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Versions: (draft-lee-pce-flexible-grid) 00 01 02

PCE Working Group                                              Y. Lee
Internet Draft                                                   SKKU
Intended status: Standard Track
Expires: March 10, 2020                               H. Zheng (Editor)
                                                                 Huawei
                                                          R. Casellas
                                                             R. Vilalta
                                                                  CTTC

                                                          D. Ceccarelli
                                                           F. Lazzeri
                                                               Ericsson



                                                    September 10, 2019


                 PCEP Extension for Flexible Grid Networks


                      draft-ietf-pce-flexible-grid-02


Abstract

   This document provides the Path Computation Element Communication
   Protocol (PCEP) extensions for the support of Routing and Spectrum
   Assignment (RSA) in Flexible Grid networks.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with
   the provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
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   at any time.  It is inappropriate to use Internet-Drafts as
   reference material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.



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   This Internet-Draft will expire on June 19, 2019.

Copyright Notice

   Copyright (c) 2019 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with
   respect to this document.  Code Components extracted from this
   document must include Simplified BSD License text as described in
   Section 4.e of the Trust Legal Provisions and are provided without
   warranty as described in the Simplified BSD License.


Table of Contents


   1. Terminology ................................................. 3
   2. Requirements Language ....................................... 3
   3. Introduction ................................................ 3
   4. Spectrum Assignment (SA) Object ............................. 4
      4.1. Frequency-Slot Selection TLV ........................... 6
      4.2. Frequency-slot Restriction Constraint TLV .............. 8
         4.2.1. Frequency-Slot Restriction Field ................. 10
   5. Encoding of a RSA Path Reply ............................... 10
      5.1. Error Indicator........................................ 11
      5.2. NO-PATH Indicator ..................................... 12
   6. Manageability Considerations ............................... 12
      6.1. Control of Function and Policy ........................ 12
      6.2. Information and Data Models ........................... 13
      6.3. Verifying Correct Operation ........................... 13
      6.4. Requirements on Other Protocols and Functional Components13
      6.5. Impact on Network Operation ........................... 13
   7. Security Considerations .................................... 13
   8. IANA Considerations ........................................ 14
      8.1. New PCEP Object........................................ 14
      8.2. New PCEP TLV: Frequency Slot Selection TLV ............. 14
      8.3. New PCEP TLV: Frequency Slot Restriction Constraint TLV. 14
      8.4. New PCEP TLV: Spectrum Allocation TLV .................. 15
      8.5. New No-Path Reasons ................................... 15
      8.6. New Error-Types and Error-Values ....................... 16
   9. References ................................................. 16



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      9.1. Normative References .................................. 16
      9.2. Informative References ................................ 17
   10. Contributors .............................................. 18
   Authors' Addresses ............................................ 19



1. Terminology

   This document uses the terminology defined in [RFC4655], [RFC5440]
   and [RFC7698].

2. 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.

3. Introduction

   [RFC4655] defines a Path Computation Element (PCE) based path
   computation architecture and explains how a Path Computation Element
   (PCE) may compute Label Switched Paths (LSP) in Multiprotocol Label
   Switching Traffic Engineering (MPLS-TE) and Generalized MPLS (GMPLS)
   networks at the request of Path Computation Clients (PCCs).  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
   Operational Support System (OSS), or may be an independent network
   server.

   The PCE communications Protocol (PCEP) is the communication protocol
   used between a PCC and a PCE, and may also be used between
   cooperating PCEs.  [RFC4657] sets out the common protocol
   requirements for PCEP.  Additional application-specific requirements
   for PCEP are deferred to separate documents.

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




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   To allow efficient allocation of optical spectral bandwidth for
   systems that have high bit-rates, the International
   Telecommunication Union Telecommunication Standardization Sector
   (ITU-T) has extended its Recommendations [G.694.1] and [G.872] to
   include a new Dense Wavelength Division Multiplexing (DWDM) grid by
   defining a set of nominal central frequencies, channel spacings, and
   the concept of the "frequency slot". In such an environment, a data-
   plane connection is switched based on allocated, variable-sized
   frequency ranges within the optical spectrum, creating what is known
   as a flexible grid (flexi-grid). [RFC7698] provides Framework and
   Requirements for GMPLS-Based Control of Flexi-Grid Dense Wavelength
   Division Multiplexing (DWDM) Networks.

