MPLS Working Group Z. Ali, Ed. Internet-Draft Cisco Systems, Inc. Intended status: Standards Track N. Neate Expires: April 25, 2010 Data Connection Ltd October 26, 2009 Signaling RSVP-TE P2MP LSPs in an Inter-domain Environment draft-ali-mpls-inter-domain-p2mp-rsvp-te-lsp-03.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. 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The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 25, 2010. Abstract Point-to-MultiPoint (P2MP) Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering Label Switched Paths (TE LSPs) may be established using signaling techniques described in [RFC4875]. However, [RFC4875] does not address issues that arise when a P2MP-TE LSP is signaled in multi-domain networks. Specifically, it does not provide a mechanism to avoid re-merges in inter-domain P2MP TE LSPs. This document provides a framework and protocol extensions for establishing and controlling P2MP MPLS and GMPLS TE LSPs in multi-domain networks. Ali & Neate Expires April 25, 2010 [Page 1] Internet-Draft RSVP-TE P2MP Inter-domain LSPs October 2009 This document borrows inter-domain TE terminology from [RFC4726], e.g., for the purposes of this document, a domain is considered to be any collection of network elements within a common sphere of address management or path computational responsibility. Examples of such domains include Interior Gateway Protocol (IGP) areas and Autonomous Systems (ASes). Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Conventions used in this document . . . . . . . . . . . . 4 2. Framework . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. RSVP-TE signaling extensions . . . . . . . . . . . . . . . . . 4 3.1. SIBLING_S2L object . . . . . . . . . . . . . . . . . . . . 4 3.1.1. Format . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1.2. Processing . . . . . . . . . . . . . . . . . . . . . . 7 3.2. Grafting . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.3. Crankback and Path Error . . . . . . . . . . . . . . . . . 8 4. Security Considerations . . . . . . . . . . . . . . . . . . . 8 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. Normative References . . . . . . . . . . . . . . . . . . . 9 6.2. Informative References . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 Intellectual Property and Copyright Statements . . . . . . . . . . 10 Ali & Neate Expires April 25, 2010 [Page 2] Internet-Draft RSVP-TE P2MP Inter-domain LSPs October 2009 1. Introduction [RFC4875] describes how to set up point-to-multipoint (P2MP) Traffic Engineering Label Switched Paths (TE LSPs) for use in MultiProtocol Label Switching (MPLS) and Generalized MPLS (GMPLS) networks. As with all other RSVP controlled LSPs, P2MP LSP state is managed using RSVP messages. While the use of RSVP messages is mostly similar to their P2P counterpart, P2MP LSP state differs from P2P LSP in a number of ways. In particular, the P2MP LSP must also handle the "re-merge" problem described in [RFC4875] section 18. The term "re-merge" refers to the situation when two S2L sub-LSPs branch at some point in the P2MP tree, and then intersect again at a another node further down the tree. This may occur due to discrepencies in the routing algorithms used by different nodes, errors in path calculation or manual configuration, or network topology changes during the establishment of the P2MP LSP. Such re- merges are inefficient due to the unnecessary duplication of data. Consequently one of the requirements for signaling P2MP LSPs is choose a P2MP path that is re-merge free. In some deployments, it may also be required to signal P2MP LSPs that are both re-merge and crossover free [RFC4875]. This requirement becomes more acute to address when P2MP LSP spans multiple domains. For the purposes of this document, a domain is considered to be any collection of network elements within a common sphere of address management or path computational responsibility. Examples of such domains include Interior Gateway Protocol (IGP) areas and Autonomous Systems (ASes). This is because in an inter- domain environment, the ingress node may not have topological visibility into other domains to be able to compute and signal a re- merge free P2MP LSP. In that case, the border node for a new domain will be given one or more loose next hops for the P2MP LSP. When processing a path message, it may not have knowledge of all of the destinations of the P2MP LSP, either because S2L sub-LSPs are split between multiple Path messages, or because not all S2L sub-LSPs pass through this border node. In that case, existing protocol mechanisms do not provide sufficient information for it to be able to expand the loose hop(s) in such a way that the overall P2MP path is guaranteed to be optimal and re-merge free. This document proposes a simple extension to provide border nodes with sufficient information about the P2MP LSP to be able to expand EROs for individual S2L sub-LSPs such that overall P2MP LSP is re- merge free. Specifically, this document defines