Network Working Group Y. Lee Internet Draft Huawei Intended status: Standard Track Expires: June 2010 G. Bernstein Grotto Networking Jonas Martensson Acreo T. Takeda NTT T. Tsuritani KDDI December 15, 2009 PCEP Requirements for WSON Impairments draft-lee-pce-wson-impairments-01.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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Abstract This memo provides application-specific requirements for the Path Computation Element communication Protocol (PCEP) for the support of Impairments in Wavelength Switched Optical Networks (WSON). From a path computation perspective, optical impairments are additional constraints on the process of determining an optical light path. 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 (no impairments).......................5 1.2. WSON IA-RWA Processes.....................................5 2. WSON PCE Architectures and Requirements........................7 2.1. RWA PCC to PCE Interface..................................8 2.1.1. A new RWA path request...............................8 2.1.2. An RWA path re-optimization request..................8 2.2. RWA-PCE to IV-PCE Interface...............................9 3. Manageability Considerations..................................10 3.1. Control of Function and Policy...........................10 3.2. Information and Data Models, e.g. MIB module.............11 3.3. Liveness Detection and Monitoring........................11 3.4. Verifying Correct Operation..............................11 Lee & Bernstein Expires June 15, 2010 [Page 2] Internet-Draft PCEP Extension for WSON Impairments December 2009 3.5. Requirements on Other Protocols and Functional Components11 3.6. Impact on Network Operation..............................11 4. Security Considerations.......................................12 5. IANA Considerations...........................................12 6. Acknowledgments...............................................12 7. References....................................................12 7.1. Normative References.....................................12 7.2. Informative References...................................13 Authors' Addresses...............................................14 Intellectual Property Statement..................................14 Disclaimer of Validity...........................................15 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 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) with impairments. 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 Lee & Bernstein Expires June 15, 2010 [Page 3] Internet-Draft PCEP Extension for WSON Impairments December 2009 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. One of the most basic questions in communications is whether one can successfully transmit information from a transmitter to a receiver within a prescribed error tolerance, usually specified as a maximum permissible bit error ratio (BER). This generally depends on the nature of the signal transmitted between the sender and receiver and the nature of the communications channel between the sender and receiver. The optical path utilized (along with the wavelength) determines the communications channel. The optical impairments incurred by the signal along the fiber and at each optical network element along the path determine whether the BER performance or any other measure of signal quality can be met for this particular signal on this particular path. Given the existing standards covering optical characteristics (impairments) and the knowledge of how the impact of impairments may be estimated along a path, [WSON-IMP] provides a framework for impairment aware path computation and establishment utilizing GMPLS protocols and the PCE architecture. Some transparent optical subnetworks are designed such that over any path the degradation to an optical signal due to impairments never exceeds prescribed bounds. This may be due to the limited geographic extent of the network, the network topology, and/or the quality of the fiber and devices employed. In such networks the path selection problem reduces to determining a continuous wavelength from source to destination (the Routing and Wavelength Assignment problem). Lee & Bernstein Expires June 15, 2010 [Page 4] Internet-Draft PCEP Extension for WSON Impairments December 2009 These networks are discussed in [WSON-Frame]. In other optical networks, impairments are important and the path selection process must be impairment-aware. In this document we first review the processes for routing and wavelength assignment (RWA) used when wavelength continuity constraints are present. We then review the processes for optical impairment aware RWA (IA-RWA). Based on selected process models we then specify requirements for PCEP to support IA-RWA. Note that requirements for PCEP to support RWA are specified in a separate document [PCEP-RWA]. The remainder of this document uses terminology from [RFC4655]. 1.1. WSON RWA Processes (no impairments) 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. Detail description of each alternative can be found in [WSON-FRAME]. 