   The terms "Routing and Spectrum Assignment" (RSA) is introduced in
   [RFC7698] to refer to the process determines a route and frequency
   slot for an LSP. Hence, when a route is computed, the spectrum
   assignment process determines the central frequency and slot width.
   The term "Spectrum Switched Optical Networks" is also introduced in
   [RFC7698] to refer to a flexi-grid enabled DWDM network that is
   controlled by a GMPLS or PCE control plane.

   This document provides PCEP extensions to support RSA in SSONs.

   Figure 2 shows one typical PCE based implementation, which is
   referred to as the Combined Routing and Spectrum Assignment (R&SA)
   [RFC7698]. With this architecture, the two processes of routing and
   spectrum assignment are accessed via a single PCE. This architecture
   is the base architecture from which the PCEP extensions are
   specified in this document.

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


               Figure 1 Combined Process (R&SA) architecture



4. Spectrum Assignment (SA) Object

   This document aligns with GMPLS extensions for PCEP [PCEP-GMPLS] for
   generic property such as label, label-set and label assignment


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   noting that frequency is a type of label. Frequency restrictions and
   constraints are also formulated in terms of labels per [RFC7579].

   Spectrum allocation can be performed by the PCE by different means:

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

     (b) By means of a Label Set where the PCE provides a range of
     potential frequency slots to allocate by each node along the path.


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

   Additionally, given a range of potential spectrums to allocate, a PC
   Request SHOULD convey the heuristic / mechanism to the allocation.

   The format Routing Backus-Naur Form (RBNF) [RFC5511] of a PCReq
   message per [RFC5440] after incorporating the Spectrum Assignment
   (SA) object is as follows:

   <PCReq Message> ::= <Common Header>

                          [<svec-list>]

                          <request-list>

      Where:

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

         <request>::= <RP>

                      <GENERALIZED ENDPOINTS>

                      [ <SA> ]

                      [other optional objects...]

   If the SA object is present in the request, it MUST be encoded after
   the GENERALIZED ENDPOINTS object.

   SA Object-Class is (TBD1) (To be assigned by IANA).

   SA Object-Type is 1.


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   The format of the Spectrum Assignment (SA) 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|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                Frequency-Slot Selection TLV                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Frequency-Slot Restriction Constraint TLV             |
   .                                                               .
   .                                                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                      Optional TLVs                          //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                            Figure 2 SA Object

   o  Reserved (16 bits)

   o  Flags (16 bits)

   One Flag bit is allocated as follows:

       M (Mode - 1 bit): M bit is used to indicate the mode of
        spectrum assignment. When M bit is set to 1, this indicates
        that the spectrum assigned by the PCE must be explicit. That
        is, the selected way to convey the allocated spectrum is by
        means of Explicit Label Control (ELC) [RFC4003] for each hop of
        a computed LSP. Otherwise, the spectrum assigned by the PCE
        needs not be explicit (i.e., it can be suggested in the form of
        label set objects in the corresponding response, to allow
        distributed SA. In such case, 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.



4.1. Frequency-Slot Selection TLV

   The Frequency-Slot Selection TLV is used to indicate the frequency-
   slot selection constraint in regard to the order of frequency-slot


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   assignment to be returned by the PCE. This TLV is only applied when
   M bit is set in the SA Object specified in Section 4. This TLV
   SHOULD NOT be present and MUST be ignored when the M bit is cleared.

   The Frequency-Slot Selection sub-TLV value field is defined as:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |S|  FSA Method  |                   Reserved                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Where:

      Frequency-Slot Assignment (FSA) Method (7 bits):

      0: unspecified (any); This does not constrain the SA method
         used by a PCC  This value is implied when the
         Frequency-Slot Selection sub-TLV is absent.

      1: First-Fit.  All the feasible frequency slots are numbered
         (based on "n" parameter), and this SA method chooses the
         available frequency-slot with the lowest index, where "n" is
         the parameter in f = 193.1 THz + n x 0.00625 THz where 193.1
         THz is the ITU-T "anchor frequency" and "n" is a positive
         integer including 0 [RFC7698].


      2: Random.  This SA method chooses a feasible frequency-slot
          value of "n" randomly.

      3-127: Unassigned.

   S (Symmetry, 1 bit):  This flag is only meaningful when the request
   is for a bidirectional LSP (see [RFC5440]).

    0 denotes requiring the same frequency-slot in both directions;
      1 denotes that different spectrums on both directions are
      allowed.

