Network Working Group                                            Y. Lee
Internet Draft                                                   Huawei
Intended status: Informational
Expires: April December 2013                                     G. Bernstein
                                                      Grotto Networking

                                                       Jonas Martensson

                                                              T. Takeda

                                                           T. Tsuritani

                                                           O. G. de Dios

                                                       October 18, 2012

                                                          June 27, 2013

       PCEP Requirements for WSON Routing and Wavelength Assignment



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   This memo provides application-specific requirements for the Path
   Computation Element communication Protocol (PCEP) for the support of
   Wavelength Switched Optical Networks (WSON). Lightpath provisioning
   in WSONs requires a routing and wavelength assignment (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 light
   path computation. Requirements for Optical impairments will be
   addressed in a separate document.

Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC-2119 0.

Table of Contents

   1. Introduction ...................................................3
      1.1. WSON RWA Processes........................................4
   2. WSON PCE Architectures and Requirements ........................5
      2.1. RWA PCC to PCE Interface..................................6
         2.1.1. RWA Computation Type and Wavelength Assignment Option6
         2.1.2. Bulk RWA path request/reply..........................7
         2.1.3. An RWA path re-optimization request/reply............7
         2.1.4. Wavelength Range Constraint..........................7
         2.1.5. Wavelength Policy Constraint.........................8
         2.1.6. Signal Processing Capability Restriction.............8
   3. Manageability Considerations ...................................8
      3.1. Control of Function and Policy............................8
      3.2. Information and Data Models, e.g. MIB module..............9
      3.3. Liveness Detection and Monitoring.........................9
      3.4. Verifying Correct Operation...............................9
      3.5. Requirements on Other Protocols and Functional Components.9
      3.6. Impact on Network Operation..............................10
   4. Security Considerations .......................................10
   5. IANA Considerations ...........................................10
   6. Acknowledgments ...............................................10
   7. References ....................................................10
      7.1. Normative References.....................................10
      7.2. Informative References...................................11
   Authors' Addresses...............................................12
   Intellectual Property Statement..................................12
   Disclaimer of Validity...........................................13

   1. Introduction

   [RFC4655] defines the PCE based 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 shown 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 PCC and 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.

   This document provides a set of application-specific PCEP
   requirements for support of path computation in Wavelength Switched
   Optical Networks (WSON).  WSON refers to WDM based optical networks
   in which switching is performed selectively based on the wavelength
   of an optical signal.

   The path in WSON is referred to as a lightpath.  A lightpath may
   span multiple fiber links and the path should be assigned a
   wavelength for each link.  A transparent optical network is made up
   of optical devices that can switch but not convert from one
   wavelength to another. In a transparent optical network, a lightpath
   operates on the same wavelength across all fiber links that it
   traverses. In such case, the lightpath is said to satisfy the
   wavelength-continuity constraint. Two lightpaths that share a common
   fiber link can not be assigned the same wavelength.  To do otherwise
   would result in both signals interfering 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 lightpath 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
   a lightpath 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 lightpath computation.

   In this document we first review the processes for routing and
   wavelength assignment (RWA) used when wavelength continuity
   constraints are present and then specify requirements for PCEP to
   support RWA. Requirements for Optical impairments will be addressed
   in a separate document.

   The remainder of this document uses terminology from [RFC4655].

                    1.1. WSON RWA Processes

   In [RFC6163] three alternative process architectures were given for
   performing routing and wavelength assignment. These are shown
   schematically in 0.

     |  +-------+  +--+  |    +-------+    +--+     +-------+    +---+
     |  |Routing|  |WA|  |    |Routing|--->|WA|     |Routing|--->|DWA|
     |  +-------+  +--+  |    +-------+    +--+     +-------+    +---+
     |   Combined        |     Separate Processes   Separate Processes
     |   Processes       |                          WA performed in a
     +-------------------+                          Distributed manner
           (a)                       (b)                    (c)

                    Figure 1. RWA process alternatives.

   These alternatives have the following properties and impact on PCEP
   requirements in this document.

   1. Combined Processes (R&WA) - Here path selection and wavelength
      assignment are performed as a single process. The requirements
      for PCC-PCE interaction with such a combined RWA process PCE is
      addressed in this document.

   2. Routing separate from Wavelength Assignment (R+WA) - Here the
      routing process furnishes one or more potential paths to the
      wavelength assignment process that then performs final path
      selection and wavelength assignment.  The requirements for PCE-
      PCE interaction with one PCE implementing the routing process and
      another implementing the wavelength assignment process are not
      addressed in this document.

   3. Routing and distributed Wavelength Assignment (R+DWA) - Here a
      standard path computation (unaware of detailed wavelength
      availability) takes place, then wavelength assignment is
      performed along this path in a distributed manner via signaling
      (RSVP-TE). This alternative should be covered by existing or
      emerging GMPLS PCEP extensions and does not present new WSON
      specific requirements.

   2. WSON PCE Architectures and Requirements

   In the previous section various process architectures for
   implementing RWA have been reviewed. Figure 2 shows one typical PCE
   based implementation, which is referred to as 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 from which the requirements
   are specified in this document.

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

              Figure 2. Combined Process (R&WA) architecture

                    2.1. RWA PCC to PCE Interface

   The requirements for the PCC to PCE interface of Figure 2 are
   specified in this section.

 2.1.1.  RWA Computation Type and Wavelength Assignment Option

   1. The PCReq Message MUST include the path computation type. This
      can be:

     (i)    Both Routing and Wavelength Assignment (RWA), or

     (ii)   Routing only.

   This requirement is needed to differentiate between the currently
   supported routing with distributed wavelength assignment option and
   combined RWA. In case of distributed wavelength assignment option,
   wavelength assignment will be performed at each node of the route.

