Network Working Group Seisho Yasukawa (NTT) Internet Draft Dimitri Papadimitriou (Alcatel) Jean Philippe Vasseur (Cisco) Adrian Farrel (Old Dog) Yuji Kamite (NTT Communications) Markus Jork (Avici) Rahul Aggarwal (Juniper) Andrew G. Malis(Tellabs) Alan Kullberg (Motorola) Expiration Date: March 2004 October 2003 Requirements for Point to Multipoint extension to RSVP-TE Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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 Point-to-Multipoint (P2MP) Traffic Engineering (TE) extensions to Multiprotocol Label Switching (MPLS). It specifies functional requirements for RSVP-TE in order to deliver P2MP applications over a MPLS TE infrastructure. It is intended that potential solutions, that specify RSVP-TE procedures for P2MP TE LSP setup, use these requirements as a guideline. It is not intended to specify solution specific details in this document. Yasukawa, et. al. [Page 1]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 It is intended that the requirements presented in this document are not limited to the requirements of packet switched networks, but also encompass the requirements of TDM, lambda and port switching networks managed by Generalized MPLS (GMPLS) protocols. Protocol solutions developed to meet the requirements set out in this document must be equally applicable to MPLS and GMPLS. Table of Contents 1. Introduction .................................................. 3 2. Definitions ................................................... 4 2.1 Acronyms .................................................. 4 2.2 Terminology ............................................... 4 2.3 Conventions ............................................... 5 3. Problem statements ............................................ 5 3.1 Motivation ................................................ 5 3.2 Requirements overview ..................................... 6 4. Application Specific Requirements ............................. 8 4.1 P2MP tunnel for IP multicast data ......................... 8 4.2 P2MP backbone network for IP multicast network ............ 9 4.3 Layer 2 Multicast Over MPLS ...............................10 4.4 VPN multicast network .....................................10 4.5 GMPLS network .............................................11 5. Requirements for P2MP capability exptension ...................12 5.1 P2MP LSP tunnels ..........................................12 5.2 P2MP explicit routing .....................................12 5.3 Explicit Path Loose Hops and Widely Scoped Abstract Nodes .13 5.4 P2MP LSP establishment, teardown, and modification mechanisms ................................................14 5.5 Failure Reporting and Error Recovery ......................14 5.6 Record route of P2MP TE LSP tunnels .......................15 5.7 Call Admission Control (CAC) and QoS control mechanism of P2MP LSP tunnels .......................................15 5.8 Rerouting of P2MP TE LSP ..................................16 5.9 IPv4/IPv6 support .........................................16 5.10 P2MP MPLS Label ..........................................16 5.11 Routing advertisement of P2MP capability .................17 5.12 Multi-Area/AS LSP ........................................17 5.13 P2MP MPLS management .....................................17 6. Security Considerations........................................17 7. Acknowledgements ..............................................17 8. References ....................................................18 9. Author's Addresses ............................................19 Yasukawa, et. al. [Page 2]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 1. Introduction This document presents a set of requirements for Point-to-Multipoint (P2MP) Traffic Engineering (TE) extensions to Multiprotocol Label Switching (MPLS). It specifies functional requirements for RSVP-TE [RFC3209] in order to deliver P2MP applications over a MPLS TE infrastructure. It is intended that potential solutions, that specify RSVP-TE procedures for P2MP TE LSP setup, use these requirements as a guideline. It is not intended to specify solution specific details in this document. It is intended that the requirements presented in this document are not limited to the requirements of packet switched networks, but also encompass the requirements of TDM, lambda and port switching networks managed by Generalized MPLS (GMPLS) protocols. Protocol solutions developed to meet the requirements set out in this document must be equally applicable to MPLS and GMPLS. Content Distribution (CD), Interactive multi-media (IMM), and VPN multicast are applications that are best supported with multicast capabilities. One possible solution would be to setup multiple P2P TE LSPs, one to each of the required egress LSRs. This requires replicating incoming packets to all the P2P LSPs at the ingress LSR to accommodate multipoint communication. This is sub-optimal. It places the replication burden on the ingress LSR and hence has very poor scaling characteristics. It also wastes bandwidth resources, memory and MPLS (e.g. label) resources in the network. Hence, to provide TE for a P2MP application in an efficient manner in a large scale environemnt, P2MP TE mechanisms are required. Existing MPLS P2P TE mechanisms have to be enhanced to support P2MP TE LSP setup. This should be achieved without running a multicast routing protocol in the network core and with maximum re-use of the existing MPLS protocols. A P2MP LSP will be setup with TE constraints and will allow efficient packet replication at various branching points in the network. RSVP-TE will be used for setting up a P2MP LSP with enhancements to existing P2P TE LSP procedures. The P2MP TE LSP setup mechanism will include the ability to add/remove receivers to/from an existing P2MP LSP. The problem statement is discussed in the following section. This document discusses various applications that can use P2MP MPLS TE. Yasukawa, et. al. [Page 3]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 Detailed requirements for the setup of a P2MP MPLS TE LSP using RSVP-TE are described. Application specific requirements are also described. 2. Definitions 2.1 Acronyms P2P: Point-to-point P2MP: Point-to-multipoint 2.2 Terminology The reader is assumed to be familiar with the terminology in [RFC3031] and [RFC3209]. P2MP TE LSP: A traffic engineered label switched path that has one unique ingress LSR (also referred to as the root) and more than one egress LSR (referred to as the leaf). P2MP path: The ordered set of LSRs and links that comprise the P2MP LSP. sub-P2MP path: A sub-P2MP path is a portion of a P2MP path starting at a particular LSR that is a member of the P2MP path and includes ALL downstream LSRs that are also members of the P2MP path. ingress LSR: It is responsible for initiating the signaling messages that set up, modify and teardown the LSP branch LSR: A LSR that has more than one downstream LSR. A branch LSR receives Yasukawa, et. al. [Page 4]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 a single MPLS frame, makes a duplicate of it, and sends each to downstream interfaces. graft LSR: A LSR that is already a member of the P2MP path and is in process of signaling a new sub-P2MP path. prune LSR: A LSR that is already a member of the P2MP path and is in process of tearing down an existing sub-P2MP path. egress LSR: One of potentially many destinations of the P2MP LSP. Note that in some P2MP paths, an egress LSR may also have one or more downstream LSRs. Such an egress LSR may also be referred to as a branch LSR. 2.3 Conventions 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 [5]. 3. Problem Statement 3.1 Motivation Content Distribution (CD), Interactive multi-media (IMM), and VPN multicast are applications that are best supported with multicast capabilities. IP Multicast provides P2MP communication. However, there are no Traffic Engineering (TE) capabilities or QoS guarantees with existing IP multicast protocols. Note that Diff-serv (see [RFC2475],[RFC2597] and [RFC3246]) combined with IP multicast routing is not sufficient for P2MP applications for many of the same reasons that it is not sufficient for unicast applications TE and constraint based routing are required to enable and scale the efficient management of network resources, mechanism to prevent congestion (including Call Admission Function combined with explicit source routing, Diffserv), and to enable sub-second rerouting around network failures. Furthermore Yasukawa, et. al. [Page 5]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 there are no existing P2MP mechanisms for carrying layer 2 or SONET/SDH multicast traffic over MPLS. TE capabilities are desirable for both these applications. One possible solution would be to setup multiple P2P TE LSPs, one to each of the required egress LSRs. This requires replicating incoming traffic to all the P2P LSPs at the ingress LSR to accommodate multipoint communication. This is clearly sub-optimal. It places the replication burden on the ingress LSR and hence has very poor scaling characteristics. It also wastes bandwidth resources, memory and MPLS (e.g. label) resources in the network. Hence, to provide MPLS TE [RFC2702] for a P2MP application in an efficient manner in a large scale environment, P2MP TE mechanisms are required. Existing MPLS P2P TE mechanisms have to be enhanced to support P2MP TE LSP setup. 