which is defined 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |X|  Type=8     |     Length    |   Reserved    | Attribute     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //              Optical Interface Class List                   //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 9: Optical Interface Class List XRO Subobject

   Refer to [RFC5521] for the definitions of X, Length, and Attribute.

   Type (7 bits):  The type of the Signaling Processing Exclusion field.
      IANA has assigned value 8 for the Optical Interface Class List XRO
      subobject type.

   Reserved bits (8 bits):  These are for future use and SHOULD be
      zeroed and ignored on receipt.

   Attribute (8 bits):  [RFC5521] defines several Attribute values; the
      only permitted Attribute values for this field are 0 (Interface)
      or 1 (Node).

   Optical Interface Class List:  This field is encoded as described in
      Section 4.1 of [RFC7581].

   The second XRO subobject type (9) is the Client Signal Information,
   which is defined 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |X|  Type=9     |     Length    |   Reserved    |  Attribute    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                Client Signal Information                    //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

             Figure 10: Client Signal Information XRO Subobject

   Refer to [RFC5521] for the definitions of X, Length, and Attribute.

   Type (7 bits):  The type of the Signaling Processing Exclusion field.
      IANA has assigned value 9 for the Client Signal Information XRO
      subobject type.

   Reserved bits (8 bits):  These are for future use and SHOULD be
      zeroed and ignored on receipt.

   Attribute (8 bits):  [RFC5521] defines several Attribute values; the
      only permitted Attribute values for this field are 0 (Interface)
      or 1 (Node).

   Client Signal Information:  This field is encoded as described in
      Section 4.2 of [RFC7581].

   The XRO needs to support the new Signaling Processing Exclusion XRO
   subobject types:

      8:  Optical Interface Class List

      9:  Client Signal Information

4.4.2.  Signal Processing Inclusion

   Similar to the XRO subobject, the PCC/PCE should be able to include
   particular types of signal processing along the path in order to
   handle client restriction or multi-domain path computation.
   [RFC5440] defines how the Include Route Object (IRO) subobject is
   used.  In this document, we add two new Signal Processing Inclusion
   subobjects.

   The IRO needs to support the new IRO subobject types (8 and 9) for
   the PCEP IRO object [RFC5440]:

      8:  Optical Interface Class List

      9:  Client Signal Information

   The encoding of the Signal Processing Inclusion subobjects is similar
   to the process in Section 4.4.1 where the 'X' field is replaced with
   the 'L' field; all the other fields remain the same.  The 'L' field
   is described in [RFC3209].

5.  Encoding of an RWA Path Reply

   This section provides the encoding of an RWA Path Reply for a
   wavelength allocation request as discussed in Section 4.

5.1.  Wavelength Allocation TLV

   Recall that wavelength allocation can be performed by the PCE by
   means of:

   (a)  Explicit Label Control (ELC) where the PCE allocates which label
        to use for each interface/node along the path.

   (b)  A Label Set where the PCE provides a range of potential labels
        to be allocated by each node along the path.

   Option (b) allows distributed label allocation (performed during
   signaling) to complete wavelength allocation.

   The type for the Wavelength Allocation TLV is 10 (see Section 8.4).
   Note that this TLV is used for both (a) and (b) above.  The TLV data
   is defined 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Reserved           |          Flags              |M|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Link Identifier                         |
   //                          . . .                              //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Allocated Wavelength(s)                    |
   //                        . . . .                              //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 11: Wavelength Allocation TLV Encoding

   Reserved (16 bits):  Reserved for future use.

   Flags field (16 bits):  One flag bit is allocated as follows:

      M (1 bit):  Wavelength Allocation Mode.

         0:  Indicates the allocation relies on the use of Label Sets.

         1:  Indicates the allocation is done using Explicit Label
            Control.

      IANA has created a new registry to manage the Flags field of the
      Wavelength Allocation TLV.

   Link Identifier:  Identifies the interface to which the assignment
      wavelength(s) is applied.  See Section 4.3.1 for encoding of the
      Link Identifier field.

   Allocated Wavelength(s):  Indicates the allocated wavelength(s) to be
      associated with the link identifier.  See Section 4.3.2 for
      encoding details.

   This TLV is carried in a PCRep message as an Attribute TLV [RFC5420]
   in the Hop Attribute subobjects [RFC7570] in the Explicit Route
   Object (ERO) [RFC5440].