   2. When the PCReq Message is RWA path computation type, the PCReq
      Message MUST further include the wavelength assignment options.
      At the minimum, the following option should be supported:

     (i)     Explicit Label Control (ELC) [RFC4003]

     (ii)    Non-Explicit labels in the form of Label Sets (This will
            allow Distributed WA at a node level where each node would
            select the wavelength from the Label Sets)

   3. The PCRep Message MUST include the route, wavelengths assigned to
      the route and indication of which wavelength assignment option
      has been applied (ELC or Label Sets).

   4. In the case where a valid path is not found, the PCRep Message
      MUST include why the path is not found (e.g., no route,
      wavelength not found, optical quality check failed, etc.)

 2.1.2. Bulk RWA path request/reply

   1. The PCReq Message MUST be able to specify an option for bulk RWA
      path request. Bulk path request is an ability to request a number
      of simultaneous RWA path requests.

   2. The PCRep Message MUST include the route, wavelength assigned to
      the route for each RWA path request specified in the original
      bulk PCReq Message.

 2.1.3. An RWA path re-optimization request/reply

   1. For a re-optimization request, the PCReq Message MUST provide the
      path to be re-optimized and include the following options:

       a. Re-optimize the path keeping the same wavelength(s)

       b. Re-optimize wavelength(s) keeping the same path

       c. Re-optimize allowing both wavelength and the path to change

   2. The corresponding PCRep Message for the re-optimized request MUST
      provide the Re-optimized path and wavelengths.

   3. In case that the path is not found, the PCRep Message MUST
      include why the path is not found (e.g., no route, wavelength not
      found, both route and wavelength not found, etc.)

 2.1.4.  Wavelength Range Constraint

   For any PCReq Message that is associated with a request for
   wavelength assignment the requester (PCC) MUST be able to specify a
   restriction on the wavelengths to be used.

   Note that the requestor (PCC) is NOT required to furnish any range
   restrictions. This restriction is to be interpreted by the PCE as a
   constraint on the tuning ability of the origination laser

 2.1.5. Wavelength Policy Constraint

   The PCReq Message May include specific operator's policy information
   for WA (E.g., random assignment, descending order, ascending order,

   The PCReq Message SHOULD be able to request, when requesting a 1+1
   connection (e.g. link disjoint paths), that both paths use the same

   Note that this is extremely useful in the case of protection with
   single transponder. Now, there is no way to specify such constraint.

   The PCReq Message SHOULD be able to request, when performing 3R,
   that wavelength may change or not.

 2.1.6. Signal Processing Capability Restriction

   The PCReq Message MUST be able to specify restrictions for signal
   compatibility either on the endpoint or any given link. The
   following signal processing capability should be supported at a

      o  Modulation Type List

      o  FEC Type List

   3. Manageability Considerations

   Manageability of WSON Routing and Wavelength Assignment (RWA) with
   PCE must address the following considerations:

                    3.1. 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:

      o  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 configuring the
   following PCEP session parameters on a PCE:

      o  The support for WSON RWA.

      o  The maximum number of bulk path requests associated with WSON
         RWA per request message.

   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.

                    3.2. Information and Data Models, e.g. MIB module

   As this document only concerns the requirements to support WSON RWA,
   no additional MIB module is defined in this document. However, the
   corresponding solution draft will list the information that should
   be added to the PCE MIB module defined in [PCEP-MIB].

                    3.3. 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].

                    3.4. 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] [RFC5440].

                    3.5. Requirements on Other Protocols and Functional

   The PCE Discovery mechanisms ([RFC5089] and [RFC5088]) may be used
   to advertise WSON RWA path computation capabilities to PCCs.

                    3.6. 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].

   4. Security Considerations

   This document has no requirement for a change to the security models
   within PCEP [RFC5440]. However the additional information
   distributed in order to address the RWA problem represents a
   disclosure of network capabilities that an operator may wish to keep
   private. Consideration should be given to securing this information.

   5. IANA Considerations

   This informational document does not make any requests for IANA

   6. Acknowledgments

   The authors would like to thank Adrian Farrel for many helpful
   comments that greatly improved the contents of this draft.

   This document was prepared using

   7. References

                    7.1. Normative References

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

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

   [RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
             Switching (GMPLS) Signaling Resource ReserVation Protocol-
             Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
             January 2003.

   [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.

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

   [PCEP-MIB] Koushik, K, et al., "PCE communication protocol(PCEP)
             Management Information Base", draft-ietf-pce-pcep-mib,
             work in progress.

                    7.2. Informative References

   [RFC6566] Lee, Y. and Bernstein, G. (Editors), D. Li and G.
             Martinelli "A Framework for the Control and Measurement of
             Wavelength Switched Optical Networks (WSON) with
             Impairments", RFC 6566, March 2012.

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

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

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

Authors' Addresses

   Young Lee (Ed.)
   Huawei Technologies
   1700 Alma
   5340 Legacy Drive, Suite 100 Building 3
   Plano, TX 75075, 75024
   Phone: (972) 509-5599 (x2240) (469) 277-5838

   Greg Bernstein (Ed.)
   Grotto Networking
   Fremont, CA, USA
   Phone: (510) 573-2237

   Jonas Martensson

   Tomonori Takeda
   NTT Corporation
   3-9-11, Midori-Cho
   Musashino-Shi, Tokyo 180-8585, Japan

   Takehiro Tsuritani
   KDDI R&D Laboratories, Inc.
   2-1-15 Ohara Kamifukuoka Saitama, 356-8502. Japan
   Phone:  +81-49-278-7357

   Oscar Gonzalez de Dios
   Telefonica Investigacion y Desarrollo
   C/ Emilio Vargas 6
   Madrid,   28043
   Phone: +34 91 3374013

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