Network Working Group IJ. Wijnands, Ed. Internet-Draft T. Eckert Intended status: Standards Track Cisco Systems, Inc. Expires: June 3, 2012 N. Leymann Deutsche Telekom M. Napierala AT&T Labs December 1, 2011 Multipoint LDP in-band signaling for Point-to-Multipoint and Multipoint- to-Multipoint Label Switched Paths draft-ietf-mpls-mldp-in-band-signaling-05 Abstract Consider an IP multicast tree, constructed by Protocol Independent Multicast (PIM), needs to pass through an MPLS domain in which Multipoint LDP (mLDP) Point-to-Multipoint and/or Multipoint-to- Multipoint Labels Switched Paths (LSPs) can be created. The part of the IP multicast tree that traverses the MPLS domain can be instantiated as a multipoint LSP. When a PIM Join message is received at the border of the MPLS domain, information from that message is encoded into mLDP messages. When the mLDP messages reach the border of the next IP domain, the encoded information is used to generate PIM messages that can be sent through the IP domain. The result is an IP multicast tree consisting of a set of IP multicast sub-trees that are spliced together with a multipoint LSP. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on June 3, 2012. Copyright Notice Wijnands, et al. Expires June 3, 2012 [Page 1] Internet-Draft In-band signaling with mLDP December 2011 Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. 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. 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. Wijnands, et al. Expires June 3, 2012 [Page 2] Internet-Draft In-band signaling with mLDP December 2011 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Conventions used in this document . . . . . . . . . . . . 4 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 2. In-band signaling for MP LSPs . . . . . . . . . . . . . . . . 5 2.1. Transiting Unidirectional IP multicast Shared Trees . . . 6 2.2. Transiting IP multicast source trees . . . . . . . . . . . 7 2.3. Transiting IP multicast bidirectional trees . . . . . . . 7 3. LSP opaque encodings . . . . . . . . . . . . . . . . . . . . . 8 3.1. Transit IPv4 Source TLV . . . . . . . . . . . . . . . . . 8 3.2. Transit IPv6 Source TLV . . . . . . . . . . . . . . . . . 8 3.3. Transit IPv4 bidir TLV . . . . . . . . . . . . . . . . . . 9 3.4. Transit IPv6 bidir TLV . . . . . . . . . . . . . . . . . . 10 4. Security Considerations . . . . . . . . . . . . . . . . . . . 10 5. IANA considerations . . . . . . . . . . . . . . . . . . . . . 11 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11 7. Contributing authors . . . . . . . . . . . . . . . . . . . . . 11 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . . 12 8.2. Informative References . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Wijnands, et al. Expires June 3, 2012 [Page 3] Internet-Draft In-band signaling with mLDP December 2011 1. Introduction The mLDP specification [I-D.ietf-mpls-ldp-p2mp] describes mechanisms for creating point-to-multipoint (P2MP) and multipoint-to-multipoint MP2MP LSPs. These LSPs are typically used for transporting enduser multicast packets. However, the mLDP specification does not provide any rules for associating particular enduser multicast packets with any particular LSP. Other drafts, like [I-D.ietf-l3vpn-2547bis-mcast], describe applications in which out- of-band signaling protocols, such as PIM and BGP, are used to establish the mapping between an LSP and the multicast packets that need to be forwarded over the LSP. This draft describes an application in which the information needed to establish the mapping between an LSP and the set of multicast packets to be forwarded over it is carried in the "opaque value" field of an mLDP FEC element. When an IP multicast tree (either a source-specific tree or a bidirectional tree) enters the MPLS network the (S,G) or (*,G) information from the IP multicast control plane state is carried in the opaque value field of the mLDP FEC message. As the tree leaves the MPLS network, this information is extracted from the FEC element and used to build the IP multicast control plane. PIM messages can be sent outside the MPLS domain. Note that although the PIM control messages are sent periodically, the mLDP messages are not. Each IP multicast tree is mapped one-to-one to a P2MP or MP2MP LSP in the MPLS network. This type of service works well if the number of LSPs that are created is under control of the MPLS network operator, or if the number of LSPs for a particular service are known to be limited in number. 