5.2.  Error Indicator

   To indicate errors associated with the RWA request, a new Error-Type
   27 (WSON RWA Error) and subsequent Error-values are defined as
   follows for inclusion in the PCEP-ERROR object:

   *  Error-Type=27; Error-value=1: If a PCE receives an RWA request and
      the PCE is not capable of processing the request due to
      insufficient memory, the PCE MUST send a PCErr message with a
      PCEP-ERROR object with Error-Type=27 and Error-value=1.  The PCE
      stops processing the request.  The corresponding RWA request MUST
      be canceled at the PCC.

   *  Error-Type=27; Error-value=2: If a PCE receives an RWA request and
      the PCE is not capable of RWA computation, the PCE MUST send a
      PCErr message with a PCEP-ERROR object with Error-Type=27 and
      Error-value=2.  The PCE stops processing the request.  The
      corresponding RWA computation MUST be canceled at the PCC.

   *  Error-Type=27; Error-value=3: If a PCE receives an RWA request and
      there are syntactical encoding errors (e.g., not exactly two link
      identifiers with the range case, unknown identifier types, no
      matching link for a given identifier, unknown Action value, etc.),
      the PCE MUST send a PCErr message with a PCEP-ERROR object with
      Error-Type=27 and Error-value=3.

5.3.  NO-PATH Indicator

   To communicate the reason(s) for not being able to find RWA for the
   path request, the NO-PATH object can be used in the corresponding
   response.  The format of the NO-PATH object body is defined in
   [RFC5440].  The object may contain a NO-PATH-VECTOR TLV to provide
   additional information about why a path computation has failed.

   This document defines a new bit flag to be carried in the Flags field
   in the NO-PATH-VECTOR TLV, which is carried in the NO-PATH object:

   Bit 23:  When set, the PCE indicates no feasible route was found that
      meets all the constraints (e.g., wavelength restriction, signal
      compatibility, etc.) associated with RWA.

6.  Manageability Considerations

   Manageability of WSON RWA with PCE must address the considerations in
   the following subsections.

6.1.  Control of Function and Policy

   In addition to the parameters already listed in Section 8.1 of
   [RFC5440], a PCEP implementation SHOULD allow configuration of the
   following PCEP session parameters on a PCC:

   *  The ability to send a WSON RWA request.

   In addition to the parameters already listed in Section 8.1 of
   [RFC5440], a PCEP implementation SHOULD allow configuration of the
   following PCEP session parameters on a PCE:

   *  The support for WSON RWA.

   *  A set of WSON-RWA-specific policies (authorized sender, request
      rate limiter, etc).

   These parameters may be configured as default parameters for any PCEP
   session the PCEP speaker participates in, or they may apply to a
   specific session with a given PCEP peer or a specific group of
   sessions with a specific group of PCEP peers.

6.2.  Liveness Detection and Monitoring

   Mechanisms defined in this document do not imply any new liveness
   detection and monitoring requirements, aside from those already
   listed in Section 8.3 of [RFC5440].

6.3.  Verifying Correct Operation

   Mechanisms defined in this document do not imply any new verification
   requirements, aside from those already listed in Section 8.4 of
   [RFC5440].

6.4.  Requirements on Other Protocols and Functional Components

   The PCEP Link-State mechanism [PCEP-LS] may be used to advertise WSON
   RWA path computation capabilities to PCCs.

6.5.  Impact on Network Operation

   Mechanisms defined in this document do not imply any new network
   operation requirements, aside from those already listed in
   Section 8.6 of [RFC5440].

7.  Security Considerations

   The security considerations discussed in [RFC5440] are relevant for
   this document; this document does not introduce any new security
   issues.  If an operator wishes to keep the information distributed by
   WSON private, PCEPS (Usage of TLS to Provide a Secure Transport for
   PCEP) [RFC8253] SHOULD be used.

8.  IANA Considerations

   IANA maintains a registry of PCEP parameters.  IANA has made
   allocations from the subregistries as described in the following
   sections.

