Network Working Group I. Nishioka Internet Draft NEC Intended Status: Standard Track Daniel King Expires: April 2008 Aria Networks November 2007 The use of SVEC (Synchronization VECtor) list for Synchronized dependent path computations draft-nishioka-pce-svec-list-01.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of 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." 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. Copyright Notice Copyright (C) The IETF Trust (2007). All rights reserved. Nishioka & King Expires April, 2008 [Page 1] Internet-Draft draft-nishioka-pce-svec-list-01.txt November 2007 Abstract A Path Computation Element (PCE) performing dependent path computations, for instance calculating a diverse working and protected path do not share common network points, would need to synchronize the computations in order to increase the probability of meeting the working and protected path disjoint objective and network resource optimization objective. This document describes the usage of multiple Synchronization VECtors (SVECs) in the SVEC list. When a PCE computes multiple sets of dependent path computation requests concurrently, it is required to use SVEC list for association among the sets of dependent path computation requests. The aim of this document is to define the association among SVECs and its processing rule. 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. Terminology.....................................................3 2. Introduction....................................................3 3. Association among SVEC..........................................5 3.1 Associated SVECs ..............................................5 3.2 Un-associated SVECs ...........................................5 4. Processing of SVEC list ........................................6 4.1 Single PCE, single domain environments..........................6 4.2 Multiple PCE, single domain environments........................6 4.3 Multiple PCE, multi domain environments.........................7 5. Manageability Considerations ..................................7 6. Security Considerations ........................................8 7. IANA Considerations ............................................8 8. References .....................................................8 8.1. Normative references ..........................................8 8.2. Informative references ........................................9 9. Authors' Addresses ............................................9 Nishioka & King Expires April, 2008 [Page 2] Internet-Draft draft-nishioka-pce-svec-list-01.txt November 2007 1. Terminology Terminology used in this document: PCC: Path Computation Client: Any client application requesting a path computation to be performed by a Path Computation Element. PCE: Path Computation Element: An entity (component, application, or network node) that is capable of computing a network path or route based on a network graph, and applying computational constraints. PCEP Peer: a neighbor element involved in a PCEP session (i.e. a PCC or a PCE). GCO: Global Concurrent Optimization: A concurrent path computation application where a set of TE paths is computed concurrently in order to efficiently utilize network resources. Associated SVECs: Multiple SVECs (Synchronization VECtors) to indicate a set of synchronized or concurrent path computations. 2. Introduction [ID.pce-pcep] describes the specifications for PCEP (Path Computation Element communication Protocol). PCEP facilitates the communication between a Path Computation Client(PCC) and a Path Computation Element (PCE), or between two PCEs based on PCE architecture [RFC4655]. PCEP interactions include path computation requests and path computation replies. [ID.pce-gco] specifies a global concurrent path computation application for the efficient use of network resources, called GCO, based on required objective functions (OFs). To compute a set of traffic-engineered paths for the GCO application, PCEP supports the synchronous and dependent path computation requests required in [RFC4657]. When a PCC or PCE sends such path computation requests to a PCE, Synchronization VECtor (SVEC) allows the PCC or PCE to specify a list of multiple path computation requests that must be synchronized along with a potential dependency. [ID.pce-pcep] defines two synchronous path computation modes using SVEC. o Bundle of a set of independent and synchronized path computation requests, o Bundle of a set of dependent and synchronized path computation requests. Nishioka & King Expires April, 2008 [Page 3] Internet-Draft draft-nishioka-pce-svec-list-01.txt November 2007 These are exclusive modes. If one of the dependency flags (i.e. Node, Link or Shared Risk Link Groups (SRLG) diverse flags) in a SVEC is set, the SVEC indicates a set of synchronous path computation requests with a dependency. In order to be synchronized among multiple sets of path computation requests with