Network Working Group R. Aggarwal Internet Draft Juniper Networks Expiration Date: December 2008 Intended Status: Proposed Standard E. Rosen Cisco Systems, Inc. T. Morin France Telecom Y. Rekhter Juniper Networks C. Kodeboniya June 16, 2008 BGP Encodings and Procedures for Multicast in MPLS/BGP IP VPNs draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of 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. Raggarwa [Page 1] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 Abstract This document describes the BGP encodings and procedures for exchanging the information elements required by Multicast in MPLS/BGP IP VPNs, as specified in [MVPN]. Raggarwa [Page 2] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 Table of Contents 1 Specification of requirements ......................... 4 2 Introduction .......................................... 5 3 Terminology ........................................... 5 4 MCAST-VPN NLRI ........................................ 6 4.1 Intra-AS I-PMSI A-D route ............................. 7 4.2 Inter-AS I-PMSI A-D route ............................. 8 4.3 S-PMSI A-D route ...................................... 8 4.4 Leaf A-D route ........................................ 9 4.5 Source Active A-D route ............................... 10 4.6 C-multicast route ..................................... 11 5 PMSI Tunnel attribute ................................. 12 6 Source AS Extended Community .......................... 14 7 VRF Route Import Extended Community ................... 14 8 PE Distinguisher Labels Attribute ..................... 15 9 MVPN Auto-Discovery/Binding ........................... 16 9.1 MVPN Auto-Discovery/Binding - Intra-AS Operations ..... 16 9.1.1 Originating Intra-AS I-PMSI A-D routes ................ 16 9.1.2 Receiving Intra-AS I-PMSI A-D routes .................. 19 9.2 MVPN Auto-Discovery/Binding - Inter-AS Operations ..... 20 9.2.1 Originating Inter-AS I-PMSI A-D routes ................ 21 9.2.2 When not to originate Inter-AS I-PMSI A-D routes ...... 22 9.2.3 Propagating Inter-AS I-PMSI A-D routes ................ 23 9.2.3.1 Propagating Inter-AS I-PMSI A-D routes - Overview ..... 23 9.2.3.2 Inter-AS I-PMSI A-D route received via EBGP ........... 24 9.2.3.2.1 Originating Leaf A-D route into EBGP .................. 25 9.2.3.3 Leaf A-D route received via EBGP ...................... 26 9.2.3.4 Inter-AS I-PMSI A-D route received via IBGP ........... 27 9.2.3.4.1 Originating Leaf A-D route into IBGP .................. 28 9.2.3.5 Leaf A-D route received via IBGP ...................... 29 9.2.3.6 Optimizing Bandwidth by IP filtering on ASBRs ......... 30 10 Non-congruent Unicast and Multicast Connectivity ...... 30 11 Exchange of C-Multicast Routing Information among PEs . 32 11.1 Originating C-multicast routes by a PE ................ 32 11.1.1 Originating routes: PIM as the C-Multicast protocol ... 32 11.1.1.1 Originating Source Tree Join C-multicast route ........ 33 11.1.1.2 Originating Shared Tree Join C-multicast route ........ 33 11.1.2 Originating routes: mLDP as the C-Multicast protocol .. 34 11.1.3 Constructing the rest of the C-multicast route ........ 34 11.1.4 Unicast Route Changes ................................. 35 11.2 Propagating C-multicast routes by an ASBR ............. 36 11.3 Receiving C-multicast routes by a PE .................. 37 11.3.1 Receiving routes: PIM as the C-Multicast protocol ..... 37 Raggarwa [Page 3] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 11.3.1.1 Receiving Source Tree Join C-multicast route .......... 37 11.3.1.2 Receiving Shared Tree Join C-multicast route .......... 38 11.3.2 Receiving routes: mLDP as the C-Multicast protocol .... 38 11.4 C-multicast routes aggregation ........................ 39 12 Using S-PMSI A-D routes to Bind C-trees to P-tunnels .. 40 12.1 Originating S-PMSI A-D routes ......................... 40 12.2 Handling S-PMSI A-D routes by ASBRs ................... 42 12.2.1 Merging S-PMSI into an I-PMSI ......................... 42 12.3 Receiving S-PMSI A-D routes by PEs .................... 43 13 Switching from Shared C-tree to Source C-tree ......... 44 13.1 Source Within a Site - Source Active Advertisement .... 45 13.2 Receiving Source Active A-D route ..................... 46 13.2.1 Pruning Sources off the Shared Tree ................... 46 14 Supporting PIM-SM without Inter-Site Shared C-trees ... 47 14.1 Discovering Active Multicast Sources .................. 47 14.2 Receiver(s) Within a Site ............................. 48 14.3 Receiving C-multicast routes by a PE .................. 50 15 Carrier's Carrier ..................................... 50 16 Scalability Considerations ............................ 50 16.1 Dampening C-multicast routes .......................... 51 16.1.1 Dampening withdrawals of C-multicast routes ........... 52 16.1.2 Dampening Source/Shared Tree Join C-multicast routes .. 52 16.2 Dampening withdrawals of Leaf A-D routes .............. 53 17 IANA Consideration .................................... 53 18 Security Considerations ............................... 53 19 Acknowledgement ....................................... 53 20 References ............................................ 54 20.1 Normative References .................................. 54 20.2 Informative References ................................ 54 21 Author's Address ...................................... 55 22 Intellectual Property Statement ....................... 56 23 Copyright Notice ...................................... 