Network Working Group Y. Rekhter Internet Draft Juniper Networks Expiration Date: September 2011 R. Aggarwal Juniper Networks T. Morin France Telecom I. Grosclaude France Telecom N. Leymann Deutsche Telekom AG S. Saad AT&T March 14, 2011 Inter-Area P2MP Segmented LSPs draft-raggarwa-mpls-seamless-mcast-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. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Rekhter [Page 1] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 Copyright and License Notice 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. Abstract This document describes procedures for building inter-area point-to- multipoint (P2MP) segmented service LSPs by partitioning such LSPs into intra-area segments and using BGP as the inter-area routing and label distribution protocol. Within each IGP area the intra-area segments are either carried over intra-area P2MP LSPs, using P2MP LSP hierarchy, or instantiated using ingress replication. The intra-area P2MP LSPs may be signaled using P2MP RSVP-TE or P2MP mLDP. If ingress replication is used in an IGP area then MP2P LDP LSPs or P2P RSVP-TE LSPs may be used in the IGP area. The applications/services that use such an inter-area service LSP may be BGP MVPN, VPLS multicast or Internet multicast over MPLS. Rekhter [Page 2] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 Table of Contents 1 Specification of requirements ......................... 4 2 Introduction .......................................... 4 3 General Assumptions and Terminology ................... 5 4 Inter-area P2MP Segmented Next-Hop Extended Community . 6 5 Discovering the P2MP FEC of the Inter-Area P2MP Service LSP 6 5.1 BGP MVPN .............................................. 6 5.2 BGP VPLS or LDP VPLS with BGP A-D ..................... 7 5.3 Internet Multicast .................................... 8 6 Egress PE Procedures .................................. 9 6.1 Determining the Upstream ABR/PE/ASBR .................. 9 6.2 Originating a Leaf Auto-Discovery Route ............... 10 6.2.1 Leaf A-D Route for MVPN and VPLS ...................... 10 6.2.2 Leaf A-D Route for Internet Multicast ................. 11 6.2.3 Constructing the Rest of the Leaf A-D Route ........... 12 6.3 PIM-SM in ASM mode for Internet Multicast ............. 12 6.3.1 Option 1 .............................................. 12 6.3.1.1 Originating Source Active auto-discovery routes ....... 13 6.3.1.2 Receiving BGP Source Active auto-discovery route by PE ....13 6.3.1.3 Handling (S, G, RPTbit) state ......................... 14 6.3.2 Option 2 .............................................. 14 6.3.2.1 Originating Source Active auto-discovery routes ....... 14 6.3.2.2 Receiving BGP Source Active auto-discovery route ...... 15 6.3.2.3 Pruning Sources off the Shared Tree ................... 15 6.3.2.4 More on handling (S, G, RPTbit) state ................. 15 7 Egress ABR Procedures ................................. 16 7.1 P2MP LSP as the Intra-Area LSP in the Egress Area ..... 18 7.1.1 RD of the received Leaf-AD route is not zero or all ones ..18 7.1.2 RD of the received Leaf A-D route is zero or all ones . 19 7.1.2.1 Internet Multicast and S-PMSI A-D Routes .............. 19 7.1.2.2 Internet Multicast and Wildcard S-PMSI A-D Routes ..... 19 7.1.3 Internet Multicast and the Expected Upstream Node ..... 19 7.1.4 P2MP LDP LSP as the Intra-Area P2MP LSP in the Egress Area 20 7.1.5 P2MP RSVP-TE LSP as the Intra-Area P2MP LSP in the Egress Area 20 7.2 Ingress Replication in the Egress Area ................ 20 8 Ingress ABR Procedures for constructing segmented inter-area P2MP LSP 21 8.1 P2MP LSP as the Intra-Area LSP in the Backbone Area ... 21 8.2 Ingress Replication in the Backbone Area .............. 22 9 Ingress PE/ASBR Procedures ............................ 22 9.1 P2MP LSP as the intra-area LSP in the ingress area .... 23 9.2 Ingress Replication in the Ingress Area ............... 23 10 Common Tunnel Type in the Ingress and Egress Areas .... 24 11 Placement of Ingress and Egress PEs ................... 24 Rekhter [Page 3] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 12 Data Plane ............................................ 25 12.1 Data Plane Procedures on an ABR ....................... 25 12.2 Data Plane Procedures on an Egress PE ................. 25 12.3 Data Plane Procedures on an Ingress PE ................ 26 12.4 Data Plane Procedures on Transit Routers .............. 27 13 IANA Considerations ................................... 27 14 Security Considerations ............................... 27 15 References ............................................ 27 15.1 Normative References .................................. 27 15.2 Informative References ................................ 28 16 Author's Address ...................................... 28 1. Specification of requirements 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]. 2. Introduction This document describes procedures for building inter-area point-to- multipoint (P2MP) segmented service LSPs by partitioning such LSPs into intra-area segments and using BGP as the inter-area routing and label distribution protocol. Within each IGP area the intra-area segments are either carried over intra-area P2MP LSPs, potentially using P2MP LSP hierarchy, or instantiated using ingress replication. The intra-area P2MP LSPs may be signaled using P2MP RSVP-TE or P2MP mLDP. If ingress replication is used in an IGP area then MP2P LDP or P2P RSVP-TE LSPs may be used in the IGP area. The applications/services that use such an inter-area service LSP may be BGP MVPN, VPLS multicast or Internet multicast over MPLS. The primary use case of such segmented P2MP service LSPs is when the PEs are in different areas but in the same AS and thousands or more of PEs require P2MP connectivity. For instance this may be the case when MPLS is pushed further to the metro edge and the metros are in different IGP areas. This may also be the case when a Service Provider's network comprises multiple IGP areas in a single Autonomous System, with a large number of PEs. Seamless MPLS is the industry term to address this case [SEAMLESS-MPLS]. Thus one of the applicabilities of this document is that it describes the multicast Rekhter [Page 4] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 procedures for seamless MPLS. It is to be noted that [BGP-MVPN], [VPLS-P2MP] already specify procedures for building segmented inter-AS P2MP service LSPs. This document complements those procedures as it extends the segmented P2MP LSP model such that it is applicable to inter-area P2MP service LSPs as well. Infact an inter-AS deployment could use inter-AS segmented P2MP LSPs as specified in [BGP-MVPN, VPLS-P2MP] where each intra-AS segment is constructed using inter-area segmented P2MP LSPs as specified in this document. 