PCEP Requirements for WSON Routing and Wavelength Assignment
Author(s): Greg Bernstein, Oscar de Dios, Takehiro Tsuritani, Young Lee, Tomonori Takeda, Jonas Martensson
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...
Network Working Group Y. Lee Internet Draft Huawei Intended status: Informational Expires: December 2013 G. Bernstein Grotto Networking Jonas Martensson Acreo T. Takeda NTT T. Tsuritani KDDI O. G. de Dios Telefonica June 27, 2013 PCEP Requirements for WSON Routing and Wavelength Assignment draft-ietf-pce-wson-routing-wavelength-09.txt 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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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. 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..........................7 2.1.3. An RWA path re-optimization request/reply............7 Lee & Bernstein Expires December 27, 2013 [Page 2] Internet-Draft PCEP Requirement for WSON RWA June 2013 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. Lee & Bernstein Expires December 27, 2013 [Page 3] Internet-Draft PCEP Requirement for WSON RWA June 2013 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. Lee & Bernstein Expires December 27, 2013 [Page 4] Internet-Draft PCEP Requirement for WSON RWA June 2013 +-------------------+ | +-------+ +--+ | +-------+ +--+ +-------+ +---+ | |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. Lee & Bernstein Expires December 27, 2013 [Page 5] Internet-Draft PCEP Requirement for WSON RWA June 2013 +----------------------------+ +-----+ | +-------+ +--+ | | | | |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.) Lee & Bernstein Expires December 27, 2013 [Page 6] Internet-Draft PCEP Requirement for WSON RWA June 2013 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. Lee & Bernstein Expires December 27, 2013 [Page 7] Internet-Draft PCEP Requirement for WSON RWA June 2013 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.) 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 wavelength. 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 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. Lee & Bernstein Expires December 27, 2013 [Page 8] Internet-Draft PCEP Requirement for WSON RWA June 2013 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. Lee & Bernstein Expires December 27, 2013 [Page 9] Internet-Draft PCEP Requirement for WSON RWA June 2013 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 action. 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 [RFC 2119] 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", RFC3471, January 2003. Lee & Bernstein Expires December 27, 2013 [Page 10] Internet-Draft PCEP Requirement for WSON RWA June 2013 [RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol- Traffic Engineering (RSVP-TE) Extensions", RFC3473, January 2003. [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC4655, August 2006. [RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE) Communication Protocol Generic Requirements", RFC4657, September 2006. [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation Element (PCE) communication Protocol", RFC5440, 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 [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", RFC6566, March 2012. [RFC6163] Y. Lee, G. Bernstein, W. Imajuku, "Framework for GMPLS and PCE Control of Wavelength Switched Optical Networks", RFC6163, April 2011. [RFC5088] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R. Zhang, "OSPF Protocol Extensions for Path Computation Element (PCE) Discovery", RFC5088, 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", RFC5089, January 2008. Lee & Bernstein Expires December 27, 2013 [Page 11] Internet-Draft PCEP Requirement for WSON RWA June 2013 Authors' Addresses Young Lee (Ed.) Huawei Technologies 5340 Legacy Drive, Building 3 Plano, TX 75024 USA Phone: (469) 277-5838 Email: firstname.lastname@example.org Greg Bernstein (Ed.) Grotto Networking Fremont, CA, USA Phone: (510) 573-2237 Email: email@example.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: firstname.lastname@example.org Takehiro Tsuritani KDDI R&D Laboratories, Inc. 2-1-15 Ohara Kamifukuoka Saitama, 356-8502. Japan Phone: +81-49-278-7357 Email: email@example.com Oscar Gonzalez de Dios Telefonica Investigacion y Desarrollo C/ Emilio Vargas 6 Madrid, 28043 Spain Phone: +34 91 3374013 Email: firstname.lastname@example.org Intellectual Property Statement The IETF Trust takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be Lee & Bernstein Expires December 27, 2013 [Page 12] Internet-Draft PCEP Requirement for WSON RWA June 2013 claimed to pertain to the implementation or use of the technology described in any IETF Document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. 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