   IANA is to allocate a new PCEP TLV type, Frequency-Slot Selection
   TLV (TBD2) in the "PCEP TLV Type Indicators" subregistry


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   (http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-tlv-type-
   indicators).


   The processing rules for this TLV are as follows:


      If a PCE does not support the attribute(s), its
      behavior is specified below:

      -  S bit clear not supported: a PathErr MUST be generated with
         The Error Code "Routing Problem" (24) with error sub-code
         "Unsupported Frequency slot Selection Symmetry value" (TBD3).

      -  FSA method not supported: a PathErr MUST be generated with the
         Error Code "Routing Problem" (24) with error sub-code
         "Unsupported Frequency Slot Assignment value" (TBD4).


4.2. Frequency-slot Restriction Constraint TLV

   For any request that contains a Frequency-slot assignment, the
   requester (PCC) must be able to specify a restriction on the
   frequency-slots 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.

   The format of the Frequency-Slot Restriction Constraint TLV is as
   follows:

   <Frequency-lot Restriction Constraint> ::=

                  (<Action>

                  <Link Identifiers> <Freq-slot Restriction>)...

   Where

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

   See Section 4.3.1 in [PCEP-WSON] for the encoding of the Link
   Identifiers Field.
   IANA is to allocate a new PCEP TLV, the Frequency slot Restriction
   Constraint TLV type (TBD5). This TLV MAY appear more than once to be
   able to specify multiple restrictions.


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   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                          |
   |                          . . .                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                Frequency Slot Restriction Field               |
   //                        . . . .                              //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 3 spectrum Restriction Constraint TLV Encoding


   o  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. Note that the Action field can be set to
         0 when unnumbered link identifier is used.



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

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



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

   o  Reserved: Reserved for future use (16 bits)


   o  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 in [PCEP-WSON] for Link Identifier
   encoding.



4.2.1. Frequency-Slot Restriction Field

   The Frequency-Slot Restriction Field of the Frequency slot
   restriction TLV is encoded as defined in section 4.2 of [RFC8363].

5. Encoding of a RSA Path Reply

   This section provides the encoding of a RSA Path Reply for frequency
   slot allocation as discussed in Section 4. Spectrum Allocation TLV

   IANA is to allocate a new PCEP TLV type, the Spectrum Allocation TLV
   type (TBD6). 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Type             |        Length               |M|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Link Identifier                           |
   |                          . . .                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Allocated Spectrum(s)                      |
   //                        . . . .                              //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 4 Spectrum Allocation TLV Encoding


   o  Type (16 bits): The type of the TLV.


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   o  Length (15 bits): The length of the TLV including the Type and
                  Length fields.

   o  M (Mode): 1 bit


      -  0 indicates the allocation is under Explicit Label Control.

      -  1 indicates the allocation is expressed in Label Sets.


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


   o  Link Identifier (variable): Identifies the interface to which
   assignment spectrum(s) is applied. See Section 3.3 for Link
   Identifier encoding.

   o  Allocated Spectrum(s) (variable): Indicates the allocated
   spectrum(s) to the link identifier. See Section 3.3.1 for encoding
   details.

   This TLV is encoded as an attributes TLV, per [RFC5420], which is
   carried in the ERO LSP Attribute Subobjects per [RFC7570].

5.1. Error Indicator

   To indicate errors associated with the RSA request, a new Error Type
   (TDB) and subsequent error-values are defined as follows for
   inclusion in the PCEP-ERROR Object:

   A new Error-Type (TBD7) and subsequent error-values are defined as
   follows:

         Error-Type=TBD7; Error-value=1: if a PCE receives a RSA
         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 (Error-Type=TDB) and an Error-
         value(Error-value=1).  The PCE stops processing the request.
         The corresponding RSA request MUST be cancelled at the PCC.






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         Error-Type=TBD7; Error-value=2: if a PCE receives a RSA
         request and the PCE is not capable of RSA computation, the PCE
         MUST send a PCErr message with a PCEP-ERROR Object (Error-
         Type=TDB) and an Error-value (Error-value=2). The PCE stops
         processing the request.  The corresponding RSA computation
         MUST be cancelled at the PCC.

5.2. NO-PATH Indicator

   To communicate the reason(s) for not being able to find RSA 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.

   One new bit flag is defined to be carried in the Flags field in the
   NO-PATH-VECTOR TLV carried in the NO-PATH Object.

         Bit TBD8: When set, the PCE indicates no feasible route was
         found that meets all the constraints (e.g., spectrum
         restriction, etc.) associated with RSA.



