Network Working Group J.L. Le Roux (Editor) Internet Draft France Telecom Category: Informational Expires:
MarchAugust 2006 February 2006 October 2005Requirements for Path Computation Element (PCE) Discovery draft-ietf-pce-discovery-reqs-02.txtdraft-ietf-pce-discovery-reqs-03.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. Abstract This document presents a set of requirements for a Path Computation Element (PCE) discovery mechanism that would allow a Path Computation Client (PCC) to discover dynamically and automatically a set of PCEs along with certain information relevant for PCE selection. It is intended that solutions that specify procedures and protocol(s)protocols or extensions to existing protocol(s)protocols for such PCE discovery satisfy these requirements. 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. Table of Contents 1. Contributors................................................2 2. Terminology.................................................3 3. Introduction................................................3 4. Problem Statement and Requirements overview.................4Overview.................4 4.1. Problem Statement...........................................4 4.2. Requirements overview.......................................5 5. Example of application scenario.............................6 6. Detailed Requirements.......................................7 6.1. PCE Information to be disclosed.............................7 6.1.1. General PCE Information (Mandatory support).................7 188.8.131.52. Discovery of PCE Location.................................7 184.108.40.206. Discovery of PCE domain(s)Domains and inter-domain functions.....7Inter-domain Functions.......8 6.1.2. Detailed PCE Information (Optional support).................8 220.127.116.11. Discovery of PCE Capabilities.............................8 18.104.22.168. Discovery of Alternate PCEs...............................9 6.2. Scope of PCE Discovery......................................9 6.2.1. Inter-AS specific requirements.............................10 6.3. PCE Information Synchronization............................10 6.4. DetectingDiscovery of PCE Liveliness...................................10deactivation..............................11 6.5. Security Requirements......................................10Policy Support.............................................11 6.6. Extensibility..............................................11Security Requirements......................................11 6.7. Scalability................................................11Extensibility..............................................12 6.8. Scalability................................................12 6.9. Operational orders of magnitudes...........................11magnitudes...........................12 6.10. Manageability considerations...............................13 7. Security Considerations....................................12Considerations....................................13 8. Acknowledgments............................................12Acknowledgments............................................13 9. References.................................................12References.................................................13 9.1. Normative references.......................................13 9.2. Informative references.....................................13 10. Authors' Addresses:........................................12Addresses:........................................13 11. Intellectual Property Statement............................13Statement............................14 1. Contributors The following are the authors that contributed to the present document: Jean-Louis Le Roux (France Telecom) Paul Mabey (Qwest Communications) Eiji Oki (NTT) Richard Rabbat (Fujitsu) Ting Wo Chung (Bell Canada) Raymond Zhang (BT Infonet) 2. Terminology Terminology used in this document LSR: Label Switch Router TE-LSP: Traffic Engineered Label Switched Path 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. PCC: Path Computation Client: any client application requesting a path computation to be performed by a Path Computation Element. IGP Area: OSPF Area or ISIS level/area ABR: IGP Area Border Router (OSPF ABR or ISIS L1L2 router) AS: Autonomous System ASBR: AS Border Router Intra-area TE LSP: A TE LSP whose path does not cross IGP area boundaries. Inter-area TE LSP: A TE LSP whose path transits through two or more IGP areas. Inter-AS MPLS TE LSP: A TE LSP whose path transits through two or more ASesASs or sub-ASessub-ASs (BGP confederations). Domain: any collection of network elements within a common sphere of address management or path computational responsibility. Examples of domains include IGP areas and Autonomous Systems. 