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+Internet Engineering Task Force (IETF) Y. Lee, Ed.
+Request for Comments: 7449 Huawei
+Category: Informational G. Bernstein, Ed.
+ISSN: 2070-1721 Grotto Networking
+ J. Martensson
+ Acreo
+ T. Takeda
+ NTT
+ T. Tsuritani
+ KDDI
+ O. Gonzalez de Dios
+ Telefonica
+ February 2015
+
+
+ Path Computation Element Communication Protocol (PCEP) Requirements
+ for Wavelength Switched Optical Network (WSON)
+ Routing and Wavelength Assignment
+
+Abstract
+
+ This memo provides application-specific requirements for the Path
+ Computation Element Communication Protocol (PCEP) for the support of
+ Wavelength Switched Optical Networks (WSONs). 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 document is not an Internet Standards Track specification; it is
+ published for informational purposes.
+
+ This document is a product of the Internet Engineering Task Force
+ (IETF). It represents the consensus of the IETF community. It has
+ received public review and has been approved for publication by the
+ Internet Engineering Steering Group (IESG). Not all documents
+ approved by the IESG are a candidate for any level of Internet
+ Standard; see Section 2 of RFC 5741.
+
+ Information about the current status of this document, any errata,
+ and how to provide feedback on it may be obtained at
+ http://www.rfc-editor.org/info/rfc7449.
+
+
+
+
+
+Lee, et al. Informational [Page 1]
+
+RFC 7449 PCEP Requirements for WSON RWA February 2015
+
+
+Copyright Notice
+
+ Copyright (c) 2015 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. Introduction ....................................................3
+ 2. WSON RWA Processes and Architecture .............................4
+ 3. Requirements ....................................................5
+ 3.1. Path Computation Type Option ...............................5
+ 3.2. RWA Processing .............................................6
+ 3.3. Bulk RWA Path Request/Reply ................................6
+ 3.4. RWA Path Reoptimization Request/Reply ......................7
+ 3.5. Wavelength Range Constraint ................................7
+ 3.6. Wavelength Assignment Preference ...........................7
+ 3.7. Signal-Processing Capability Restriction ...................8
+ 4. Manageability Considerations ....................................8
+ 4.1. Control of Function and Policy .............................8
+ 4.2. Information and Data Models (e.g., MIB Module) .............9
+ 4.3. Liveness Detection and Monitoring ..........................9
+ 4.4. Verifying Correct Operation ................................9
+ 4.5. Requirements on Other Protocols and Functional Components ..9
+ 4.6. Impact on Network Operation ................................9
+ 5. Security Considerations .........................................9
+ 6. References .....................................................10
+ 6.1. Normative References ......................................10
+ 6.2. Informative References ....................................10
+ Acknowledgments....................................................11
+ Authors' Addresses.................................................11
+
+
+
+
+
+
+
+
+
+
+
+Lee, et al. Informational [Page 2]
+
+RFC 7449 PCEP Requirements for WSON RWA February 2015
+
+
+1. Introduction
+
+ [RFC4655] defines the PCE-based architecture and explains how a Path
+ Computation Element (PCE) may compute Label Switched Paths (LSPs) in
+ networks controlled by Multiprotocol Label Switching Traffic
+ Engineering (MPLS-TE) and Generalized MPLS (GMPLS) 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; it may be within an optical switching element, a Network
+ Management System (NMS), or an Operational Support System (OSS), or
+ it may be an independent network server.
+
+ The Path Computation Element Communication Protocol (PCEP) is the
+ communication protocol used between a PCC and PCE; it 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 (WSONs). 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 cases,
+ the lightpath is said to satisfy the wavelength-continuity
+ 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
+
+
+
+Lee, et al. Informational [Page 3]
+
+RFC 7449 PCEP Requirements for WSON RWA February 2015
+
+
+ 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].
+
+ 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].
+
+2. WSON RWA Processes and Architecture
+
+ In [RFC6163], three alternative process architectures were given for
+ performing routing and wavelength assignment. These are shown
+ schematically in Figure 1, where R stands for Routing, WA for
+ Wavelength Assignment, and DWA for Distributed Wavelength Assignment.