3.2. Requirements Overview This document is proposing requirements for the setup of P2MP TE LSPs. This should be achieved without running a multicast routing protocol in the network core and with maximum re-use of the existing MPLS protocols. Note that the use of MPLS forwarding to carry the multicast traffic may also be useful in the context of some network design where it is being desired to avoid running some multicast routing protocol like PIM [PIM-SM] or BGP (which might be required for the use of PIM). A P2MP LSP will be setup with TE constraints and will allow efficient MPLS packet replication at various branching points in the network. RSVP-TE will be used for setting up a P2MP LSP with enhancements to existing P2P TE LSP procedures. The P2MP TE LSP setup mechanism will include the ability to add/remove receivers to/from an existing P2MP LSP and should support all the TE LSP management procedures defined for P2P TE LSP (like the non disruptive rerouting (so called "Make before break" procedure). The computation of P2MP TE paths is implementation dependent and is beyond the scope of the solutions that are built with this document as a guideline. The MPLS WG will specify how to build solutions for the setup a P2MP TE LSP. The usage of those solutions will be application dependent and is out of the scope of this draft. Yasukawa, et. al. [Page 6]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 Consider the following figure. Source 1 (S1) | I-LSR1 | | | | R2----E-LSR3--LSR1 LSR2---E-LSR2--Receiver 1 (R1) | : R3----E-LSR4 E-LSR5 | : | : R4 R5 Figure 1. The above figure shows I(Ingress)-LSR1, E(Egress)-LSR2, E-LSR3 and E-LSR4. I-LSR1 is attached to a traffic source that is generating traffic for a P2MP application. E-LSR2, E-LSR3 and E-LSR4 are attached to receivers that are interested in receiving traffic for the application. The following are the objectives that we wish to achieve: a) A P2MP TE LSP path information which satisfies various constrains is pre-determined and supplied to ingress I-LSR1. Typical constraints are bandwidth requirements, resource class affinities, fast rerouting, preemption, along with several potential other constraints. There should not be any restriction on the possibility to support the set of constraints already defined for point to point TE LSPs. b) Set up a P2MP TE LSP from I-LSR1 to E-LSR2, E-LSR3 and E-LSR4 using the path information which could have been computed by some off-line or on-line algorithms. c) In this case, the branch LSR1 should replicate incoming packets and send them to E-LSR3 and E-LSR4. d) The P2MP TE LSP should be setup by enhancing existing RSVP-TE P2P procedures and without any requirement for multicast routing protocol in the network core. e) The solution should provide the ability to gracefully modify P2MP TE LSP (i.e add/remove some part of the p2mp TE LSP without requiring to entirely tearing down or setting up a completely new p2mp TE LSP). Such operations should be performed in a non traffic disruptive fashion. In this case, a sub-P2MP path LSR2->E-LSR5 is grafted and pruned based on Yasukawa, et. al. [Page 7]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 traffic destination change. 