Network Working Group                                            Y. Lee
Internet Draft                                                   Huawei
Intended status: Informational
Expires: September 2011 January 2012                                      G. Bernstein
                                                      Grotto Networking

                                                        Jonas Martensson
                                                                   Acreo

                                                              T. Takeda
                                                                    NTT

                                                           T. Tsuritani
                                                                    KDDI

                                                         March 10,

                                                           July 6, 2011

       PCEP Requirements for WSON Routing and Wavelength Assignment

               draft-ietf-pce-wson-routing-wavelength-04.txt

               draft-ietf-pce-wson-routing-wavelength-05.txt

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Abstract

   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",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   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..........................6
         2.1.3. An RWA path re-optimization request/reply............7
         2.1.4. Wavelength Range Constraint..........................7
         2.1.5. Wavelength Policy Constraint.........................7

   3. Manageability Considerations...................................8
      3.1. Control of Function and Policy............................8
      3.2. Information and Data Models, e.g. MIB module..............8
      3.3. Liveness Detection and Monitoring.........................8 Monitoring.........................9
      3.4. Verifying Correct Operation...............................9
      3.5. Requirements on Other Protocols and Functional Components.9
      3.6. Impact on Network Operation...............................9
   4. Security Considerations........................................9
   5. IANA Considerations............................................9
   6. Acknowledgments................................................9 Acknowledgments...............................................10
   7. References....................................................10
      7.1. Normative References.....................................10
      7.2. Informative References...................................10 References...................................11
   Authors' Addresses...............................................11
   Intellectual Property Statement..................................12
   Disclaimer of Validity...........................................12 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.

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

                         1.1. WSON RWA Processes

   In [WSON-Frame] three alternative process architectures were given
   for performing routing and wavelength assignment. These are shown
   schematically in Figure 1.

     +-------------------+
     |  +-------+  +--+  |    +-------+    +--+     +-------+    +---+
     |  |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
   transmitter.

      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,
   etc.)
      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 minimum:

      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]

                         3.5. Requirements on Other Protocols and
                            Functional Components

   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

   A future revision of this document will present requests to IANA for
   codepoint allocation.

       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 2-Word-v2.0.template.dot.

       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
             2009.

   [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

   [WSON-IMP] 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, draft-ietf-ccamp-wson-impairments, work in
             progress.

   [WSON-Frame] Lee, Y. and Bernstein, G. (Editors), and W. Imajuku,
             "Framework for GMPLS and PCE Control of Wavelength Switched
             Optical Networks", draft-ietf-ccamp-rwa-wson-framework,
             work in progress.

   [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 Drive, Suite 100
   Plano, TX 75075, USA
   Phone: (972) 509-5599 (x2240)
   Email: ylee@huawei.com
   Greg Bernstein (Ed.)
   Grotto Networking
   Fremont, CA, USA
   Phone: (510) 573-2237
   Email: gregb@grotto-networking.com

   Jonas Martensson
   Acreo
   Email:Jonas.Martensson@acreo.se

   Tomonori Takeda
   NTT Corporation
   3-9-11, Midori-Cho
   Musashino-Shi, Tokyo 180-8585, Japan
   Email: takeda.tomonori@lab.ntt.co.jp

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

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