8.1.  New PCEP Object: Wavelength Assignment Object

   As described in Section 4.1, a new PCEP object is defined to carry
   wavelength-assignment-related constraints.  IANA has allocated the
   following in the "PCEP Objects" subregistry [PCEP-NUMBERS]:

   +====================+======+==========================+===========+
   | Object-Class Value | Name | Object-Type              | Reference |
   +====================+======+==========================+===========+
   | 42                 | WA   | 0: Reserved              | RFC 8780  |
   +--------------------+------+--------------------------+-----------+
   |                    |      | 1: Wavelength Assignment | RFC 8780  |
   +--------------------+------+--------------------------+-----------+

                                 Table 1

8.2.  WA Object Flag Field

   As described in Section 4.1, IANA has created the "WA Object Flag
   Field" subregistry under the "Path Computation Element Protocol
   (PCEP) Numbers" registry [PCEP-NUMBERS] to manage the Flags field of
   the WA object.  New values are to be assigned by Standards Action
   [RFC8126].  Each bit should be tracked with the following qualities:

   *  Bit number (counting from bit 0 as the most significant bit)

   *  Capability description

   *  Defining RFC

   The initial contents of this registry are shown below.  One bit has
   been allocated for the flag defined in this document:

   +======+============================+===========+
   | Bit  | Description                | Reference |
   +======+============================+===========+
   | 0-14 | Unassigned                 |           |
   +------+----------------------------+-----------+
   | 15   | Wavelength Allocation Mode | RFC 8780  |
   +------+----------------------------+-----------+

                        Table 2

8.3.  New PCEP TLV: Wavelength Selection TLV

   In Section 4.2, a new PCEP TLV is defined to indicate wavelength
   selection constraints.  IANA has made the following allocation in the
   "PCEP TLV Type Indicators" subregistry [PCEP-NUMBERS]:

   +=======+======================+===========+
   | Value | Description          | Reference |
   +=======+======================+===========+
   | 8     | Wavelength Selection | RFC 8780  |
   +-------+----------------------+-----------+

                     Table 3

8.4.  New PCEP TLV: Wavelength Restriction TLV

   In Section 4.3, a new PCEP TLV is defined to indicate wavelength
   restrictions.  IANA has made the following allocation in the "PCEP
   TLV Type Indicators" subregistry [PCEP-NUMBERS]:

   +=======+========================+===========+
   | Value | Description            | Reference |
   +=======+========================+===========+
   | 9     | Wavelength Restriction | RFC 8780  |
   +-------+------------------------+-----------+

                      Table 4

8.5.  Wavelength Restriction TLV Action Values

   As described in Section 4.3, IANA has created the new "Wavelength
   Restriction TLV Action Values" subregistry under the "Path
   Computation Element Protocol (PCEP) Numbers" registry [PCEP-NUMBERS]
   to manage the Action values of the Action field of the Wavelength
   Restriction TLV.  New values are assigned by Standards Action
   [RFC8126].  Each value should be tracked with the following
   qualities:

   *  Value

   *  Meaning

   *  Defining RFC

   The initial contents of this registry are shown below:

   +=======+=================+===========+
   | Value | Meaning         | Reference |
   +=======+=================+===========+
   | 0     | Inclusive List  | RFC 8780  |
   +-------+-----------------+-----------+
   | 1     | Inclusive Range | RFC 8780  |
   +-------+-----------------+-----------+
   | 2-255 | Unassigned      |           |
   +-------+-----------------+-----------+

                   Table 5

8.6.  New PCEP TLV: Wavelength Allocation TLV

   In Section 5.1, a new PCEP TLV is defined to indicate the allocation
   of the wavelength(s) by the PCE in response to a request by the PCC.
   IANA has made the following allocation in "PCEP TLV Type Indicators"
   subregistry [PCEP-NUMBERS]:

   +=======+=======================+===========+
   | Value | Description           | Reference |
   +=======+=======================+===========+
   | 10    | Wavelength Allocation | RFC 8780  |
   +-------+-----------------------+-----------+

                      Table 6

8.7.  Wavelength Allocation TLV Flag Field

   As described in Section 5.1, IANA has created a new "Wavelength
   Allocation TLV Flag Field" subregistry under the "Path Computation
   Element Protocol (PCEP) Numbers" registry [PCEP-NUMBERS] to manage
   the Flags field of the Wavelength Allocation TLV.  New values are to
   be assigned by Standards Action [RFC8126].  Each bit should be
   tracked with the following qualities:

   *  Bit number (counting from bit 0 as the most significant bit)

   *  Capability description

   *  Defining RFC

   One bit is defined for the flag defined in this document.  The
   initial contents of this registry are shown below:

   +======+============================+===========+
   | Bit  | Description                | Reference |
   +======+============================+===========+
   | 0-14 | Unassigned                 |           |
   +------+----------------------------+-----------+
   | 15   | Wavelength Allocation Mode | RFC 8780  |
   +------+----------------------------+-----------+

                        Table 7

8.8.  New PCEP TLV: Optical Interface Class List TLV

   In Section 4.4, a new PCEP TLV is defined to indicate the Optical
   Interface Class List.  IANA has made the following allocation in the
   "PCEP TLV Type Indicators" subregistry [PCEP-NUMBERS]:

   +=======+==============================+===========+
   | Value | Description                  | Reference |
   +=======+==============================+===========+
   | 11    | Optical Interface Class List | RFC 8780  |
   +-------+------------------------------+-----------+

                         Table 8

8.9.  New PCEP TLV: Client Signal Information TLV

   In Section 4.4, a new PCEP TLV is defined to indicate the Client
   Signal Information.  IANA has made the following allocation in the
   "PCEP TLV Type Indicators" subregistry [PCEP-NUMBERS]:

   +=======+===========================+===========+
   | Value | Description               | Reference |
   +=======+===========================+===========+
   | 12    | Client Signal Information | RFC 8780  |
   +-------+---------------------------+-----------+

                        Table 9

8.10.  New Bit Flag for NO-PATH-VECTOR TLV

   In Section 5.3, a new bit flag is defined to be carried in the Flags
   field in the NO-PATH-VECTOR TLV, which is carried in the NO-PATH
   object.  This flag, when set, indicates that no feasible route was
   found that meets all the RWA constraints (e.g., wavelength
   restriction, signal compatibility, etc.) associated with an RWA path
   computation request.

   IANA has made the following allocation for this new bit flag in the
   "NO-PATH-VECTOR TLV Flag Field" subregistry [PCEP-NUMBERS]:

   +=====+========================+===========+
   | Bit | Description            | Reference |
   +=====+========================+===========+
   | 23  | No RWA constraints met | RFC 8780  |
   +-----+------------------------+-----------+

                     Table 10

8.11.  New Error-Types and Error-Values

   In Section 5.2, new PCEP error codes are defined for WSON RWA errors.
   IANA has made the following allocations in the "PCEP-ERROR Object
   Error Types and Values" subregistry [PCEP-NUMBERS]:

   +============+================+========================+===========+
   | Error-Type | Meaning        | Error-value            | Reference |
   +============+================+========================+===========+
   | 27         | WSON RWA error | 0: Unassigned          | RFC 8780  |
   +------------+----------------+------------------------+-----------+
   |            |                | 1: Insufficient memory | RFC 8780  |
   +------------+----------------+------------------------+-----------+
   |            |                | 2: RWA computation not | RFC 8780  |
   |            |                | supported              |           |
   +------------+----------------+------------------------+-----------+
   |            |                | 3: Syntactical         | RFC 8780  |
   |            |                | encoding error         |           |
   +------------+----------------+------------------------+-----------+
   |            |                | 4-255: Unassigned      | RFC 8780  |
   +------------+----------------+------------------------+-----------+

                                 Table 11

8.12.  New Subobjects for the Exclude Route Object

   The "Path Computation Element Protocol (PCEP) Numbers" registry
   contains a subregistry titled "XRO Subobjects" [PCEP-NUMBERS].  Per
   Section 4.4.1, IANA has added the following subobjects that can be
   carried in the XRO:

   +=======+==============================+===========+
   | Value | Description                  | Reference |
   +=======+==============================+===========+
   | 8     | Optical Interface Class List | RFC 8780  |
   +-------+------------------------------+-----------+
   | 9     | Client Signal Information    | RFC 8780  |
   +-------+------------------------------+-----------+

                         Table 12

8.13.  New Subobjects for the Include Route Object

   The "Path Computation Element Protocol (PCEP) Numbers" registry
   contains a subregistry titled "IRO Subobjects" [PCEP-NUMBERS].  Per
   Section 4.4.2, IANA has added the following subobjects that can be
   carried in the IRO:

   +=======+==============================+===========+
   | Value | Description                  | Reference |
   +=======+==============================+===========+
   | 8     | Optical Interface Class List | RFC 8780  |
   +-------+------------------------------+-----------+
   | 9     | Client Signal Information    | RFC 8780  |
   +-------+------------------------------+-----------+

                         Table 13

8.14.  Request for Updated Note for LMP TE Link Object Class Type

   The "TE_LINK Object Class type name space (Value 11)" registry was
   created for the Link Management Protocol (LMP) [RFC4204].  As
   discussed in Section 4.3.1, IANA has added the following note at the
   top of the "TE_LINK Object Class type name space (Value 11)" registry
   [LMP-PARAM]:

      These values have additional usage for the Link Identifier Type
      field.