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 [RFC2119]. 1.2. Terminology IP multicast tree : An IP multicast distribution tree identified by an source IP address and/or IP multicast destination address, also refered to as (S,G) and (*,G). Wijnands, et al. Expires June 3, 2012 [Page 4] Internet-Draft In-band signaling with mLDP December 2011 RP: The PIM Rendezvous Point. SSM: PIM Source Specific Multicast. ASM: PIM Any Source Multicast. mLDP : Multipoint LDP. Transit LSP : An P2MP or MP2MP LSP whose FEC element contains the (S,G) or (*,G) identifying a particular IP multicast distribution tree. In-band signaling : Using the opaque value of a mLDP FEC element to carry the (S,G) or (*,G) indentifying a particular IP multicast tree. P2MP LSP: An LSP that has one Ingress LSR and one or more Egress LSRs. MP2MP LSP: An LSP that connects a set of leaf nodes, acting indifferently as ingress or egress. MP LSP: A multipoint LSP, either a P2MP or an MP2MP LSP. Ingress LSR: Source of the P2MP LSP, also referred to as root node. Egress LSR: One of potentially many destinations of an LSP, also referred to as leaf node in the case of P2MP and MP2MP LSPs. Transit LSR: An LSR that has one or more directly connected downstream LSRs. 2. In-band signaling for MP LSPs Suppose an LSR, call it D, is attached to a network that is capable of MPLS multicast and IP multicast, and D is required to create a IP Wijnands, et al. Expires June 3, 2012 [Page 5] Internet-Draft In-band signaling with mLDP December 2011 multicast tree due to a certain IP multicast event, like a PIM Join, MSDP Source Announcement (SA) [RFC3618], BGP Source Active auto- discovery route [I-D.rekhter-pim-sm-over-mldp] or Rendezvous Point (RP) discovery. Suppose that D can determine that the IP multicast tree needs to travel through the MPLS network until it reaches some other LSR, U. For instance, when D looks up the route to the Source or RP [RFC4601] of the IP multicast tree, it may discover that the route is a BGP route with U as the BGP next hop. Then D may chose to set up a P2MP or MP2MP LSP, with U as root, and to make that LSP become part of the IP multicast distribution tree. Note that other methods are possible to determine that an IP multicast tree is to be transported across an MPLS network using P2MP or MP2MP LSPs, these methods are outside the scope of this document. Source or RP addresses that are reachable in a VPN context are outside the scope of this document. Multicast groups that operate in PIM Dense-Mode are outside the scope of this document. In order to establish a multicast tree via a P2MP or MP2MP LSP using in-band signaling the source and the group will be encoded into an mLDP opaque TLV encoding [I-D.ietf-mpls-ldp-p2mp]. The type of encoding depends on the IP version. The tree type (P2MP or MP2MP) depends on whether this is a source specific or a bidirectional multicast tree. The root of the tree is the BGP next-hop that was found during the route lookup on the source or RP. Using this information a mLDP FEC is created and the LSP is build towards the root of the LSP. When an LSR receives a label mapping or withdraw and discovers it is the root of the identified P2MP or MP2MP LSP, then the following procedure is executed. If the opaque encoding of the FEC indicates this is a Transit LSP (indicated by the opaque type), the opaque TLV is decoded and the multicast source and group is passed to the multicast code. If the multicast tree information is received via a label mapping, the multicast code will add the downstream LDP neighbor to the olist of the corresponding (S,G) or (*,G) state, creating such state if it does not already exist. If it is due to a label withdraw, the multicast code will remove the downstream LDP neighbor from the olist of the corresponding (S,G) or (*,G) state. From this point on normal PIM processing will occur. 2.1. Transiting Unidirectional IP multicast Shared Trees Nothing prevents PIM shared trees, used by PIM-SM in the ASM service model, from being transported across a MPLS core. However, it is not possible to prune individual sources from the shared tree without the Wijnands, et al. Expires June 3, 2012 [Page 6] Internet-Draft In-band signaling with mLDP December 2011 use of an additional out-of-band signaling protocol, like PIM or BGP [I-D.rekhter-pim-sm-over-mldp]. For that reason transiting Shared Trees across a Transit LSP is outside the scope of this draft. 