3. General Assumptions and Terminology This document assumes BGP is used as an inter-area routing and label distribution protocol for the unicast IPv4 /32 or IPv6 /128 routes for the PEs. This document also assumes ABRs act as Route Reflectors (RR) for these routes. Within an AS a P2MP service LSP is partitioned into 3 segments: ingress area segment, backbone area segment, and egress area segment. Within each area a segment is carried over an intra-area P2MP LSP or instantiated using ingress replication. When intra-area P2MP LSPs are used to instantiate the intra-area segments there could be either 1:1 or n:1 mapping between intra-area segments of the inter-area P2MP service LSP and a given intra-area P2MP LSP. The latter is realized using P2MP LSP hierarchy with upstream-assigned labels [RFC5331]. For simplicity we assume that P2MP LSP hierarchy is used even with 1:1 mapping, in which case the upstream-assigned label could be an implicit NULL. When intra-area segments of the inter-area P2MP service LSP are instantiated using ingress replication, then multiple such segments may be carried in the same P2P RSVP-TE or MP2P LDP LSP. This can be achieved using downstream-assigned labels alone. The ingress area segment of a P2MP service LSP is rooted at a PE (or at an ASBR in the case where the P2MP service LSP spans multiple ASes). The leaves of this segment are other PEs/ASBRs and ABRs in the same area as the root PE. The backbone area segment is rooted at an ABR that is connected to the ingress area (ingress ABR), and has as its leaves ABRs that are connected to the egress area(s) or PEs in the backbone area. The egress area segment is rooted at an ABR in the egress area (egress ABR), and has as its leaves PEs and ASBR in that egress area (the latter covers the case where the P2MP service LSP spans multiple ASes). Note that for a given P2MP service LSP there may be more than one backbone segment, each rooted at its own Rekhter [Page 5] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 ingress ABR, and more than one egress area segment, each rooted at its own egress ABR. 4. Inter-area P2MP Segmented Next-Hop Extended Community This document defines a new BGP Extended Community "Inter-area P2MP Next-Hop" extended community. This is an IP address specific Extended Community, of an extended type and is transitive across AS boundaries [RFC4360]. A PE or an ABR or an ASBR constructs the Inter-area P2MP Segmented Next-Hop Extended Community as follows: - The Global Administrator field MUST be set to an IP address of the PE or ASBR or ABR that originates or advertises the route, which carries the P2MP Next-Hop Extended Community. For example this address may be the loopback address or the PE, ASBR or ABR that advertises the route. - The Local Administrator field MUST be set to 0. The detailed usage of this extended community is described in the following sections. 5. Discovering the P2MP FEC of the Inter-Area P2MP Service LSP The P2MP FEC identifies the inter-area P2MP service LSP. The egress PEs need to learn this P2MP FEC in order to initiate the creation of the egress area segment of the P2MP inter-area service LSP. The P2MP FEC of the inter-area P2MP LSP is learned by the egress PEs either by configuration, or based on the application-specific procedures (e.g., MVPN-specific procedures, VPLS-specific procedures). 5.1. BGP MVPN Egress PEs discover the P2MP FEC of the service LSPs used by BGP MVPN using the I-PMSI or S-PMSI A-D routes that are originated by the ingress PEs or ASBRs following the procedures of [BGP-MVPN], along with modifications as described in this document. The NLRI of such routes encodes the P2MP FEC. The procedures in this document require that at least one ABR in a given IGP area act as Route Reflector for MVPN auto-discovery (A-D) routes. Rekhter [Page 6] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 The "Leaf Information Required" flag MUST be set in the P-Tunnel attribute carried in such routes, when originated by the ingress PEs or ASBRs. Before any Leaf auto discovery route is advertised by a PE or ABR in the same area, as described in the following sections, an I-/S-PMSI auto-discovery route is advertised either with an explicit Tunnel Type and Tunnel Identifier in the PMSI Tunnel Attribute, if the Tunnel Identifier has already been assigned, or with a special Tunnel Type of "No tunnel information present" otherwise. When the I/S-PMSI routes are re-advertised by an ABR, "Leaf Information Required" flag MUST be set in the P-Tunnel attribute present in the routes. Note that the procedures in the above paragraph apply when intra-area segments are realized by either intra-area P2MP LSPs or by ingress replication. When BGP MVPN I-PMSI or S-PMSI A-D routes are advertised or propagated to signal Inter-area P2MP service LSPs, they MUST carry the Inter-area P2MP Segmented Next-Hop Extended Community. This Extended Community MUST be included in the I/S-PMSI A-D route by the PE or ASBR that originates such a route and the Global Administrator field MUST be set to the advertising PE or ASBR's IP address. This Extended Community MUST also be included by ABRs as they re-advertise such routes. An ABR MUST set the Global Administrator field of the P2MP Segmented Next-Hop Extended Community to its own IP address. This allows ABRs and PEs/ASBRs to follow the procedures in this document when these procedures differ from those in [BGP-MVPN]. To avoid requiring ABRs to participate in the propagation of C- multicast routes, this document requires ABRs NOT to modify BGP Next Hop when re-advertising Inter-AS I-PMSI A-D routes. For consitancy this document requires ABRs to NOT modify BGP Next-Hop when re- advertising both Intra-AS and Inter-AS I/S-PMSI A-D routes. The egress PEs may advertise the C-multicast routes to RRs that are different than the ABRs. However ABRs still can be configured to be the Route Reflectors for C-multicast routes, in which case they will participate in the propagation of C-multicast routes. 5.2. BGP VPLS or LDP VPLS with BGP A-D Egress PEs discover the P2MP FEC of the service LSPs used by VPLS, using the VPLS A-D routes that are originated by the ingress PEs [BGP-VPLS, VPLS-AD] or S-PMSI A-D routes that are originated by the ingress PE [VPLS-P2MP]. The NLRI of such routes encodes the P2MP FEC. The "Leaf Information Required" flag MUST be set in the P-Tunnel attribute carried in such routes. Before any Leaf auto discovery route is advertised by a PE or ABR in its own area, as described in Rekhter [Page 7] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 the following sections, an VPLS/S-PMSI autodiscovery route is advertised either with an explicit Tunnel Type and Tunnel Identifier in the PMSI Tunnel Attribute, if the Tunnel Identifier has already been assigned, or with a special Tunnel Type of "No tunnel information present" otherwise. When VPLS A-D or S-PMSI A-D routes are advertised or propagated to signal Inter-area P2MP service LSPs, they MUST carry the Inter-area P2MP Segmented Next-Hop Extended Community. This Extended Community MUST be included in the A-D route by the PE or ASBR that originates such a route and the Global Administrator field MUST be set to the advertising PE or ASBR's IP address. This Extended Community MUST also be included by ABRs as they re-advertise such routes. An ABR MUST set the Global Administrator field of the P2MP Segmented Next- Hop Extended Community to its own IP address. This allows ABRs and PEs/ASBRs to follow the procedures in this document when these procedures differ from those in [VPLS-P2MP]. Note that the procedures in the above paragraph apply when intra-area segments are realized by either intra-area P2MP LSPs or by ingress replication. The procedures in this document require that at least one ABR in a given area act as Route Reflector for MVPN auto-discovery (A-D) routes. These ABRs/RRs MUST NOT modify BGP Next Hop when re- advertising these A-D routes. 