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <https://www.rfc-editor.org/info/rfc3209>.

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630,
              DOI 10.17487/RFC3630, September 2003,
              <https://www.rfc-editor.org/info/rfc3630>.

   [RFC5329]  Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed.,
              "Traffic Engineering Extensions to OSPF Version 3",
              RFC 5329, DOI 10.17487/RFC5329, September 2008,
              <https://www.rfc-editor.org/info/rfc5329>.

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://www.rfc-editor.org/info/rfc5440>.

   [RFC6205]  Otani, T., Ed. and D. Li, Ed., "Generalized Labels for
              Lambda-Switch-Capable (LSC) Label Switching Routers",
              RFC 6205, DOI 10.17487/RFC6205, March 2011,
              <https://www.rfc-editor.org/info/rfc6205>.

   [RFC7570]  Margaria, C., Ed., Martinelli, G., Balls, S., and B.
              Wright, "Label Switched Path (LSP) Attribute in the
              Explicit Route Object (ERO)", RFC 7570,
              DOI 10.17487/RFC7570, July 2015,
              <https://www.rfc-editor.org/info/rfc7570>.

   [RFC7579]  Bernstein, G., Ed., Lee, Y., Ed., Li, D., Imajuku, W., and
              J. Han, "General Network Element Constraint Encoding for
              GMPLS-Controlled Networks", RFC 7579,
              DOI 10.17487/RFC7579, June 2015,
              <https://www.rfc-editor.org/info/rfc7579>.

   [RFC7581]  Bernstein, G., Ed., Lee, Y., Ed., Li, D., Imajuku, W., and
              J. Han, "Routing and Wavelength Assignment Information
              Encoding for Wavelength Switched Optical Networks",
              RFC 7581, DOI 10.17487/RFC7581, June 2015,
              <https://www.rfc-editor.org/info/rfc7581>.

   [RFC7688]  Lee, Y., Ed. and G. Bernstein, Ed., "GMPLS OSPF
              Enhancement for Signal and Network Element Compatibility
              for Wavelength Switched Optical Networks", RFC 7688,
              DOI 10.17487/RFC7688, November 2015,
              <https://www.rfc-editor.org/info/rfc7688>.

   [RFC7689]  Bernstein, G., Ed., Xu, S., Lee, Y., Ed., Martinelli, G.,
              and H. Harai, "Signaling Extensions for Wavelength
              Switched Optical Networks", RFC 7689,
              DOI 10.17487/RFC7689, November 2015,
              <https://www.rfc-editor.org/info/rfc7689>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8253]  Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
              "PCEPS: Usage of TLS to Provide a Secure Transport for the
              Path Computation Element Communication Protocol (PCEP)",
              RFC 8253, DOI 10.17487/RFC8253, October 2017,
              <https://www.rfc-editor.org/info/rfc8253>.

   [RFC8779]  Margaria, C., Ed., Gonzalez de Dios, O., Ed., and F.
              Zhang, Ed., "Path Computation Element Communication
              Protocol (PCEP) Extensions for GMPLS", RFC 8779,
              DOI 10.17487/RFC8779, July 2020,
              <https://www.rfc-editor.org/info/rfc8779>.

9.2.  Informative References

   [LMP-PARAM]
              IANA, "Link Management Protocol (LMP) Parameters",
              <https://www.iana.org/assignments/lmp-parameters/>.

   [PCEP-LS]  Lee, Y., Zheng, H., Ceccarelli, D., Wang, W., Park, P.,
              and B. Yoon, "PCEP Extension for Distribution of Link-
              State and TE information for Optical Networks", Work in
              Progress, Internet-Draft, draft-lee-pce-pcep-ls-optical-
              09, 9 March 2020, <https://tools.ietf.org/html/draft-lee-
              pce-pcep-ls-optical-09>.

   [PCEP-NUMBERS]
              IANA, "Path Computation Element Protocol (PCEP) Numbers",
              <https://www.iana.org/assignments/pcep/>.