+
+ +-------------------+
+ | +-------+ +--+ | +-------+ +--+ +-------+ +---+
+ | | R | |WA| | | R |--->|WA| | R |--->|DWA|
+ | +-------+ +--+ | +-------+ +--+ +-------+ +---+
+ | Combined | Separate Processes Separate Processes
+ | Process | 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 Process (R&WA)
+
+ Path selection and wavelength assignment are performed as a
+ single process. The requirements for PCC-PCE interaction with a
+ PCE implementing such a combined RWA process are addressed in
+ this document.
+
+
+
+
+Lee, et al. Informational [Page 4]
+
+RFC 7449 PCEP Requirements for WSON RWA February 2015
+
+
+ (b) Routing Separate from Wavelength Assignment (R+WA)
+
+ 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)
+
+ A standard path computation (unaware of detailed wavelength
+ availability) takes place, and 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
+ should be covered by GMPLS PCEP extensions; it does not present
+ new WSON-specific requirements.
+
+ The various process architectures for implementing RWA have been
+ reviewed above. Figure 2 shows one typical PCE-based implementation,
+ which is referred to as the Combined Process (R&WA). With this
+ architecture, the two processes of routing and wavelength assignment
+ are accessed via a single PCE. This architecture is the base
+ architecture from which the requirements are specified in this
+ document.
+
+ +----------------------------+
+ +-----+ | +-------+ +--+ |
+ | | | |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:
+
+ (a) Both RWA, or
+
+ (b) Routing only.
+
+
+
+Lee, et al. Informational [Page 5]
+
+RFC 7449 PCEP Requirements for WSON RWA February 2015
+
+
+ This requirement is needed to differentiate between the currently
+ supported routing with distributed wavelength assignment option and
+ combined RWA. For the distributed wavelength assignment option,
+ wavelength assignment will be performed at each node of the route.
+
+3.2. RWA Processing
+
+ As discussed in Section 2, various RWA processing options should be
+ supported in a PCEP request/reply.
+
+ (a) When the request is an RWA path computation type, the request
+ MUST further include the wavelength assignment options. At
+ minimum, the following options 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 an 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).
+
+ (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, 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 the 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 requests. A bulk path request provides an ability to
+ request a number of simultaneous RWA path requests.
+
+ (b) The PCEP response MUST include the path and the assigned
+ wavelength for each RWA path request specified in the original
+ bulk request.
+
+
+
+
+
+
+Lee, et al. Informational [Page 6]
+
+RFC 7449 PCEP Requirements for WSON RWA February 2015
+
+
+3.4. RWA Path Reoptimization Request/Reply
+
+ This section provides a number of requirements concerning RWA path
+ reoptimization processing in PCEP.
+
+ (a) For a reoptimization request, the request MUST provide both the
+ path and current wavelength to be reoptimized and MAY include
+ the following options:
+
+ (i) Reoptimize the path keeping the same wavelength(s)
+
+ (ii) Reoptimize wavelength(s) keeping the same path
+
+ (iii) Reoptimize allowing both the wavelength and the path to
+ change
+
+ (b) The corresponding response to the reoptimized request MUST
+ provide the reoptimized path and wavelengths even when the
+ request asked for the path or the wavelength to remain
+ unchanged.
+
+ (c) In the 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, both, etc.). Note that 'wavelength not
+ found' may include several sub-cases such as wavelength
+ continuity not met, unsupported FEC/Modulation type, etc.
+
+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 labels or label sets. 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
+
+ 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.
+
+
+
+
+
+Lee, et al. Informational [Page 7]
+
+RFC 7449 PCEP Requirements for WSON RWA February 2015
+
+
+ (a) An RWA computation type request MAY include the requester
+ preference for random assignment, descending order, ascending
+ order, etc. A response SHOULD follow the requester preference
+ unless it conflicts with the operator's policy.
+
+ (b) 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 a single transponder (e.g., 1+1 link disjoint
+ paths).
+
+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 the source and at the destination.
+
+ The PCC MUST be allowed to specify the signal type at the endpoints
+ (i.e., at the source and at the destination). The following signal-
+ processing capabilities should be supported at a minimum:
+
+ 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 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:
+
+
+
+
+
+
+
+Lee, et al. Informational [Page 8]
+
+RFC 7449 PCEP Requirements for WSON RWA February 2015
+
+
+ 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
+
+ As this document only concerns the requirements to support WSON RWA,
+ no additional MIB module is defined in this document. However, the
+ corresponding solution document will list the information that should
+ be added to the PCE MIB module defined in [RFC7420].
