Internet Engineering Task Force Q. Zhao Internet-Draft Huawei Technology Intended status: Standards Track Z. Ali Expires: January 12, 2011 T. Saad Cisco Systems D. King Old Dog Consulting July 11, 2010 PCE-based Computation Procedure To Compute Shortest Constrained P2MP Inter-domain Traffic Engineering Label Switched Paths draft-zhao-pce-pcep-inter-domain-p2mp-procedures-05 Abstract The ability to compute paths for constrained point-to-multipoint (P2MP) Traffic Engineering Label Switched Paths(TE LSPs) across multiple domains has been identified as a key requirement for the deployment of P2MP services in MPLS and GMPLS networks. The Path Computation Element (PCE) has been recognized as an appropriate technology for the determination of inter-domain paths of P2MP TE LSPs. This document describes the procedures and extensions to the PCE communication Protocol (PCEP) to handle requests and responses for the computation of inter-domain paths for P2MP TE LSPs. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on January 12, 2011. Copyright Notice Zhao, et al. Expires January 12, 2011 [Page 1] Internet-Draft PCEP P2MP Procedures July 2010 Copyright (c) 2010 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 5 4. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 7 5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 7 6. Object Functions . . . . . . . . . . . . . . . . . . . . . . . 8 7. P2MP Path Computation Procedures . . . . . . . . . . . . . . . 9 7.1. Core Tree Computation Procedures . . . . . . . . . . . . . 10 7.2. Sub Tree Computation Procedures . . . . . . . . . . . . . 10 7.3. PCEP Protocol Extensions . . . . . . . . . . . . . . . . . 10 7.3.1. The Extension of RP Object . . . . . . . . . . . . . . 10 7.3.2. The PCE Sequence Object . . . . . . . . . . . . . . . 11 8. Manageability Considerations . . . . . . . . . . . . . . . . . 13 9. Control of Function and Policy . . . . . . . . . . . . . . . . 13 10. Information and Data Models . . . . . . . . . . . . . . . . . 13 11. Liveness Detection and Monitoring . . . . . . . . . . . . . . 13 12. Verifying Correct Operation . . . . . . . . . . . . . . . . . 13 13. Requirements on Other Protocols and Functional Components . . 13 14. Impact on Network Operation . . . . . . . . . . . . . . . . . 14 15. Security Considerations . . . . . . . . . . . . . . . . . . . 14 16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14 18. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 18.1. Normative References . . . . . . . . . . . . . . . . . . . 14 18.2. Informative References . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 Zhao, et al. Expires January 12, 2011 [Page 2] Internet-Draft PCEP P2MP Procedures July 2010 1. Introduction Multicast services are increasingly in demand for high-capacity applications such as multicast Virtual Private Networks (VPNs), IP- television (IPTV) which may be on-demand or streamed, and content- rich media distribution (for example, software distribution, financial streaming, or data-sharing). The ability to compute constrained Traffic Engineering Label Switched Paths (TE LSPs) for point-to-multipoint (P2MP) LSPs in Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) networks across multiple domains. A domain can be defined as a collection of network elements within a common sphere of address management or path computational responsibility such as an IGP area or an Autonomous Systems. The applicability of the Path Computation Element (PCE) [RFC4655] for the computation of such paths is discussed in [RFC5671], and the requirements placed on the PCE communications Protocol (PCEP) for this are given in [PCE-P2MP-REQ]. This document describes how multiple PCE techniques can be combined to address the requirements. These mechanisms include the use of the per-domain path computation technique specified in [RFC5152], extensions to the backward recursive path computation (BRPC) technique specified in [RFC5441] for P2MP LSP path computation in an inter-domain environment, and a new procedure for core-tree based path computation defined in this document. These three mechanisms are suitable for different environments (topologies, administrative domains, policies, service requirements, etc.) and can also be effectively combined. 