5.3. Internet Multicast This section describes how the egress PEs discover the P2MP FEC when the application is internet multicast. In the case where Internet multicast uses PIM-SM in ASM mode the following assumes that an inter-area P2MP service LSP could be used to either carry traffic on a shared (*,G), or a source (S,G) tree. An egress PE learns the (S/*, G) of a multicast stream as a result of receiving IGMP or PIM messages on one of its IP multicast interfaces. This (S/*, G) forms the P2MP FEC of the inter-area P2MP service LSP. For each (S/*,G) for which an inter-area P2MP service LSP is instantiated, there may exist a distinct inter-area P2MP service LSP or multiple inter-area P2MP service LSPs may be aggregated using a wildcard (*, *) S-PMSI. Note that this document does not require the use of (*, G) Inter-area P2MP service LSPs when Internet multicast uses PIM-SM in ASM mode. Infact PIM-SM in ASM mode may be supported entirely by using (S, G) Rekhter [Page 8] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 trees alone. 6. Egress PE Procedures This section describes egress PE procedures for constructing segmented inter-area P2MP LSP. The procedures in this section apply irrespective of whether the egress PE is in a leaf IGP area, or the backbone area or even in the same IGP area as the ingress PE/ASBR. In order to support Internet Multicast an egress PE MUST auto- configure an import Route Target with the global administrator field set to the AS of the PE and the local administrator field set to 0. Once an egress PE discovers the P2MP FEC of an inter-area segmented P2MP service LSP, it MUST propagate this P2MP FEC in BGP in order to construct the segmented inter-area P2MP service LSP. This propagation uses BGP Leaf auto-discovery routes. 6.1. Determining the Upstream ABR/PE/ASBR The egress PE discovers the P2MP FEC of an inter-area P2MP Segmented Service LSP as described in section 5. When an egress PE discovers this P2MP FEC it MUST first determine the upstream node to reach such a FEC. If the egress PE is in the egress area and the ingress PE is not in the that egress area, then this upstream node would be the egress ABR. If the egress PE is in the backbone area and the ingress PE is not in the backbone area, then this upstream node would be the ingress ABR. If the egress PE is in the same area as the ingress PE then this upstream node would be the ingress PE. If the application is MVPN or VPLS then the upstream node's IP address is the IP address determined from the Global Administrator field of the Inter-area P2MP Segmented Next-hop Extended Community. As described in section 5 this Extended Community MUST be carried in the MVPN or VPLS A-D route from which the P2MP FEC of the inter-area P2MP Segmented Service LSP is determined. If the application is Internet Multicast then the unicast routes to multicast sources/RPs SHOULD carry the VRF Route Import Extended Community [BGP-MVPN] where the IP address in the Global Administrator field is set to the IP address of the PE or ASBR advertising the unicast route. The Local Administrator field of this community MUST be set to 0. If it is not desirable to advertise the VRF Route Import Extended Community in unicast routes, then unicast routes to multicast sources/RPs MUST be advertised using the multicast SAFI Rekhter [Page 9] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 i.e. SAFI 2 and the VRF Route Import Extended Community MUST be carried in such routes. Further if the application is internet multicast then the BGP unicast routes that advertise the route to the IP address of PEs or ASBRs or ABRs SHOULD carry the Inter-area P2MP Segmented Next-Hop Extended Community where the IP address in the Global Administrator field is set to the IP address of the PE or ASBR or ABR advertising the unicast route. The Local Administrator field of this community MUST be set to 0. If it is not desirable to advertise the P2MP Segmented Import Extended Community in BGP unicast routes, then unicast routes to ABRs, ASBRs or PEs MUST be advertised using the multicast SAFI i.e. SAFI 2 and the Inter-area P2MP Segmented Next-hop Extended Community MUST be carried in such routes. The procedures for handling the next-hop of SAFI 2 routes are the same as those of handling regular Unicast routes and follow [SEAMLESS-MPLS]. In order to determine the upstream node address the egress PE first determines the ingress PE. The egress PE determines the best route to reach S/RP. The ingress PE address is the IP address determined from the Global Administrator field of the VRF Route Import Extended Community, that is present in this route. The egress PE now finds the best unicast route to reach the ingress PE. The upstream node address is the IP address determined from the Global Administrator field of the Inter-area P2MP Segmented Next-Hop Extended Community, that is present in this route. 6.2. Originating a Leaf Auto-Discovery Route If the P2MP FEC was derived from a MVPN or VPLS A-D route then the egress PE MUST originate a Leaf auto-discovery (A-D) route if the MVPN or VPLS A-D route carries a P-Tunnel Attribute with the "Leaf Information Required" flag set. If the P2MP FEC was derived from an Internet Multicast S/*, G and the upstream node's address is not the same as the egress PE, then the egress PE MUST originate a Leaf auto-discovery (A-D) route. 6.2.1. Leaf A-D Route for MVPN and VPLS If the P2MP FEC was derived from MVPN or VPLS A-D routes then the Route Key field of the Leaf A-D route contains the NLRI of the A-D route from which the P2MP FEC was derived. This follows procedures for constructing Leaf A-D routes described in [BGP-MVPN, VPLS-P2MP]. Rekhter [Page 10] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 6.2.2. Leaf A-D Route for Internet Multicast If the application is internet multicast then the MCAST-VPN NLRI of the Leaf A-D route is constructed as follows: The Route Key field of MCAST-VPN NLRI has the following format: +-----------------------------------+ | RD (8 octets) | +-----------------------------------+ | Multicast Source Length (1 octet) | +-----------------------------------+ | Multicast Source (Variable) | +-----------------------------------+ | Multicast Group Length (1 octet) | +-----------------------------------+ | Multicast Group (Variable) | +-----------------------------------+ | Ingress PE's IP address | +-----------------------------------+ RD is set to 0 for (S,G) state and all 1s for (*,G) state, Multicast Source is set to S for (S,G) state or RP for (*,G) state, Multicast Group is set to G, Multicast Source Length and Multicast Group Length is set to either 4 or 16 (depending on whether S/RP and G are IPv4 or IPv6 addresses). The Ingress PE's IP address is determined as described in the section "Determining the Upstream ABR/PE/ASBR". The Originating Router's IP address field of MCAST-VPN NLRI is set to the address of the local PE (PE that originates the route). Thus the entire MCAST-VPN NLRI of the route has the following format: +-----------------------------------+ | RD (8 octets) | +-----------------------------------+ | Multicast Source Length (1 octet) | +-----------------------------------+ | Multicast Source (Variable) | +-----------------------------------+ | Multicast Group Length (1 octet) | +-----------------------------------+ | Multicast Group (Variable) | +-----------------------------------+ | Ingress PE's IP address | Rekhter [Page 11] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 +-----------------------------------+ | Originating Router's IP address | +-----------------------------------+ When the PE deletes (S,G)/(*,G) state that was created as a result of receiving PIM or IGMP messages on one of its IP multicast interfaces, if the PE previousely originated a Leaf auto-discovery route for that state, then the PE SHOULD withdraw that route. 