2.2. Transiting IP multicast source trees IP multicast source trees can either be created via PIM operating in SSM mode [RFC4607] or ASM mode [RFC4601]. When PIM-SM is used in ASM mode, the usual means of discovering active sources is to join a sparse mode shared tree. However, this document does not provide any method of establishing a sparse mode shared tree across an MPLS network. To apply the technique of this document to PIM-SM in ASM mode, there must be some other means of discovering the active sources. One possible means is the use of MSDP [RFC3618]. Another possible means is to use BGP Source Active auto-discovery routes, as documented in [I-D.rekhter-pim-sm-over-mldp]. However, the method of discovering the active sources is outside the scope of this document, and as a result this document does not specify everything that is needed to support the ASM service model using in-band signaling. The source and group addresses are encoded into the a transit TLV as specified in Section 3.1 and Section 3.2. 2.3. Transiting IP multicast bidirectional trees Bidirectional IP multicast trees [RFC5015] MUST be transported across a MPLS network using MP2MP LSPs. A bidirectional tree does not have a specific source address; the group address, subnet mask and RP are relevant for multicast forwarding. This document does not provide procedures to discover RP to group mappings dynamically across an MPLS network and assumes the RP is statically defined. Support of dynamic RP mappings in combination with in-band signaling is outside the scope of his document. The RP for the group is used to select the ingress LSR and root of the LSP. The group address is encoded according to the rules of Section 3.3 or Section 3.4, depending on the IP version. The subnet mask associated with the bidirectional group is encoded in the Transit TLV. There are two types of bidirectional states in IP multicast, the group specific state and the RP state. The first type is typically created due to receiving a PIM join and has a subnet mask of 32 for IPv4 and 128 for IPv6. The latter is typically created via the static RP mapping and has a variable subnet mask. The RP state is used to build a tree to the RP and used for sender only branches. Each state (group specific and RP state) will result in a separate MP2MP LSP. The merging of the two MP2MP LSPs will be done by PIM on the root LSR. No speccial procedures are nessesary for PIM to merge the two LSPs, each LSP is effectively treated as a Wijnands, et al. Expires June 3, 2012 [Page 7] Internet-Draft In-band signaling with mLDP December 2011 PIM enabled interface. Please see [RFC5015] for more details. For transporting the packets of a sender only branch we create a MP2MP LSP. Other sender only branches will receive these packets and will not forward them because there are no receivers. These packets will be dropped. If that affect is undesireable some other means of transport has to be established to forward packets to the root of the tree, like a Multi-Point to Point LSP for example. A technique to unicast packets to the root of a P2MP or MP2MP LSP is documented in [I-D.rosen-l3vpn-mvpn-mspmsi] section 3.2.2.1 and [I-D.ietf-mpls-ldp-p2mp] section 3. 3. LSP opaque encodings This section documents the different transit opaque encodings. 3.1. Transit IPv4 Source TLV 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 | Source +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Group +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: 3 (to be assigned by IANA). Length: 8 octets Source: IPv4 multicast source address, 4 octets. Group: IPv4 multicast group address, 4 octets. 3.2. Transit IPv6 Source TLV Wijnands, et al. Expires June 3, 2012 [Page 8] Internet-Draft In-band signaling with mLDP December 2011 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 | Source ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ | Group ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: 4 (to be assigned by IANA). Length: 32 octets Source: IPv6 multicast source address, 16 octets. Group: IPv6 multicast group address, 16 octets. 