4. Application Specific Requirements This section describes some of the applications that P2MP MPLS TE is applicable to along with application specific requirements, if any. 4.1 P2MP tunnel for IP multicast data One typical scenario is to use P2MP TE LSPs as P2MP tunnels of multicast data traffic (e.g. IP mcast). In this scenario, a P2MP LSP tunnel is established between an ingress LSR which accomodates IP multicast source and several egress LSRs which accomodate several IP multicast receivers. Instead of using IP multicast routing protocol in the network core, a P2MP LSP tunnel is established over the network and IP multicast data are tunnelled from an ingress LSR node to multiple egress leaf LSRs with the data replication at the branch LSRs in the network core. Figure 2 shows this example. Note that a P2MP TE LSP can be established over multiple AREAs/ASs. Mcast Source | +---------------I-LSR0----------------+ | | | | LSR0 +----E-LSR2---R2 | / \ / | R1---E-LSR1---LSR2-----LSR1 LSR3----LSR4----E-LSR3---R3 | / \ \ | | / \ +----E-LSR4---R4 +-------B-LSR1---------B-LSR2---------+ +-------- / ------++------ \ ---------+ | | || | R5---E-LSR5--------LSR5 || IPmcast Network | | / \ || | +-E-LSR6---E-LSR7-++----MR0--MR1------+ | | | | R6 R7 R8 R9 Figure 2 Yasukawa, et. al. [Page 8]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 4.2 P2MP backbone network for IP multicast network In this scenario, P2MP TE LSPs are utilized to construct a P2MP backbone network for multicast network (e.g. IPmcast network). Each IP multicast access networks is interconnected by a P2MP TE LSP. A P2MP LSP is established from an ingress LSR which accomodates IP multicast network that has a Mcast Source to multiple egress LSRs which accomodate an IP multicast network. In this scenario, ingress/egress LSRs placed at the edge of multicast network must handle IP multicast routing protocol. This means that each ingress/egress LSR exchanges IP multicast routing messages as neighbour router. Figure 3 shows a network example of this scenario. A P2MP LSP is established from a I-LSR1 to E-LSR2, E-LSR3, E-LSR4 and each ingress/egress LSR exchanges the multicast routing messages each other. As specified in the section on the problem statement it should be possible for a solution to add/remove egress LSRs to/from the P2MP MPLS TE LSP. IP multicast group membership distribution between the egress LSRs may change frequently. This in turn may require a potential P2MP MPLS TE solution, that is suitable for IP multicast, to handle additions/deletions of egress LSRs at a rapid rate. It is recommended to support a message exchange mechanism on top of P2MP LSP setup mechanism to support multicast (S, G) Join/ Leave and to allow the ingress LSR to hold sufficient information in order to optimise multicast FEC on sender nodes. Though several schemes exist to handle this scenario, these are out of scope of this document. This document only describes requirements to setup a P2MP TE LSP. Yasukawa, et. al. [Page 9]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 Mcast Source | +-----MR-----+ | | | | MR | +------|-----+ +---------------I-LSR1----------------+ | // ||| \\ | | // ||| \\ | | // |LSR| \\ | | ___//____/|_____\\____ | | / // ||| \\ \ | | | // ||| \\ | | +-----E-LSR2----E-LSR3-----E-LSR4-----+ +---- / ---++------|------++--- \ ----+ | | || | || | | R1---MR---MR || MR || MR__ | | / \ || / \ || / \ \MR---R8 +--MR--MR--++----MR--MR---++--MR--MR--+ | | | | | | R2 R3 R4 R5 R6 R7 Figure 3 4.3 Layer 2 Multicast Over MPLS Existing layer 2 networks offer multicast video services. These are typically carried using layer 2 NBMA technology such as ATM or layer 2 BA technology such as Ethernet. It may be desirable to deliver these layer 2 multicast services over a converged MPLS infrastructure where P2MP TE LSPs are used instead. 4.4 VPN multicast network In this scenario, P2MP TE LSPs are utilized to construct a provider network which can deliver VPN multicast service(s) to its customers. A P2MP TE LSP is established between all the PE routers which accommodate the customer private network(s) that handle the IP multicast packets. Each PE router must handle VPN instance. For example, in Layer3 VPN like BGP/MPLS based IP VPN [BGP/MPLS IP VPNs], this means that each PE router must handle both private multicast VRF tables and common multicast routing and forwarding table. And each PE router exchanges private multicast routing information between the corresponding PE routers. It is Yasukawa, et. al. [Page 10]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 desirable that P2MP MPLS TE can be used for Layer3 VPN's data transmission. Another example is Layer2 VPN that supports multipoint LAN connectivity service. In Ethernet network environment, IP multicast data is flooded to the appropriate Ethernet port(s). In Ethernet multipoint L2 VPN service provided by MPLS, this function is achieved by switching MPLS encapsulated frames towards the relevant PE nodes. But if existing P2P TE LSPs are used as tunnels between PEs, any ingress PE must duplicate the frames and the send them to the corresponding PEs. This means data stream is flooded just from ingress PE, which will waste provider's network resources. So, for Layer 2 VPNs, it is desirable that P2MP MPLS TE LSPs are used for data transmission instead of P2P MPLS TE LSPs, contributing in turn to savings of network resources. 