6. Manageability Considerations

   Manageability of SSON Routing and Spectrum Assignment (RSA) with PCE
   must address the following considerations:

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 configuring the
   following PCEP session parameters on a PCC:

         The ability to send a Flexi-Grid RSA request.

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

         The support for Flexi-Grid RSA .

         A set of Flexi-Grid RSA specific policies (authorized sender,
         request rate limiter, etc).




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   These parameters may be configured as default parameters for any
   PCEP session the PCEP speaker participates in, or 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. Information and Data Models

   Extensions to the PCEP YANG module may include to cover the Flexi-
   Grid RSA information introduced in this document. Liveness Detection
   and Monitoring

   Mechanisms defined in this document do not imply any new liveness
   detection and monitoring requirements in addition to 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 in addition to those already listed in
   section 8.4 of [RFC5440]


6.4. Requirements on Other Protocols and Functional Components

   The PCE Discovery mechanisms ([RFC5089] and [RFC5088]) may be used
   to advertise Flexi-Grid RSA path computation capabilities to PCCs.
   This draft has requirements on other protocols (ERO objects, etc.
   which are under TEAS or CCAMP.)




6.5. Impact on Network Operation

   Mechanisms defined in this document do not imply any new network
   operation requirements in addition to those already listed in
   section 8.6 of [RFC5440].



7. Security Considerations

   This document has no requirement for a change to the security models
   within PCEP. However, the additional information distributed in
   order to address the RSA problem represents a disclosure of network


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   capabilities that an operator may wish to keep private.
   Consideration should be given to securing this information.



8. IANA Considerations

   IANA is requested to make allocations from the sub-registries as
   described in the following sections.

8.1. New PCEP Object

   As described in Section 4.1, a new PCEP Object is defined to carry
   frequency-slot assignment related constraints. IANA is to allocate
   the following from "PCEP Objects" sub-registry
   (http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-objects):



   Object Class  Name Object              Reference
   Value           Type
   ---------------------------------------------------------

   TBD1       SA   1: Spectrum Assignment   [This.I-D]


8.2. New PCEP TLV: Frequency Slot Selection TLV

   As described in Sections 4.2, a new PCEP TLV is defined to indicate
   spectrum selection constraints. IANA is to allocate this new TLV
   from the "PCEP TLV Type Indicators" subregistry
   (http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-tlv-type-
   indicators).

   Value         Description           Reference
   ---------------------------------------------------------
   TBD2         Spectrum Selection     [This.I-D]

8.3. New PCEP TLV: Frequency Slot Restriction Constraint TLV

   As described in Section 4.3, a new PCEP TLV is defined to indicate
   wavelength restriction constraints. IANA is to allocate this new TLV
   from the "PCEP TLV Type Indicators" subregistry



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   (http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-tlv-type-
   indicators).

   Value         Description           Reference
   ---------------------------------------------------------
   TBD5         Frequency Slot Restriction   [This.I-D]
                     Constraint


8.4. New PCEP TLV: Spectrum Allocation TLV

   As described in Section 5, a new PCEP TLV is defined to indicate the
   allocation of freq-slots(s) by the PCE in response to a request by
   the PCC. IANA is to allocate this new TLV from the "PCEP TLV Type
   Indicators" subregistry
   (http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-tlv-type-
   indicators).

   Value         Description           Reference
   ---------------------------------------------------------
   TBD6         Spectrum Allocation   [This.I-D]



8.5. New No-Path Reasons

   As described in Section 4.3, a new bit flag are defined to be
   carried in the Flags field in the NO-PATH-VECTOR TLV carried in the
   NO-PATH Object. This flag, when set, indicates that no feasible
   route was found that meets all the RSA constraints (e.g., spectrum
   restriction, signal compatibility, etc.) associated with a RSA path
   computation request.

   IANA is to allocate this new bit flag from the "PCEP NO-PATH-VECTOR
   TLV Flag Field" subregistry
   (http://www.iana.org/assignments/pcep/pcep.xhtml#no-path-vector-
   tlv).

   Bit      Description           Reference
   -----------------------------------------------------
   TBD8     No RSA constraints met   [This.I-D]




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8.6. New Error-Types and Error-Values

   As described in Section 5.1, new PCEP error codes are defined for
   WSON RWA errors. IANA is to allocate from the ""PCEP-ERROR Object
   Error Types and Values" sub-registry
   (http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-error-object).