3.3. Transit IPv4 bidir TLV 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 | Mask Len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RP | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Group | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: 5 (to be assigned by IANA). Length: 9 octets Mask Len: The number of contiguous one bits that are left justified and used as a mask, 1 octet. Wijnands, et al. Expires June 3, 2012 [Page 9] Internet-Draft In-band signaling with mLDP December 2011 RP: Rendezvous Point (RP) IPv4 address used for encoded Group, 4 octets. Group: IPv4 multicast group address, 4 octets. 3.4. Transit IPv6 bidir TLV 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 | Mask Len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RP ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Group ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: 6 (to be assigned by IANA). Length: 33 octets Mask Len: The number of contiguous one bits that are left justified and used as a mask, 1 octet. RP: Rendezvous Point (RP) IPv6 address used for encoded group, 16 octets. Group: IPv6 multicast group address, 16 octets. 4. Security Considerations The same security considerations apply as for the base LDP specification, as described in [RFC5036]. Wijnands, et al. Expires June 3, 2012 [Page 10] Internet-Draft In-band signaling with mLDP December 2011 5. IANA considerations This document requires allocation from the 'LDP MP Opaque Value Element basic type' name space managed by IANA. The values requested are: Transit IPv4 Source TLV type - 3 Transit IPv6 Source TLV type - 4 Transit IPv4 Bidir TLV type - 5 Transit IPv6 Bidir TLV type - 6 6. Acknowledgments Thanks to Eric Rosen for his valuable comments on this draft. Also thanks to Yakov Rekhter, Adrial Farrel, Uwe Joorde and Loa Andersson for providing comments on this draft. 7. Contributing authors Below is a list of the contributing authors in alphabetical order: Toerless Eckert Cisco Systems, Inc. 170 Tasman Drive San Jose, CA, 95134 USA E-mail: eckert@cisco.com Nicolai Leymann Deutsche Telekom Winterfeldtstrasse 21 Berlin, 10781 Germany E-mail: n.leymann@telekom.de Maria Napierala AT&T Labs 200 Laurel Avenue Middletown, NJ 07748 USA E-mail: mnapierala@att.com Wijnands, et al. Expires June 3, 2012 [Page 11] Internet-Draft In-band signaling with mLDP December 2011 IJsbrand Wijnands Cisco Systems, Inc. De kleetlaan 6a 1831 Diegem Belgium E-mail: ice@cisco.com 8. References 8.1. Normative References [RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP Specification", RFC 5036, October 2007. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [I-D.ietf-mpls-ldp-p2mp] Minei, I., Kompella, K., Wijnands, I., and B. Thomas, "Label Distribution Protocol Extensions for Point-to- Multipoint and Multipoint-to-Multipoint Label Switched Paths", draft-ietf-mpls-ldp-p2mp-11 (work in progress), October 2010. 8.2. Informative References [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", RFC 4601, August 2006. [RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for IP", RFC 4607, August 2006. [RFC5015] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano, "Bidirectional Protocol Independent Multicast (BIDIR- PIM)", RFC 5015, October 2007. [RFC3618] Fenner, B. and D. Meyer, "Multicast Source Discovery Protocol (MSDP)", RFC 3618, October 2003. [I-D.ietf-l3vpn-2547bis-mcast] Aggarwal, R., Bandi, S., Cai, Y., Morin, T., Rekhter, Y., Rosen, E., Wijnands, I., and S. Yasukawa, "Multicast in MPLS/BGP IP VPNs", draft-ietf-l3vpn-2547bis-mcast-10 (work in progress), January 2010. [I-D.rekhter-pim-sm-over-mldp] Wijnands, et al. Expires June 3, 2012 [Page 12] Internet-Draft In-band signaling with mLDP December 2011 Rekhter, Y., Aggarwal, R., and N. Leymann, "Carrying PIM-SM in ASM mode Trees over P2MP mLDP LSPs", draft-rekhter-pim-sm-over-mldp-02 (work in progress), August 2010. [I-D.rosen-l3vpn-mvpn-mspmsi] Boers, A., Cai, Y., Napierala, M., Rosen, E., and I. Wijnands, "MVPN: Optimized use of PIM via MS-PMSIs", draft-rosen-l3vpn-mvpn-mspmsi-08 (work in progress), January 2011. Authors' Addresses IJsbrand Wijnands (editor) Cisco Systems, Inc. De kleetlaan 6a Diegem 1831 Belgium Email: ice@cisco.com Toerless Eckert Cisco Systems, Inc. 170 Tasman Drive San Jose CA, 95134 USA Email: eckert@cisco.com Nicolai Leymann Deutsche Telekom Winterfeldtstrasse 21 Berlin 10781 Germany Email: n.leymann@telekom.de Wijnands, et al. Expires June 3, 2012 [Page 13] Internet-Draft In-band signaling with mLDP December 2011 Maria Napierala AT&T Labs 200 Laurel Avenue Middletown NJ 07748 USA Email: mnapierala@att.com Wijnands, et al. Expires June 3, 2012 [Page 14]