2. Terminology Terminology used in this document is consistent with the related MPLS/GMPLS and PCE documents [RFC4461], [RFC4655], [RFC4875], [RFC5376], [RFC5440], [RFC5441]. [RFC5671], and [PCE-P2MP-REQ]. ABR: Area Border Routers. Routers used to connect two IGP areas (areas in OSPF or levels in IS-IS). ASBR: Autonomous System Border Routers. Routers used to connect together ASes of the same or different Service Providers via one or more Inter-AS links. Boundary Node (BN): a boundary node is either an ABR in the context of inter-area Traffic Engineering or an ASBR in the context of inter-AS Traffic Engineering. Zhao, et al. Expires January 12, 2011 [Page 3] Internet-Draft PCEP P2MP Procedures July 2010 Entry BN of domain(n): a BN connecting domain(n-1) to domain(n) along a determined sequence of domains. Exit BN of domain(n): a BN connecting domain(n) to domain(n+1) along a determined sequence of domains. Inter-AS TE LSP: A TE LSP that crosses an AS boundary. Inter-area TE LSP: A TE LSP that crosses an IGP area boundary. LSR: Label Switching Router. LSP: Label Switched Path. PCC: Path Computation Client. Any client application requesting a path computation to be performed by the 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. PCE(i) is a PCE with the scope of domain(i). TED: Traffic Engineering Database. VSPT: Virtual Shortest Path Tree. P2MP LSP Path Tree: A set of LSRs and TE links that comprise the path of a P2MP TE LSP from its ingress LSR to all of its egress LSRs. Core Tree: The core tree is a P2MP tree where the root is the ingress LSR, the transit node and branch node are the BNs of the transit domains and the leaf nodes are the leaf BNs of the leaf domains. Root Boundary Node: The egress LSR from the root domain on the path of the P2MP LSP. Root Domain: The domain that includes the ingress (root) LSR. Transit/branch Domain: A domain that has an upstream and one or more downstream neighbour domain. Leaf Domain: A domain that doesn't has a downstream neighbor domain. Leaf Boundary Nodes: The entry boundary node in the leaf domain. Leaf Nodes: The LSR which is the P2MP LSP's final Zhao, et al. Expires January 12, 2011 [Page 4] Internet-Draft PCEP P2MP Procedures July 2010 Destination. The lead Nodes can be in Root Domain, Transit Domain and Leaf Domain. OF: Objective Function: A set of one or more optimization criterion (criteria) used for the computation of a single path (e.g. path cost minimization), or the synchronized computation of a set of paths (e.g. aggregate bandwidth consumption minimization, etc.). See [RFC4655] and [PCE-OF]. Path Domain Sequence: The known sequence of domains for a path between root and leaf. PCE Sequence: The known sequence of PCEs for calcaulting a path between root and leaf. PCE Topology Tree: A list of PCE Sequences which has all the PCE Sequence for each path of the P2MP LSP path tree. PCE(i): A PCE that performs path computations for domain(i). VSPT: Virtual Shortest Path Tree [RFC5441]. 3. Problem Statement The Path Computation Element (PCE) defined in [RFC4655] is an entity that is capable of computing a network path or route based on a network graph, and applying computational constraints. A Path Computation Client (PCC) may make requests to a PCE for paths to be computed. [RFC4875] describes how to set up P2MP TE LSPs for use in MPLS and GMPLS networks. The PCE is identified as a suitable application for the computation of paths for P2MP TE LSPs [RFC5671]. [RFC5441] specifies a procedure relying on the use of multiple PCEs to compute (P2P) inter-domain constrained shortest paths across a predetermined sequence of domains, using a backward recursive path computation technique. The technique can be combined with the use of path keys [RFC5520] to preserve confidentiality across domains, which is sometimes required when domains are managed by different Service Providers. The PCE communication Protocol (PCEP) [RFC5440] is extended for point-to-multipoint(P2MP) path computation requests and in [PCE-P2MP- EXT]. However, that specification does not provide all the necessary mechanisms to request the computation of inter-domain P2MP TE LSPs. Zhao, et al. Expires January 12, 2011 [Page 5] Internet-Draft PCEP P2MP Procedures July 2010 As discussed in [RFC4461], a P2MP tree is a graphical representation of all TE links that are committed for a particular P2MP LSP. In other words, a P2MP tree is a representation of the corresponding P2MP tunnel on the TE network topology. A sub-tree is a part of the P2MP tree describing how the root or an intermediate P2MP LSPs minimizes packet duplication when P2P TE sub-LSPs traverse common links. As described in [RFC5671] the computation of a P2MP tree requires three major pieces of information. The first is the path from the ingress LSR of a P2MP LSP to each of the egress