+
+4.3. Liveness Detection and Monitoring
+
+ This document does not define any new mechanisms that imply any new
+ liveness detection and monitoring requirements in addition to those
+ already listed in Section 8.3 of [RFC5440].
+
+4.4. Verifying Correct Operation
+
+ This document does not define any new mechanisms that imply 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
+
+ This document does not define any new mechanisms that imply 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.
+
+
+
+Lee, et al. Informational [Page 9]
+
+RFC 7449 PCEP Requirements for WSON RWA February 2015
+
+
+ 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.
+
+6. References
+
+6.1. Normative References
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997,
+ <http://www.rfc-editor.org/info/rfc2119>.
+
+ [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
+ Computation Element (PCE)-Based Architecture", RFC 4655,
+ August 2006, <http://www.rfc-editor.org/info/rfc4655>.
+
+ [RFC5440] Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path Computation
+ Element (PCE) Communication Protocol (PCEP)", RFC 5440,
+ March 2009, <http://www.rfc-editor.org/info/rfc5440>.
+
+6.2. Informative References
+
+ [RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
+ Switching (GMPLS) Signaling Resource ReserVation Protocol-
+ Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
+ January 2003, <http://www.rfc-editor.org/info/rfc3473>.
+
+ [RFC4657] Ash, J., Ed., and J. Le Roux, Ed., "Path Computation
+ Element (PCE) Communication Protocol Generic
+ Requirements", RFC 4657, September 2006,
+ <http://www.rfc-editor.org/info/rfc4657>.
+
+ [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,
+ <http://www.rfc-editor.org/info/rfc5088>.
+
+ [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,
+ <http://www.rfc-editor.org/info/rfc5089>.
+
+ [RFC6163] Lee, Y., Ed., Bernstein, G., Ed., and W. Imajuku,
+ "Framework for GMPLS and Path Computation Element (PCE)
+ Control of Wavelength Switched Optical Networks (WSONs)",
+ RFC 6163, April 2011,
+ <http://www.rfc-editor.org/info/rfc6163>.
+
+
+
+Lee, et al. Informational [Page 10]
+
+RFC 7449 PCEP Requirements for WSON RWA February 2015
+
+
+ [RFC7420] Koushik, A., Stephan, E., Zhao, Q., King, D., and J.
+ Hardwick, "Path Computation Element Communication Protocol
+ (PCEP) Management Information Base (MIB) Module", RFC
+ 7420, December 2014,
+ <http://www.rfc-editor.org/info/rfc7420>.
+
+Acknowledgments
+
+ The authors would like to thank Adrian Farrel, Cycil Margaria, and
+ Ramon Casellas for many helpful comments that greatly improved the
+ content of this document.
+
+Authors' Addresses
+
+ Young Lee (editor)
+ Huawei Technologies
+ 5340 Legacy Drive, Building 3
+ Plano, TX 75245
+ United States
+
+ Phone: (469) 277-5838
+ EMail: leeyoung@huawei.com
+
+
+ Greg Bernstein (editor)
+ Grotto Networking
+ Fremont, CA
+ United States
+
+ Phone: (510) 573-2237
+ EMail: gregb@grotto-networking.com
+
+
+ Jonas Martensson
+ Acreo
+ Isafjordsgatan 22
+ 164 40 Kista
+ Sweden
+
+ EMail: Jonas.Martensson@acreo.se
+
+
+
+
+
+
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+
+ Tomonori Takeda
+ NTT Corporation
+ 3-9-11, Midori-Cho
+ Musashino-Shi, Tokyo 180-8585
+ Japan
+
+ EMail: tomonori.takeda@ntt.com
+
+
+ Takehiro Tsuritani
+ KDDI R&D Laboratories, Inc.
+ 2-1-15 Ohara Kamifukuoka Saitama, 356-8502
+ Japan
+
+ Phone: +81-49-278-7806
+ EMail: tsuri@kddilabs.jp
+
+
+ Oscar Gonzalez de Dios
+ Telefonica
+ Distrito Telefonica, ed. Sur 3, Pta 3, Ronda de la Comunicacion
+ Madrid, 28050
+ Spain
+
+ Phone: +34 913129647
+ EMail: oscar.gonzalezdedios@telefonica.com
+
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