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Versions: (draft-lee-pce-wson-routing-wavelength) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 RFC 7449

Network Working Group                                            Y. Lee
Internet Draft                                                   Huawei
Intended status: Informational                             G. Bernstein
Expires: April 2015                                   Grotto Networking
                                                       Jonas Martensson
                                                                  Acreo
                                                              T. Takeda
                                                                    NTT
                                                           T. Tsuritani
                                                                   KDDI
                                                          O. G. de Dios
                                                             Telefonica

                                                       October 28, 2014


       PCEP Requirements for WSON Routing and Wavelength Assignment


               draft-ietf-pce-wson-routing-wavelength-15.txt


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 PCEP extensions in support of
   optical impairments will be addressed in a separate document.

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
   months and may be updated, replaced, or obsoleted by other documents
   at any time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."





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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 [RFC2119].

Table of Contents


   1. Introduction...................................................3
   2. WSON RWA Processes & Architecture..............................4
   3. Requirements...................................................6
      3.1. Path Computation Type Option..............................6
      3.2. RWA Processing............................................6
      3.3. Bulk RWA Path Request/Reply...............................7
      3.4. RWA Path Re-optimization Request/Reply....................7
      3.5. Wavelength Range Constraint...............................8
      3.6. Wavelength Assignment Preference..........................8
      3.7. Signal Processing Capability Restriction..................8
   4. Manageability Considerations...................................9
      4.1. Control of Function and Policy............................9
      4.2. Information and Data Models, e.g. MIB module..............9
      4.3. Liveness Detection and Monitoring........................10
      4.4. Verifying Correct Operation..............................10


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      4.5. Requirements on Other Protocols and Functional Components10
      4.6. Impact on Network Operation..............................10
   5. Security Considerations.......................................10
   6. IANA Considerations...........................................11
   7. Acknowledgments...............................................11
   8. References....................................................11
      8.1. Normative References.....................................11
      8.2. Informative References...................................11
   Authors' Addresses...............................................12
   Intellectual Property Statement..................................13
   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)-controlled 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 communication 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


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   constraint. Two lightpaths that share a common fiber link cannot 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 path from origin to destination. It is, however, to be noted
   that wavelength converters may be limited for cost reasons, 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 computations.

   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].

2. WSON RWA Processes & Architecture

   In [RFC6163] three alternative process architectures were given for
   performing routing and wavelength assignment. These are shown
   schematically in Figure 1. R stands for Routing, WA for Wavelength
   Assignment, and DWA for Distributed Wavelength Assignment.














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     +-------------------+
     |  +-------+  +--+  |    +-------+    +--+     +-------+    +---+
     |  |   R   |  |WA|  |    |   R   |--->|WA|     |   R   |--->|DWA|
     |  +-------+  +--+  |    +-------+    +--+     +-------+    +---+
     |   Combined        |     Separate Processes   Separate Processes
     |   Processes       |                          WA performed in a
     +-------------------+                          distributed manner
           (a)                       (b)                    (b')

                    Figure 1. RWA process alternatives

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

   (a)   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.

   (b)   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.

   (b')  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 is a
         particular case of R+WA and it should be covered by GMPLS PCEP
         extensions and does not present new WSON-specific
         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.


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


              Figure 2. Combined Process (R&WA) architecture

3. Requirements

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

   3.1.  Path Computation Type Option

   A PCEP request MAY include the path computation type. This can be:

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

     (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.

   3.2. RWA Processing

   (a)   When the request is a RWA path computation type, the request
      MUST further include the wavelength assignment options. At the
      minimum, the following option should be supported:

         (i)    Explicit Label Control (ELC) [RFC3473]

         (ii)   A set of recommended labels for each hop. The PCC can
                select the label based on local policy.

     Note that option (ii) may also be used in R+WA or R+DWA.



   (b)   In case of a RWA computation type, the response MUST include
      the wavelength(s) assigned to the path and an indication of which
      label assignment option has been applied (ELC or label set).


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   (c)   In the case where a valid path is not found, the response MUST
      include why the path is not found (e.g., network disconnected,
      wavelength not found, or both, etc.). Note that 'wavelength not
      found' may include several sub-cases such as wavelength
      continuity not met, unsupported FEC/Modulation type, etc.



   3.3. Bulk RWA Path Request/Reply

   Sending simultaneous path requests for "routing only" computation is
   supported by PCEP specification [RFC5440]. To remain consistent the
   following requirements are added.