3. Introduction The PCEPCE-based network Architecture [PCE-ARCH] defines a Path Computation Element (PCE) as an entity capable of computing TE-LSPsTE-LSP paths based on a network graph, and applying computational constraints. A PCE serves path computation requests sent by Path Computation Clients (PCC). A PCC is a client application requesting a path computation to be performed by a PCE. This can be, for instance, an LSR requesting a path for a TE-LSP for which it is the head-end, or a PCE requesting a path computation of another PCE (inter-PCE communication). The communication between a PCC and a PCE requires a client-server protocol whose generic requirements are listed in [PCE-COM-REQ]. There are several motivations for the adoption of a PCE-based architecture to perform a path computation. They are listed in [PCE- ARCH]. This includes applications such as CPU intensive path computation, inter-domain path computation and backup path computation.The PCE based architecture requires, of course,that a PCC be aware of the location of one or more PCEs in its domain, and also potentially of some PCEs in other domains, e.g. in case of inter-domain path computation. In that context it would be highly desirable to define a mechanism for automatic and dynamic PCE discovery, which would allow PCCs to automatically discover a set of PCEs, includingto determine additional information required for PCE selection, and to dynamically detect new PCEs or any modification of PCE'sthe PCEs' information. This includes the discovery by a PCC of a set of one or more PCEs in its domain, and potentially in some other domains. The latter is a desirable function in the case of inter-domain path computationcomputation, for example. This document lists a set of functional requirements for such an automatic and dynamic PCE discovery mechanism. Section 4 points out the problem statement. Section 5 illustrates an application scenario. FinallyFinally, section 6 addresses detailed requirements. It is intended that solutions that specify procedures and protocol(s)protocols or protocol(s)protocol extensions for suchPCE discovery satisfy these requirements. There is no intent either to specify solution-specific requirements or to make any assumption on the protocol(s)protocols that could be used for the discovery. Note that requirements listed in this document apply equally to PCEs that are capable of computing paths in MPLS-TE-enabled networks and PCEs that are capable of computing paths in GMPLS-enabled networks (and PCEs capable of both). It is also important to note that the notion of a PCC encompasses a PCE acting as PCC when requesting a path computation of another PCE (inter-PCE communication). Hence, this document does not make the distinction between PCE discovery by PCCs and PCE discovery by PCEs. 4. Problem Statement and Requirements overviewOverview 4.1. Problem Statement A routing domain maymay, in practicepractice, be comprised of multiple PCEs: -The- The path computation load may be balanced among a set of PCEs to improve scalability; -For- For the purpose of redundancy, primary and backup PCEs may be used; -PCEs- PCEs may have distinct path computation capabilities (multi- constrained path computation, backup path computation...); -Incomputation, etc.); - In an inter-domain context there can be several PCEs with distinct inter-domain functions (inter-area, inter-AS, inter-layer),inter- layer), each PCE being responsible for path computation in one or more domains. As an example, in a multi-area network made of one backbone area and N peripheral areas, and where inter-area MPLS-TE path computation relies on multiple-PCE path computation with ABRs acting as PCEs, the backbone area would comprise at least N PCEs. In existing multi-area networks, N can be quite large (e.g. beyond fifty).In order to allow for effective PCE selection by PCCsPCCs, that is to select the appropriate PCE based on its capabilities and perform efficient load balancing of requests, a PCC hasneeds to know the location of PCEs in its domain, along with some information relevant to PCE selection, and also potentially needs to know the location of some PCEs in other domains, for inter-domain path computation purpose. Such PCE information could be learnt through manual configuration, on each PCC, of the set of PCEs along with their capabilities. Such a manual configuration approach may be sufficient, and even desired in some particular