LSRs, the second is the traffic engineering related parameters, and the third is the branch capability information. Generally, an inter-domain P2MP tree (i.e., a P2MP tree with source and at least one destination residing in different domains) is particularly difficult to compute even for a distributed PCE architecture. For instance, while the BRPC recursive path computation may be well-suited for P2P paths, P2MP path computation involves multiple branching path segments from the source to the multiple destinations. As such, inter-domain P2MP path computation may result in a plurality of per-domain path options that may be difficult to coordinate efficiently and effectively between domains. That is, when one or more domains have multiple ingress and/or egress border nodes, there is currently no known technique for one domain to determine which border routers another domain will utilize for the inter-domain P2MP tree, and no way to limit the computation of the P2MP tree to those utilized border nodes. A trivial solution to the computation of inter-domain P2MP tree would be to compute shortest inter-domain P2P paths from source to each destination and then combine them to generate an inter-domain, shortest-path-to-destination P2MP tree. This solution, however, cannot be used to trade cost to destination for overall tree cost (i.e., it cannot produce a Steiner tree) and in the context of inter- domain P2MP LSPs it cannot be used to reduce the number of domain border nodes that are transited. Computing P2P LSPs individually is not an acceptable solution for computing a P2MP tree. Even per domain path computation [RFC5152] can be used to compute P2P multi-domain paths, but it does not guarantee to find the optimal path which crosses multiple domains. Furthermore, constructing a P2MP tree from individual source to leaf P2P LSPs does not guarantee to produce a least-cost tree. This approach may also be considered to have scaling issues during LSP setup. That is, the LSP to each leaf is signaled separately, and each border node must perform path computation for each leaf. Apart from path computation difficulties faced due to the inter- domain topology visibility issues, the computation of the minimum Zhao, et al. Expires January 12, 2011 [Page 6] Internet-Draft PCEP P2MP Procedures July 2010 P2MP Steiner tree, i.e. one which guarantees the least cost resulting tree, is an NP-complete problem. Moreover, adding and/or removing a single destination to/from the tree may result in an entirely different tree. In this case, the frequent Steiner I tree computation process may prove computationally intensive, and the resulting frequent tunnel reconfiguration may even cause network destabilization. There are several heuristic algorithms presented in the literature that approximate the result within polynomial time that are applicable within the context of a single-domain. This document presents a solution, and procedures and extensions to PCEP to support P2MP inter-domain path computation. 4. Assumptions It is assumed that due to deployment and commercial limitations (e.g., inter-AS peering agreements) the sequence of domains for a path (the path domain tree) will be known in advance. The examples and scenarios used in this document are also based on the following assumptions: o The PCE that serves each domain in the path domain tree is known, and the set of PCEs and their relationships is propagated to each PCE during the first exchange of path computation requests; o Each PCE knows about any leaf LSRs in the domain it serves; o The boundary nodes to use on the LSP are pre-determined and form path of the path domain tree. In this version of the document we do not consider multi-homed domains. Additional assumptions are documented in [RFC5441] and will not be repeated here. 5. Requirements This section summarizes the requirements specific to computing inter- domain P2MP paths. In these requirements we note that the actual computation times by any PCE implementation are outside the scope of this document, but we observe that reducing the complexity of the required computations has a beneficial effect on the computation time regardless of implementation. Additionally, reducing the number of message exchanges and the amount of information exchanged will reduce the overall computation time for the entire P2MP tree. We refer to the "Complexity of the computation" as the impact on these aspects of Zhao, et al. Expires January 12, 2011 [Page 7] Internet-Draft PCEP P2MP Procedures July 2010 path