6.2.3. Constructing the Rest of the Leaf A-D Route The Next Hop field of the MP_REACH_NLRI attribute of the route SHOULD be set to the same IP address as the one carried in the Originating Router's IP Address field of the route. When Ingress Replication is used to instantiate the egress area segment then the Leaf A-D route MUST carry a downstream assigned label in the P-Tunnel Attribute where the P-Tunnel type is set to Ingress Replication. A PE MUST assign a distinct MPLS label for each Leaf A-D route originated by the PE. To constrain distribution of this route, the originating PE constructs an IP-based Route Target community by placing the IP address of the upstream node in the Global Administrator field of the community, with the Local Administrator field of this community set to 0. The originating PE then adds this Route Target Extended Community to this Leaf auto-discovery route. The upstream node's address is as determined in section 6.1. The PE then advertises this route to the upstream node. 6.3. PIM-SM in ASM mode for Internet Multicast This specification allows two options for supporting Internet Multicast with PIM-SM in ASM mode. The first option does not transit IP multicast shared trees over the MPLS network. The second option does transit shared trees over the MPLS network and relies on shared tree to source tree switchover. 6.3.1. Option 1 This option does not transit IP multicast shared trees over the MPLS network. Therefore, when an (egress) PE creates (*, G) state (as a result of receiving PIM messages on one of its IP multicast interfaces), the PE does not propagate this state using Leaf A-D Rekhter [Page 12] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 routes. 6.3.1.1. Originating Source Active auto-discovery routes Whenever as a result of receiving PIM Register or MSDP messages an RP discovers a new multicast source the RP SHOULD originate a BGP Source Active auto-discovery route. Similarly whenever as a result of receiving MSDP messages a PE, that is not configured as a RP, discovers a new multicast source the PE SHOULD originate a BGP Source Active auto-discovery route. The BGP Source Active auto-discovery route carries a single MCAST-VPN NLRI constructed as follows: + The RD in this NLRI is set to 0. + The Multicast Source field MUST be set to S. The Multicast Source Length field is set appropriately to reflect this. + The Multicast Group field MUST be set to G. The Multicast Group Length field is set appropriately to reflect this. To constrain distribution of the Source Active auto-discovery route to the AS of the advertising RP this route SHOULD carry the NO_EXPORT Community ([RFC1997]). Using the normal BGP procedures the Source Active auto-discovery route is propagated to all other PEs within the AS. Whenever the RP discovers that the source is no longer active, the RP MUST withdraw the Source Active auto-discovery route, if such a route was previousely advertised by the RP. 6.3.1.2. Receiving BGP Source Active auto-discovery route by PE When as a result of receiving PIM messages on one of its IP multicast interfaces an (egress) PE creates in its Tree Information Base (TIB) a new (*, G) entry with a non-empty outgoing interface list that contains one or more IP multicast interfaces, the PE MUST check if it has any Source Active auto-discovery routes for that G. If there is such a route, S of that route is reachable via an MPLS interface, and the PE does not have (S, G) state in its TIB for (S, G) carried in the route, then the PE originates a Leaf A-D routes carrying that (S, G), as specified in Section "Leaf A-D Route for Internet Multicast". When an (egress) PE receives a new Source Active auto-discovery route, the PE MUST check if its TIB contains an (*, G) entry with the same G as carried in the Source Active auto-discovery route. If such Rekhter [Page 13] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 an entry is found, S is reachable via an MPLS interface, and the PE does not have (S, G) state in its TIB for (S, G) carried in the route, then the PE originates a Leaf A-D routes carrying that (S, G), as specified in Section "Leaf A-D Route for Internet Multicast". 6.3.1.3. Handling (S, G, RPTbit) state Creation and deletion of (S, G, RPTbit) state on a PE that resulted from receiving PIM messages on one of its IP multicast interfaces does not result in any BGP actions by the PE. 6.3.2. Option 2 This option does transit IP multicast shared trees over the MPLS network. Therefore, when an (egress) PE creates (*, G) state (as a result of receiving PIM messages on one of its IP multicast interfaces), the PE does propagate this state using Leaf A-D routes. 6.3.2.1. Originating Source Active auto-discovery routes Whenever a PE creates an (S, G) state as a result of receiving Leaf A-D routes associated with Internet multicast service, if S is reachable via one of the IP multicast capable interfaces, and the PE determines that G is in the PIM-SM in ASM mode range, the PE MUST originate a BGP Source Active auto-discovery route. The route carries a single MCAST-VPN NLRI constructed as follows: + The RD in this NLRI is set to 0. + The Multicast Source field MUST be set to S. The Multicast Source Length field is set appropriately to reflect this. + The Multicast Group field MUST be set to G. The Multicast Group Length field is set appropriately to reflect this. To constrain distribution of the Source Active auto-discovery route to the AS of the advertising PE this route SHOULD carry the NO_EXPORT Community ([RFC1997]). Using the normal BGP procedures the Source Active auto-discovery route is propagated to all other PEs within the AS. Whenever the PE deletes the (S, G) state that was previously created as a result of receiving a Leaf A-D route for (S, G), the PE that deletes the state MUST also withdraw the Source Active auto-discovery Rekhter [Page 14] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 route, if such a route was advertised when the state was created. 6.3.2.2. Receiving BGP Source Active auto-discovery route Procedures for receiving BGP Source Active auto-discovery routes are the same as with Option 1. 