56 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]. Raggarwa [Page 4] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 2. Introduction This document describes the BGP encodings and procedures for exchanging the information elements required by Multicast in MPLS/BGP IP VPNs, as specified in [MVPN]. This document assumes a thorough familiarity with procedures, concepts and terms described in [MVPN]. This document defines a new NLRI, MCAST-VPN NLRI. The MCAST-VPN NLRI is used for MVPN auto-discovery, advertising MVPN to I-PMSI tunnel binding, advertising to S-PMSI tunnel binding, VPN customer multicast routing information exchange among PEs, choosing a single forwarder PE, and for procedures in support of co-locating a C-RP on a PE. This document specifies two new BGP attributes, P-Multicast Service Interface Tunnel (PMSI Tunnel) attribute, and PE Distinguisher Label attribute. This document also defines two new BGP Extended Communities, Source AS Extended Community and VRF Route Import Extended Community. 3. Terminology In the context of this document we will refer to the MVPN auto- discovery/binding information carried in BGP as "auto-discovery routes" ("A-D routes"). For a given MVPN there are the following types of A-D routes: + Intra-AS I-PMSI A-D route; + Inter-AS I-PMSI A-D route; + S-PMSI A-D route; + Leaf A-D route; + Source Active A-D route. In the context of this document we will refer to the MVPN customers multicast routing information carried in BGP as "C-multicast routes". For a given MVPN there are the following types of C-multicast routes: + Shared Tree Join route; Raggarwa [Page 5] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 + Source Tree Join route; For each MVPN present on a PE, the PE maintains a Tree Information Base (MVPN-TIB). This is the same as TIB defined in [RFC4601], except that instead of a single TIB a PE maintains multiple MVPN-TIBs, one per each MVPN. Throughout this draft we will use the term "VPN-IP route" to mean a route which is either in the VPN-IPv4 address family [RFC4364] or in the VPN-IPv6 address family [RFC4659]. 4. MCAST-VPN NLRI This document defines a new BGP NLRI, called the MCAST-VPN NLRI. Following is the format of the MCAST-VPN NLRI: +-----------------------------------+ | Route Type (1 octet) | +-----------------------------------+ | Length (1 octet) | +-----------------------------------+ | Route Type specific (variable) | +-----------------------------------+ The Route Type field defines encoding of the rest of MCAST-VPN NLRI (Route Type specific MCAST-VPN NLRI). The Length field indicates the length in octets of the Route Type specific field of MCAST-VPN NLRI. This document defines the following Route Types for A-D routes: + 1 - Intra-AS I-PMSI A-D route; + 2 - Inter-AS I-PMSI A-D route; + 3 - S-PMSI A-D route; + 4 - Leaf A-D route; + 5 - Source Active A-D route. This document defines the following Route Types for C-multicast routes: Raggarwa [Page 6] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 + 6 - Shared Tree Join route; + 7 - Source Tree Join route; The MCAST-VPN NLRI is carried in BGP [RFC4271] using BGP Multiprotocol Extensions [RFC4760] with an AFI of 1 or 2 and an SAFI of MCAST-VPN. The NLRI field in the MP_REACH_NLRI/MP_UNREACH_NLRI attribute contains the MCAST-VPN NLRI (encoded as specified above). The value of the AFI field in the MP_REACH_NLRI/MP_UNREACH_NLRI attribute that carries the MCAST-VPN NLRI determines whether the Multicast Source and Multicast Group addresses carried in the S-PMSI A-D routes, Source Active A-D routes, and C-multicast routes are IPv4 or IPv6 addresses (AFI 1 indicates IPv4 addresses, AFI 2 indicates IPv6 addresses). In order for two BGP speakers to exchange labeled MCAST-VPN NLRI, they must use BGP Capabilities Advertisement to ensure that they both are capable of properly processing such NLRI. This is done as specified in [RFC4760], by using capability code 1 (multiprotocol BGP) with an AFI of 1 or 2 and an SAFI of MCAST-VPN. The following describes the format of the Route Type specific MCAST- VPN NLRI for various Route Types defined in this document. 4.1. Intra-AS I-PMSI A-D route An Intra-AS I-PMSI A-D route type specific MCAST-VPN NLRI consists of the following: +-----------------------------------+ | RD (8 octets) | +-----------------------------------+ | Originating Router's IP Addr | +-----------------------------------+ The RD is encoded as described in [RFC4364]. Usage of Intra-AS I-PMSI A-D routes is described in Section "MVPN Auto-Discovery/Binding - Intra-AS Operations". Raggarwa [Page 7] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 4.2. Inter-AS I-PMSI A-D route An Inter-AS I-PMSI A-D route type specific MCAST-VPN NLRI consists of the following: +-----------------------------------+ | RD (8 octets) | +-----------------------------------+ | Source AS (4 octets) | +-----------------------------------+ The RD is encoded as described in [RFC4364]. The Source AS contains an Autonomous System number. Two octets AS numbers are encoded in the two low order octets of the Source AS field, with the the two high order octets set to zero. Usage of Inter-AS I-PMSI A-D routes is described in Section "MVPN Auto-Discovery/Binding - Inter-AS Operations". 4.3. S-PMSI A-D route An S-PMSI A-D route type specific MCAST-VPN NLRI consists of the following: +-----------------------------------+ | RD (8 octets) | +-----------------------------------+ | Multicast Source Length (1 octet) | +-----------------------------------+ | Multicast Source (Variable) | +-----------------------------------+ | Multicast Group Length (1 octet) | +-----------------------------------+ | Multicast Group (Variable) | +-----------------------------------+ | Originating Router's IP Addr | +-----------------------------------+ The RD is encoded as described in [RFC4364]. The Multicast Source field contains the C-S address. If the Multicast Source field contains an IPv4 address, then the value of the Multicast Source Length field is 32. If the Multicast Source field contains an IPv6 address, then the value of the Multicast Source Length field is 128. Raggarwa [Page 8] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 The Multicast Group field contains the C-G address or C-Generic LSP Identifier Value (use of C-Generic LSP Identifier Value is described in Section "Receiving routes: mLDP as the C-Multicast protocol"). If the Multicast Group field contains an IPv4 address or a C-Generic LSP Identifier Value, then the value of the Multicast Group Length field is 32. If the Multicast Group field contains an IPv6 address, then the value of the Multicast Group Length field is 128. Usage of other values of the Multicast Source Length and Multicast Group Length fields is outside the scope of this document. Usage of S-PMSI A-D routes is described in Section "Using S-PMSI A-D routes to Bind C-trees to P-tunnels". 