Network Working Group Seisho Yasukawa (NTT) Internet Draft Editor Category: Informational Expiration Date: February 2005 September 2004 Requirements for Point to Multipoint Traffic Engineered MPLS LSPs <draft-ietf-mpls-p2mp-requirement-04.txt> Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, or will be disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. 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/1id-abstracts.html 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 Engineered (TE) Multiprotocol Label Switching (MPLS) Label Switched Paths (LSPs). It specifies functional requirements for solutions in order to deliver P2MP applications over a MPLS TE infrastructure. It is intended that solutions that specify procedures for P2MP TE LSP setup satisfy these requirements. There is no intent to either specify solution specific details in this document or application specific requirements. Yasukawa, et. al. [Page 1]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 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 L2SC, 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 attempt to be equally applicable to MPLS and GMPLS. Yasukawa, et. al. [Page 2]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 Table of Contents 1. Introduction .................................................. 04 2. Definitions ................................................... 07 2.1 Acronyms .................................................. 07 2.2 Terminology ............................................... 07 2.3 Conventions ............................................... 09 3. Problem Statement ............................................. 09 3.1 Motivation ................................................ 09 3.2. Requirements Overview .................................... 10 4. Examples of candidate applications that may require P2MP TE LSP 12 4.1 P2MP TE LSP for IP multicast data ......................... 13 4.2 P2MP TE backbone network for IP multicast network ........ 13 4.3 Layer 2 Multicast Over MPLS .............................. 14 4.4 VPN multicast network ..................................... 15 4.5 GMPLS Networks ............................................ 16 5. Detailed requirements for P2MP TE extensions .................. 16 5.1 P2MP LSP tunnels .......................................... 16 5.2 P2MP explicit routing ..................................... 17 5.3 Explicit Path Loose Hops and Widely Scoped Abstract Nodes . 18 5.4 P2MP TE LSP establishment, teardown, and modification mecha 19 5.5 Fragmentation ............................................. 19 5.6 Failure Reporting and Error Recovery ...................... 20 5.7 Record route of P2MP TE LSP tunnels ....................... 21 5.8 Call Admission Control (CAC) and QoS Control mechanism .... 21 5.9 Variation of LSP Parameters ............................... 22 5.10 Re-optimization of P2MP TE LSPs .......................... 22 5.11 Tree Remerge ............................................. 23 5.12 Data Duplication ......................................... 24 5.13 IPv4/IPv6 support ........................................ 24 5.14 P2MP MPLS Label .......................................... 24 5.15 Routing advertisement of P2MP capability ................. 24 5.16 Multi-Area/AS LSP ........................................ 25 5.17 Multi-access LANs ........................................ 25 5.18 P2MP MPLS OAM ............................................ 25 5.19 Scalability .............................................. 26 5.20 Backwards Compatibility .................................. 28 5.21 GMPLS .................................................... 28 5.22 Requirements for Hierarchical P2MP TE LSPs ............... 29 5.23 P2MP Crankback routing ................................... 29 6. Security Considerations ....................................... 29 7. Acknowledgements .............................................. 30 8. References .................................................... 30 8.1 Normative References ...................................... 30 8.2 Informational References .................................. 31 9. Editor's Address .............................................. 32 10. Authors' Addresses ........................................... 32 11. Intellectual Property Consideration .......................... 34 Yasukawa, et. al. [Page 3]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 12. Full Copyright Statement ..................................... 34 1. Introduction Existing MPLS Traffic Engineering (MPLS-TE) allows for strict QoS guarantees, resources optimization, and fast failure recovery, but is limited to P2P applications. There are P2MP applications like Content Distribution, Interactive Multimedia and VPN multicast that would also benefit from these TE capabilities. This clearly motivates enhancements of the base MPLS-TE tool box in order to support P2MP applications. [RFC2702] specifies requirements for traffic engineering over MPLS. It describes traffic engineering in some detail, and those definitions and objectives are equally applicable to traffic engineering in a point-to-multipoint service environment. They are not repeated here, but it is assumed that the reader is fully familiar with them. [RFC2702] also explains how MPLS is particularly suited to traffic engineering, and presents the following eight reason. 1. Explicit label switched paths which are not constrained by the destination based forwarding paradigm can be easily created through manual administrative action or through automated action by the underlying protocols. 2. LSPs can potentially be efficiently maintained. 3. Traffic trunks can be instantiated and mapped onto LSPs. 4. A set of attributes can be associated with traffic trunks which modulate their behavioral characteristics. 5. A set of attributes can be associated with resources which constrain the placement of LSPs and traffic trunks across them. 6. MPLS allows for both traffic aggregation and disaggregation whereas classical destination only based IP forwarding permits only aggregation. 7. It is relatively easy to integrate a "constraint-based routing" framework with MPLS. 8. A good implementation of MPLS can offer significantly lower overhead than competing alternatives for Traffic Engineering. These points are equally applicable to point-to-multipoint traffic engineering. Points 1. and 7. are particularly important. That is, the traffic flow for a point-to-multipoint LSP is not constrained to the path or paths that it would follow during multicast routing or shortest path destination-based routing, but Yasukawa, et. al. [Page 4]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 can be explicitly controlled through manual or automated action. Further, the explicit paths that are used may be computed using algorithms based on a variety of constraints to produce all manner of tree shapes. For example, an explicit path may be cost-based [STEINER], shortest path, QoS-based, or may use some fair-cost QoS algorithm. Such computations are potentially bound to be more complex and varied than anything available in the multicast forwarding paradigm. [RFC2702] also describes the functional capabilities required to fully support Traffic Engineering over MPLS in large networks. 