a dependency, it is necessary to use other SVECs. It is important for the PCE, when performing path computations, to synchronize any path computation requests with a dependency. For example, consider two diverse path computation requests to compute for protected end-to-end services with disjointed working and protected paths. If the diverse path requests are computed sequentially, fulfillment of the initial diverse path computation without consideration of the second diverse path computation and disjoint constraint, may result in the PCE providing sub-optimal results for the second one, or fail to meet the disjoint requirement altogether. This document defines the handling of synchronous path computation for PCE and multiple set of path computation request with a dependency. The following scenarios are specifically described: o Single domain, single PCE, dependent and synchronized path computation request. o Multi-domain, multiple-PCE, dependent and synchronized path computation request. The association among multiple SVECs and the processing rules to support multiple sets of synchronized dependent path computation requests, is also described in this document. Path computation algorithms for the associated path computation requests are out of scope in this draft. The SVEC association and its processing rule do not require any extension to PCEP message and object formats, while it enable GCO for multiple diverse paths. In addition, the use of multiple SVECs is not restricted to only SRLG, Node and Link diversity currently defined in the SVEC object, [ID.pce-pcep], but is also available for other dependent path computation requests. The SVEC association is available to both Multiple PCE path computation as well as a single PCE path computation. Nishioka & King Expires April, 2008 [Page 4] Internet-Draft draft-nishioka-pce-svec-list-01.txt November 2007 3. Association among SVECs This section describes the associations among SVECs in a SVEC list. 3.1 Associated SVECs Associated SVECs mean that there are relationships among multiple SVECs. Request-IDs in the SVEC objects are used to indicate the association among SVEC objects. If the same request-IDs exist in more than two SVECs, this indicates associated SVECs. When associating among SVECs, only one request-ID may in the SVEC object may be contained in the other SVEC object. This contributes to reducing the message size of PCEP request. Even in this case, all of the path computation requests are synchronized. Below is an example of associated SVECs. In this example the first SVEC and the other SVECs are associated, and path computation requests from Request-ID#1 to Request-ID#Z must be synchronized. without dependency flags Request-ID #1, Request-ID #3, Request-ID #4... , Request-ID #X with one or more dependency flags Request-ID #1, Request-ID #2 with one or more dependency flags Request-ID #4, Request-ID #5 ........ without dependency flag Request-ID #X, Request-ID #Y, Request-ID #Z Note that path computation requests that do not have other SVECs, like Request-ID #3, may be contained in the associated SVEC. This request is also synchronized. 3.2 Non-associated SVECs Non-associated SVECs mean that there are no relationships among SVECs. If SVEC objects in PECP request messages do not have the same request-ID, the relationship among these SVECs is not associated. Below is an example of non-associated SVECs that does not contain any same request-IDs. Nishioka & King Expires April, 2008 [Page 5] Internet-Draft draft-nishioka-pce-svec-list-01.txt November 2007 with one or more dependency flags Request-ID #1, Request-ID #2 with one or more dependency flags Request-ID #4, Request-ID #5 ........ without dependency flags Request-ID #X, Request-ID #Y, Request-ID #Z 4. Processing of SVEC list 4.1 Single PCE, single domain environments When PCEP receives PCReq messages with more than two SVEC objects in the SVEC list, PCEP MUST first check the request-IDs in all SVEC objects in order to identify any associations among them. The SVEC objects MAY be received in a single or multiple PCReq message(s). In the later case, the PCE may start a SyncTimer as recommended in [ID.pce-pcep]. After receiving the whole path computation requests, the analysis for associated SVECs MUST be started. If there are no matching request-IDs in the different SVEC objects, these SVEC objects are not associated, and then each set of path computation requests in the non-associated SVEC objects MUST be computed separately. If there are matching request-IDs in the different SVEC objects, these SVEC objects are associated, and then all path computation requests in the associated SVEC objects SHOULD be treated in a synchronous manner for GCO application. If the PCE does not have capability to handle the associated SVEC objects, it SHOULD send a PCErr message with Error-Type="Capability not supported". 