Network Working Group Y.L. Bao Internet-Draft X.H. Fu Intended status: Informational G. Xie Expires: April 22, 2010 ZTE Corporation October 19, 2009 A Path Computation Element (PCE) Application for Pre-configured Routing draft-bao-pce-pre-configured-routing-00 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." 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 22, 2010. Copyright Notice Copyright (c) 2009 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract Pre-configured routing is a routing scheme that except primary route operator configures one or multiple routes which will be used as Y.L. Bao, et al. Expires April 22, 2010 [Page 1] Internet-Draft PCE App for Pre-configured Routing October 2009 recovery route when the primary route fails for a service previously. This document improves this traditional routing shceme, and PCE (Paht Computation Element) is applied for pre-configured routing. Furthermore, this document also presents a detailed set of PCC-PCE (Path Computation Client) communication protocol requirements and defines PCEP (Path Computation Element Communication Protocol) extensions for PCEP. Table of Contents 1. Conventions used in this document . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Application of pre-configured Routing . . . . . . . . . . . . . 3 4. Architecture Analysis and Requirement . . . . . . . . . . . . . 4 4.1. Architecture Analysis . . . . . . . . . . . . . . . . . . . 4 4.2. Requirements to PCE . . . . . . . . . . . . . . . . . . . . 5 4.3. Requirements to PCEP . . . . . . . . . . . . . . . . . . . 5 5. Extensions to PCEP and Procedures . . . . . . . . . . . . . . . 6 5.1. New Flag Of The LSPA Object . . . . . . . . . . . . . . . . 6 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 7.1. New Flag Of The LSPA Object . . . . . . . . . . . . . . . . 6 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 9. Normative References . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Y.L. Bao, et al. Expires April 22, 2010 [Page 2] Internet-Draft PCE App for Pre-configured Routing October 2009 1. 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]. 2. Introduction Pre-configured routing is a very useful approach to achieve service resteration. Generally, except primary route, operator also sets a group of routes (usually with priority), i.e. pre-configured route set,for a service. When the primary route fails, router can select a proper resteration route from pre-configured route set. By this way, faster resteration can be achieved. Since pre-configured routes are pre-configured by management plane, it can't be updated when network state changes dynamically. In some cases, e.g. a fiber on the pre-configured route is cut, if operator can't update pre-configured routes in time, the pre-configured routes will become unavailable. Otherwise, generally the pre-configured routes will be verified whether it is available before it is used to signal a connection. This is also due to the problem that pre- configured routes can't be updated timely. So this will introduce another problem that time delay will affect service recovery. This document introduces a PCE-based pre-configured routing method, which uses PCE to update pre-configured route at the policy of network management. This method helps to optimize network resources and avoid the unavailablity of pre-configured routes. 3. Application of pre-configured Routing As illustrated in figure 1, an example network is comprised of 9 nodes and an external PCE. Suppose there is a service between A and I. In order to create the connection, source node A request a working path. And PCE responds node A with path A-D-I. However, to provide fast recovery when primary path A-D-I fails, node A can also request additional pre-configured routes. And PCE reponds with path A-B-C-I and A-E-F-G-H-I providing node A requested 2 pre-configured routes. To provide the availability of pre-configured routes, PCE can dynamically upade these routes according to the local policy. For example, PCE can be configured to update Pre-configured route when network status changes, or a 30 seconds timer expires etc. In figure 1, Assume PCE is configured to update pre-configured route Y.L. Bao, et al. Expires April 22, 2010 [Page 3] Internet-Draft PCE App for Pre-configured Routing October 2009 as network status changes, when link BC failed, PCE will aucomatically compute and send route A-B-D-I to source node A to refresh previously requested pre-configured route. If primary path fails, e.g. the fiber on link AD is cut, node A can use pre-configured route A-B-C-I to recovery service between A and I without requesting PCE again. +=====+ | PCE | +=====+ +---+ +---+ .--------+ B +----------+ C + / +-+-+ +-+-+ / \ \ / \ `--------. / \ \ +-+-+ +-+-+ +-+-+ | A +---------------+ D +-------------------+ I | +-+-+ +-+-+ +-+-+ \ / / \ / / \ / / +-+-+ +-+-+ +-+-+ +-+-+ | E +-------+ F +-------+ G +-------+ H | +---+ +---+ +---+ +---+ Figure 1: Example of Application of Pre-configured Routing 4. Architecture Analysis and Requirement 4.1. Architecture Analysis [RFC4655] introduced 5 PCE models which can be categorized according to whether PCE functionality is integrated into the network element. Under this methodology, two groups of PCE model, i.e. composite PCE and external PCE, is generated. For composite PCE, due to the resource limitation of the card, the power of CPU is relatively weak, so the PCE capability is also limited. However, compared to composite PCE, external PCE has more resources (i.e. memory and CPU power etc), and it even can be presented as a dedicated server. Therefore, external PCE is more powerful than composite PCE. The application of pre-configured routing will increase compuataion burden to PCE. Due to its powerful computation capability, external PCE is more adequate than composite PCE. However, if there is not much application of pre-configured Y.L. Bao, et al. Expires April 22, 2010 [Page 4] Internet-Draft PCE App for Pre-configured Routing October 2009 routing, composite PCE can also operate well. [RFC4655] also describes stateful PCE and stateless PCE. For statefull PCE, there is a strict synchronization between the PCE and not only the network states (in term of topology and resource information), but also the set of computed paths and reserved resources in use in the network. So, it is easier to applying pre- configured routing on stateful PCE. Furthermore, considering the PCE failure, if an implementation has a backup PCE, then the primary and backup PCE MUST keep strict synchronization. And switching to the backup PCE can't affect the correctness of path computation However, the selection of PCE model, stateful PCE or stateless PCE is out of this document. And the synchronizt between primary and backup PCE is also out of this document, the operator can make a selection according to network deployment. 4.2. Requirements to PCE In order to support pre-configured routing, PCE SHOULD record pre- configured route information, and maintain its status. When network status changes, PCE SHOULD compute the affected pre-configured routes. However, PCE MAY also compute pre-configured routes in idle state to obtain the optimized pathes. The policy for PCE compute pre-configured routes SHOULD be able to configured. 4.3. Requirements to PCEP [RFC4657] gives detailed generic requirements for PCE communication protocol. However, in orderto support pre-configured routing, specific extensions to PCEP is required. For PCReq, it SHOULD be possible for PCC to request pre-configured route. When PCE receives a request identified with pre-configured routing, it SHOULD perform path computation accroding to the required policy, e.g. node disjoint, link disjoint and SRLG disjoint etc. And in the response message, PCE SHOULD able to specify which one is pre-exsiting route. If mulitple pre-configured routes are requested, PCE SHOULD give each pre-configured route a priority in PCRep message. If PCE doesn't support pre-configured routing it SHOULD give a negative response, and the reason for computation failure. When network status changes, PCE SHOULD re-compute pre-configured routes according the configured policy. If new better pre-configured route is computed, PCE should send it to PCC. There are two options for PCE to send pre-configured route as follows: Y.L. Bao, et al. Expires April 22, 2010 [Page 5] Internet-Draft PCE App for Pre-configured Routing October 2009 PCRep is used to respond route computation result naturally. If it is used to send pre-configured route, a new flag SHOULD be defined to indicate the route carried is pre-configured route. 5. Extensions to PCEP and Procedures 5.1. New Flag Of The LSPA Object The LSPA (LSP Attributes defined in [RFC5440]) object specifies various TE LSP attributes to be taken into account by the PCE during path computation. The LSPA object can be carried within a PCReq message, or a PCRep message. In order to support pre-configured route in PCReq and PCRep message, a new flag, Pre-Configured Route flag, is defined in LSPA (LSP Attributes) object. The definition of Pre-Configured Route flag is: Bit Number Name Flag 22 Pre-Configured Route When PCC requests pre-configured route, it SHOULD set Pre-Configured Route flag in LSPA object. And PCE SHOULD also set this flag, when it sends computed pre-configured route to PCC. If PCE can't recognize Pre-Configured Route flag, a PCErr message SHOULD be sent with an Error-Type=2 (Capability not supported). 6. Security Considerations This document has no requirement for a change to the security models within PCEP and associated protocols. 7. IANA Considerations 7.1. New Flag Of The LSPA Object A new flag of the LSPA object (specified in [RFC5440]) is defined in this document. Pre-Configured Route Flag Bit Number Name Flag Reference 22 Pre-Configured Route This document Y.L. Bao, et al. Expires April 22, 2010 [Page 6] Internet-Draft PCE App for Pre-configured Routing October 2009 8. Acknowledgements The RFC text was produced using Marshall Rose's xml2rfc tool. 9. 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. [RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE) Communication Protocol Generic Requirements", RFC 4657, September 2006. [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, March 2009. Authors' Addresses Yuanlin Bao ZTE Corporation 5F, R&D Building 3, ZTE Industrial Park, XiLi LiuXian Road Nanshan District, Shenzhen 518055 P.R.China Phone: +86 755 26773731 Email: bao.yuanlin@zte.com.cn URI: http://www.zte.com.cn/ Xihua Fu ZTE Corporation West District,ZTE Plaza,No.10,Tangyan South Road,Gaoxin District Xi An 710065 P.R.China Phone: +8613798412242 Email: fu.xihua@zte.com.cn URI: http://www.zte.com.cn/ Y.L. Bao, et al. Expires April 22, 2010 [Page 7] Internet-Draft PCE App for Pre-configured Routing October 2009 Gang Xie ZTE Corporation ZTE Plaza, No.19, Huayuan Road East, Haidian District Bei Jing 100191 P.R.China Phone: +8613798412242 Email: xie.gang@zte.com.cn URI: http://www.zte.com.cn/ Y.L. Bao, et al. Expires April 22, 2010 [Page 8]