   [RFC3471]  Berger, L., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Functional Description",
              RFC 3471, DOI 10.17487/RFC3471, January 2003,
              <https://www.rfc-editor.org/info/rfc3471>.

   [RFC4203]  Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
              Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
              <https://www.rfc-editor.org/info/rfc4203>.

   [RFC4204]  Lang, J., Ed., "Link Management Protocol (LMP)", RFC 4204,
              DOI 10.17487/RFC4204, October 2005,
              <https://www.rfc-editor.org/info/rfc4204>.

   [RFC4655]  Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
              Computation Element (PCE)-Based Architecture", RFC 4655,
              DOI 10.17487/RFC4655, August 2006,
              <https://www.rfc-editor.org/info/rfc4655>.

   [RFC5420]  Farrel, A., Ed., Papadimitriou, D., Vasseur, JP., and A.
              Ayyangar, "Encoding of Attributes for MPLS LSP
              Establishment Using Resource Reservation Protocol Traffic
              Engineering (RSVP-TE)", RFC 5420, DOI 10.17487/RFC5420,
              February 2009, <https://www.rfc-editor.org/info/rfc5420>.

   [RFC5521]  Oki, E., Takeda, T., and A. Farrel, "Extensions to the
              Path Computation Element Communication Protocol (PCEP) for
              Route Exclusions", RFC 5521, DOI 10.17487/RFC5521, April
              2009, <https://www.rfc-editor.org/info/rfc5521>.

   [RFC6163]  Lee, Y., Ed., Bernstein, G., Ed., and W. Imajuku,
              "Framework for GMPLS and Path Computation Element (PCE)
              Control of Wavelength Switched Optical Networks (WSONs)",
              RFC 6163, DOI 10.17487/RFC6163, April 2011,
              <https://www.rfc-editor.org/info/rfc6163>.

   [RFC6566]  Lee, Y., Ed., Bernstein, G., Ed., Li, D., and G.
              Martinelli, "A Framework for the Control of Wavelength
              Switched Optical Networks (WSONs) with Impairments",
              RFC 6566, DOI 10.17487/RFC6566, March 2012,
              <https://www.rfc-editor.org/info/rfc6566>.

   [RFC7446]  Lee, Y., Ed., Bernstein, G., Ed., Li, D., and W. Imajuku,
              "Routing and Wavelength Assignment Information Model for
              Wavelength Switched Optical Networks", RFC 7446,
              DOI 10.17487/RFC7446, February 2015,
              <https://www.rfc-editor.org/info/rfc7446>.

   [RFC7449]  Lee, Y., Ed., Bernstein, G., Ed., Martensson, J., Takeda,
              T., Tsuritani, T., and O. Gonzalez de Dios, "Path
              Computation Element Communication Protocol (PCEP)
              Requirements for Wavelength Switched Optical Network
              (WSON) Routing and Wavelength Assignment", RFC 7449,
              DOI 10.17487/RFC7449, February 2015,
              <https://www.rfc-editor.org/info/rfc7449>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

Acknowledgments

   The authors would like to thank Adrian Farrel, Julien Meuric, Dhruv
   Dhody, and Benjamin Kaduk for many helpful comments that greatly
   improved the contents of this document.

Contributors

   Fatai Zhang
   Huawei Technologies

   Email: zhangfatai@huawei.com


   Cyril Margaria
   Nokia Siemens Networks
   St. Martin Strasse 76
   81541 Munich
   Germany

   Phone: +49 89 5159 16934
   Email: cyril.margaria@nsn.com


   Oscar Gonzalez de Dios
   Telefonica Investigacion y Desarrollo
   C/ Emilio Vargas 6
   28043 Madrid
   Spain

   Phone: +34 91 3374013
   Email: ogondio@tid.es


   Greg Bernstein
   Grotto Networking
   Fremont, CA
   United States of America

   Phone: +1 510 573 2237
   Email: gregb@grotto-networking.com


Authors' Addresses

   Young Lee (editor)
   Samsung Electronics

   Email: younglee.tx@gmail.com


   Ramon Casellas, Editor (editor)
   CTTC
   Carl Friedrich Gauss 7
   PMT Ed B4 Av.
   08860 Castelldefels Barcelona
   Spain

   Phone: +34 936452916
   Email: ramon.casellas@cttc.es