computation time as various parameters of the topology and the P2MP LSP are changed. Its also important that the solution preserves confidentiality across domains, which is required when domains are managed by different Service Providers. Other than the requirements specified in [RFC5376], a number of requirements specific to P2MP are detailed below: 1. The computed P2MP LSP should be optimal when only considering the paths among the BNs. 2. Grafting and pruning of multicast destinations in a domain should have no impact on other domains and on the paths among BNs. 3. The complexity of the computation for each sub-tree within each domain should be dependent only on the topology of the domain and it should be independent of the domain sequence. 4. The number of PCEP request and reply messages should be independent of the number of multicast destinations in each domain. 5. Specifying the domain entry and exit nodes. 6. Specifying which nodes should be used as branch nodes. 7. Reoptimization of existing sub-trees. 8. Computation of P2MP paths that need to be diverse from existing P2MP paths. 6. Object Functions During the computation of a single or a set of P2MP TE LSPs a request to meet specific optimization criteria, called an Objective Function (OF), may be requested. The computation of one or more P2MP TE-LSPs maybe subject to an OF in order to select the "best" candidate paths. A variety of objective functions have been identified as being important during the computation of inter-domain P2MP LSPs. These are: 1. The sub-tree within each domain should be optimized, which can be either the Minimum cost tree [PCE-P2MP-REQ] or Shortest path tree [PCE-P2MP-REQ]. Zhao, et al. Expires January 12, 2011 [Page 8] Internet-Draft PCEP P2MP Procedures July 2010 2. The P2MP LSP paths should be optimal while only considering the entry and exit nodes of each domain as the transit, branch and leaf nodes of the P2MP LSP path. (That is, the Core Tree should be optimized.) 3. It should be possible to limit the number of entry points to a domain. 4. It should be possible to force the branches for all leaves within a domain to be in that domain. 7. P2MP Path Computation Procedures The following sections describe the core tree based procedures to satisfy the requirements specified in the previous section. A core tree based solution provides an optimal inter-domain P2MP TE LSP and meets the requirements and OFs outlined in previous sections. A core tree is a path tree with nodes from each domain corresponding to the PCE topology which satisfies the following conditions: o The root of the core tree is the ingress LSR in the root domain; o The leaf of the core tree is the entry node in the leaf domain; o The transit and branch nodes of the core tree are from the entry and exit nodes from the transit and branch domains. Procedure Phase 1: Build the P2MP LSP Core Tree. In this phase, the core tree, where the root is the ingress LSR, the transit node and branch node are the BNs of the transit domains and the leaf nodes are the leaf BNs of the leaf domains, is computed. Procedure Phase 2: Grafting destinations to the P2MP LSP Core Tree. Once the core tree is built, the grafting of all the leaf nodes from each domain to the core tree can be achieved by a number of algorithms. One algorithm for doing this phase is that the root PCE will send the request with C bit set for the path computation to the destination(s) directly to the PCE where the destination(s) belong(s) along with the core tree computed from the phase 1. Zhao, et al. Expires January 12, 2011 [Page 9] Internet-Draft PCEP P2MP Procedures July 2010 7.1. Core Tree Computation Procedures Computing the complete P2MP LSP path tree is done in two phases: The algorithms to compute the optimal large core tree are outside scope of this document. In the case that the number of domains and the number of BNs are not big, the following extended BRPC based procedure can be used to compute the core tree. BRPC Based Core Tree Path Computation Procedure: 1. Using the BRPC procedures to compute the VSPT(i) for each leaf BN(i), i=1 to n, where n is the total number of entry nodes for all the leaf domains. In each VSPT(i), there are a number of P(i) paths. 