4.4. Leaf A-D route A Leaf A-D route type specific MCAST-VPN NLRI consists of the following: +-----------------------------------+ | Route Key (variable) | +-----------------------------------+ | Originating Router's IP Addr | +-----------------------------------+ Leaf A-D routes may be originated as a result of processing a received Inter-AS I-PMSI A-D route or S-PMSI A-D route. A Leaf A-D route is originated in these situations only if the received route has a PMSI Tunnel attribute whose "Leaf Information Required" bit is set to 1. If a Leaf A-D route is originated as a result of processing one of the received routes specified in the previous paragraph, the Route Key of the Leaf A-D route is set to the NLRI of the received route. Details of the use of the Leaf A-D route may be found in Sections "Originating Leaf A-D route into EBGP", "Leaf A-D route received via EBGP", "Originating Leaf A-D route into IBGP", "Leaf A-D route received via IBGP", and "Receiving S-PMSI A-D routes by PEs". Raggarwa [Page 9] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 4.5. Source Active A-D route A Source Active A-D route type specific MCAST-VPN NLRI consists of the following: +-----------------------------------+ | RD (8 octets) | +-----------------------------------+ | Multicast Source Length (1 octet) | +-----------------------------------+ | Multicast Source (Variable) | +-----------------------------------+ | Multicast Group Length (1 octet) | +-----------------------------------+ | Multicast Group (Variable) | +-----------------------------------+ The RD is encoded as described in [RFC4364]. The Multicast Source field contains the C-S address. If the Multicast Source field contains an IPv4 address, then the value of the Multicast Source Length field is 32. If the Multicast Source field contains an IPv6 address, then the value of the Multicast Source Length field is 128. Use of the Source Active A-D routes with the Multicast Source Length field of 0 is outside the scope of this document. The Group Address field contains the C-G address. If the Multicast Group field contains an IPv4 address, then the value of the Multicast Group Length field is 32. If the Multicast Group field contains an IPv6 address, then the value of the Multicast Group Length field is 128. Source Active A-D routes with a Multicast group belonging to the Source Specific Multicast (SSM) range (as defined in [RFC4607], and potentially extended locally on a router) MUST NOT be advertised by a router and MUST be discarded if received. Usage of Source Active A-D routes is described in Sections "Switching from Shared C-tree to Source C-tree", and "Supporting PIM-SM without Inter-Site Shared C-trees". Raggarwa [Page 10] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 4.6. C-multicast route A Shared Tree Join route and a Source Tree Join route type specific MCAST-VPN NLRI consists of the following: +-----------------------------------+ | RD (8 octets) | +-----------------------------------+ | Source AS (4 octets) | +-----------------------------------+ | Multicast Source Length (1 octet) | +-----------------------------------+ | Multicast Source (Variable) | +-----------------------------------+ | Multicast Group Length (1 octet) | +-----------------------------------+ | Multicast Group (Variable) | +-----------------------------------+ The RD is encoded as described in [RFC4364]. The Source AS contains an Autonomous System number. Two octets AS numbers are encoded in the low order two octets of the Source AS field. For a Shared Tree Join route the Multicast Source field contains the C-RP address; for a Source Tree Join route the Multicast Source field contains the C-S address. If the Multicast Source field contains an IPv4 address, then the value of the Multicast Source Length field is 32. If the Multicast Source field contains an IPv6 address, then the value of the Multicast Source Length field is 128. The Group Address field contains the C-G address or C-Generic LSP Identifier Value. If the Multicast Group field contains an IPv4 address or C-Generic LSP Identifier Value, then the value of the Multicast Group Length field is 32. If the Multicast Group field contains an IPv6 address, then the value of the Multicast Group Length field is 128. Usage of C-multicast routes is described in Section "Exchange of C- Multicast Routing Information among PEs". Raggarwa [Page 11] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 5. PMSI Tunnel attribute This document defines and uses a new BGP attribute, called P- Multicast Service Interface Tunnel (PMSI Tunnel) attribute. This is an optional transitive BGP attribute. The format of this attribute is defined as follows: +---------------------------------+ | Flags (1 octet) | +---------------------------------+ | Tunnel Type (1 octets) | +---------------------------------+ | MPLS Label (3 octets) | +---------------------------------+ | Tunnel Identifier (variable) | +---------------------------------+ The Flags field has the following format: 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ | reserved |L| +-+-+-+-+-+-+-+-+ This document defines the following flags: + Leaf Information Required (L) The Tunnel Type identifies the type of the tunneling technology used to establish the PMSI tunnel. The