6.3.2.3. Pruning Sources off the Shared Tree If after receiving a new Source Active auto-discovery route for (S,G) a PE determines that (a) it has the (*, G) entry in its TIB, (b) the incoming interface list (iif) for that entry contains one of the IP interfaces, (c) a MPLS LSP is in the outgoing interface list (oif) for that entry, and (d) the PE does not originate a Leaf A-D route for (S,G), then the PE MUST transition the (S,G,rpt) downstream state to the Prune state. [Conceptually the PIM state machine on the PE will act "as if" it had received Prune(S,G,Rpt) from some other PE, without actually having received one.] Depending on the (S,G,rpt) state on the iifs, this may result in the PE using PIM procedures to prune S off the Shared (*,G) tree. Transitioning the state machine to the Prune state SHOULD be done after a delay that is controlled by a timer. The value of the timer MUST be configurable. The purpose of this timer is to ensure that S is not pruned off the shared tree until all PEs have had time to receive the Source Active A-D route for (S,G). The PE MUST keep the (S,G,rpt) downstream state machine in the Prune state for as long as (a) the outgoing interface list (oif) for (*, G) contains a MPLS LSP, and (b) the PE has at least one Source Active auto-discovery route for (S,G), and (c) the PE does not originate the Leaf A-D route for (S,G). Once either of these conditions become no longer valid, the PE MUST transition the (S,G,rpt) downstream state machine to the NoInfo state. Note that except for the scenario described in the first paragraph of this section, in all other scenarios relying solely on PIM procedures on the PE is sufficient to ensure the correct behavior when pruning sources off the shared tree. 6.3.2.4. More on handling (S, G, RPTbit) state Creation and deletion of (S, G, RPTbit) state on a PE that resulted from receiving PIM messages on one of its IP multicast interfaces does not result in any BGP actions by the PE. Rekhter [Page 15] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 7. Egress ABR Procedures This section describes Egress ABR Procedures for constructing segmented inter-area P2MP LSP. When an egress ABR receives a Leaf auto-discovery route and the Route Target extended community carried by the route contains the IP address of this ABR, then the following procedures will be executed. If the RD of the received A-D route is not set to all 0s or all 1s, then the egress ABR MUST find a S-PMSI or I-PMSI route whose NLRI has the same value as the Route Key field of the received Leaf A-D route. If such a matching route is found then the Leaf A-D route MUST be accepted else it MUST be discarded. If the Leaf A-D route is accepted and if its the first Leaf A-D route update for the Route Key field in the route or the withdrawl of the last Leaf A-D route for the Route Key field then the following procedures will be executed. If the RD of the received A-D route is set to all 0s or all 1s then the received Leaf A-D route is for Internet Multicast. In that case for the following procedure the Route Prefix is set to all fields of the Route Key minus the Ingress PE address. If this is the first Leaf A-D route update for this Route Prefix or the withdrawl of the last Leaf A-D route for the Route Prefix then the following procedures will be executed. While generating a Leaf A-D route update, the egress ABR originates a Leaf A-D route, whose MCAST-VPN NLRI is constructed as follows. The Route Key field of MCAST-VPN NLRI is the same as the Route Key field of MCAST-VPN NLRI of the received Leaf A-D route. The Originating Router's IP address field of MCAST-VPN NLRI is set to the address of the local ABR (the ABR that originates the route). In The Next Hop field of the MP_REACH_NLRI attribute of the route SHOULD be set to the same IP address as the one carried in the Originating Router's IP Address field of the route. To constrain distribution of this route the originating egress ABR constructs an IP-based Route Target community by placing the IP address of the upstream node in the Global Administrator field of the community, with the Local Administrator field of this community set to 0, and sets the Extended Communities attribute of this Leaf auto- discovery route to that community. The upstream node's IP address is the IP address determined from the Global Administrator field of the Inter-area P2MP Segmented Next-hop Extended Community, where this Extended Community is obtained as Rekhter [Page 16] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 follows. When the Leaf A-D route is for MVPN or VPLS then this Extended Community is the one included in the I-S/PMSI A-D route that matches the Leaf A-D route. When the Leaf A-D route is for Internet Multicast then this Extended Community is obtained from the best unicast route to the Ingress PE. The Ingress PE address is determined from the received Leaf A-D route. The best unicast route MUST first be determined from multicast SAFI i.e., SAFI 2 routes, if present. The ABR then advertises this Leaf A-D route to the upstream node in the backbone area. Mechanisms specific in RFC4684 for constrained BGP route distribution can be used along with this specification to ensure that only the needed PE/ABR will have to process a said Leaf auto-discovery route. When Ingress Replication is used to instantiate the backbone area segment then the Leaf A-D route originated by the egress ABR MUST carry a downstream assigned label in the P-Tunnel Attribute where the P-Tunnel type is set to Ingress Replication. An ABR MUST assign a distinct MPLS label for each Leaf A-D route originated by the ABR. In order to support Internet Multicast an egress ABR MUST auto- configure an import Route Target with the global administrator field set to the AS of the ABR and the local administrator field set to 0. When the Leaf A-D route is for Internet Multicast and if the following conditions hold true: - Its not the first Leaf A-D route for the Route Prefix, where the Route Prefix is determined as described above - The set of ingress PEs associated with the Route Prefix changes as a result of the new Leaf A-D route. - The ABR determines based on local policy to propagate the Leaf A-D route towards a different ingress PE than the one to which the Leaf A-D route is being currently propagated. Then the egress ABR MUST originate the Leaf A-D route as described in this section. If the received Leaf A-D route is the last Leaf A-D route for the Route Key for MVPN or VPLS or for the Route Prefix, as described above, for Internet Multicast, then the ABR must withdraw the Rekhter [Page 17] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 previously advertised Leaf A-D route. 7.1. P2MP LSP as the Intra-Area LSP in the Egress Area This section describes procedures for using intra-area P2MP LSPs in the egress area. The procedures that are common to both P2MP RSVP-TE and P2MP LDP are described first, followed by procedures that are specific to the signaling protocol. When P2MP LSPs are used as the intra-area LSPs, note that an existing intra-area P2MP LSP may be used solely for a particular inter-area P2MP service LSP, or for other inter-area P2MP service LSPs as well. The choice between the two options is purely local to the egress ABR. The first option provides one-to-one mapping between inter-area P2MP service LSPs and intra-area P2MP LSPs; the second option provides many-to-one mapping, thus allowing to aggregate forwarding state. 