4.5 GMPLS Network GMPLS supports only P2P TE-LSPs just like MPLS. GMPLS enhances MPLS to support four new classes of interfaces Layer-2 Switch Capable (L2SC), Time-Division Multiplex (TDM), Lambda Switch Capable (LSC) and Fiber-Switch Capable (FSC) in addition to Packet Switch Capable (PSC) already supported by MPLS. All of these interface classes have so far been limited to P2P TE LSPs (see [RFC 3473] and [RFC 3471]). The requirement for P2MP services for non-packet switch interfaces is similar to that for PSC interfaces. In particular, cable distribution services such as video distribution are prime candidates to use P2MP features. Therefore, it is a requirement that all the features/mechanisms (and protocol extensions) that will be defined to provide MPLS P2MP TE LSPs will be equally applicable to P2MP PSC and non-PSC TE-LSPs. This also means that solutions for MPLS P2MP TE-LSPs when applied to GMPLS P2MP PSC and non-PSC TE-LSPs shall be backward and forward compatible with the other features of GMPLS including: o control and data plane separation (IF_ID RSVP_HOP and IF_ID ERROR_SPEC), o full support of numbered and unnumbered TE links (see [RFC 3477] and [GMPLS-ROUTING]), o use of the GENERALIZED_LABEL_REQUEST and the GENERALIZED_LABEL (C-Type 2 and 3) in conjunction with the LABEL_SET and the ACCEPTABLE_LABEL_SET object, o processing of the ADMIN_STATUS object, o processing of the PROTECTION object, o support of Explicit Label Control, Yasukawa, et. al. [Page 11]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 o processing of the Path_State_Removed Flag, o handling of Graceful Deletion procedures. In addition, since non-PSC TE-LSPs may have to be processed in environments where the "P2MP capability" could be limited, specific constraints may also apply during the P2MP TE Path computation. Being technology specific, these constraints are outside the scope of this document. However, technology independent constraints (i.e. constraints that are applicable independently of the LSP class) should be allowed during P2MP TE LSP message processing. It has to be emphasized that path computation and management techniques shall be as close as possible than those being used for PSC P2P and P2MP TE LSPs. 5. Requirements for P2MP capability extension 5.1 P2MP LSP tunnels The P2MP RSVP-TE extensions MUST be applicable to signaling LSPs of different traffic types. For example, it must be possible to signal a P2MP LSP to carry any kind of payload being packet or non-packet based (including frame, cell, TDM un/structured, etc.) Carrying IP multicast or Ethernet traffic within a P2MP tunnel are typical examples. As with P2P MPLS technology[RFC3031], traffic is classified with FEC in this extension. All packets which belong to a particular FEC and which travel from a particular node MUST follow the same P2MP path. In order to scale to a large number of branches, P2MP TE LSPs should be identified by unique identifier that is constant for the whole LSP regardless of the number of branches and/or leaves. Therefore, the identification of the P2MP session by its destination addresses is not adequate. 5.2 P2MP explicit routing Various optimizations in P2MP path formation need to be applied to meet various needs such as bandwidth guarantees, delay requirements, and minimization of the total P2MP path cost. The P2MP TE solution therefore MUST provide a means of establishing arbitrary P2MP paths. Figure 4 shows two typical examples. Yasukawa, et. al. [Page 12]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 A A | / \ B B C | / \ / \ C D E F G | / \ / \/ \ / \ D--E*-F*-G*-H*-I*-J*-K*--L H I J KL M N O Steiner P2MP path SPF P2MP path Figure 4 Examples of P2MP LSP topology One example is Steiner[STEINER] P2MP path (Cost minimum P2MP path). This P2MP path is suitable for constructing cost minimum P2MP path. To realize this P2MP path, several intermediate LSRs must be both MPLS data terminating LSR and transit LSR (LSR E, F, G, H, I, J, K, in the figure). This means that the LSR must perform both label swapping and popping at the same time. Therefore, the P2MP TE solution MUST