situations, (e.g. inter-AS PCE discovery, where manual configuration of neighbor PCEs may be preferred for security reasons), but it obviously faces several limitations: -This- This may imply a substantial configuration overhead (see the above example with N PCEs); -Thisoverhead; - This would not allow a PCC to dynamically detect that a new PCE is available, that an existing PCE is no longer available, or that there is a change in the PCE's information. Furthermore, as with any manual configuration approach, this may lead to undesirablethere is a risk of configuration errors. As an example, in a multi-area network made up of one backbone area and N peripheral areas, and where inter-area MPLS-TE path computation relies on multiple-PCE path computation with ABRs acting as PCEs, the backbone area would comprise at least N PCEs, and the configuration of PCC would be too cumbersome (e.g. in existing multi-area networks, N can be beyond fifty). Hence, an automated PCE discovery mechanism allowing a PCC to dynamically discover a set of PCEs is highly desirable. 4.2. Requirements overview A PCE discovery mechanism that satisfies the requirements set forth in this document MUST allow a PCC to automatically discover the location of one or more of the PCEs in its domain and also, potentially,domain. Where inter-domain path computation is required, the PCE discovery method MUST allow a PCC to automatically discover the location of PCEs in other domains, of interest fordomains that can assist with inter-domain path computation purpose.computation. A PCE discovery mechanism MUST allow a PCC to discover the set of one or more domains under the path computation responsibility ofwhere a PCE.PCE has TE topology visibility and can compute paths. It MUST also allow the discovery of the potential inter-domain function(s)path computation functions of a PCE (inter-area, inter-AS, inter-layer…).inter- AS, inter-layer, etc.). A PCE discovery mechanism MUST allow the control of the discovery scope, that is the set of one or more domains (areas, ASs) where information related to a given PCE has to be disclosed. A PCE discovery mechanism MUST allow PCCs in a given discovery scope to dynamically discover that a new PCE has appeared or that there is a change in PCE's information. ItA PCE discovery mechanism MUST alsoallow PCCs to dynamically discover that a PCE is no longer available. TheA PCE discovery MUST be secure.support security procedures. In particular, key consideration MUST be given in terms of how to establish a trust model for PCE discovery. OPTIONALLY a PCE discovery mechanism MAY be used so as to disclose a set of detailed PCE capabilities.capabilities so that the PCC may make advanced and informed choices about which PCE to use. 5. Example of application scenario <----------------AS1--------------------> <----AS2--- Area 1 Area 0 Area 2 R1---------R3-----R5-------R6-----------R9----------R11----R13 | | | | | | | | | | R2---------R4-----R7-------R8-----------R10---------R12----R14 | | -- |S1| -- Figure 1 Figure 1 aboveillustrates a multi-area/AS network with several PCEs: -The- The ABR R3 is a PCE that can take part in inter area path computation. It can compute paths in area 1 and area 0; -The- The ABR R6 is a PCE that can take part in inter-area path computation. It can compute paths in area 0 and area2; -The- The ASBR R9 is a PCE that can take part in inter-AS path computation,computation. It is responsible for path computation in AS1 towards AS2; -The- The ASBR R12 is a PCE that can take part in inter-AS path computation,computation. It is responsible for path computation in AS2 towards AS1; -The- The server S1 is a PCE that can be used to compute diverse paths and backup paths in area 1. TheBy meeting the requirements set out in this document, the PCE discovery mechanism will allow: -each LSR- each PCC in areas 1 and 0 to dynamically discover R3, as a PCE for inter-area path computation as well as its path computation domains: area1computation, and area0; -each LSRthat R3 can compute paths in area0 and area1; - each PCC in areas 0 and 2 to dynamically discover R6, as a PCE for inter-area path computation, as well as its path computation domains:and that R6 can compute paths in area2 and area0; -each LSR- each PCC in AS1 and some PCEsone or more PCCs in AS2 to dynamically discover R9 as a PCE for inter-AS path computation in AS1 towards AS2; -each LSR- each PCC in AS2 and some PCEsone or more PCCs in AS1 to dynamically discover R12 as a PCE for inter-AS path computation in AS2 towards AS1; -each LSR- each PCC in area 1 to dynamically discover S1, as a PCE for diverseintra- area path computation in area1, and backupoptionally to discover its path computation in area1.capabilities (diverse path computation and backup path computation). 