7.1.1. RD of the received Leaf-AD route is not zero or all ones When the RD of the received Leaf A-D route is not set to zero or all ones then the ABR MUST re-advertise in the egress area the MVPN/VPLS A-D route, that matches the Leaf A-D route to signal the binding of the intra-area P2MP LSP to the inter-area P2MP service LSP. This must be done ONLY if a) such a binding hasn't already been advertised or b) The binding has changed. The re-advertised route MUST carry the Inter-area P2MP Segmented Next-Hop Extended Community. The PMSI Tunnel attribute of the re-advertised route specifies either an intra-area P2MP RSVP-TE LSP or an intra-area P2MP LDP LSP rooted at the ABR and MUST also carry an upstream assigned MPLS label. The upstream-assigned MPLS label MUST be set to implicit NULL if the mapping between the inter-area P2MP service LSP and the intra-area P2MP LSP is one-to-one. If the mapping is many-to-one the intra-area segment of the inter-area P2MP service LSP (referred to as the "inner" P2MP LSP) is constructed by nesting the inter-area P2MP service LSP in an intra-area P2MP LSP (referred to as the "outer" intra-area P2MP LSP), by using P2MP LSP hierarchy based on upstream- assigned MPLS labels [RFC 5332]. If segments of multiple MVPN or VPLS S-PMSI service LSPs are carried over a given intra-area P2MP LSP, each of these segments MUST carry a distinct upstream-assigned label, even if all these service LSPs are for (C-S/*, C-G/*)s from the same MVPN/VPLS. Therefore, an ABR maintains an LFIB state for each of the (C-S/*, C-G/*)s carried over S-PMSIs traversting this ABR (that applies to both the ingress and Rekhter [Page 18] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 the egress ABRs). 7.1.2. RD of the received Leaf A-D route is zero or all ones When the RD of the received Leaf A-D route is set to zero or all ones then this is the case of inter-area P2MP service LSP being associated with the Internet multicast service. The procedures for this are described below. 7.1.2.1. Internet Multicast and S-PMSI A-D Routes This section applies only if it is desirable to send a particular Internet Multicast flow to only those egress PEs that have receivers in a particular (S, G) or a particular (*, G) multicast flow. The egress ABR MUST originate a S-PMSI A-D route. The PMSI Tunnel attribute of the route MUST contain the identity of the intra-area P2MP LSP and an upstream assigned MPLS label. The RD, Multicast Source Length, Multicast Source, Multicast Group Length (1 octet), and Multicast Group fields of the NLRI of this route are the same as of the Leaf A-D route. The egress ABR MUST advertise this route into the backbone area. The Route Target of this route is an AS specific route-target with the AS set to the AS of the advertising ABR while the local administrator field is set to 0. 7.1.2.2. Internet Multicast and Wildcard S-PMSI A-D Routes It may be desirable for an ingress PE to aggregate Internet Multicast routes over a single Inter-area P2MP LSP. This can be achieved using wildcard, i.e., (*,*) S-PMSI A-D routes. An ingress PE MAY advertise a wildcard S-PMSI route as described in section "Ingress PE Procedures". If the ingress PE does indeed originate such a route the egress ABR would receive this route from the ingress ABR and MUST re- advertise it with the PMSI Tunnel Attribute containing the identifier of the intra-area P2MP LSP in the egress area and an upstream assigned label assigned to the inter-area wildcard S-PMSI. 7.1.3. Internet Multicast and the Expected Upstream Node If the mapping between the inter-area P2MP service LSP for Internet multicast service and the intra-area P2MP LSP is many-to-one then an egress PE must be able to determine whether a given multicast packet for a particular (S, G) is received from the "expected" upstream node. The expected node is the node towards which the Leaf A-D route Rekhter [Page 19] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 is sent by the egress PE. Packets received from another upstream node for that (S, G) MUST be dropped. To allow the egress PE to determine the sender upstream node, the intra-area P2MP LSP must be signaled with no PHP, when the mapping between the inter-area P2MP service LSP for Internet multicast service and the intra-area P2MP LSP is many-to-one. Further the egress ABR MUST first push onto the label stack the upstream assigned label advertised in the S-PMSI route, if the label is not an Implicit NULL. 7.1.4. P2MP LDP LSP as the Intra-Area P2MP LSP in the Egress Area The procedures above are sufficient if P2MP LDP LSPs are used as the Intra-area P2MP LSP in the Egress area. 7.1.5. P2MP RSVP-TE LSP as the Intra-Area P2MP LSP in the Egress Area If P2MP RSVP-TE LSP is used as the the intra-area LSP in the egress area, then the egress ABR can either (a) graft the leaf (whose IP address is specified in the received Leaf auto-discovery route) into an existing P2MP LSP rooted at the egress ABR, and use that LSP for carrying traffic for the inter-area segmented P2MP service LSP, or (b) originate a new P2MP LSP to be used for carrying (S,G). When the RD of the received Leaf A-D route is zero or all ones, then the procedures are as described in section 7.1.2 ("RD of the received Leaf A-D route is zero or all ones"). Note also that the SESSION object that the egress ABR would use for the intra-area P2MP LSP need not encode the P2MP FEC from the received Leaf auto-discovery route. 7.2. Ingress Replication in the Egress Area When Ingress Replication is used to instantiate the egress area segment then the Leaf A-D route advertised by the egress PE MUST carry a downstream assigned label in the P-Tunnel Attribute where the P-Tunnel type is set to Ingress Replication. We will call this the egress PE downstream assigned label. The egress ABR MUST forward packets received from the backbone area intra-area segment, for a particular inter-area P2MP LSP, to all the egress PEs from which the egress ABR has imported a Leaf A-D route for the inter-area P2MP LSP. A packet to a particular egress PE is Rekhter [Page 20] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 encapsulated, by the egress ABR, using a MPLS label stack the bottom label of which is the egress PE downstream assigned label. The top label is the P2P RSVP-TE or the MP2P LDP label to reach the egress PE. Note that these procedures ensures that an egress PE always receives packets only from the expected upstream PE. 8. Ingress ABR Procedures for constructing segmented inter-area P2MP LSP When an ingress ABR receives a Leaf auto-discovery route and the Route Target extended community carried by the route contains the IP address of this ABR, then the following procedures will be executed. These procedures are the same as in the section "Egress ABR Procedures" with egress ABR replaced with ingress ABR, backbone area replaced with ingress area and backbone area segment replaced with ingress area segment. In order to support Internet Multicast the ingress ABR MUST auto- configure an import Route Target with the global administrator field set to the AS of the ABR and the local administrator field set to 0. 