2. When the root PCE has computed all the VSPT(i), i=1 to n, take one path from each VSPT and form a set of paths, we call it a PathSet(j), j=1 to M, where M=P(1)xP(2)...xP(n); 3. For each PathSet(j), there are n S2L (Source to Leaf BN) paths and form these n paths into a Core Tree(j); 4. There will be M number of Core Trees computed from step3. Apply the OF to each of these M Core Trees and find the optimal Core Tree. 7.2. Sub Tree Computation Procedures The algorithms to compute the optimal large sub tree are outside scope of this document. In the case that the number of destinations and the number of BNs within a domain are not big, the incremental procedure based on p2p path computation usign the OSPF can be used. 7.3. PCEP Protocol Extensions 7.3.1. The Extension of RP Object The extended format of the RP object body to include the C bit is as follows: The C bit is added in the flag bits field of the RP object to signal the receiver of the message that the request/reply is for inter- domain P2MP Core Tree or not. Zhao, et al. Expires January 12, 2011 [Page 10] Internet-Draft PCEP P2MP Procedures July 2010 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Flags |C|O|B|R| Pri | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Request-ID-number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Optional TLV(s) // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: RP Object Body Format The following flag is added in this draft: C bit ( P2MP Core Tree bit - 1 bit): 0: This indicates that this is normal PCReq/PCRrep for P2MP. 1: This indicates that this is PCReq or PCRep message for inter- domain Core Tree P2MP. When the C bit is set, then the request message should have the Core Tree passed along with the destinations which and then graphed to the tree. 7.3.2. The PCE Sequence Object The PCE Sequence Object is added to the existing PCE protocol. A list of this objects will represent the PCE topology tree. A list of Sequence Objects can be exchanged between PCEs during the PCE capability exchange or on the first path computation request message between PCEs. In this case, the request message format needs to be changed to include the list of PCE Sequence Objects for the PCE inter-domain P2MP calculation request. Each PCE Sequence can be obtained from the domain sequence for a specific path. All the PCE sequences for all the paths of P2MP inter-domain form the PCE Topology Tree of the P2MP LSP. The format of the new PCE Sequence Object for IPv4 (Object-Type 3) is as follows: Zhao, et al. Expires January 12, 2011 [Page 11] Internet-Draft PCEP P2MP Procedures July 2010 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Object-Class | OT |Res|P|I| Object Length (bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 address for root PCE | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 address for the downstream PCE | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 address for the downstream PCE | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | !! | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 address for the PCE corresponding to the leafDomain | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: The New PCE Sequence Object Body Format for IPv4 The format of the new PCE Sequence Object for IPv6 (Object-Type 3) is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Object-Class | OT |Res|P|I| Object Length (bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv6 address for root PCE | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv6 address for the downstream PCE | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv6 address for the downstream PCE | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | !! | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv6 address for the PCE corresponding to the leafDomain | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: The New PCE Sequence Object Body Format for IPv6 Zhao, et al. Expires January 12, 2011 [Page 12] Internet-Draft PCEP P2MP Procedures July 2010 8. Manageability Considerations [PCE-P2MP-REQ] describes various manageability requirements in support of P2MP path computation when applying PCEP. This section describes how manageability requirements mentioned in [PCE-P2MP-REQ] are supported in the context of PCEP extensions specified in this document. Note that [RFC5440] describes various manageability considerations in PCEP, and most of manageability requirements mentioned in [PCE-P2MP P2MP] are already covered there. 9. Control of Function and Policy In addition to configuration parameters listed in [RFC5440], the following parameters MAY be required. o P2MP path computations enabled or disabled. o Advertisement of P2MP path computation capability enabled or disabled (discovery protocol, capability exchange). 10. Information and Data Models As described in [PCE-P2MP-REQ], MIB objects MUST be supported for PCEP extensions specified in this document. 