6. Detailed Requirements 6.1. PCE Information to be disclosed We distinguish two levels of PCE information to be disclosed by thea PCE discovery mechanism: -General information, whose disclosure- General information. Disclosure MUST be supported by the PCE discovery mechanism. -Detailed information, whose disclosure- Detailed information. Disclosure MAY be supported by the PCE discovery mechanism. The PCE discovery mechanism MUST allow disclosingdisclosure of general PCE information that will allow PCCs to select appropriate PCEs. This comprises discovery of PCE location, PCE domain(s)domains supported by the PCEs, and potentialPCE inter-domain function(s).functions. The PCE discovery mechanism MAY also allow disclosingdisclosure of detailed PCE information. This comprises discovery ofany or all information about PCE path computation capabilities and alternate PCEs. This information is not strictly speakingpart of PCE discovery; this is additional information that can facilitate the selection of a PCE.PCE by a PCC. Support of the exchange of this information is optional in the context of the PCE discovery mechanism itself. This does not mean that the availability of this information is optional in the PCE architecture. SuchPCE-based architecture, but such information could also be obtained by other mechanisms, such as for instancethe PCC-PCE communication protocol. 6.1.1. General PCE Information (Mandatory support) 22.214.171.124. Discovery of PCE Location The PCE discovery mechanism MUST allow discovering,the discovery, for a given PCE, of the IPv4 and/or IPv6 address to be used to reach the PCE. This address will typically be a loop-back address that is always reachable, if there is any connectivity to the PCE. This address will be used by PCCs to communicate with a PCE, thanks tothrough a PCC-PCE communication protocol. 126.96.36.199. Discovery of PCE domain(s)Domains and inter-domain functionsInter-domain Functions Inter-domain path computation is a key application of the PCE architecture. This can rely on a multiple-PCE path computation, where PCEs in each domain compute a part of the end-to-end path and collaborate with each other to find the end-to-end-path. ThisInter-domain path computation can also rely on a single-PCE path computation where a PCE has visibility inside multiple domains and can compute an entire end-to-end inter-domain path.path (that is a path from the inter- domain TE-LSP head-end to the inter-domain TE-LSP tail end). Hence the PCE discovery mechanism MUST allow discoveringthe discovery of the set of one or more domains under the path computation responsibility of a PCE, i.e.where a PCE has visibility and can compute paths. These domains cancould be identified using a domain identifier: For instance, an IGP area can be identified by the Area ID (OSPF or ISIS), and an AS can be identified by the AS number. Also the PCE discovery mechanism MUST allow discovering the potential inter-domain function(s)discovery of athe inter- domain functions of a PCE, i.e. ifwhether a PCE can be used to compute or to take part in the computation of end-to-end paths across domains.domain borders. The inter-domain functions include: inter-area,include non exhaustively: inter- area, inter-AS orand inter-layer path computation. Note that these functions are not mutually exclusive. Note that the inter-domain functions differare not necessarily inferred from the set of domains under control ofwhere a PCE.PCE has visibility. For instance a PCE may have visisbilityvisibility limited to a single domain, but may be able to take part into the computation of inter-domain paths, by collaborating with PCEs in other domains. Conversely, a PCE may have visibility in multiple domains but the operator may not want that the PCE be used for inter-domain path computations. The PCE discovery mechanisms MUST also allow discoveringdiscovery of the set of one or more domain(s) towardsdomains toward which a PCE can compute paths. For instance in an inter-AS path computation context, there may be several PCEs in an AS, each one responsible for taking part in the computation of inter-AS path towardspaths toward a set of one or more destination ASes,ASs, and a PCC must discover the destination ASesASs each PCE is responsible for. 6.1.2. Detailed PCE Information (Optional support) 188.8.131.52. Discovery of PCE Capabilities In the case where there are several PCEs with distinct capabilities