type determines the syntax and semantics of the Tunnel Identifier field. This document defines the following Tunnel Types: + 0 - No tunnel information present + 1 - RSVP-TE P2MP LSP + 2 - mLDP P2MP LSP + 3 - PIM-SSM Tree + 4 - PIM-SM Tree + 5 - PIM-Bidir Tree + 6 - Ingress Replication + 7 - mLDP MP2MP LSP If the MPLS Label field is non-zero, then it contains an MPLS label encoded as 3 octets, where the high-order 20 bits contain the label value. Absence of MPLS Label is indicated by setting the MPLS Label field to zero. When the type is set to "No tunnel information present", the PMSI Raggarwa [Page 12] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 Tunnel attribute carries no tunnel information (no Tunnel Identifier). This may be used to enable explicit tracking for a particular customer multicast flow (by setting the Leaf Information Required flag to 1), but without binding this flow to a particular provider tunnel (by omitting any tunnel information). When the type is set to RSVP-TE P2MP LSP, the Tunnel Identifier is as carried in the RSVP-TE P2MP LSP SESSION Object [RSVP-TE-P2MP]. When the type is set to mLDP P2MP LSP, the Tunnel Identifier is a P2MP FEC Element [mLDP]. When the type is set to PIM-SM Tree, the Tunnel Identifier is . The node that originated the attribute MUST use the address carried in the Sender Address as the source IP address for the IP/GRE encapsulation of the MVPN data. When the type is set to PIM-SSM Tree, the Tunnel Identifier is . The node that originates the attribute MUST use the address carried in the P-Root Node Address as the source IP address for the IP/GRE encapsulation of the MVPN data. The P-Multicast Group element of the Tunnel identifier of the Tunnel attribute MUST NOT be expected to be the same group for all Intra-AS A-D routes for the same MVPN. According to [RFC4607], the group address can be locally allocated by the originating PE without any consideration for the group address used by other PE on the same MVPN. When the type is set to PIM-Bidir Tree, the Tunnel Identifier is . The node that originated the attribute MUST use the address carried in the Sender Address as the source IP address for the IP/GRE encapsulation of the MVPN data. When the type is set to PIM-SM or PIM-Bidir tree, then the P- Multicast group element of the Tunnel identifier of the Tunnel attribute SHOULD be the same multicast group address for all Intra-AS I-PMSI A-D routes for the same MVPN originated by PEs within a given AS. How this multicast group address is chosen is outside the scope of this specification. When the type is set to Ingress Replication the Tunnel Identifier carries the unicast tunnel endpoint IP address of the local PE that is to be this PE's receiving endpoint address for the tunnel. When the type is set to mLDP MP2MP LSP, the Tunnel Identifier is an MP2MP FEC Element [mLDP]. Raggarwa [Page 13] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 The use of mLDP MP2MP LSPs as Provider tunnels (P-tunnels) requires procedures which are outside the scope of this document. The PMSI Tunnel attribute is used in conjunction with Intra-AS I-PMSI A-D routes, Inter-AS I-PMSI A-D routes, S-PMSI A-D routes, and Leaf A-D routes. 6. Source AS Extended Community This document defines a new BGP extended community called Source AS. The Source AS is an AS specific extended community, of an extended type, and is transitive across AS boundaries [RFC4360]. The Global Administrator field of this community MUST be set to the autonomous system number of the PE. The Local Administrator field of this community MUST be set to 0. If for a given MVPN BGP is used for exchanging C-multicast routes, or if segmented inter-AS tunnels are used, then when a PE that has sites of that MVPN connected to it originates a (unicast) route to VPN-IP addresses, the PE MUST include in the BGP Update message that carries this route the Source AS extended community. The usage of a received Source AS extended community is described in Section "Constructing the rest of the C-multicast route". 7. VRF Route Import Extended Community This document defines a new BGP extended community called VRF Route Import. The VRF Route Import is an IP address specific extended community, of an extended type, and is transitive across AS boundaries [RFC4360]. To support MVPN, in addition to the import/export Route Target(s) extended communities used by the unicast routing, each VRF on a PE MUST have an import Route Target extended community. We refer to this Route Target as the "C-multicast Import RT", as this Route Target controls imports of C-multicast routes into a particular VRF. A PE constructs C-multicast Import RT as follows: Raggarwa [Page 14] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 + The Global Administrator field of the C-multicast Import RT MUST be set to an IP address of the PE. This address SHOULD be common for all the VRFs on the PE (e.,g., this address may be PE's loopback address). + The Local Administrator field of the C-multicast Import RT associated with a given VRF contains a 2 octets long number that uniquely identifies that VRF within the PE that contains the VRF (procedures for assigning such numbers are purely local to the PE, and outside the scope of this document). The way C-multicast Import RT is constructed, it uniquely identifies a VRF. A PE that has site(s) of a given MVPN connected to it needs to communicate the value of the C-multicast Import RT associated with the VRF of that MVPN on the PE to all other PEs that have sites of that MVPN. To accomplish this a PE that originates a (unicast) route to VPN-IP addresses MUST include in the BGP Updates message that carries this route the VRF Route Import extended community that has the value of the C-multicast Import RT of the VRF associated with the route, except if it is known a priori that none of these addresses will act as multicast sources and/or RP, in which case the (unicast) route need not carry the VRF Route Import extended community. If a PE uses Route Target Constrain [RT-CONSTRAIN], the PE SHOULD advertise all such C-multicast Import RTs using Route Target Constrains (note that doing this requires just a single Route Target Constraint advertisement by the PE). This allows each C-multicast route to reach only the relevant PE. To constrain distribution of the Route Target Constrain routes to the AS of the advertising PE these routes SHOULD carry the NO_EXPORT Community ([RFC1997]). Usage of VRF Route Import extended community is described in Section "Constructing the rest of the C-multicast route". 