1.2. WSON IA-RWA Processes In [WSON-IMP] impairments were addressed by adding an "impairment validation" (IV) process. For approximate impairment validation three process alternatives were given in [WSON-IMP] and are shown in Figure 2. Since there are many possible alternative combinations, these are just three examples. Please note that the requirements for all possible architectures can be reduced to the cases in Figure 3 in section 2. Lee & Bernstein Expires June 15, 2010 [Page 5] Internet-Draft PCEP Extension for WSON Impairments December 2009 +-----------------------------------+ | +--+ +-------+ +--+ | | |IV| |Routing| |WA| | | +--+ +-------+ +--+ | | | | Combined Processes | +-----------------------------------+ (a) +--------------+ +----------------------+ | +----------+ | | +-------+ +--+ | | | IV | | | |Routing| |WA| | | |candidates| |----->| +-------+ +--+ | | +----------+ | | Combined Processes | +--------------+ +----------------------+ (b) +-----------+ +----------------------+ | +-------+ | | +--+ +--+ | | |Routing| |------->| |WA| |IV| | | +-------+ | | +--+ +--+ | +-----------+ | Distributed Processes| +----------------------+ (c) Figure 2 Process flows for the three main approximate impairment architectural alternatives. These alternatives have the following properties and impact on PCEP requirements in this document. 1. Combined IV and RWA Process - Here the processes of impairment validation, routing and wavelength assignment are aggregated into a single PCE. The requirements for PCC-PCE interaction with such a combined IV-RWA process PCE is addressed in this document. 2. IV-Candidates + RWA Process - As explained in [WSON-IMP] separating the impairment validation process from the RWA process maybe necessary to deal with impairment sharing constraints. In this architecture one PCE computes impairment candidates and another PCE uses this information while performing RWA. The requirements for PCE-to-PCE interaction of this architecture will be addressed in this document. Lee & Bernstein Expires June 15, 2010 [Page 6] Internet-Draft PCEP Extension for WSON Impairments December 2009 3. Routing + Distributed WA and IV - Here a standard path computation (unaware of detailed wavelength availability or optical impairments) takes place, then wavelength assignment and impairment validation 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 we reviewed various process architectures for implementing RWA with and without regard for optical impairment. In Figure 3 we reduce these alternatives to two PCE based implementations. In Figure 3(a) we show the three processes of routing, wavelength assignment and impairment validation accessed via a single PCE. The implementation details of the interactions of the processes are not subject to standardization in this case only the PCC to PCE communications. In Figure 3(b) the impairment validation process is implemented in a separate PCE. Here the RWA-PCE acts as a coordinator and the PCC to RWA-PCE interface will be the same as in Figure 3(a), however in this case we have additional requirements for the RWA-PCE to IV-PCE interface. +-----------------------------------+ +-----+ | +--+ +-------+ +--+ | | | | |IV| |Routing| |WA| | | PCC |<----->| +--+ +-------+ +--+ | | | | | +-----+ | PCE | +-----------------------------------+ (a) +----------------------+ +--------------+ +-----+ | +-------+ +--+ | | | | | | |Routing| |WA| | | IV | | PCC |<----->| +-------+ +--+ |<--->| candidates | | | | | | | +-----+ | RWA-PCE (coordinator)| | IV-PCE | +----------------------+ +--------------+ (b) Figure 3 PCE architectures for RWA. Lee & Bernstein Expires June 15, 2010 [Page 7] Internet-Draft PCEP Extension for WSON Impairments December 2009 2.1. RWA PCC to PCE Interface The PCC to PCE interface of Figure 3(a) and the PCC to RWA-PCE (coordinator) interface of Figure 3(b) are the same and we will cover both in this section. The following requirements for these interfaces are arranged by use cases: 2.1.1. A new RWA path request/reply 1. The PCReq Message MAY include some specific measure of optical signal quality to which all feasible paths should conform: o The BER limit o Q factor o OSNR + Margin o PMD If the PCReq Message does not include the BER limit and no default BER limit is provisioned at the PCE then the PCE will return an error specifying that a BER limit must be provided. Margin" means "insurance" (e.g. 3~6dB) for suppliers and operators against unpredictable degradation and unestimatable degradation due to fiber nonlinearity and mismatched wavelength along the path. 2. The PCRep Message MUST include the route, wavelengths assigned to the route and an indicator that says if the path conforms to the required quality or not. 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, BER failure, etc.) 2.1.2. An RWA path re-optimization request/reply 1. If a BER limit was required in the original path request then a BER limit MUST be furnished in the re-optimization request. Otherwise, furnishing a BER limit is optional. 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, BER failure, etc.) Lee & Bernstein Expires June 15, 2010 [Page 8] Internet-Draft PCEP Extension for WSON Impairments December 2009 2.2. RWA-PCE to IV-PCE Interface In [WSON-IMP] a sequence diagram for the interaction of the PCC, RWA- PCE and IV-PCE of Figure 3(b) was given and is repeated here in Figure 4. The interface between the PCC and the RWA-PCE (acting as the coordinator) was covered in section 2.1. +---+ +-------------+ +-----------------+ |PCC| |RWA-Coord-PCE| |IV-Candidates-PCE| +-+-+ +------+------+ +---------+-------+ ...