8.1. P2MP LSP as the Intra-Area LSP in the Backbone Area If the RD of the received Leaf A-D route is not zero, and P2MP LSP is used as the the intra-area LSP in the backbone area, then the procedures for binding the backbone area segment of the inter-area P2MP LSP to the intra-area P2MP LSP in the backbone area, are the same as in section "Egress ABR Procedures" and sub-section "P2MP LSP as the Intra-Area LSP in the Egress Area". When the RD of the received Leaf A-D route is zero, as is the case where the inter-area service P2MP LSP is associated with the Internet multicast service, then the procedures are the same as in section "Egress ABR Procedures", and and sub-section "P2MP LSP as the Intra- Area LSP in the Egress Area", with egress ABR replaced with the ingress ABR. It is to be noted that if the backbone area uses wildcard S-PMSI then the egress area also must use wildcard S-PMSI for Internet Multicast or the ABRs must merge the wildcard S-PMSI onto the egress area (S, G) or (*, G) S-PMSI. The procedures for such merge require IP processing on the ABRs. Rekhter [Page 21] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 8.2. Ingress Replication in the Backbone Area When Ingress Replication is used to instantiate the backbone area segment then the Leaf A-D route advertised by the egress ABR MUST carry a downstream assigned label in the P-Tunnel Attribute where the P-Tunnel type is set to Ingress Replication. We will call this the egress ABR downstream assigned label. The egress ABR MUST assign a distinct MPLS label for each Leaf A-D route originated by the ABR. The ingress ABR MUST forward packets received from the ingress area intra-area segment, for a particular inter-area P2MP LSP, to all the egress ABRs from which the ingress ABR has imported a Leaf A-D route for the inter-area P2MP LSP. A packet to a particular egress ABR is encapsulated, by the inress ABR, using a MPLS label stack the bottom label of which is the egress ABR downstream assigned label. The top label is the P2P RSVP-TE or the MP2P LDP label to reach the egress ABR. 9. Ingress PE/ASBR Procedures This section describes Ingress PE/ASBR procedures for constructing segmented inter-area P2MP LSP. When an ingress PE/ASBR receives a Leaf auto-discovery route and the Route Target extended community carried by the route contains the IP address of this PE/ASBR, then the following procedures will be executed. If the RD of the received A-D route is not set to all 0s or all 1s, then the egress ABR MUST find a S-PMSI or I-PMSI route whose NLRI has the same value as the Route Key field of the received Leaf A-D route. If such a matching route is found then the Leaf A-D route MUST be accepted else it MUST be discarded. If the Leaf A-D route is accepted then it MUST be processed as per MVPN or VPLS procedures. If the RD of the received A-D route is set to all 0s or all 1s then the received Leaf A-D route is for Internet Multicast. In that case for the following procedure the Route Prefix is set to all fields of the Route Key minus the Ingress PE address. If this is the first Leaf A-D route update for this Route Prefix or the withdrawl of the last Leaf A-D route for the Route Prefix then the following procedures will be executed. The information carried in the MCAST-VPN NLRI of the route MUST be decoded. The PIM implementation should set its upstream (S/RP,G) state machine in Joined state for the (S/RP, G) received via a Leaf auto-discovery route update. Likewise, the PIM implementation should set its upstream (S/RP, G) state machine in Pruned state for the (S/RP, G) received via a Leaf auto-discovery Rekhter [Page 22] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 route withdrawl. 9.1. P2MP LSP as the intra-area LSP in the ingress area If the RD of the received Leaf A-D route is not zero, and P2MP LSP is used as the the intra-area LSP in the ingress area, then the procedures for binding the ingress area segment of the inter-area P2MP LSP to the intra-area P2MP LSP in the ingress area, are the same as in section "Egress ABR Procedures" and sub-section "P2MP LSP as the Intra-Area LSP in the Egress Area". When the RD of the received Leaf A-D route is zero, as is the case where the inter-area service P2MP LSP is associated with the Internet multicast service, then the ingress PE may originate a S-PMSI route with the RD, multicast source, multicast group fields being the same as those in the received Leaf A-D route. Further an ingress PE may originate a wildcard S-PMSI route as per the procedures in [MVPN-WILDCARD-SPMSI] with the RD set to 0. This route may be originated by the ingress PE based on configuration or based on the import of a Leaf A-D route with RD set to 0. If an ingress PE originates such a route, then the ingress PE may decide not to originate (S, G) or (*, G) S-PMSI routes. It is to be noted that if ingress area uses wildcard S-PMSI then the backbone area also must use wildcard S-PMSI for Internet Multicast or the ABRs must merge the wildcard S-PMSI onto the backbone area (S, G) or (*, G) S-PMSI. The procedures for such merge require IP processing on the ABRs. 9.2. Ingress Replication in the Ingress Area When Ingress Replication is used to instantiate the ingress area segment then the Leaf A-D route advertised by the ingress ABR MUST carry a downstream assigned label in the P-Tunnel Attribute where the P-Tunnel type is set to Ingress Replication. We will call this the ingress ABR downstream assigned label. The ingress ABR MUST assign a distinct MPLS label for each Leaf A-D route originated by the ABR. The ingress PE/ASBR MUST forward packets received from the CE, for a particular inter-area P2MP LSP, to all the ingress ABRs from which the ingress PE/ASBR has imported a Leaf A-D route for the inter-area P2MP LSP. A packet to a particular ingress ABR is encapsulated, by the inress PE/ASBR, using a MPLS label stack the bottom label of which is the ingress ABR downstream assigned label. The top label is the P2P RSVP-TE or the MP2P LDP label to reach the ingress ABR. Rekhter [Page 23] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 10. Common Tunnel Type in the Ingress and Egress Areas For a given inter-area service P2MP LSP, the PE/ASBR that is the root of that LSP controls the tunnel type of the intra-area P-tunnel that carries the ingress area segment of that LSP. However, the tunnel type of the intra-area P-tunnel that carries the backbone area segment of that LSP may be different from the tunnel type of the intra-area P-tunnels that carry the ingress area segment and the egress area segment of that LSP. In that situation if for a given inter-area P2MP LSP it is desirable/necessary to use the same tunnel type for the intra-area P-tunnels that carry the ingress area segment and the egress area segment of that LSP, then the following procedures on the ingress ABR and egress ABR provide this functionality. When an ingress ABR re-advertises into the backbone area a BGP MVPN I-PMSI, or S-PMSI A-D route, or VPLS A-D route, the ingress ABR places the PMSI Tunnel attribute of this route into the ATTR_SET BGP Attribute [L3VPN-IBGP], adds this attribute to the re-advertised route, and then replaces the original PMSI Tunnel attribute with a new one (note, that the Tunnel type of the new attribute may be different from the Tunnel type of the original attribute). When an egress ABR re-advertises into the egress area a BGP MVPN I- PMSI or S-PMSI A-D route, or VPLS A-D route, if the route carries the ATTR_SET BGP attribute [L3VPN-IBGP], then the ABR sets the Tunnel type of the PMSI Tunnel attribute in the re-advertised route to the Tunnel type of the PMSI Tunnel attribute carried in the ATTR_SET BGP attribute, and removes the ATTR_SET from the route. 11. Placement of Ingress and Egress PEs As described in earlier sections, procedures in this document allow the placement of ingress and egress PEs in the backbone area. They also allow the placement of egress PEs in the ingress area or the placement of ingress PEs in the egress area. For instance ABRs in the backbone area may act as ingress and egress PEs for Internet Multicast, as per the ingress and egress PE definition in this document. This may be the case if the service is Internet Multicast and relies on Internet Multicast in the ingress and egress areas and its desirable to carry Internet Multicast over MPLS in the backbone area. This may also be the case if the service is Multicast VPN and the P-tunnel technology in the ingress and egress areas uses PIM based IP/GRE P-tunnels. As far as the ABRs are concerned PIM signaling for such P-Tunnels is handled as per the ingress/egress PE Internet Multicast procedures in this document. To Rekhter [Page 24] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 facilitate this the ABRs may advertise their loopback addresses in BGP using multicast-SAFI i.e., SAFI 2, if non-congruence between unicast and multicast is desired. 