8. PE Distinguisher Labels Attribute This document defines a new BGP attribute, called PE Distinguisher Labels attribute. This is an optional transitive BGP attribute. The format of this attribute is defined as follows: +---------------------------------+ | PE Address | +---------------------------------+ | Label (3 octets) | +---------------------------------+ Raggarwa [Page 15] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 ....... +---------------------------------+ | PE Address | +---------------------------------+ | Label (3 octets) | +---------------------------------+ Usage of this attribute is described in [MVPN-ARCH]. 9. MVPN Auto-Discovery/Binding This section specifies procedures for the auto-discovery of MVPN memberships and the distribution of information used to instantiate I-PMSIs. There are two MVPN auto-discovery/binding mechanisms, dubbed "intra- AS" and "inter-AS" respectively. The intra-AS mechanisms provide auto-discovery/binding within a single AS. The intra-AS mechanisms also provide auto-discovery/binding across multiple ASes when non-segmented inter-AS tunnels are being used. The inter-AS mechanisms provide auto-discovery/binding across multiple ASes when segmented inter-AS tunnels are being used. Note that if a multi-AS system uses option (a) of section 10 of [RFC4364], the notion of inter-AS tunnels does not apply, and so it needs only the intra-AS mechanisms. 9.1. MVPN Auto-Discovery/Binding - Intra-AS Operations This section describes exchanges of Intra-AS I-PMSI A-D routes originated/received by PEs within the same AS, or if non-segmented inter-AS tunnels are used, then by all PEs. 9.1.1. Originating Intra-AS I-PMSI A-D routes To participate in the MVPN auto-discovery/binding a PE router that has a given VRF of a given MVPN MUST, except for the cases specified further down in this section, originate an Intra-AS I-PMSI A-D route and advertises this route in IBGP. The route is constructed as follows. Raggarwa [Page 16] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 The route carries a single MCAST-VPN NLRI with the RD set to the RD of the VRF, and the Originating Router's IP Address field set to the IP address that the PE places in the Global Administrator field of the VRF Route Import extended community of the VPN-IP routes advertised by the PE. Note that the tuple uniquely identifies a given multicast VRF. The route carries the PMSI Tunnel attribute if and only if an I-PMSI is used for the MVPN (the conditions under which an I-PMSI is used can be found in [MVPN]). Depending on the technology used for the P- tunnel for the MVPN on the PE, the PMSI Tunnel attribute of the Intra-AS I-PMSI A-D route is constructed as follows. + If the PE that originates the advertisement uses a P-Multicast tree for the P-tunnel for the MVPN, the PMSI Tunnel attribute MUST contain the identity of the tree (note that the PE could create the identity of the tree prior to the actual instantiation of the tree). + A PE that uses a P-Multicast tree for the P-tunnel MAY aggregate two or more MVPNs present on the PE onto the same tree. In this case in addition to carrying the identity of the tree, the PMSI Tunnel attribute MUST carry an MPLS upstream assigned label which the PE has bound uniquely to the MVPN associated with this update (as determined by its RTs). If the PE has already advertised Intra-AS I-PMSI A-D routes for two or more MVPNs that it now desires to aggregate, then the PE MUST re-advertise those routes. The re-advertised routes MUST be the same as the original ones, except for the PMSI Tunnel attribute and the label carried in that attribute. + If the PE that originates the advertisement uses ingress replication for the P-tunnel for the MVPN, the route MUST include the PMSI Tunnel attribute with the Tunnel Type set to Ingress Replication and Tunnel Identifier set to a routable address of the PE. The PMSI Tunnel attribute MUST carry a downstream assigned MPLS label. This label is used to demultiplex the MVPN traffic received over a unicast tunnel by the PE. + The Leaf Information Required flag of the PMSI Tunnel attribute MUST be set to zero, and MUST be ignored on receipt. Discovery of PE capabilities in terms of what tunnels types they support is outside the scope of this document. Within a given AS PEs participating in an MVPN are expected to advertise tunnel bindings whose tunnel types are supported by all other PEs that are participating in this MVPN and are part of the same AS. In addition, Raggarwa [Page 17] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 in the inter-AS scenario with non-segmented inter-AS tunnels, the tunnel types have to be supported by all PEs that are participating in this MVPN, irrespective of whether these PEs are in the same AS or not. 