___ (a) | | | ````---...____ | | | ```-->| | | | | | |--..___ (b) | | | ```---...___ | | | ```---->| | | | | | | | | (c) ___...| | | ___....---'''' | | |<--'''' | | | | | | | | (d) ___...| | | ___....---''' | | |<--''' | | | | | | | | Figure 4 Sequence diagram for the interactions between PCC, RWA- Coordinating-PCE and the IV-Candidates-PCE. The interface between the RWA-Coord-PCE and the IV-Candidates-PCE is specified by the following requirements: 1. The PCReq Message from the RWA-Coord-PCE to the IV-PCE MUST include an indicator that more than one (candidate) path between source and destination is desired. 2. The PCReq message from the RWA-Coord-PCE to the IV-Candidates-PCE MUST include a limit on the number of optical impairment qualified paths to be returned by the IV-PCE. Lee & Bernstein Expires June 15, 2010 [Page 9] Internet-Draft PCEP Extension for WSON Impairments December 2009 3. The PCReq message from the RWA-Coord-PCE to the IV-Candidates-PCE MAY include wavelength constraints. Note that optical impairments are wavelength sensitive and hence specifying a wavelength constraint may help limit the search for valid paths. This requirement has been already covered in [PCEP-RWA] and is presented here for an illustration purpose. 4. The PCRep Message from the IV-Candidates-PCE to RWA-Coord-PCE MUST include a set of optical impairment qualified paths along with any wavelength constraints on those paths. 5. The PCRep Message from the IV-Candidates-PCE to RWA-Coord-PCE MUST indicate "no path found" in case where a valid path is not found. 6. The PCReq Message from the RWA-PCE to the IV-PCE MAY include one or more specified paths and wavelengths that is to be verified by the IV-PCE. This requirement is necessary when the IV-PCE is allowed to verify specific paths. Note that once the Combined RWA Process PCE receives the resulting paths from the IV Candidates PCE, then the Combined RWA PCE computes RWA for the IV qualified candidate paths and sends the result back to the PCC. 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 [PCEP], 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 [PCEP], 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 synchronized path requests associated with WSON RWA per request message. Lee & Bernstein Expires June 15, 2010 [Page 10] Internet-Draft PCEP Extension for WSON Impairments December 2009 o A set of WSON RWA specific policies (authorized sender, request rate limiter, etc). 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 Extensions to the PCEP MIB module defined in [PCEP-MIB] should be defined, so as to cover the WSON RWA information introduced in this document. A future revision of this document will list the information that should be added to the MIB module. 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 [PCEP]. 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 [PCEP] 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 [PCEP]. Lee & Bernstein Expires June 15, 2010 [Page 11] Internet-Draft PCEP Extension for WSON Impairments December 2009 4. Security Considerations This document has no requirement for a change to the security models within PCEP [PCEP]. 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. Lee & Bernstein Expires June 15, 2010 [Page 12] Internet-Draft PCEP Extension for WSON Impairments December 2009 [RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE) Communication Protocol Generic Requirements", RFC 4657, September 2006. [PCEP] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation Element (PCE) communication Protocol (PCEP) - Version 1", draft-ietf-pce-pcep, work in progress. 7.2. Informative References [WSON-Frame] Bernstein, G. and Lee, Y. (Editors), and W. Imajuku, "A Framework for the Control and Measurement of Wavelength Switched Optical Networks (WSON) with Impairments draft-bernstein-ccamp-wson-impairments-02.txt, work in progress. [WSON-IMP] Bernstein, G. and Lee, Y. (Editors), and D. Li, "Framework for GMPLS and PCE Control of Wavelength Switched Optical Networks", draft-bernstein-ccamp-wavelength-switched, work in progress. [PCEP-RWA] Y. Lee, G. Bernstein, J. Martensson, T. Takeda and T. Otani, "PCEP Requirements for WSON Routing and Wavelength Assignment", draft-lee-pce-wson-routing-wavelength, 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. Lee & Bernstein Expires June 15, 2010 [Page 13] Internet-Draft PCEP Extension for WSON Impairments December 2009 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 2-1-15 Ohara, Fujimino, Saitama, 356-8502, JAPAN KDDI R&D Laboratories Inc. Phone: +81-49-278-7806 Email: tsuri@kddilabs.jp 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 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. Copies of Intellectual Property disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or Lee & Bernstein Expires June 15, 2010 [Page 14] Internet-Draft PCEP Extension for WSON Impairments December 2009 users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement any standard or specification contained in an IETF Document. Please address the information to the IETF at ietf-ipr@ietf.org. 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