support a mechanism that can setup this kind of terminate LSR between a ingress LSR and egress LSRs. Another example is CSPF (Constraint Shortest Path Fast) P2MP path. By some metric (which can be set upon any specific criteria like the delay, bandwidth, a combination of those), one can calculate a cost minimum P2MP path. This P2MP path is suitable for carrying real time traffic. To support explicit setup of any reasonable P2MP path shape, a P2MP TE solution must support some form of explicit source-based control of the P2MP path. This can be used by the ingress LSR to setup the P2MP LSP. Being implementation specific (more precisely dependent of the data structure specific representation and its processing), the detailed method for controlling the P2MP TE LSP topology depends on how the control plane represents the P2MP TE LSP data plane entity. For instance, a P2MP TE LSP can be simply represented by its individual branches or as a whole. Here also, effectiveness of the potential solutions is left outside the scope of this document. In any case, it is expected that this control must be driven by the ingress LSR. 5.3 Explicit Path Loose Hops and Widely Scoped Abstract Nodes A P2MP path is completely specified if all of the required Yasukawa, et. al. [Page 13]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 branches and hops between a sender and leaf LSR are indicated. A P2MP path is partially specified if only a subset of intermediate branches and hops are indicated. This may be achieved using loose hops in the explicit path, or using widely scoped abstract nodes such as IPv4 prefixes shorter than 32 bits or AS numbers. A partially specified P2MP path may be particularly useful in inter-area and inter-AS situations. Protocol solutions SHOULD include a way to specify loose hops and widely scoped abstract nodes in the explicit source- based control of the P2MP path as defined in the previous section. Where this support is provided, protocol solutions MUST allow downstream LSRs to apply further explicit control to the P2MP path to resolve a partially specified path into a (more) completely specified path. Protocol solutions MUST allow the P2MP path to be completely specified at the ingress where sufficient information exists to allow the full path to be computed. In all cases, the egress nodes of the P2MP LSP must be fully specified. 5.4 P2MP LSP establishment, teardown, and modification mechanisms The P2MP TE solution must support large scale P2MP TE LSPs establishment and teardown in a scalable manner. In addition to whole P2MP TE LSP establishment and teardown mechanism, it SHOULD implement partial P2MP path modification mechanism. For the purpose of adding sub-P2MP TE LSPs for existing P2MP TE LSP, the extension SHOULD support grafting mechanism. For the purpose of deleting a sub-P2MP TE LSPs from existing P2MP TE LSP, the extension SHOULD support pruning mechanism. It is RECOMMENDED that these grafting and pruning operations do not cause any additional processing in nodes except along the path to the grafting and pruning node and its downstream nodes. 5.5 Failure Reporting and Error Recovery Failure events may cause egress nodes or sub-P2MP LSPs to become detached from the P2MP LSP. These events must be reported upstream as Yasukawa, et. al. [Page 14]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 for a P2P LSP. Protection and recovery techniques SHOULD be applied to the LSP to build new sub-P2MP LSPs or use backup sub-P2MP LSPs to restore the data to the severed egress nodes. The report of the failure of delivery to fewer than all of the egress nodes SHOULD NOT cause automatic teardown of the P2MP LSP. That is, while some egress nodes remain connected to the P2MP path it should be a matter of local policy at the ingress whether the P2MP LSP is retained. When all egress node downstreams of a branch node have become disconnected from the P2MP path, and the branch node is unable to restore connectivity to any of them through recovery or protection mechanisms, the branch node MAY remove itself from the P2MP path. Since the faults that severed the various downstream egress nodes from the P2MP path may be disperate, the branch node MUST report all such errors to its upstream neighbor. 