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. By default the distribution of the Intra-AS I-PMSI A-D routes is controlled by the same Route Targets as the ones used for the distribution of VPN-IP unicast routes. That is, by default the Intra- AS I-PMSI A-D route MUST carry the export Route Target used by the unicast routing. If any other PE has one of these Route Targets configured as an import Route Target for a VRF present on the PE, it treats the advertising PE as a member in the MVPN to which the VRF belongs. The default could be modified via configuration by having a set of Route Targets used for the Intra-AS I-PMSI A-D routes being distinct from the ones used for the VPN-IP unicast routes (see also Section "Non-congruent Unicast and Multicast Connectivity"). To constrain distribution of the intra-AS membership/binding information to the AS of the advertising PE the BGP Update message originated by the advertising PE SHOULD carry the NO_EXPORT Community ([RFC1997]). Note that if non-segmented inter-AS P-tunnels are being used, then the Intra-AS I-PMSI routes need to be distributed to other ASes and MUST NOT carry the NO_EXPORT community. When BGP is used to exchange C-multicast routes, originating an Intra-AS I-PMSI A-D route for a given MVPN by a given PE is OPTIONAL if (a) it is known a priori that none of the MVPN sites connected to the PE have multicast sources, (b) the PE does not use ingress replication for incoming multicast traffic of that MVPN, and (c) none of the other PEs that have VRFs of that MVPN use RSVP-TE P2MP LSPs for that MVPN. When BGP is used to exchange C-multicast routes, originating an Intra-AS I-PMSI A-D route for a given MVPN by a given PE is also OPTIONAL if it is known a priori that none of the MVPN sites connected to the PE have multicast receivers, and the PE uses ingress replication for that MVPN. Raggarwa [Page 18] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 9.1.2. Receiving Intra-AS I-PMSI A-D routes When a PE receives a BGP Update message that carries an Intra-AS I- PMSI A-D route such that (a) at least one of the Route Targets of the route matches one of the import Route Targets configured for a particular VRF on the local PE, (b) either the route was originated by some other PE within the same AS as the local PE, or the MVPN associated with the VRF uses non-segmented inter-AS tunnels, and (c) the BGP route selection determines that this is the best route with respect to the NLRI carried by the route, the PE performs the following. If the route carries the PMSI Tunnel attribute then: + If the Tunnel Type in the PMSI Tunnel attribute is set to Ingress Replication, then the MPLS label and the address carried in the Tunnel Identifier field of the PMSI Tunnel attribute should be used when the local PE sends multicast traffic to the PE that originated the route. + If the Tunnel Type in the PMSI Tunnel attribute is set to mLDP P2MP LSP, or mLDP MP2MP LSP, or PIM-SSM tree, or PIM-SM tree, or PIM-Bidir tree, the PE SHOULD join as soon as possible the P- Multicast tree whose identity is carried in the Tunnel Identifier. + If the Tunnel Type in the PMSI Tunnel attribute is set to RSVP-TE P2MP LSP, then the PE that originated the route MUST establish an RSVP-TE P2MP LSP with the local PE as a leaf. This LSP may have been established before the local PE receives the route, or may be established after the local PE receives the route. + The receiving PE has to establish the appropriate state to properly handle the traffic received on the P-Multicast tree. + If the PMSI Tunnel attribute does not carry a label, then all packets that are received on the P-Multicast tree, as identified by the PMSI Tunnel attribute, are forwarded using the VRFs that has at least one of its import Route Targets that matches one of the Route Targets of the received Intra-AS I-PMSI A-D route. + If the PMSI Tunnel attribute has the Tunnel Type set to mLDP P2MP LSP, or PIM-SSM tree, or PIM-SM tree, or PIM-Bidir tree, or RSVP- TE P2MP LSP, and the attribute also carries an MPLS label, then this is an upstream assigned label, and all packets that are received on the P-Multicast tree, as identified by the PMSI Tunnel attribute, with that upstream assigned label are forwarded using the VRFs that has at least one of its import Route Target Raggarwa [Page 19] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 that matches one of the Route Targets of the received Intra-AS I- PMSI A-D route. Irrespective of whether the route carries the PMSI Tunnel attribute, if the local PE uses RSVP-TE P2MP LSP for sending (multicast) traffic from the VRF to the sites attached to other PEs, then the local PE uses the Originating Router's IP address information carried in the route to add the PE that originated the route as a leaf node to the LSP. 9.2. MVPN Auto-Discovery/Binding - Inter-AS Operations This section applies only to the case where segmented inter-AS tunnels are used. An Autonomous System Border Router (ASBR) may be configured to support a particular MVPN as follows: + An ASBR MUST be be configured with a set of (import) Route Targets (RTs) that specifies the set of MVPNs supported by the ASBR. These Route Targets control acceptance of Intra-AS/Inter-AS I-PMSI A-D routes by the ASBR. As long as unicast and multicast connectivity are congruent, this could be the same set of Route Targets as the one used for supporting unicast (and therefore would not require any additional configuration above and beyond of what is required for unicast). Note that instead of being configured, the ASBR MAY obtain this set of (import) Route Targets (RTs) by using Route Target Constrain [RT-CONSTRAIN]. + The ASBR MUST be (auto-)configured with an import Route Target called "ASBR Import RT". ASBR Import RT controls acceptance of Leaf A-D routes and C-multicast routes by the ASBR, and is used to constrain distribution of both Leaf A-D routes and C-multicast routes (see Section "Exchange of C-Multicast Routing Information among PEs"). ASBR Import RT is an IP address specific Route Target. The Global Administrator field of the ASBR Import RT MUST be set to the IP address carried in the Next Hop of all the Inter-AS I-PMSI A-D routes and S-PMSI A-D routes advertised by this ASBR (if the ASBR uses different Next Hops, then the ASBR MUST be (auto-)configured with multiple ASBR Import