a mechanism for including a list of addresses in a Path message sent to a border node, each of which is the next ERO hop address for an S2L sub-LSP Ali & Neate Expires April 25, 2010 [Page 3] Internet-Draft RSVP-TE P2MP Inter-domain LSPs October 2009 that is not itself included in the Path message. The border node can then compute a P2MP route for the complete P2MP LSP even when signaling just a subset of the S2L sub-LSPs, thus guaranteeing that the final P2MP path is optimal and re-merge free within that domain. The need for finding an end-to-end path that is re-merge free also increases chances of crankbacks during setting up P2MP LSPs as compared to their P2P counterparts. Nonetheless, crankback mechanisms for P2MP LSPs are not addressed by [RFC4875]. This document also describes how crankback signaling extensions for MPLS and GMPLS RSVP-TE defined in [RFC4920] apply to setting up P2MP TE LSPs. The solution also does not guarantee optimization of the overall P2MP tree across all domains. PCE can be used, instead, to address optimization of the overall P2MP tree [REFERENCE NOT FOUND]. 1.1. Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC-2119. 2. Framework TBA 3. RSVP-TE signaling extensions This section describes the signaling extensions required to address the above-mentioned functionality. 3.1. SIBLING_S2L object The SIBLING_S2L object is signaled in RSVP-TE Path messages and describes related addresses for Sibling S2L sub-LSPs that should be considered when doing loose ERO hop expansion. 3.1.1. Format The IPv4 SIBLING_S2L object (Class = TBA, C-Type = TBA) has the format: Ali & Neate Expires April 25, 2010 [Page 4] Internet-Draft RSVP-TE P2MP Inter-domain LSPs October 2009 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 address of the border node | | IPv4 address from related sibling S2L sub-LSP 1 | | IPv4 address from related sibling S2L sub-LSP 2 | | IPv4 address from related sibling S2L sub-LSP 1 | // // | IPv4 address from related sibling S2L sub-LSP last | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type 0x01 IPv4 address Length The Length contains the total length of the object in bytes, including the Type and Length fields. The Length is variable depending on the addresses in the list. IPv4 address of the border node IPv4 address of the target border node, where ERO extension for this and related S2L sub-LSPs of the P2MP LSP is desired. This address MUST match one of the IPv4 addresses contained in the ERO with L flag. IPv4 address from related sibling S2L sub-LSP x IPv4 address of a node on another sibling S2L sub-LSP x, which is signaled in a separate Path message but which also require ERO extension at the border node contained in IPv4 address of the border node field. Together this list contains all addresses on a given P2MP LSP to which the border node needs to expand the EROs. The IPv6 SIBLING_S2L object (Class = TBA, C-Type = TBA) has the format: Ali & Neate Expires April 25, 2010 [Page 5] Internet-Draft RSVP-TE P2MP Inter-domain LSPs October 2009 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv6 address of the border node | | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv6 address from related sibling S2L sub-LSP 1 | | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv6 address from related sibling S2L sub-LSP 2 | | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv6 address from related sibling S2L sub-LSP 1 | | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // // | IPv6 address from related sibling S2L sub-LSP last | | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type 0x02 IPv6 address Length The Length contains the total length of the object in bytes, including the Type and Length fields. The Length is variable depending on the addresses in the list. IPv6 address of the border node IPv6 address of the target border node, where ERO extension for this and related S2L sub-LSPs of the P2MP LSP is desired. This address MUST match one of the IPv6 addresses contained in the ERO with L flag. Ali & Neate Expires April 25, 2010 [Page 6] Internet-Draft RSVP-TE P2MP Inter-domain LSPs October 2009 IPv6 address from related sibling S2L sub-LSP x IPv6 address of a node on another sibling S2L sub-LSP x, which is signaled in a separate Path message but which also require ERO extension at the border node contained in IPv6 address of the border node field. Together this list contains all addresses on a given P2MP LSP to which the border node needs to expand the EROs. 3.1.2. Processing 3.1.2.1. Multiple S2L Sub-LSPs in Each Path Message When multiple S2L sub-LSPs are carried in each Path message it is RECOMMENDED that P2MP LSP is partitioned in such a way that the Path message to a border node, where ERO expansion is desired, contains all S2Ls of the P2MP LSP that transit through that domain. This provides the border node with information about all the loose ERO hops it needs to expand. It may be that signaling all those S2L sub-LSPs in the same Path message is not possible because doing so would exceed the size limit for the message, or because not all S2L sub-LSPs enter the domain through the same border node. Procedures to handle those cases will be addressed in a later version of this document. 