12. Data Plane This section describes the data plane procedures on the ABRs, ingress PEs, egress PEs and transit routers. 12.1. Data Plane Procedures on an ABR When procedures in this document are followed to signal inter-area P2MP Segmented LSPs then ABRs are required to perform only MPLS switching. When an ABR receives a MPLS packet from an "incoming" intra-area segment of the inter-area P2MP Segmented LSP, it forwards the packet, based on MPLS switching, onto another "outgoing" intra- area segment of the inter-area P2MP Segmented LSP. If the outgoing intra-area segment is instantiated using a P2MP LSP, and if there is a one-to-one mapping between the outgoing intra-area segment and the P2MP LSP, then the ABR MUST pop the incoming segment's label stack and push the label stack of the outgoing P2MP LSP. If there is a many-to-one mapping between outgoing intra-area segments and the P2MP LSP then the ABR MUST pop the incoming segment's label stack and first push the upstream assigned label corresponding to the outgoing intra-area segment, if such a label has been assigned, and then push the label stack of the outgoing P2MP LSP. If the outgoing intra-area segment is instantiated using ingress replication then the ABR must pop the incoming segment's label stack and replicate the packet once to each leaf ABR or PE of the outgoing intra-area segment. The label stack of the packet sent to each such leaf MUST first include a downstream assigned label assigned by the leaf to the segment, followed by the label stack of the P2P or MP2P LSP to the leaf. 12.2. Data Plane Procedures on an Egress PE An egress PE must first identify the inter-area P2MP segmented LSP based on the incoming label stack. After this identification the egress PE must forward the packet using the application that is bound to the inter-area P2MP segmented LSP. Note that the application specific forwarding for MVPN service may Rekhter [Page 25] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 require the egress PE to determine whether the packets were received from the expected sender PE. When the application is MVPN then the FEC of an inter-area P2MP Segmented LSP is at the granularity of the sender PE. Note that MVPN intra-AS I-PMSI A-D routes and S-PMSI A-D routes both carry the Originating Router IP Address. Thus an egress PE could associate the data arriving on P-tunnels advertised by these routes with the Originating Router IP Address carried by these routes which is the same as the ingress PE. Since a unique label stack is associated with each such FEC, the egress PE can determine the sender PE from the label stack. Likewise for VPLS service for the purposes of MAC learning the egress PE must be able to determine the "VE-ID" from which the packets have been received. The FEC of the VPLS A-D routes carries the VE-ID. Thus an egress PE could associate the data arriving on P-tunnels advertised by these routes with the VE-ID carried by these routes. Since a unique label stack is associated with each such FEC, the egress PE can perform MAC learning for packets received from a given VE-ID. When the application is Internet Multicast it is sufficient for the label stack to include identification of the sender upstream node. When P2MP LSPs are used this requires that PHP MUST be turned off. When Ingress Replication is used the egress PE knows the incoming downstream assigned label to which it has bound a particlar (S/*, G) and must accept packets with only that label for that (S/*. G). 12.3. Data Plane Procedures on an Ingress PE The Ingress PE must perform application specific forwarding procedures to identify the outgoing inta-area segment of an incoming packet. If the outgoing intra-area segment is instantiated using a P2MP LSP, and if there is a one-to-one mapping between the outgoing intra-area segment and the P2MP LSP, then the ingress PE MUST encapsulate the packet in the label stack of the outgoing P2MP LSP. If there is a many-to-one mapping between outgoing intra-area segments and the P2MP LSP then the PE MUST first push the upstream assigned label corresponding to the outgoing intra-area segment, if such a label has been assigned, and then push the label stack of the outgoing P2MP LSP. If the outgoing intra-area segment is instantiated using ingress replication then the PE must replicate the packet once to each leaf ABR or PE of the outgoing intra-area segment. The label stack of the packet sent to each such leaf MUST first include a downstream Rekhter [Page 26] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 assigned label assigned by the leaf to the segment, followed by the label stack of the P2P or MP2P LSP to the leaf. 12.4. Data Plane Procedures on Transit Routers When procedures in this document are followed to signal inter-area P2MP Segmented LSPs then tansit routers in each area perform only MPLS switching. 13. IANA Considerations This document defines a new BGP Extended Community called "Inter-area P2MP Segmented Next-Hop". This community is IP Address Specific, of an extended type, and is transitive. A codepoint for this community should be assigned both from the IPv4 Address Specific Extended Community registry, and from the IPv6 Address Specific Extended Community registry. The same code point should be assigned from both registries. 14. Security Considerations These will be spelled out in a future revision. 15. References 15.1. Normative References [RFC5332] T. Eckert, E. Rosen, R. Aggarwal, Y. Rekhter, RFC5332 [RFC2119] "Key words for use in RFCs to Indicate Requirement Levels.", Bradner, March 1997 [MVPN-BGP] "BGP Encodings and Procedures for Multicast in MPLS/BGP IP VPNs", R. Aggarwal, E. Rosen, T. Morin, Y. Rekhter, draft-ietf- l3vpn-2547bis-mcast-bgp [[VPLS-P2MP] "Multicast in VPLS", R. Aggarwal, Y. Kamite, L. Fang, draft-ietf-l2vpn-vpls-mcast [L3VPN-IBGP] "Internal BGP as PE-CE protocol", Pedro Marques, et al., draft-ietf-l3vpn-ibgp, work in progress Rekhter [Page 27] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 15.2. Informative References [SEAMLESS-MPLS] "Seamless MPLS Architecture", N. Leymann et. al., draft-leymann-mpls-seamless-mpls 16. Author's Address Yakov Rekhter Juniper Networks 1194 North Mathilda Ave. Sunnyvale, CA 94089 Email: yakov@juniper.net Rahul Aggarwal Juniper Networks 1194 North Mathilda Ave. Sunnyvale, CA 94089 Phone: +1-408-936-2720 Email: rahul@juniper.net Thomas Morin France Telecom R & D 2, avenue Pierre-Marzin 22307 Lannion Cedex France Email: thomas.morin@francetelecom.com Irene Grosclaude France Telecom R & D 2, avenue Pierre-Marzin 22307 Lannion Cedex France Email: irene.grosclaude@orange-ftgroup.com Nicolai Leymann Deutsche Telekom AG Winterfeldtstrasse 21 Berlin 10781 DE Email: n.leymann@telekom.de Samir Saad AT&T Email: ss2539@att.com Rekhter [Page 28] Internet Draft draft-raggarwa-mpls-seamless-mcast-03.txt March 2011 Rekhter [Page 29]