1. A set of attributes associated with traffic trunks which collectively specify their behavioral characteristics. 2. A set of attributes associated with resources which constrain the placement of traffic trunks through them. These can also be viewed as topology attribute constraints. 3. A "constraint-based routing" framework which is used to select paths for traffic trunks subject to constraints imposed by items 1) and 2) above. The constraint-based routing framework does not have to be part of MPLS. However, the two need to be tightly integrated together. These basic requirements also should be supported by point-to-multipoint traffic engineering. 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 solutions to deliver P2MP TE LSPs. For the sake of illustration, RSVP-TE [RFC3209] is one possible candidate to provide such a solution so as to deliver P2MP TE LSPs. It is intended that solutions that specify procedures for P2MP TE LSP setup satisfy these requirements. There is no intent to either specify solution specific details in this document or application specific requirements. 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 attempt to be equally applicable to MPLS and GMPLS. Yasukawa, et. al. [Page 5]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 Content Distribution (CD), Interactive multi-media (IMM), and VPN multicast are applications that are best supported with multicast capabilities. For some of them , there is a requirement to use P2MP TE LSPs. One possible way to map P2MP flows onto LSPs in a MPLS network is 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 as 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 (that is, with scalable impact on signaling and protocol state) in a large-scale environment, P2MP TE mechanisms are required specifically to support P2MP TE LSPs. As of now, existing MPLS TE mechanisms such as [RFC3209] do not support P2MP TE LSPs so new mechanisms must be developed. This should be achieved without requiring the use of a multicast routing protocol in the network core, and with maximum re-use of the existing MPLS protocols: in particular, MPLS Traffic Engineering. That is, the separation between routing and signaling that exists in the P2P TE network should be maintained within the P2MP TE network, and the construction of the TEDB from which P2MP TE LSP paths are computed should not be constrained to use a multicast protocol. A P2MP TE LSP will be set up with TE constraints and will allow efficient packet or data replication at various branching points in the network. Note that the notion of "efficient" packet replication is relative and may have different meanings depending on the objectives (see section 5.2). For instance, RSVP-TE could be used for setting up a P2MP TE LSP with enhancements to existing P2P TE LSP procedures. P2MP TE LSP setup mechanisms MUST include the ability to add/remove receivers to/from an existing P2MP TE LSP. Note that with existing multicast routing mechanisms, multicast traffic cannot currently benefit from P2P TE LSPs. Hence, Call Admission Control for P2P TE LSP cannot take into account the bandwidth used for multicast traffic. P2MP TE will allow the bandwidth used by both the unicast and multicast traffics to be counted by means of CAC. Yasukawa, et. al. [Page 6]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 This document is organized as follows: Section 2 provides a set of definitions used throughout the document. The problem statement is then discussed in Section 3. for the sake of illustration, this document lists various applications that could make use P2MP TE LSP. Detailed application-specific requirements as far as P2MP TE LSP is concerned are out of the scope of this document. Detailed requirements for the support of applications that require P2MP MPLS TE LSPs are described in section 4. The requirement for Multipoint-to-Point and Multipoint-to-Multipoint TE LSPs are outside of the scope of this document. 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 one or more egress LSRs (also referred to as the leaf). P2MP tree: The ordered set of LSRs and links that comprise the path of a P2MP TE LSP from its ingress LSR to all of its egress LSRs. ingress LSR: The LSR that is responsible for initiating the signaling messages that set up the P2MP TE LSP. egress LSR: Yasukawa, et. al. [Page 7]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 One of potentially many destinations of the P2MP TE LSP. Egress LSRs may also be referred to as leaf nodes or leaves. bud LSR: An LSR that is an egress, but also has one or more directly connected downstream LSRs. branch LSR: An LSR that has more than one directly connected downstream LSR. graft LSR: An LSR that is already a member of the P2MP tree and is in process of signaling a new sub-P2MP tree. prune LSR: An LSR that is a member of the P2MP tree and is in process of tearing down an existing sub-P2MP tree. P2MP-ID (Pid): A unique identifier of a P2MP TE LSP, that is constant for the whole LSP regardless of the number of branches and/or leaves. 2.2.1 Terminology for Partial LSPs It is convenient to sub-divide P2MP trees for functional and representational reasons. a tree may be divided in two dimensions: - A division may be made along the length of the tree. For example, the tree may be split into two components each running from the ingress LSR to a discrete set of egress LSRs - A tree may be divided at a branch LSR (or any transit LSR) to produce a component of the tree that runs from the branch (or transit) LSR to all downsetram egress LSRs. These two methods of splitting the P2MP tree can be combined, so it is useful to introduce some terminology to allow the partitioned trees to be clearly described. Use the following designations: Source (ingress) LSR - S Leaf (egress) LSR - L Branch LSR - B Transit LSR - X Yasukawa, et. al. [Page 8]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 Define three terms: Sub-LSP A component of the P2MP LSP that runs from one LSR to another without (or ignoring) any branches. Sub-tree A component of the P2MP LSP that runs from one LSR to more than one other LSR by branching. Tree A component of the P2MP LSP that runs from one LSR to all downstream LSRs. Using these new concepts we can define any combination or split of the P2MP tree. For example: S2L sub-LSP The path from the source to one specific leaf. S2L sub-tree The path from the source to a set of leaves. B2L tree The path from a branch LSR to all downstream leaves. X2X sub-LSP A component of the P2MP LSP that is a simple path with no branches. 