11. Liveness Detection and Monitoring There are no additional considerations beyond those expressed in [RFC5440], since [PCE-P2MP-REQ] does not address any additional requirements. 12. Verifying Correct Operation There are no additional considerations beyond those expressed in [RFC5440], since [PCE-P2MP-REQ] does not address any additional requirements. 13. Requirements on Other Protocols and Functional Components As described in [PCE-P2MP-REQ], the PCE MUST obtain information about the P2MP signaling and branching capabilities of each LSR in the Zhao, et al. Expires January 12, 2011 [Page 13] Internet-Draft PCEP P2MP Procedures July 2010 network. Protocol extensions specified in this document does not provide such capability. Other mechanisms MUST be present. 14. Impact on Network Operation It is expected that use of PCEP extensions specified in this document will not have significant impact on network operations. 15. Security Considerations As described in [PCE-P2MP-REQ], P2MP path computation requests are more CPU-intensive and also use more link bandwidth. Therefore, it may be more vulnerable to denial of service attacks. Therefore, it is more important that implementations conform to security requirements of [RFC5440], and the implementer utilize those security features. 16. IANA Considerations A new flag of the RP object (specified in [RFC5440]) is defined in this document. TBD. 17. Acknowledgements The authors would like to thank Adrian Farrel and Dan Tappan for their valuable comments on this draft. 18. References 18.1. Normative References [1] Vasseur, JP. and JL. Le Roux, "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, March 2009. [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [3] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang, "OSPF Protocol Extensions for Path Computation Element (PCE) Zhao, et al. Expires January 12, 2011 [Page 14] Internet-Draft PCEP P2MP Procedures July 2010 Discovery", RFC 5088, January 2008. [4] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang, "IS-IS Protocol Extensions for Path Computation Element (PCE) Discovery", RFC 5089, January 2008. [5] Yasukawa, S. and A. Farrel, "PCC-PCE Communication Requirements for Point to Multipoint Multiprotocol Label Switching Traffic Engineering (MPLS-TE)", draft-ietf-pce-p2mp-req-05 (work in progress), January 2010. [6] Yasukawa, S. and A. Farrel, "Applicability of the Path Computation Element (PCE) to Point-to-Multipoint (P2MP) Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering (TE)", draft-ietf-pce-p2mp-app-02 (work in progress), August 2009. [7] Yasukawa, S., "Signaling Requirements for Point-to-Multipoint Traffic-Engineered MPLS Label Switched Paths (LSPs)", RFC 4461, April 2006. [8] Bitar, N., Zhang, R., and K. Kumaki, "Inter-AS Requirements for the Path Computation Element Communication Protocol (PCECP)", RFC 5376, November 2008. [9] Aggarwal, R., Papadimitriou, D., and S. Yasukawa, "Extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) for Point-to-Multipoint TE Label Switched Paths (LSPs)", RFC 4875, May 2007. [10] Roux, J., Vasseur, J., and Y. Lee, "Encoding of Objective Functions in the Path Computation Element Communication Protocol (PCEP)", draft-ietf-pce-of-06 (work in progress), December 2008. [11] Nishioka, I. and D. King, "The use of SVEC (Synchronization VECtor) list for Synchronized dependent path computations", draft-ietf-pce-pcep-svec-list-05 (work in progress), June 2010. [12] Vasseur, JP., Zhang, R., Bitar, N., and JL. Le Roux, "A Backward-Recursive PCE-Based Computation (BRPC) Procedure to Compute Shortest Constrained Inter-Domain Traffic Engineering Label Switched Paths", RFC 5441, April 2009. 18.2. Informative References [13] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, August 2006. Zhao, et al. Expires January 12, 2011 [Page 15] Internet-Draft PCEP P2MP Procedures July 2010 Authors' Addresses Quintin Zhao Huawei Technology 125 Nagog Technology Park Acton, MA 01719 US Email: qzhao@huawei.com Zafar Ali Cisco Systems Email: zali@cisco.com Tarek Saad Cisco Systems US Email: tsaad@cisco.com Daniel King Old Dog Consulting UK Email: daniel@olddog.co.uk Contributors' Addresses David Amzallag British Telecommunications plc UK Email: david.Amzallag@bt.com Fabien Verhaeghe Thales Communication France 160 Bd Valmy 92700 Colombes France Email: fabien.verhaeghe@gmail.com Kenji Kumaki KDDI R&D Laboratories, Inc. Japan Email: ke-kumaki@kddi.com Zhao, et al. Expires January 12, 2011 [Page 16]