available, a PCC has to select one or more appropriate PCEs. For that purpose the PCE discovery mechanism MAY be used so as to disclosesupport the disclosure of some detailed PCE capabilities. For the sake of illustration this could include for instance somethe following path computation related PCE capabilities: -The capability to compute MPLS-TE and/or GMPLS paths; -The type of- The link and pathconstraints supported: e.g. bandwidth, affinities, delay; -Theaffinities. - The path constraints supported: maximum IGP/TE cost, maximum hop count; - The objective functions supported: e.g. shortest constrainedpath, shortest bounded delaywidest path; -The- The capability to compute multiple paths in a synchronized manner:correlated paths: e.g. diverse path computation,paths, load balanced paths computation; -Somepaths; - The capability to compute bidirectional paths; - The GMPLS technology specific capabilities:constraints supported: e.g. the supported interface switching capabilities, the support for multi-layer path computation;encoding types. And this could also include some specific PCE capabilities: -The- The capability to handle request prioritization; -The capability to authenticate PCCs and to be authenticated. -The- The maximum size of a request message; - The maximum number of path computationrequests per message -Thein a request message; - The PCE computation power (static parameters to be used for weighted load balancing of requests)requests). Such information regarding PCE capabilities could then be used by a PCC to select an appropriate PCE from a list of candidate PCEs. Note that the exact definition and description of PCE capabilities is out of the scope of this document. It is expected that this will be described in one or more separate document(s)documents which may be application specific. It is paramount that dynamic discovery of PCE capabilities MUST NOT generate an excessive amount of information and SHOULD be limited to a small set of generic capabilities. If required, the exhaustive discovery of all detailed PCE capabilities could be ensured by means of the PCC-PCE communication protocol. Actually a tradeoff should be found between capability discovery by the PCE discovery mechanism and by the PCC-PCE communication protocol. One of the objectives of the PCE discovery mechanism is to help PCCs to select appropriate PCEs and limit the likelihood of PCC- PCE session rejections that may occur in case a PCE cannot support a given capability.184.108.40.206. Discovery of Alternate PCEs In the case of a PCE failure, a PCC has to select another PCE, if one is available. It could be useful in various situations, for a PCE to indicate a set of one or more alternate PCEs that can be selected in case athe given PCE fails. Hence the PCE Discovery mechanism MAY allow the discovery, for a given PCE, of the location of one or more assigned alternate PCEs. The PCE Discovery mechanism MAY also allow the discovery, for a given PCE, of the set of one oreor more PCEs for which it acts as alternate PCE. 6.2. Scope of PCE Discovery The PCE Discovery mechanism MUST allow thecontrol of the scope of the PCE information discovery (IGP Area, AS, set of AS)disclosure on a per PCE basis. In other words it MUST allow tocontrol of to which PCC or group of PCCs the information related to a PCE may be disclosed. The choice for the discovery scope of a given PCE MUST include at least the followings: -Allfollowings settings: - All PCCs in a single IGP area -All- All PCCs in a set of adjacent IGP areas -All- All PCCs in a single AS -All- All PCCs in a set of ASes -AASs - A set of one or more PCCs in a set of one or more ASes ParticularlyASs In particular, this also implies that the PCE Discovery mechanism MUST allow for the discovery of PCE information across IGP areas and across AS boundaries. Note that itThe discovery scope MUST be configurable on a per PCE basis. It MUST be possible to deactivate PCE discovery on a per PCE basis. 