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]. 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 Yasukawa, et. al. [Page 9]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 (see [RFC2475],[RFC2597] and [RFC3246]) combined with IP multicast routing may not be sufficient for P2MP applications for many of the same reasons that it is not sufficient for unicast applications. Note also that multicast trees provided by existing IP multicast routing protocols are not optimal from a bandwidth usage perspective, which may lead to significant bandwidth wasting. TE and Constraint Based Routing, including Call Admission Control(CAC), explicit source routing and bandwidth reservation, is required to enable efficient resource usage and strict QoS guarantees. Furthermore 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; the related set of application requirements are outside of the scope of this document and might require special pseudowire encapsulation. 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 as 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 (that is, with scalable impact on signaling and protocol state) in a large scale environment, P2MP TE mechanisms are required. Existing MPLS P2P TE mechanisms have to be enhanced to support P2MP TE LSP. 3.2. Requirements Overview This document states basic requirements for the setup of P2MP TE LSPs and a solution SHOULD satisfy them without requiring that a multicast routing protocol is used, although such a protocol MUST NOT be prohibited. The mechanism used to construct the TED from which the paths of P2MP trees are computed is out of scope of this document although it is desirable to maximize the re-use of existing MPLS TE techniques and protocols. Note that the use of MPLS forwarding to carry the multicast traffic may also be useful in the context of some network designs where it might be 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 TE LSP path will be computed taking into account various Yasukawa, et. al. [Page 10]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 constraints such as bandwidth, affinities, required level of protection and so on. The solution MUST allow for the computation of P2MP TE LSP paths satisfying constraints with the objective of supporting various optimization criteria such as delays, bandwidth consumption in the network, or any other combinations. This document does not restrict the choice of signaling protocol used to set up a P2MP TE LSP, but it should be noted that [RFC3468] states ... the consensus reached by the Multiprotocol Label Switching (MPLS) Working Group within the IETF to focus its efforts on "Resource Reservation Protocol (RSVP)-TE: Extensions to RSVP for Label-Switched Paths (LSP) Tunnels" (RFC 3209) as the MPLS signaling protocol for traffic engineering applications... The P2MP TE LSP setup mechanism MUST include the ability to add/remove egress LSRs to/from an existing P2MP TE LSP and MUST allow for the support of all the TE LSP management procedures already defined for P2P TE LSP such as the non disruptive rerouting (the so called "Make before break" procedure). The computation of P2MP TE trees is implementation dependent and is beyond the scope of the solutions that are built with this document as a guideline. A separate document(s) will specify how to build P2MP TE LSPs. The usage of those solutions will be application dependent and is out of the scope of this document. However, it is a requirement that those solutions attempt to be applicable to GMPLS as well as to MPLS so that only a single set of solutions are developed. 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 Yasukawa, et. al. [Page 11]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 Figure 1 shows a single ingress (I-LSR1), and four egresses(E-LSR2, E-LSR3, E-LSR4 and E-LSR5). I-LSR1 is attached to a traffic source that is generating traffic for a P2MP application. Receivers R1, R2, R3 and R4 are attached to E-LSR2, E-LSR3 and E-LSR4. The following are the objectives of P2MP LSP establishment and use. a) A P2MP TE LSP tree which satisfies various constraints is pre-determined and supplied to ingress I-LSR1. Note that no assumption is made on whether the tree is provided to I-LSR1 or computed by I-LSR1. Note that the solution SHOULD also allow for the support of partial path by means of loose routing. Typical constraints are bandwidth requirements, resource class affinities, fast rerouting, preemption, to mention a few of them. There should not be any restriction on the possibility to support the set of constraints already defined for point to point TE LSPs. A new constraint may specify which LSRs should be used as branch points for the P2MP LSR in order to take into account some LSR capabilities or network constraints. b) A P2MP TE LSP is set up from I-LSR1 to E-LSR2, E-LSR3 and E-LSR4 using the tree information. c) In this case, the branch LSR1 should replicate incoming packets or data and send them to E-LSR3 and E-LSR4. d) If a new receiver (R5) expresses an interest in receiving traffic, a new tree is determined and a sub-P2MP tree from LSR2 to E-LSR5 is grafted onto the P2MP tree. LSR2 becomes a branch LSR. 4. Examples of candidate applications that may require P2MP TE LSP This section describes some of the candidate applications that P2MP MPLS TE is applicable to. The purpose of this section is not to mandate how P2MP TE LSPs must be used in certain application scenarios. Rather it is to illustrate some of the potential application scenarios so as to highlight the features and functions that any P2MP solution must provide in order to be of wide use and applicability. This section is not meant to be exhaustive, and P2MP is not limited to the described applications. Yasukawa, et. al. [Page 12]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 4.1 P2MP TE LSP for IP multicast data One typical scenario is to use P2MP TE LSPs as P2MP tunnels carrying multicast data traffic (e.g. IP mcast). In this scenario, a P2MP TE LSP is established between an ingress LSR which supports IP multicast source and several egress LSRs which support several IP multicast receivers. A P2MP TE LSP is established over the network and IP multicast data are tunneled from an ingress LSR node to multiple egress leaf LSRs with data replication at the branch LSRs in the network core. Figure 2 shows an example. Note that a P2MP TE LSP can be established over multiple areas/ASs and that the egress LSRs may deliver data into an IP multicast network. 