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." Lee & Bernstein Expires April 28, 2015 [Page 1] Internet-Draft PCEP Requirement for WSON RWA October 2014 The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 28, 2009. Copyright Notice Copyright (c) 2014 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. 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 Lee & Bernstein Expires April 28, 2015 [Page 2] Internet-Draft PCEP Requirement for WSON RWA October 2014 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 Lee & Bernstein Expires April 28, 2015 [Page 3] Internet-Draft PCEP Requirement for WSON RWA October 2014 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. Lee & Bernstein Expires April 28, 2015 [Page 4] Internet-Draft PCEP Requirement for WSON RWA October 2014 +-------------------+ | +-------+ +--+ | +-------+ +--+ +-------+ +---+ | | 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. Lee & Bernstein Expires April 28, 2015 [Page 5] Internet-Draft PCEP Requirement for WSON RWA October 2014 +----------------------------+ +-----+ | +-------+ +--+ | | | | |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). Lee & Bernstein Expires April 28, 2015 [Page 6] Internet-Draft PCEP Requirement for WSON RWA October 2014 (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. Lee & Bernstein Expires April 28, 2015 [Page 7] Internet-Draft PCEP Requirement for WSON RWA October 2014 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: Lee & Bernstein Expires April 28, 2015 [Page 8] Internet-Draft PCEP Requirement for WSON RWA October 2014 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]. Lee & Bernstein Expires April 28, 2015 [Page 9] Internet-Draft PCEP Requirement for WSON RWA October 2014 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. Lee & Bernstein Expires April 28, 2015 [Page 10] Internet-Draft PCEP Requirement for WSON RWA October 2014 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. Lee & Bernstein Expires April 28, 2015 [Page 11] Internet-Draft PCEP Requirement for WSON RWA October 2014 [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 Lee & Bernstein Expires April 28, 2015 [Page 12] Internet-Draft PCEP Requirement for WSON RWA October 2014 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 Lee & Bernstein Expires April 28, 2015 [Page 13]