   Error-    Meaning       Error-Value     Reference
   Type
   ---------------------------------------------------------------


   TBD7     Flexi-Grid RSA Error   1: Insufficient     [This.I-D]
                                Memory

                           2: RSA computation  [This.I-D]
                             Not supported

8.7. New Error-Values for Existing Error Type (24)

   As discussed in Section 4.1, two new PathErr values for the Existing
   Error Type (24) are to be allocated:

   Meaning                   Error-Value     Reference

   ---------------------------------------------------------------
   Unsupported Frequency slot
   Selection Symmetry value        TBD3              [This.I-D]

   Unsupported Frequency Slot
   Assignment value             TBD4              [This.I-D]


9. References

9.1. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4003] Berger, L., "GMPLS Signaling Procedure for Egress
             Control", RFC 4003, February 2005.


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   [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
             Element (PCE) communication Protocol", RFC 5440, March
             2009.

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

   [RFC5088] Le Roux, JL, JP. Vasseur, Y. Ikejiri, and R. Zhang, "OSPF
             Protocol Extensions for Path Computation Element (PCE)
             Discovery," RFC 5088, January 2008.

   [RFC5089] Le Roux, JL, JP. Vasseur, Y. Ikejiri, and R. Zhang, "IS-IS
             Protocol Extensions for Path Computation Element (PCE)
             Discovery," RFC 5089, January 2008.

   [RFC8174] B. Leiba, "Ambiguity of Uppercase vs Lowercase in RFC 2119
             Key Words", RFC 8174, May 2017.

9.2. Informative References

   [PCEP-GMPLS] Margaria, et al., "PCEP extensions for GMPLS", draft-
             ietf-pce-gmpls-pcep-extensions, work in progress.

   [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
             Element (PCE)-Based Architecture", RFC 4655, August 2006.

   [RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE)
             Communication Protocol Generic Requirements", RFC 4657,
             September 2006.

   [RFC5420] Farrel, A. "Encoding of Attributes for MPLS LSP
             Establishment Using Resource Reservation Protocol Traffic
             Engineering (RSVP-TE)", RFC 5420, February 2009.

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

   [RFC7449] Lee, Y., et. al., "PCEP Requirements for WSON Routing and
             Wavelength Assignment", RFC 7449, February 2015.

   [RFC7570] Margaria, et al., "Label Switched Path (LSP) Attribute in
             the Explicit Route Object (ERO)", RFC 7570, July 2015.





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   [RFC7579] Bernstein and Lee, "General Network Element Constraint
             Encoding for GMPLS Controlled Networks", RFC 7579, June
             2015.

   [PCEP-WSON] Y. Lee (Ed.), and R. Casellas (Ed.), "PCEP Extension for
             WSON Routing and Wavelength Assignment", draft-ietf-pce-
             wson-rwa-ext, work in progress.

   [RFC7698] O. Gonzalez de Dios, R. Casellas, editors, "Framework and
             Requirements for GMPLS-Based Control of Flexi-Grid Dense
             Wavelength Division Multiplexing (DWDM) Networks", RFC
             7698, November 2015.

   [RFC8363] X. Zhang, H. Zheng, R. Casellas, O. Gonzalez de Dios, D.
             Ceccarelli, "GMPLS OSPF-TE Extensions in Support of Flexi-
             Grid Dense Wavelength Division Multiplexing (DWDM)
             Networks", RFC8363, May 2018.

   [G.694.1] "Spectral grids for WDM applications: DWDM frequency
             grid", ITU-T G.694.1, February 2012.

   [G.872] "Architecture of optical transport networks", ITU-T G.872,
             January 2017.



10. Contributors





















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Authors' Addresses

   Young Lee
   Sung Kyun Kwan University
   Email: younglee.tx@gmail.com


   Haomian Zheng (Editor)
   Huawei Technologies
   Email: zhenghaomian@huawei.com


   Ramon Casellas
   CTTC
   Av. Carl Friedrich Gauss n7
   Castelldefels, Barcelona 08860
   Spain

   Email: ramon.casellas@cttc.es


   Ricard Vilalta
   CTTC
   Email: ricard.vilalta@cttc.es


   Daniele Ceccarelli
   Ericsson AB
   Gronlandsgatan 21
   Kista - Stockholm
   Email: daniele.ceccarelli@ericsson.com

   Francesco Lazzeri
   Ericsson
   Via Melen 77
   Genova - Italy
   Email: francesco.lazzeri@ericsson.com












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