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 4.2 P2MP TE backbone network for IP multicast network P2MP TE LSPs are applicable in a backbone network to construct or support a multicast network(e.g. IPmcast network). The IP multicast access networks are interconnected by P2MP TE LSPs. A P2MP TE LSP is established from an ingress LSR which accommodates an IP multicast network that has a multicast source to multiple egress LSRs which each accommodate an IP multicast network. Yasukawa, et. al. [Page 13]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 In this scenario, ingress/egress LSRs placed at the edge of multicast network handle an IP multicast routing protocol. This means that the ingress/egress LSRs exchange IP multicast routing messages as neighbor routers. Figure 3 shows a network example of this scenario. A P2MP TE LSP is established from a I-LSR1 to E-LSR2, E-LSR3, E-LSR4 and the ingress/egress LSR exchanges the multicast routing messages with each other. 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. 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 Broadcast Access 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. For instance, several SPs provision P2MP ATM VCs for TV/ADSL Yasukawa, et. al. [Page 14]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 services. These P2MP VCs are setup between a video server and a set of ATM DSLAMs. Each channel is carried in a distinct P2MP VC. These VC maybe be routed independently, or may all be nested into a unique PVC, connecting the video sever to all DSLAMs. Such service could benefit from a P2MP MPLS-TE control plane. An option is to setup a permanent P2MP TE LSP between the video server and all DSLAMs, that would correspond to a PVC carrying all channel VCs. In this case each DSLAM receives all channels, even if there are no receivers that are registered for a given channel. This ensure fast zapping, but lead to significant bandwidth wasting. A second option is to setup a distinct P2MP TE LSP per channel. If a client, behind a DSLAM, zaps to a new channel, then the DSLAM has to be added to the P2MP TE LSP carrying this channel using a P2MP TE grafting procedure, if it is not already egress LSR for that LSP. Pruning procedure has to be used to remove a DSLAM from the P2MP TE LSP when there is no longer any client behind the DSLAM, watching the channel. 4.4 VPN multicast network In this scenario, P2MP TE LSPs could be utilized to construct a provider network which can deliver VPN multicast service(s) to its customers. It is, however, not a requirement that VPN multicast services be delivered using P2MP TE LSPs. 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 a VPN instance. For example, in Layer3 VPNs like BGP/MPLS based IP VPNs [BGPMPLS-VPN], 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. In case of high rate source, the need for P2MP TE LSP can be envisaged for Layer3 VPN data transmission. Another example is a Layer2 VPN that supports multipoint LAN connectivity service. In an Ethernet network environment, IP multicast data is flooded to the appropriate Ethernet port(s). An Ethernet multipoint Layer2 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 send them to the corresponding PEs. This means the data stream is Yasukawa, et. al. [Page 15]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 flooded just from the ingress PE, which will waste the provider's network resources. So, for Layer 2 VPNs that are required to support multicast traffic, it might be desirable that P2MP MPLS TE LSPs are used for data transmission with an appropriate layer 2 encapsulation technique (for example, pseudo wire) instead of P2P MPLS TE LSPs, contributing in turn to savings of network resources. This document does not set requirements for how multicast VPNs are provided, but it does set requirements for the function that must be available in P2MP MPLS solutions. Therefore, it is not a requirement that multicast VPNs utilize P2MP TE LSPs, but it is a requirement that P2MP MPLS solutions should be capable of supporting multicast VPNs. As already pointed out, application-specific requirements are out of the scope of this document. 4.5 GMPLS Networks GMPLS currently 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 [RFC3473] 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 reasonable attempts must be made to make all the features/mechanisms (and protocol extensions) that will be defined to provide MPLS P2MP TE LSPs equally applicable to P2MP PSC and non-PSC TE-LSPs. If the requirements of non-PSC networks over-complicate the PSC solution a decision may be taken to separate the solutions. This decision must be taken in full consultation with the MPLS and CCAMP working groups. 5. Detailed requirements for P2MP TE extensions 5.1 P2MP LSP tunnels The P2MP TE extensions MUST be applicable to the signaling of LSPs of different traffic types. For example, it MUST be possible to signal a P2MP TE LSP to carry any kind of payload being packet or Yasukawa, et. al. [Page 16]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 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 a FEC in this extension. All packets which belong to a particular FEC and which travel from a particular node MUST follow the same P2MP tree. In order to scale to a large number of branches, P2MP TE LSPs SHOULD be identified by a unique identifier (the P2MP ID or Pid) 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 tree formation need to be applied to meet various QoS requirements and operational constraints. Some P2MP applications may request a bandwidth guaranteed P2MP tree which satisfies end-to-end delay requirements. And some operators may want to set up a cost minimum P2MP tree by specifying branch LSRs explicitly. The P2MP TE solution therefore MUST provide a means of establishing arbitrary P2MP trees under the control of an external tree computation process or path configuration process or dynamic tree computation process located on the ingress LSR. Figure 4 shows two typical examples. 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 tree SPF P2MP tree Figure 4 Examples of P2MP TE LSP topology One example is the Steiner P2MP tree (Cost minimum P2MP tree) Yasukawa, et. al. [Page 17]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 [STEINER]. This P2MP tree is suitable for constructing a cost minimum P2MP tree so as to minimize the bandwidth consumption in the core. To realize this P2MP tree, several intermediate LSRs must be both MPLS data terminating LSRs and transit LSRs (LSRs E, F, G, H, I, J and K in the figure 4). This means that the LSRs 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 bud LSR between an ingress LSR and egress LSRs. Note that this includes constrained Steiner trees that allow for the computation of a minimal cost trees with some other constraints such as a bounded delay between the source and every receiver. Another example is a CSPF (Constraint Shortest Path First) P2MP tree. By some metric (which can be set upon any specific criteria like the delay, bandwidth, a combination of those), one can calculate a shortest path P2MP tree. This P2MP tree is suitable for carrying real time traffic. The solution MUST allow the operator to make use of any tree computation technique. In the former case an efficient/optimal tree is defined as a minimal cost tree (Steiner tree) whereas in the later case it is defined as the tree that provides shortest path between the source and any receiver. To support explicit setup of any reasonable P2MP tree shape, a P2MP TE solution MUST support some form of explicit source-based control of the P2MP tree which can explicitly include particular LSRs as branch nodes. This can be used by the ingress LSR to setup the P2MP TE LSP. For instance, a P2MP TE LSP can be simply represented as a whole tree or by its individual branches. 