5.6 Record route of P2MP TE LSP tunnels Being able to identify the established topology of P2MP LSP is very important for various purpose:Management, operation of some local recovery mechanism like Fast Reroute [FRR]. A network operator uses this information to manage P2MP LSP. Therefore, topology information MUST be collected and updated after P2MP LSP establishment and modification process. For this purpose, conventional Record Route mechanism is useful. As with other conventional mechanism, this information should be forwarded upstream towards the sender node. The P2MP TE solution MUST support a mechanism which can collect and update P2MP path topology information after P2MP LSP establishment and modification process. It is RECOMMENDED that those information are collected in a data format by which the sendor node can recognize the P2MP path topology without involving some complicated data calculation process. 5.7 Call Admission Control (CAC) and QoS Control mechanism of P2MP LSP tunnels P2MP LSP share network resource with P2P LSP. Therefore it is important to use CAC and QoS as P2P LSP for easy and scalable operation. In particular, it should be highlighted that because Yasukawa, et. al. [Page 15]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 mutliacst traffic cannot make use of point to point TE LSP, multicast traffic cannot be easily taken into account by point to point in order to perform CAC. The use of P2MP TE LSP will now allow for an accounting of the unicast and multicast traffic for bandwidth reservation. P2MP TE solution MUST both supports FF and SE reservation style. P2MP TE solution MUST be applicable to Diffserv-enabled network that can provide consistent QoS control in P2MP LSP traffic. This solution SHOULD also satisfy DS-TE requirement [RFC3564] and interoprable smoothly with current P2P DS-TE protocol specification. 5.8 Rerouting of P2MP TE LSP The detection of a more optical path and network resource failure(s) (such as link(s) and node(s)) are examples of situation where P2MP TE LSP re-routing is needed. While re-routing is in progress, an important requirement is avoiding traffic disruption. An additional requirement is avoiding double bandwidth reservation (over the common parts between the old and new LSP) through the use of resource sharing. Make-before-break (see [RFC 3209]) delivers simultaneously a solution to these requirements. Make-Before-Break MUST be supported for a P2MP TE LSP to ensure that there is no traffic disruption when the P2MP TE LSP is rerouted. And a P2MP TE solution MUST support P2MP fast rerouting mechanism to handle P2MP applications sensitive to traffic disruption. 5.9 IPv4/IPv6 support A P2MP TE solution MUST be applicable to IPv4/IPv6. 5.10 P2MP MPLS Label A P2MP TE solution MUST support establishment of both P2P and P2MP TE LSP and MUST NOT impede the operation of P2P LSPs within the same network. A P2MP TE solution MUST be specified in such a way that it allows P2MP and P2P LSPs to be signaled on the same interface. Labels for P2MP TE LSPs and P2P TE LSPs MAY be assigned from shared or dedicated label space(s). Label space shareability is implementation specific. Yasukawa, et. al. [Page 16]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 5.11 Routing advertisement of P2MP capability This document has identified several high-level requirements for enhancements to routing protocols to support P2MP MPLS. These are needed to facilitate the computation of P2MP paths using TE constraints so that explicit source-control may be applied to the LSP paths as they are signaled through the network. These requirements include but not restricted to: - the ability of an LSR to support branching - the ability of an LSR to act as an egress and a branch for the same LSP. The applicability of these requirements is for further study. These requirements are developed in a separate document. 5.12 Multi-Area/AS LSP P2MP TE solution SHOULD support multi-Area/AS LSP. 5.13 P2MP MPLS management The MPLS MIB should be enhanced to provide P2MP TE LSP management. P2MP TE LSPs MUST have a unique identifier whose definition MAY be partially or entirely shared with P2P TE LSP identifiers used for management purposes. 6. Security Considerations Security considerations will be addressed in a future revision of this document. 