3.1.2.2. Single S2L Sub-LSP in Each Path Message When each Path message contains only one S2L sub-LSP, the following procedures MAY be followed to achieve ERO expansion in a re-merge free and a more cost effective manner. As specified in [RFC3209], loose hops are listed in the ERO object of the RSVP Path message with the L flag of the IPv4 or the IPv6 prefix sub-object set. When the ERO in the Path message of a P2MP LSP contains a loose hop, the Path message MAY (optionally) contain a SIBLING_S2L object for each loose hop specified in the ERO. 3.2. Grafting Grafting for an S2L sub-LSP is achieved by the ingress node signaling it with the same P2MP ID and LSP ID, via existing or new border nodes with loose hop expansion. If an existing border node is used along the path, the border node locally finds how ERO expansions for other siblings of the P2MP LSP transiting through this border node is done and expands the route of new S2L such that it's re-merge free. Ali & Neate Expires April 25, 2010 [Page 7] Internet-Draft RSVP-TE P2MP Inter-domain LSPs October 2009 3.3. Crankback and Path Error Crankback procedures for rerouting around failures for P2P RSVP-TE LSPs are defined in [RFC4920]. These techniques can also be applied to P2MP LSPs, as decribed in this section. It is RECOMMENDED that boundary re-routing or segment-based re- routing is requested for P2MP LSPs traversing multiple domains. This is because border nodes that are expanding loose hops are typically best placed to correct any re-merge errors that occur within their domain, not the ingress node. If a node on the path of the P2MP LSP is unable to find a route that can supply the required resources or is not re-merge free, it SHOULD generate a Path Error message for the subset of the S2L sub-LSPs which it is not able to route. For this purpose the node SHOULD try to find a minimum subset of S2L sub-LSPs for which the Path Error needs to be generated. This rule applies equally to the case where multiple S2L Sub-LSPs are signaled using one Path message, as to the case where a single S2L Sub-LSP is signaled in each Path message. GMPLS Notify messages do not include S2L_SUB_LSP objects and cannot be used to send errors for a subset of the S2L sub-LSPs in a Path message. For that reason, the node SHOULD use a Path Error message rather than a Notify message to communicate the error. In the case of a re-merge error, the node SHOULD use the Error Code "Routing Problem" and the Error Value "ERO resulted in re-merge" as specified in [RFC4875]. A border node receiving a Path Error should attempt to re-route according to the crankback procedures defined in [RFC4920]. In the case of a re-merge error for which some of the re-merging S2L sub- LSPs do not pass through the border node, it should propagate the Path Error usptream. The first node through which all S2L sub-LSPs concerned transit which receives the Path Error and is allowed to perform crankback procedures should re-route the S2L sub-LSPs concerned to all use the same border node. 4. Security Considerations Security considerations and requirements from [RFC4875] and [RFC4875] apply equally to this document. Furthermore, there are some additional security considerations that may be induced by the use of "Related Addresses for Sibling S2L sub-LSP" object defined in this document. These security considerations will be added in a later version of the draft. Ali & Neate Expires April 25, 2010 [Page 8] Internet-Draft RSVP-TE P2MP Inter-domain LSPs October 2009 5. IANA Considerations Code points for "Related Addresses for Sibling S2L sub-LSP" object defined in this document will be required. Much of the details here are TBA. 6. References 6.1. Normative References [RFC4875] Aggarwal, R., Papadimitriou, D., and S. Yasukawa, "Extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) for Point-to-Multipoint TE Label Switched Paths (LSPs)", RFC 4875, May 2007. [RFC4920] Farrel, A., Satyanarayana, A., Iwata, A., Fujita, N., and G. Ash, "Crankback Signaling Extensions for MPLS and GMPLS RSVP-TE", RFC 4920, July 2007. 6.2. Informative References [RFC4726] Farrel, A., Vasseur, J., and A. Ayyangar, "A Framework for Inter-Domain Multiprotocol Label Switching Traffic Engineering", RFC 4726, November 2006. [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. Authors' Addresses Zafar Ali (editor) Cisco Systems, Inc. Email: zali@cisco.com Nic Neate Data Connection Ltd 100 Church Street Enfield EN2 6BQ United Kingdom Email: nhn@dataconnection.com Ali & Neate Expires April 25, 2010 [Page 9] Internet-Draft RSVP-TE P2MP Inter-domain LSPs October 2009 Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. 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The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Ali & Neate Expires April 25, 2010 [Page 10]