5.3 Explicit Path Loose Hops and Widely Scoped Abstract Nodes A P2MP tree is completely specified if all of the required branches and hops between a sender and leaf LSR are indicated. A P2MP tree 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 tree might be particularly useful in inter-area and inter-AS situations although P2MP requirements for inter-area and inter-AS are beyond the scope of this document. Protocol solutions SHOULD include a way to specify loose hops and widely scoped abstract nodes in the explicit source-based control of the P2MP tree as defined in the previous section. Where this Yasukawa, et. al. [Page 18]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 support is provided, protocol solutions MUST allow downstream LSRs to apply further explicit control to the P2MP tree to resolve a partially specified tree into a (more) completely specified tree. Protocol solutions MUST allow the P2MP tree to be completely specified at the ingress where sufficient information exists to allow the full tree to be computed. In all cases, the egress nodes of the P2MP TE LSP must be fully specified. In case of a tree being computed by some downstream LSRs (e.g. the case of hops specified as loose hops), the solution MUST provide the ability for the ingress LSR of the P2MP TE LSP to learn the full P2MP tree. Note that this requirement MAY be relaxed in some environments (e.g. Inter-AS) where confidentiality must be preserved. 5.4 P2MP TE LSP establishment, teardown, and modification mechanisms The P2MP TE solution MUST support establishment, maintenance and teardown of P2MP TE LSPs in a scalable manner. This MUST include both the existence of very many LSPs at once, and the existence of very many destinations for a single P2MP LSP. In addition to P2MP TE LSP establishment and teardown mechanism, it SHOULD implement partial P2MP tree modification mechanism. For the purpose of adding sub-P2MP TE LSPs to an existing P2MP TE LSP, the extensions SHOULD support a grafting mechanism. For the purpose of deleting a sub-P2MP TE LSPs from an existing P2MP TE LSP, the extensions SHOULD support a 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. Moreover, both grafting and pruning operations MUST not be traffic disruptive for the traffic currently forwarded along the P2MP tree. 5.5 Fragmentation The P2MP TE solution MUST handle the situation where a single protocol message cannot contain all of the information necessary to signal the establishment of the P2MP LSP. It MUST be possible to establish the LSP in these circumstances. This situation may arrise in either of the following circumstances. a. The ingress LSR cannot signal the whole tree in a single Yasukawa, et. al. [Page 19]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 message. b. The information in a message expands to be too large (or is discovered to be too large) at some transit node. This may occur because of some increase in the information that needs to be signaled or because of a reduction in the size of signaling message that is supported. The solution to these problems SHOULD NOT rely on IP fragmentation, it is RECOMMENDED to rely on some protocol procedures specific to the signaling solution. It is NOT RECOMMENDED that fragmented protocol messages are re-combined at any downstream LSR. 5.6 Failure Reporting and Error Recovery Failure events may cause egress nodes or sub-P2MP LSPs to become detached from the P2MP TE LSP. These events MUST be reported upstream as for a P2P LSP. The solution SHOULD provide recovery techniques such as protection and restoration allowing recovery of any impacted sub-P2MP TE LSPs. In particular, a solution MUST provide fast protection mechanisms applicable to P2MP TE LSP similar to the solutions specified in [FRR] for P2P TE LSPs. Note also that no assumption is made on whether backup paths for P2MP TE LSPs should or should not be shared with P2P TE LSPs backup paths. Note that the functions specified in [FRR] are currently specific to packet environments and do not apply to non-packet environments. Thus, while solutions MUST provide fast protection mechanisms similar to those specified in [FRR], this requirement is limited to the subset of the solution space that applies to packet switched networks only. Note that other application-specific requirement documents may introduce even more stringent requirement such as non packet loss, at the cost of some increased bandwidth consumption. The solution SHOULD also support the ability to meet other network recovery requirements such as bandwidth protection and bounded propagation delay increase along the backup path during failure. A P2MP TE solution MUST support P2MP fast protection mechanism to handle P2MP applications sensitive to traffic disruption. The report of the failure of delivery to fewer than all of the Yasukawa, et. al. [Page 20]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 egress nodes SHOULD NOT cause automatic teardown of the P2MP TE LSP. That is, while some egress nodes remain connected to the P2MP tree it should be a matter of local policy at the ingress whether the P2MP LSP is retained. When all egress nodes downstream of a branch node have become disconnected from the P2MP tree, and the some branch node is unable to restore connectivity to any of them by means of some recovery or protection mechanisms, the branch node MAY remove itself from the P2MP tree provided that it is not also an egress LSR. Since the faults that severed the various downstream egress nodes from the P2MP tree may be disparate, the branch node MUST report all such errors to its upstream neighbor. The ingress node can then decide to re-compute the path to those particular egress nodes, around the failure point. Solutions MAY include the facility for transit LSRs and particularly branch nodes to recompute sub-P2MP trees to restore them after failures. In the event of successful repair, error notifications SHOULD NOT be reported to upstream nodes, but the new paths are reported if route recording is in use. Crankback requirements are discussed in Section 5.23. 