7. Acknowledgements The authors would like to thank George Swallow, Ichiro Inoue and Dean Cheng for his review and suggestion of an earlier draft of this document. Yasukawa, et. al. [Page 17]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 8. References [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V. and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, December 2001. [RFC3031] Rosen, E., Viswanathan, A. and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, January 2001. [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z. and W. Weiss, "An Architecture for Differentiated Services", RFC 2475, December 1998. [RFC2597] Heinanen, J., Baker, F., Weiss, W. and J. Wroclawski, "Assured Forwarding PHB Group", RFC 2597, June 1999. [RFC3246] Davie, B., Charny, A., Bennet, J.C.R., Benson, K., Le Boudec, J.Y., Davari, S., Courtney, W., Firioiu, V. and D. Stiliadis, "An Expedited Forwarding PHB (Per-Hop Behavior)", RFC 3246, March 2002. [RFC2362] D. Estrin, D. Farinacci, A. Helmy, D. Thaler, S. Deering, M. Handley, V. Jacobson, C. Liu, P. Sharma, L. Wei, "Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification.", RFC 2362, June 1998. [RFC2702] D. Awduche, J. Malcolm, J. Agogbua, M. O'Dell, J. McManus, "Requirements for Traffic Engineering Over MPLS", RFC2702, September 1999 [PIM-SM] B. Fenner, M. Hadley, H. Holbrook, I. Kouvelas, "Protocol Independent Multicast - Sparse Mode (PIM-SM):Protocol Specification (Revised)", draft-ietf-pim-sm-v2-new-08.txt, October 2003. [BGP/MPLS IP VPNs] E. Rosen, Y.Rekhter, Editor, "BGP/MPLS IP VPNs", draft-ietf-l3vpn-rfc2547bis-01.txt, September 2003 [RFC3471] Berger, L., Editor, "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description", RFC 3471, January 2003. [RFC3473] Berger, L., Editor, "Generalized Multi-Protocol Label Switching (GMPLS) Signaling - Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC 3473, January 2003. [RFC3477] K. Kompella, Y. Rekhter, "Signalling Unnumbered Links in Resource ReSerVation Protocol -Traffic Engineering (RSVP-TE)", RFC3477, January 2003. Yasukawa, et. al. [Page 18]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 [GMPLS-ROUTING] K. Kompella, Y. Rekhter, Editor, "Routing Extensions in Support of Generalized Multi-Protocol Label Switching", draft-ietf-ccamp-gmpls-routing-08.txt, October 2003. [STEINER] H. Salama, et al., "Evaluation of Multicast Routing Algorithm for Real-Time Communication on High-Speed Networks," IEEE Journal on Selected Area in Communications, pp.332-345, 1997 [DJIKSTRA] E. W. Djikstra, "A note on two problem in connection with graphs," Numerische Mathematik, vol.1, pp.269-271, 1959 [IPMCAST-MPLS] D. Ooms, B. Sales, W. Livens, A. Acharya, F. Griffoul and F. Ansari, "Overview of IP Multicast in a Multi-Protocol Label Switching (MPLS) Environment", RFC3353, August 2002. [FRR] P. Pan, D. Gan, G. Swallow, J. P. Vasseur, D. Cooper, A. Atlas, M. Jork,"Fast Reroute Extensions to RSVP-TE for LSP Tunnels", draft-ietf-mpls-rsvp-lsp-fastreroute-03.txt, July 2003 [RFC3564] F. Le Faucheur, W. Lai, "Requirements for Support of Differentiated Services-aware MPLS Traffic Engineering", RFC3564, July 2003 [OSPF-TE] D. Katz, D. Yeung, K. Kompella, "Traffic Engineering Extensions to OSPF Version 2", draft-katz-yeung-ospf-traffic-08.txt, September 2002 [IS-IS-TE] Henk Smit, Tony Li, "IS-IS extensions for Traffic Engineering", draft-ietf-isis-traffic-04.txt, December 2002 9. Author's Addresses Seisho Yasukawa NTT Network Service Systems Laboratories, NTT Corporation 9-11, Midori-Cho 3-Chome Musashino-Shi, Tokyo 180-8585 Japan Phone: +81 422 59 4769 EMail: yasukawa.seisho@lab.ntt.co.jp Dimitri Papadimitriou (Alcatel) Francis Wellensplein 1, B-2018 Antwerpen, Belgium Phone : +32 3 240 8491 EMail: dimitri.papadimitriou@alcatel.be Yasukawa, et. al. [Page 19]  Internet Draft draft-yasukawa-mpls-p2mp-requirement-01.txt October 2003 JP Vasseur Cisco Systems, Inc. 300 Beaver Brook Road Boxborough , MA - 01719 USA Email: jpv@cisco.com Yuji Kamite NTT Communications Corporation Innovative IP Architecture Center, Tokyo Opera City Tower 21F, 20-2, 3-chome, Nishi-Shinjuku, Shinjuku-ku, Tokyo, 163-1421, Japan. EMail: y.kamite@ntt.com Rahul Aggarwal Juniper Networks 1194 North Mathilda Ave. Sunnyvale, CA 94089 Email: rahul@juniper.net Alan Kullberg Motorola Computer Group 120 Turnpike Rd. Southborough, MA 01772 Email: alan.kullberg@motorola.com Adrian Farrel Old Dog Consulting Phone: +44 (0) 1978 860944 EMail: adrian@olddog.co.uk Markus Jork Avici Systems 101 Billerica Avenue N. Billerica, MA 01862 email: mjork@avici.com phone: +1 978 964 2142 Andrew G. Malis Tellabs 2730 Orchard Parkway San Jose, CA 95134 Phone: +1 408 383 7223 Email: andy.malis@tellabs.com Yasukawa, et. al. [Page 20]