RTs, one per each such Next Hop). The Local Administrator field of the ASBR Import RT MUST be set to 0. If the ASBR supports Route Target Constrain [RT-CONSTRAIN], the ASBR SHOULD advertise its ASBR Import RT within its own AS using Route Target Constrains. To constrain distribution of the Route Raggarwa [Page 20] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 Target Constrain routes to the AS of the advertising ASBR these routes SHOULD carry the NO_EXPORT Community ([RFC1997]). + The ASBR MUST be configured with the tunnel types for the intra- AS segments of the MVPNs supported by the ASBR, as well as (depending on the tunnel type) the information needed to create the PMSI attribute for these tunnel types. Note that instead of being configured, the ASBR MAY derive the tunnel types from the Intra-AS I-PMSI A-D routes received by the ASBR. + If the ASBR originates an Inter-AS I-PMSI A-D route for a particular MVPN present on some of the PEs within its own AS, the ASBR MUST be (auto-)configured with an RD for that MVPN. It is RECOMMENDED that one of the following two options be used: (1) To allow more aggregation of Inter-AS I-PMSI A-D routes it is recommended that all the ASBRs within an AS that are configured to originate an Inter-AS I-PMSI A-D route for a particular MVPN be configured with the same RD (although for a given MVPN each AS may assign this RD on its own, without coordination with other ASes). (2) To allow more control over spreading MVPN traffic among multiple ASBRs within a given AS it is recommended for each ASBR to have a distinct RD per each MVPN, in which case such an RD SHOULD be auto-configured. If an ASBR is configured to support a particular MVPN, the ASBR MUST participate in the intra-AS MVPN auto-discovery/binding procedures for that MVPN within the ASBR's own AS, as specified in Section "MVPN Auto-Discovery/Binding - Intra-AS Operations". Moreover, in addition to the above the ASBR performs procedures described in Sections "Originating Inter-AS I-PMSI A-D routes", "When not to originate Inter-AS I-PMSI A-D routes", and "Propagating Inter- AS I-PMSI A-D routes". 9.2.1. Originating Inter-AS I-PMSI A-D routes For a given MVPN configured on an ASBR when the ASBR determines (using the intra-AS auto-discovery procedures) that at least one of the PEs of its own AS has (directly) connected site(s) of the MVPN, the ASBR originates an Inter-AS I-PMSI A-D route and advertises it in EBGP. The route is constructed as follows: Raggarwa [Page 21] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 + The route carries a single MCAST-VPN NLRI with the RD set to the RD configured for that MVPN on the ASBR, and the Source AS set to the Autonomous System number of the ASBR. + The route carries the PMSI Tunnel attribute if and only if an I- PMSI is used for the MVPN. The Tunnel Type in the attribute is set to Ingress Replication; the Leaf Information Required flag is set to 1; the the attribute carries no MPLS labels. + The Next Hop field of the MP_REACH_NLRI attribute is set to a routable IP address of the ASBR. + The default policy for aggregation of Intra-AS I-PMSI A-D routes into an Inter-AS I-PMSI A-D route is that a given Inter-AS I-PMSI A-D route aggregates only the Intra-AS I-PMSI A-D routes that carry exactly the same set of RTs (note that this set may have just one RT). In this case an Inter-AS I-PMSI A-D route originated by an ASBR carries exactly the same RT(s) as the RT(s) carried by the Intra-AS I-PMSI A-D routes that the ASBR aggregates into that Inter-AS I-PMSI A-D route. An implementation MUST support the default policy for aggregation of Intra-AS I- PMSI A-D routes into an Inter-AS I-PMSI A-D route. + The default policy for aggregation could be modified via configuration on the ASBR. An implementation MAY support such functionality. Modified policy MUST include rules for constructing RTs carried by the Inter-AS I-PMSI A-D routes originated by the ASBR. An Inter-AS I-PMSI A-D route for a given indicates presence of the MVPN sites connected to one or more PEs of the AS. An Inter-AS I-PMSI A-D route originated by an ASBR aggregates Intra- AS I-PMSI A-D routes originated within the ASBR's own AS. Thus while the Intra-AS I-PMSI A-D routes originated within an AS are at the granularity of within that AS, outside of that AS the (aggregated) Inter-AS I-PMSI A-D routes could be at the granularity of . 9.2.2. When not to originate Inter-AS I-PMSI A-D routes If for a given MVPN and a given AS all of its sites connected to the PEs within the AS known a priori to have no multicast sources, then ASBRs of that AS MAY refrain from originating an Inter-AS I-PMSI A-D route for that MVPN at all. Raggarwa [Page 22] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 9.2.3. Propagating Inter-AS I-PMSI A-D routes An Inter-AS I-PMSI A-D route for a given MVPN originated by an ASBR within a given AS is propagated via BGP to other ASes. 9.2.3.1. Propagating Inter-AS I-PMSI A-D routes - Overview Suppose that an ASBR A installs an Inter-AS I-PMSI A-D route for MVPN V that originated at a particular AS, AS1. The BGP next hop of that route becomes A's "upstream multicast hop" on a multicast distribution tree for V that is rooted at AS1. When the Inter-AS I- PMSI A-D routes have been distributed to all the necessary ASes, they define a "reverse path" from any AS that supports MVPN V back to AS1. For instance, if AS2 supports MVPN V, then there will be a reverse path for MVPN V from AS2 to AS1. This path is a sequence of ASBRs, the first of which is in AS2, and the last of which is in AS1. Each ASBR in the sequence is the BGP next hop of the previous ASBR in the sequence on the given Inter-AS I-PMSI A-D route. This reverse path information can be used to construct a unidirectional multicast distribution tree for MVPN V, containing all the ASes that support V, and having AS1 at the root. We call such a tree an "inter-AS