5.7 Record route of P2MP TE LSP tunnels Being able to identify the established topology of P2MP TE LSP is very important for various purposes such as management and operation of some local recovery mechanisms like Fast Reroute [FRR]. A network operator uses this information to manage P2MP TE LSPs. Therefore, topology information MUST be collected and updated after P2MP TE LSP establishment and modification process. The P2MP TE solution MUST support a mechanism which can collect and update P2MP tree topology information after P2MP LSP establishment and modification process. For example, the P2P MPLS TE mechanism of route recording could be extended and used if RSVP-TE was used as the P2MP signaling protocol. It is RECOMMENDED that the information is collected in a data format by which the sender node can recognize the P2MP tree topology without involving some complicated data calculation process. The solution MUST support the recording of both outgoing interfaces and node-id [NODE-ID]. 5.8 Call Admission Control (CAC) and QoS Control mechanism of P2MP TE LSPs Yasukawa, et. al. [Page 21]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 P2MP TE LSPs may share network resource with P2P TE LSPs. Therefore it is important to use CAC and QoS in the same way as P2P TE LSPs for easy and scalable operation. In particular, it should be highlighted that because Multicast traffic cannot make use of P2P TE LSP, multicast traffic cannot be easily taken into account by P2P TE LSPs when performing CAC. The use of P2MP TE LSP will now allow for an accounting of the unicast and multicast traffic for bandwidth reservation. P2MP TE solutions MUST support both resource sharing and exclusive resource utilization to facilitate co-existence with other LSPs to the same destination(s). P2MP TE solution MUST be applicable to DiffServ-enabled networks that can provide consistent QoS control in P2MP LSP traffic. Any solution SHOULD also satisfy the DS-TE requirements [RFC3564] and interoperate smoothly with current P2P DS-TE protocol specifications. Note that this requirement document does not make any assumption on the type of bandwidth pool used for P2MP TE LSPs which can either be shared with P2P TE LSP or be dedicated for P2MP use. 5.9 Variation of LSP Parameters Various parameters to an LSP (such as priority, bandwidth, etc.) are signaled along each branch of the LSP. Any solution MUST NOT allow for variance of these parameters. That is, - no attributes set and signaled by the ingress of a P2MP LSP may be varied by downstream LSRs - there MUST be homogenous QoS from the root to all leaves. THIS IS A PROVISIONAL REQUIREMENT STILL OPEN FOR DISCUSSION. 5.10 Re-optimization of P2MP TE LSPs The detection of a more optimal path (for example, one with a lower overall cost) is an example of a situation where P2MP TE LSP re-routing may be required. While re-routing is in progress, an important requirement is avoiding double bandwidth reservation (over the common parts between the old and new LSP) thorough the use of resource sharing. Yasukawa, et. al. [Page 22]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 Make-before-break MUST be supported for a P2MP TE LSP to ensure that there is minimal traffic disruption when the P2MP TE LSP is re-routed. It is possible to achieve make-before-break that only applies to a sub-P2MP tree without impacting the data on all of the other parts of the P2MP tree. The solution SHOULD allow for make-before-break re-optimization of any subdivision of the P2MP LSP (S2L sub-tree, S2X sub-LSP, S2L sub-LSP, X2L sub-tree, B2L sub-tree, X2L tree, or B2L tree) with no impact on the rest of the P2MP LSP (no label reallocation, no change in identifiers, etc.). The solution SHOULD also provide the ability for the ingress LSR to have a strict control on the re-optimization process. Such re-optimization MAY be initiated by the sub-tree root branch node (that is, the branch node MAY setup a new sub-tree, then splice traffic on the new subtree and delete the former sub-tree). THE REQUIREMENT FOR RE-OPTIMIZATION BY SUB-TREE ROOT BRANCH IS STILL OPEN FOR DISCUSSION 5.11 Tree Remerge It is possible for a single transit LSR to receive multiple signaling messages for the same P2MP LSP but for different sets of desinations. These messages may be received from the same or different upstream nodes and may need to be passed on to the same or different downstream nodes. This situation may arise as the result of the signaling solution definition or implementation options within the signaling solution. Further, it may happen during make-before-break reoptimization (section 5.9), or as a result of signaling message fragmentation (section 5.5). It is even possible that it is necessary to construct distinct upstream branches in order to achieve the correct label choices in certain switching technologies managed by GMPLS (for example, photonic cross-connects where the selection of a particular lambda for the downstream branches is only available on differnt upstream switches). The solution MUST handle the case where multiple signaling messages for the same P2MP LSP are received at a single transit LSR with the end result of all receivers being added to the P2MP LSP. Yasukawa, et. al. [Page 23]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 THIS REQUIREMENT IS STILL UNDER DISCUSSION 5.12 Data Duplication Data duplication refers to the receipt by any recipient of duplicate instances of the data. In a packet environment this means the receipt of duplicate packets - although this should be a benign (if inefficient) situation, it may be catastrophic in certain existing and deployed applications. In a non-packet environment this means the duplication in time of some part of the signal that may lead to the replication of data or to the scrambling of data. Data duplication may legitimately arrise in various scenarios including re-optimization of active LSPs as described in the previous section, and protection of LSPs. Thus, it is impractical to regulate against data duplication in this document. Instead, the solution MUST provide a mechanism to resolve, limit or avoid data duplication at either or both of: - the point at which the data path diverges - the point at which the data paths converge. THE EXTENT TO WHICH DATA DUPLICATION MAY BE TOLERATED (in time or in a count of bits or packets) IS FOR FURTHER STUDY. 5.13 IPv4/IPv6 support Any P2MP TE solution MUST be equally applicable to IPv4 and IPv6. 5.14 P2MP MPLS Label A P2MP TE solution MUST support establishment of both P2P and P2MP TE LSPs and MUST NOT impede the operation of P2P TE LSPs within the same network. A P2MP TE solution MUST be specified in such a way that it allows P2MP and P2P TE 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. 