6.3. PCE Information Synchronization6.2.1. Inter-AS specific requirements When using a PCE-based approach for inter-AS path computation, a PCC in one AS may need to learn information related to inter-AS capable PCEs located in other ASs. For that purpose, and as pointed out in the previous section, the PCE discovery mechanism MUST allow disclosure of information related to inter-AS capable PCEs across AS boundaries. Such inter-AS PCE discovery must be carefully controlled. For security and confidentiality reasons, particularly in an inter- provider context, the discovery mechanism MUST allow the discovery scope to be limited to a set of ASs and MUST also provide control of the PCE information to be disclosed across ASs. This is achieved by applying policies (See also section 6.4). This implies the capability to contain a PCE advertisement to a restricted set of one or more ASs, and to filter and translate any PCE parameter (PCE domains, PCE inter-domain functions, PCE capabilities, etc.) in disclosures that cross AS borders. For the sake of illustration, it may be useful to disclose detailed PCE information (such as detailed capabilities) locally in the PCE's AS but only general information (such as location and supported domains) in other ASs. 6.3. PCE Information Synchronization The PCE discovery mechanism MUST allow a PCC to detectdiscover any change in the information related to a PCE.PCE that it has previously discovered. This includes changes to both general information (e.g. a change in the PCE domain(s) modification),domains supported), and detailed information if supported (e.g. capability modification).a modification of the PCE's capabilities). In addition itaddition, the PCE discovery mechanism MUST be possibleallow to dynamically detectdiscover new PCEs. ThePCEs in a given discovery scope. Note that there is no requirement for real-time detection of these changes, the PCE Discovery Mechanism SHOULD rather allow such detection underdiscovery of these changes in an order of magnitude of 60 seconds.seconds, and the operator should have the ability to configure the Discovery delay. Note that PCE information is relatively staticstatic, and is expected to be fairly stable and notto not change frequently. 6.4. DetectingDiscovery of PCE Livelinessdeactivation The PCE discovery mechanism MUST allow a PCC to detectdiscover when a PCE that it has previously discovered is no longer alive or is deactivated. This allows a PCC to rapidly switch to another PCE (for instance a predefined alternate PCE), and thus minimizesmay help reducing or avoiding path computation service disruption. TheNote that there is no requirement for real-time detection of PCE discovery mechanismfailure/deactivation, the PCE Discovery Mechanism SHOULD rather allow such detection underdiscovery in an order of magnitude of 60 seconds. Note that such detection couldseconds, and the operator should have the ability to configure the Discovery delay. 6.5. Policy Support The PCE Discovery mechanism MUST allow for policies to restrict the discovery scope to a set of authorized domains, to control and restrict the type and nature of the information to be disclosed, and also to filter and translate some information at domains borders. It MUST be ensured bypossible to apply these policies on a per PCE basis. The way these policies could be managed is out of the PCC-PCE communication protocol (see [PCE-COM-REQ]). 6.5.scope of this document. Note that the Discovery mechanisms MUST allow disclosing policy information so as to control the disclosure policies at domain boundaries. Also, it MUST be possible to apply different policies when disclosing PCE information to different domains. 6.6. Security Requirements The threefive major threats related to PCE discovery mechanisms are: -Impersonation- Impersonation of PCE -InterceptionPCE; - Interception of PCE discovery information -Falsification(sniffing); - Falsification of PCE discovery information -Informationinformation; - Information disclosure to non-authorized PCCs.PCCs (PCC spoofing). - DoS Attacks Note that security of the PCE Discovery procedures is of particular importance in an inter-AS context, where PCE discovery may increase the vulnerability to attacks and the consequences of these attacks. Hence mechanisms MUST be defined to ensure authentication, integrityauthenticity, integrity, privacy, and privacycontainment of PCE discovery information: -There- There MUST be a mechanism to authenticate discovery information -Thereinformation; - There MUST be a mechanism to verify discovery information integrity -Thereintegrity; - There MUST be a mechanism to encrypt discovery information -Thereinformation; - There MUST be a mechanism to restrict the scope of discovery to a set of authorized PCCs. In particular, the identity of anyPCCs and to filter PCE information disclosed at domain boundaries (as per defined in 6.5). Mechanisms MUST onlybe learnt by authorized PCCs (see also 6.2). This is of particular importancedefined in an inter-AS context, where PCE discovery may increase the vulnerabilityorder to attacks andlimit the consequencesimpact of these attacks. Thea DoS attack on the PCE discovery mechanism MUST deliver the operational security objectives where required. The overall security objectives of privacy, authentication, and integrity may take on varying level of importance. These objectives MAY be met by other established meansprocedure (e.g. filter out excessive PCE information change and protocols.flapping PCEs). Also, key consideration MUST be given in terms of how to establish a trust model for PCE discovery. The PCE discovery mechanism MUST explicitly support a specific set of one oreor more trust model(s). 