4.2 Multi-PCE, single domain environments Currently no mechanisms exist to manage co-ordination of dependent SVEC requests between multiple PCE`s in the same domain. If a PCC sends a path computation request to a PCE and then sends a second service path computation request, which is required to be disjoint from the first service, and this request is sent to a different PCE in the domain, no SVEC object correlation function between the PCEs is currently available. Equally, associated SVECs are not sent to the different PCEs in the domain. Nishioka & King Expires April, 2008 [Page 6 Internet-Draft draft-nishioka-pce-svec-list-01.txt November 2007 4.3 Multi-PCE, multi-domain environments When more than two PCEs are used to concurrently compute a protected end-to-end path across multiple domains, additional processing may be required. If the PCReq message contains multiple associated SVEC objects and these SVEC objects contain path computation requests that will be sent to the next PCE along the path computation chain. Intermediate PCEs receiving such PCReq messages MAY re-construct associations among SVEC objects, and then send PCReq messages to corresponding next PCEs. If the associated SVECs is re-constructed at the intermediate PCE, the PCE MUST NOT start path computation until all PCRep messages are received from neighbor PCEs. In addition, it is not recommended that SVEC objects coming from different PCReq messages are re-constructed. This may contribute to resource optimization from network operator`s point of view, but it is unrealistic in the case of multiple PCE path computation. 5. Manageability considerations This section describes manageability considerations specified in [ID.pce-mngabl-reqs]. 5.1. Control of Function and Policy In addition to section 8.1 to [ID.pce-pcep], PCEP implementation SHOULD allow the configuration of association among SVECs on PCCs. o the capability to configure SVEC association. 5.2. Information and Data Models, e.g. MIB modules There are no additional parameters for MIB modules. 5.3. Liveness Detection and Monitoring The associated SVEC in this document allows PCEs to compute optimal sets of diverse path. This type of path computation may require more time to obtain its results. Therefore, it is recommended for PCEP to support PCE monitoring mechanism specified in [ID.pce-monitor]. Nishioka & King Expires April, 2008 [Page 7] Internet-Draft draft-nishioka-pce-svec-list-01.txt November 2007 5.4. Verifying Correct Operation Section 8.4 in [ID.pce-pcep] provides the sufficient descriptions for this document. So, there are no additional considerations. 5.5. Requirements on Other Protocols and Functional Components This document does not require anything on other protocol and functional components. 5.6. Impact on Network Operation Section 8.6 in [ID.pce-pcep] provides the sufficient descriptions for this document. So, there are no additional considerations. 6. Security Considerations This document defines the usage of SVEC list, and does not have any extensions for PCEP protocol. Therefore the security of this document depends on that of PCEP protocol. 7. IANA Considerations This document has no specific extension for PCEP messages, objects and its parameters and does not require any registry assignment. 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] A. Farrel, JP. Vasseur and J. Ash, "A Path Computation Element (PCE)-Based Architecture," RFC 4655, September 2006. [RFC4657] J. Ash and J.L. Le Roux, "Path Computation Element (PCE) Communication Protocol Generic Requirements," RFC 4757, September 2006. Nishioka & King Expires April, 2008 [Page 8] Internet-Draft draft-nishioka-pce-svec-list-01.txt November 2007 8.2 Informative References [ID.pce-pcep] JP. Vasseur and JL. Le Roux, "Path Computation Element(PCE) communication Protocol (PCEP) - Version 1," draft-ietf-pce-pcep-08 Work in progress, Jan. 2007. [ID.pce-gco] Y. Lee, JL. Le Roux, D. King and E. Oki, "Path Computation Element Communication Protocol (PCECP) Requirements and Protocol Extensions In Support of Global Concurrent Optimization," draft-ietf-pce-global-concurrent-optimization-00 Work in progress June 2007. [ID.pce-mngabl-reqs] A. Farrel, "Inclusion of Manageability Sections in PCE Working Group Drafts," draft-ietf-pce-manageability-requirements-02 Work in progress, Feb. 2007. [ID.pce-monitor] JP. Vasseur, JL. Le Roux and Y. Ikejiri, "A set of monitoring tools for Path Computation Element based Architecture, "draft-ietf-pce-monitoring-00.txt Work in progress, Sep. 2007. 9. Authors' Addresses Itaru Nishioka NEC Corp. 1753 Shimonumabe, Kawasaki, Kanagawa 211-8555 Japan Phone: +81 44 396 3287 Email: i-nishioka@cb.jp.nec.com Daniel King Aria Networks 44/45 Market Place, Chippenham, SN15 3HU, United Kingdom Phone: +44 7790 775187 Email: daniel.king@aria-networks.com Nishioka & King Expires April, 2008 [Page 9] Internet-Draft draft-nishioka-pce-svec-list-01.txt November 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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