   (a)   A PCEP request 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.

   (b)   The PCEP response MUST include the path and the assigned
      wavelength assigned for each RWA path request specified in the
      original bulk request.



   3.4. RWA Path Re-optimization Request/Reply

   1. For a re-optimization request, the request MUST provide both the
      path and current wavelength to be re-optimized and MAY 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 the wavelength and the path to
          change

   2. The corresponding response to the re-optimized request MUST
      provide the re-optimized path and wavelengths even when the
      request asked for the path or the wavelength to remain unchanged.

   3. In case that the new path is not found, the response MUST include
      why the path is not found (e.g., network disconnected, wavelength
      not found, or both, etc.). Note that 'wavelength not found' may
      include several sub-cases such as wavelength continuity not met,
      unsupported FEC/Modulation type, etc.



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   3.5. Wavelength Range Constraint

   For any RWA computation type request, the requester (PCC) MUST be
   allowed to specify a restriction on the wavelengths to be used. The
   requester MAY use this option to restrict the assigned wavelength
   for explicit label or label set. This restriction may for example
   come from the tuning ability of a laser transmitter, any optical
   element, or a policy-based restriction.

   Note that the requester (e.g., PCC) is not required to furnish any
   range restrictions.

   3.6. Wavelength Assignment Preference

   1. A RWA computation type request MAY include the requester
     preference for, e.g., random assignment, descending order,
     ascending order, etc. A response SHOULD follow the requestor
     preference unless it conflicts with operator's policy.

   2. A request for two or more paths MUST allow the requester to
     include an option constraining the paths to have the same
     wavelength(s) assigned. This is useful in the case of protection
     with single transponder (e.g., 1+1 link disjoint paths).


   In a network with wavelength conversion capabilities (e.g. sparse 3R
   regenerators), a request SHOULD be able to indicate whether a
   single, continuous wavelength should be allocated or not. In other
   words, the requesting PCC SHOULD be able to specify the precedence
   of wavelength continuity even if wavelength conversion is available.



   3.7. Signal Processing Capability Restriction

   Signal processing compatibility is an important constraint for
   optical path computation. The signal type for an end-to-end optical
   path must match at source and at destination.

   The PCC MUST be allowed to specify the signal type at the endpoints
   (i.e., at source and at destination). The following signal
   processing capabilities should be supported at a minimum:



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      o  Modulation Type List

      o  FEC Type List



   The PCC MUST also be allowed to state whether transit modification
   is acceptable for the above signal processing capabilities.



4. Manageability Considerations

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

   4.1. 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.


   4.2. 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].




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   4.3. Liveness Detection and Monitoring

   No new mechanism is defined in this document that implies any new
   liveness detection and monitoring requirements in addition to those
   already listed in section 8.3 of [RFC5440].


   4.4. Verifying Correct Operation

   No new mechanism is defined in this document that implies any new
   verification requirements in addition to those already listed in
   section 8.4 of [RFC5440]


   4.5. Requirements on Other Protocols and Functional Components

   If PCE discovery mechanisms ([RFC5089] and [RFC5088]) were to be
   extended for technology-specific capabilities, advertising WSON RWA
   path computation capability should be considered.


   4.6. Impact on Network Operation

   No new mechanism is defined in this document that implies any new
   network operation requirements in addition to those already listed
   in section 8.6 of [RFC5440].



5. 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.

   Solutions that address the requirements in this document need to
   verify that existing PCEP security mechanisms adequately protect the
   additional network capabilities and must include new mechanisms as
   necessary.








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6. IANA Considerations

   This informational document does not make any requests for IANA
   action.



7. Acknowledgments

   The authors would like to thank Adrian Farrel, Cycil Margaria and
   Ramon Casellas for many helpful comments that greatly improved the
   contents of this draft.

   This document was prepared using 2-Word-v2.0.template.dot.

8. References

   8.1. Normative References

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

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



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





   8.2. Informative References

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

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



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   [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.

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






Authors' Addresses

   Young Lee (Ed.)
   Huawei Technologies
   5340 Legacy Drive, Building 3
   Plano, TX 75245, USA
   Phone: (469)277-5838
   Email: leeyoung@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



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   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

   Oscar Gonzalez de Dios
   Telefonica Investigacion y Desarrollo
   C/ Emilio Vargas 6
   Madrid,   28043
   Spain
   Phone: +34 91 3374013
   Email: ogondio@tid.es



































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