6.6.models. 6.7. Extensibility The PCE discovery mechanism MUST be flexible and extensible so as to easily allow for the inclusion of someadditional PCE information that could be defined in the future. 220.127.116.11. Scalability The PCE discovery mechanism MUST be designed to scale well with an increase of any of the following parameters: -Number- Number of PCCs discovering a given PCE; -Number- Number of PCEs to be discovered by a given PCC; -Number- Number of domains in the discovery scope; Particularly, in case routing protocols (IGP, BGP) are extended to supportscope. The PCE discovery, the extensionsdiscovery mechanism MUST NOT cause a degradationhave an adverse effect in the performance of other protocols (especially routing protocol performance. The same applies to a signaling solutionand signaling) already operating in the network. Note that could serve for this discovery. 6.8. Operational orders of magnitudes This section gives minimum order of magnitude estimates of whatthere is no scalability requirement with regards to the PCE discovery mechanism should support Number of PCCs discovering a given PCE: 1000 Numberamount of PCEsinformation to be discovered by a given PCC: 100 (e.g. inter-area case with ABRs acting as PCE). Number of IGP areas in the discovery scope: 100 Number of ASes in the discovery scope: 100exchanged. Information disclosed in the PCE discovery mechanism is relatively static. Changes in PCE information may occur as result of PCE configuration updates, PCE deployment/activation or PCE deactivation/suppression, and should not occur as a result of the PCE activity itself. Hence, this information is quite stable and will not change frequently. 6.9. Operational orders of magnitudes This section gives minimum order of magnitude estimates of what the PCE discovery mechanism should support. - Number of PCCs discovering a given PCE: 1000 - Number of PCEs to be discovered by a given PCC: 100 6.10. Manageability considerations Manageability of PCE discovery MUST addresses the following considerations: - need for a MIB module for PCE discovery; - configuration implications for the protocol. 7. Security Considerations This document is a requirement document and hence does not raise by itself any particular security issue. A set of security requirements that MUST be addressed when considering the design and deployment of a PCE Discovery mechanism have been identified in section 18.104.22.168. 8. Acknowledgments We would like to thank Benoit Fondeviole, Thomas Morin, Emile Stephan, Jean-Philippe Vasseur, Dean Cheng, Adrian Farrel, Renhai Zhang, Mohamed Boucadair, Eric Gray, Igor Bryskin, Dimitri Papadimitriou, Arthi Ayyangar andAyyangar, Andrew DolganowDolganow, Lou Berger, Nabil Bitar, and Kenji Kumaki for their useful comments and suggestions. 9. References 9.1. Normative references [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3667] Bradner, S., "IETF Rights in Contributions", BCP 78, RFC 3667, February 2004. [RFC3668] Bradner, S., "Intellectual Property Rights in IETF Technology", BCP 79, RFC 3668, February 2004.[PCE-ARCH] Farrel, A., Vasseur, J.P., Ash, J., "Path Computation Element (PCE) Architecture", draft-ietf-pce-architecture, work in progress. 9.2. Informative references [PCE-COM-REQ] Ash, J., Le Roux, J.L., " PCE"PCE Communication Protocol Generic Requirements", draft-ietf-pce-comm-protocol-gen-reqs, work in progress. 10. Authors' Addresses: Jean-Louis Le Roux (Editor) France Telecom 2, avenue Pierre-Marzin 22307 Lannion Cedex FRANCE Email: email@example.com Paul Mabey Qwest Communications 950 17th Street, Denver, CO 80202, USA Email: firstname.lastname@example.org Eiji Oki NTT Midori-cho 3-9-11 Musashino-shi, Tokyo 180-8585, JAPAN Email: email@example.com Richard Rabbat Fujitsu Laboratories of America 1240 East Arques Ave, MS 345 Sunnyvale, CA 94085 USA Email: firstname.lastname@example.org Ting Wo Chung Bell Canada 181 Bay Street, Suite 350 Toronto, Ontario, M5J 2T3 CANADA, Email: email@example.com Raymond Zhang BT Infonet 2160 E. Grand Ave. El Segundo, CA 90025 USA Email: firstname.lastname@example.org 11. 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