5.15 Routing advertisement of P2MP capability Several high-level requirements have been identified to determine the capabilities of LSRs within a P2MP network. The aim of such information is to facilitate the computation of P2MP trees using TE constraints within a network that contains LSRs that do not all have the same capabilities levels with respect to P2MP signaling and data forwarding. Yasukawa, et. al. [Page 24]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 These capabilities include, but are not limited 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 ability of an LSR to support P2MP MPLS-TE signalling. It is expected that it may be appropriate to gather this information through extensions to TE IGPs (see [RFC3630] and [IS-IS-TE]), but the precise requirements and mechanisms are out of the scope of this document. It is expected that a separate document will cover this requirement. 5.16 Multi-Area/AS LSP P2MP TE solutions SHOULD support multi-area/AS P2MP TE LSPs. The precise requirements in support of multi-area/AS P2MP TE LSPs is out of the scope of this document. It is expected that a separate document will cover this requirement. 5.17 Multi-access LANs P2MP MPLS TE may be used to traverse network segments that are provided by multi-access media such as Ethernet. In these cases, it is also possible that the entry point to the network segment is a branch point of the P2MP LSP. Two options clearly exist: - the branch point replicates the data and transmits multiple copies onto the segment - the branch point sends a single copy of the data to the segment and relies on the exit points to discriminate the reception of the data. The first option has a significant scaling issue since all replicated data must be sent through the same port and carried on the same segment. Thus, a solution SHOULD provide a mechanism for a branch node to send a single copy of the data onto a multi-access network and reach multiple (adjacent) downstrem nodes. 5.18 P2MP MPLS OAM Management of P2MP LSPs is as important as the management of P2P LSPs. The MPLS and GMPLS MIB modules MUST be enhanced to provide P2MP TE Yasukawa, et. al. [Page 25]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 LSP management. In order to facilitate correct management, P2MP TE LSPs MUST have unique identifiers. OAM facilities will have special demands in P2MP environments especially within the context of tracing the paths and connectivity of P2MP TE LSPs. The precise requirements and mechanisms for OAM are out of the scope of this document. It is expected that a separate document will cover these requirements. 5.19 Scalability Scalability is a key requirement in P2MP MPLS systems. Solutions MUST be designed to scale well with an increase in the number of any of the following: - the number of recipients - the number of branch points - the number of branches. Both scalability of performance and operation MUST be considered. Key considerations SHOULD include: - the amount of refresh processing associated with maintaining a P2MP TE LSP. - the amount of protocol state that must be maintained by ingress and transit LSRs along a P2MP tree. - the number of protocol messages required to set up or tear down a P2MP LSP as a function of the number of egress LSRs. - the number of protocol messages required to repair a P2MP LSP after failure or perform make-before-break. - the amount of protocol information transmitted to manage a P2MP TE LSP (i.e. the message size). - the amount of potential routing extensions. - the amount of control plane processing required by the ingress, transit and egress LSRs to add/delete a branch LSP to/from an existing P2MP LSP. It is expected that the applicability of each solution will be evaluated with regards to the aforementioned scalability criteria. 5.19.1 Absolute Limits THIS IS SECTION DESCRIBES PROVISIONAL REQUIREMENTS STILL OPEN FOR DISCUSSION. In order to achieve the best solution for the problem space it is Yasukawa, et. al. [Page 26]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 helpful to clarify the boundaries for P2MP TE LSPs. - Number of recipients. A P2MP TE LSP MUST reduce to similar scaling properties as a P2P LSP when the number of recipients reduces to one. It is important to classify the problem as a Traffic Engineering problem. It is anticipated that the initial deployments of P2MP TE LSPs may be limited to only several hundred recipients, but also that future deployments may require significantly larger numbers. An acceptable solution, therefore, is one that scales linearly with the number of recipients. Solutions that scale worse than linear (that is, exponential or polynomial) are not acceptable whatever the number of recipients they could support - Number of branch points. Solutions MUST support all possiblities from one extreme of a single branch point that forks to all leaves on a separate branch, to the greatest number of branch points which is (n-1) for n recipients. Assumptions MUST NOT be made in the solution regarding which topology is more common, and the solution MUST be designed to ensure scalability in all topologies. - Dynamics of P2MP tree. Recall that the mechanisms for determining which recipients should be added to an LSP, and for adding and removing recipients from that group are out of the scope of this document. Nevertheless, it is useful to understand the expected rates of arrival and departure of recipients since this can impact the selection of solution techniques. Again, it must be recall that this document is limited to Traffic Engineering, and in this model the rate of change of recipients may be expected to be lower than in an IP multicast group. Although the absolute number of recipients coming and going is the important element for determining the scalability of a solution, it may be noted that a percentage may be a more comprehensible measure but that this is not as significant for LSPs with a small number of recipients. A working figure for an established P2MP TE LSP is less than 10% churn per day. That is, a relatively slow rate of churn. We could say that a P2MP LSP would be shared by multiple multicast groups and dynamics of P2MP LSP would be relatively small. Considering applicability that P2MP LSP to use L2 multi-access path technology, we can consider stable P2MP L2 path even when we transfer IP multicast traffic over the path. Solutions MUST optimize around such relatively low rates of change Yasukawa, et. al. [Page 27]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 and are NOT REQUIRED to optimize for significantly higher rates of change. - Rate of change within the network. It is also important to understand the scaling with regard to changes within the network. That is, one of the features of a P2MP TE LSP is that it can be robust or protected against network failures, and can be re-optimized to take advantage of newly available network resources. It is more important that a solution be optimized for scaling with respect to recovery and re-optimization of the LSP, than for change in the recipients, because P2MP is used as a TE tool. The solution MUST follow this distinction. 