From 4bfd864f10b68b71482b35c818559068ef8d5797 Mon Sep 17 00:00:00 2001 From: Thomas Voss Date: Wed, 27 Nov 2024 20:54:24 +0100 Subject: doc: Add RFC documents --- doc/rfc/rfc7449.txt | 675 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 675 insertions(+) create mode 100644 doc/rfc/rfc7449.txt (limited to 'doc/rfc/rfc7449.txt') diff --git a/doc/rfc/rfc7449.txt b/doc/rfc/rfc7449.txt new file mode 100644 index 0000000..ca09ef8 --- /dev/null +++ b/doc/rfc/rfc7449.txt @@ -0,0 +1,675 @@ + + + + + + +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, + . + + [RFC4655] Farrel, A., Vasseur, J.-P., 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 (PCEP)", RFC 5440, + March 2009, . + +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, . + + [RFC4657] Ash, J., Ed., and J. Le Roux, Ed., "Path Computation + Element (PCE) Communication Protocol Generic + Requirements", RFC 4657, September 2006, + . + + [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, + . + + [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, + . + + + +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, + . + +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 + + + + + + + + + + + +Lee, et al. Informational [Page 11] + +RFC 7449 PCEP Requirements for WSON RWA February 2015 + + + 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 + + + + + + + + + + + + + + + + + + + + + + + + + +Lee, et al. Informational [Page 12] + -- cgit v1.2.3