5.20 Backwards Compatibility It SHOULD be an aim of any P2MP solution to offer as much backward compatibility as possible. An ideal which is probably impossible to achieve would be to offer P2MP services across legacy MPLS networks without any change to any LSR in the network. If this ideal cannot be achieved, the aim SHOULD be to use legacy nodes as both transit non-branch LSRs and egress LSRs. It is a further requirement for the solution that any LSR that implements the solution SHALL NOT be prohibited by that act from supporting P2P TE LSPs using existing signaling mechanisms. That is, unless administratively prohibited, P2P TE LSPs MUST be supported through a P2MP network. Also, it is a requirement that P2MP TE LSPs MUST be able to co-exist with IP unicast and IP multicast networks. 5.21 GMPLS Solutions for MPLS P2MP TE-LSPs when applied to GMPLS P2MP PSC or non-PSC TE-LSPs MUST be backward and forward compatible with the other features of GMPLS including: - control and data plane separation (IF_ID RSVP_HOP and IF_ID ERROR_SPEC), - full support of numbered and unnumbered TE links (see [RFC 3477] and [GMPLS-ROUTE]), - use of the GENERALIZED_LABEL_REQUEST, the GENERALIZED_LABEL (C-Type 2 and 3), the SUGGESTED_LABEL and the RECOVERY_LABEL, Yasukawa, et. al. [Page 28]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 in conjunction with the LABEL_SET and the ACCEPTABLE_LABEL_SET object, - processing of the ADMIN_STATUS object, - processing of the PROTECTION object, - support of Explicit Label Control, - processing of the Path_State_Removed Flag, - handling of Graceful Deletion procedures. - E2E and Segment Recovery procedures. - support of Graceful Restart 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 to those being used for PSC P2P TE LSPs and P2MP TE LSPs. 5.22 Requirements for Hierarchical P2MP TE LSPs [LSP-HIER] defines concepts and procedures for P2P LSP hierarchy. These procedures SHOULD be extended to support P2MP LSP hierarchy. The P2MP MPLS-TE solution SHOULD support the concept of region and region hierarchy (PSC1<PSC2<PSC3<PSC4<L2SC<TDM<LSC<FSC). Particularly it SHOULD allow a Region i P2MP TE LSP to be nested into a region j P2MP TE LSP or multiple region j P2P TE LSPs, providing that i<j. The precise requirements and mechanisms for this function are out of the scope of this document. It is expected that a separate document will cover these requirements. 5.23 P2MP Crankback routing P2MP solutions SHOULD support crankback requirements as defined in [CRANKBACK]. In particular, they SHOULD provide sufficient information to a branch LSR from downstream LSRs to allow the branch LSR to re-route a sub-tree around any failures or problems in the network. 6. Security Considerations Yasukawa, et. al. [Page 29]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 This requirements document does not define any protocol extensions and does not, therefore, make any changes to any security models. It should be noted that P2MP signaling mechanisms built on P2P RSVP-TE signaling are likely to inherit all of the security techniques and problems associated with RSVP-TE. These problems may be exacerbated in P2MP situations where security relationships may need to maintained between an ingress and multiple egresses. Such issues are similar to security issues for IP multicast. It is a requirement that documents offering solutions for P2MP LSPs MUST have detailed security sections. 7. Acknowledgements The authors would like to thank George Swallow, Ichiro Inoue, Dean Cheng, Lou Berger and Eric Rosen for their review and suggestions. 8. References 8.1 Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [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. [RFC2702] D. Awduche, J. Malcolm, J. Agogbua, M. O'Dell, J. McManus, "Requirements for Traffic Engineering Over MPLS", RFC2702, September 1999. [RFC3031] Rosen, E., Viswanathan, A. and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, January 2001. [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. [RFC3246] Davie, B., Charny, A., Bennet, J.C.R., Benson, K., Le Boudec, J.Y., Davari, S., Courtney, W., Firioiu, V. and Yasukawa, et. al. [Page 30]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 D. Stiliadis, "An Expedited Forwarding PHB (Per-Hop Behavior)", RFC 3246, March 2002. [RFC3667] Bradner, S., "IETF Rights in Contributions", BCP 78, RFC 3667, February 2004. [RFC3668] Bradner, S., Ed., "Intellectual Property Rights in IETF Technology", BCP 79, RFC 3668, February 2004. 8.2 Informational References [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. [RFC3564] F. Le Faucheur, W. Lai, "Requirements for Support of Differentiated Services-aware MPLS Traffic Engineering", RFC 3564, July 2003. [RFC3630] D. Katz, D. Yeung, K. Kompella, "Traffic Engineering Extensions to OSPF Version 2", RFC 3630, September 2003. [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-10.txt, July 2004. [BGPMPLS-VPN] E. Rosen, Y.Rekhter, Editor, "BGP/MPLS IP VPNs", draft-ietf-l3vpn-rfc2547bis-02.txt, September 2004. [GMPLS-ROUTE] 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 Yasukawa, et. al. [Page 31]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 Communications, pp.332-345, 1997. [FRR] P. Pan, G. Swallow, A. Atlas, "Fast Reroute Extensions to RSVP-TE for LSP Tunnels", draft-ietf-mpls-rsvp-lsp- fastreroute-07.txt, August 2004. [IS-IS-TE] Henk Smit, Tony Li, "Intermediate System to Intermediate System (IS-IS) Extensions for Traffic Engineering (TE)", RFC 3784, June 2004. [CRANKBACK] A. Farrel, A. Satyanarayana, A. Iwata, N. Fujita, G. Ash, S. Marshall, "Crankback Signaling Extensions for MPLS Signaling", draft-ietf-ccamp-crankback-02.txt, July 2004. [LSP-HIER] K. Kompella, Y. Rekhter, "LSP Hierarchy with Generalized MPLS TE", draft-ietf-mpls-lsp-hierarchy- 08.txt, September 2002. [NODE-ID] Vasseur, Ali and Sivabalan, "Definition of an RRO node- id subobject", draft-ietf-mpls-nodeid-subobject-01.txt, June 2003. 9. Editor's Address Seisho Yasukawa 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 10. Authors' Addresses Dimitri Papadimitriou Alcatel Francis Wellensplein 1, B-2018 Antwerpen, Belgium Phone : +32 3 240 8491 Email: dimitri.papadimitriou@alcatel.be Yasukawa, et. al. [Page 32]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 JP Vasseur Cisco Systems, Inc. 300 Beaver Brook Road Boxborough, MA 01719, USA Email: jpv@cisco.com Yuji Kamite NTT Communications Corporation Tokyo Opera City Tower 3-20-2 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 Phone: +1 978 964 2142 Email: mjork@avici.com 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 33]
Internet Draft draft-ietf-mpls-p2mp-requirement-04.txt September 2004 Jean-Louis Le Roux France Telecom 2, avenue Pierre-Marzin 22307 Lannion Cedex France Email: jeanlouis.leroux@francetelecom.com 11. Intellectual Property Consideration The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. 12. Full Copyright Statement Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Yasukawa, et. al. [Page 34]