tree". Multicast data originating in MVPN sites connected to PEs within a given AS will travel downstream along the tree which is rooted at that AS. The path along an inter-AS tree is a sequence of ASBRs; it is still necessary to specify how the multicast data gets from a given ASBR to the set of ASBRs which are immediately downstream of the given ASBR along the tree. This is done by creating "segments": ASBRs in adjacent ASes will be connected by inter-AS segments, ASBRs in the same AS will be connected by "intra-AS segments". An ASBR initiates creation of an intra-AS segment when the ASBR receives an Inter-AS I-PMSI A-D route from an EBGP neighbor. Creation of the segment is completed as a result of distributing via IBGP this route within the ASBR's own AS. For a given inter-AS tunnel each of its intra-AS segments could be constructed by its own independent mechanism. Moreover, by using upstream assigned labels within a given AS multiple intra-AS segments of different inter-AS tunnels of either the same or different MVPNs may share the same P-Multicast tree. If the P-Multicast tree that serves as a particular intra-AS segment of an inter-AS tunnel is created by a multicast control protocol that uses receiver-initiated joins (e.g, mLDP, any PIM variant), and this Raggarwa [Page 23] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 P-Multicast tree does not aggregate multiple segments, then all the information needed to create that segment is present in the PMSI Tunnel attribute of the Inter-AS I-PMSI A-D routes. But if the P- Multicast tree that serves as the segment is created by a protocol that does not use receiver-initiated joins (e.g., RSVP-TE, ingress unicast replication), or if this P-Multicast tree aggregates multiple segments (irrespective of the multicast control protocol used to create the tree), then it is also necessary to use Leaf A-D routes. The precise conditions under which Leaf A-D routes need to be used are described in subsequent sections. Since (aggregated) Inter-AS I-PMSI A-D routes could have granularity of , an MVPN that is present in N ASes could have total of N inter-AS tunnels. Thus for a given MVPN the number of inter-AS tunnels constituting the I-PMSIs is independent of the number of PEs that have this MVPN. The precise rules for distributing and processing the Inter-AS I-PMSI A-D routes across ASes are given in the following sections. 9.2.3.2. Inter-AS I-PMSI A-D route received via EBGP When an ASBR receives from one of its EBGP neighbors a BGP Update message that carries an Inter-AS I-PMSI A-D route, if (a) at least one of the Route Targets carried in the message matches one of the import Route Targets configured on the ASBR, and (b) the ASBR determines that the received route is the best route for its NLRI, the ASBR re-advertises this route to other PEs and ASBRs within its own AS (handling of this route by other PEs and ASBRs is described in Section "Inter-AS I-PMSI A-D route received via IBGP"). When re-advertising an Inter-AS I-PMSI A-D route the ASBR MUST set the Next Hop field of the MP_REACH_NLRI attribute to a routable IP address of the ASBR. If the received Inter-AS I-PMSI A-D route carries the PMSI Tunnel attribute, then depending on the technology used to instantiate the intra-AS segment of the inter-AS tunnel the ASBR constructs the PMSI Tunnel attribute of the re-advertised Inter-AS I-PMSI A-D route as follows. + If the ASBR uses ingress replication for the intra-AS segment of the inter-AS tunnel, the re-advertised route MUST carry the PMSI Tunnel attribute with the Tunnel Type set to Ingress Replication, but no MPLS labels. Raggarwa [Page 24] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 + If the ASBR uses a P-Multicast tree for the intra-AS segment of the inter-AS tunnel, the PMSI Tunnel attribute MUST contain the identity of the tree (note that the ASBR could create the identity of the tree prior to the actual instantiation of the tree). If in order to instantiate the tree the ASBR needs to know the leaves of the tree, then the ASBR obtains this information from the Leaf A-D routes received from other PEs/ASBRs in ASBR's own AS (as described in Section "Leaf A-D route received via IBGP") by setting the Leaf Information Required flag in the PMSI Tunnel attribute to 1. + An ASBR that uses a P-Multicast tree as the intra-AS segment of the inter-AS tunnel MAY aggregate two or more MVPNs present on the ASBR onto the same tree. In this case in addition to the identity of the tree, the PMSI Tunnel attribute MUST carry an MPLS upstream-assigned label which the PE has bound uniquely to the MVPN associated with this update (as determined by its RTs). If the ASBR has already advertised Inter-AS I-PMSI A-D routes for two or more MVPNs that it now desires to aggregate, then the ASBR MUST re-advertise those routes. The re-advertised routes MUST be the same as the original ones, except for the PMSI Tunnel attribute and the MVPN label. 9.2.3.2.1. Originating Leaf A-D route into EBGP In addition the ASBR MUST send to the EBGP neighbor from whom it received the Inter-AS I-PMSI A-D route, a BGP Update message that carries a Leaf A-D route constructed as follows. + The route carries a single MCAST-VPN NLRI with the Route Key field set to the MCAST-VPN NLRI of the Inter-AS I-PMSI A-D route received from that neighbor and the Originating Router's IP address set to the IP address of the ASBR (this MUST be a routable IP address). + The Leaf A-D route MUST include the PMSI Tunnel attribute with the Tunnel Type set to Ingress Replication, and the Tunnel Identifier set to a routable address of the advertising router. The PMSI Tunnel attribute MUST carry a downstream assigned MPLS label that is used by the advertising router to demultiplex the MVPN traffic received over a unicast tunnel from the EBGP neighbor. Raggarwa [Page 25] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 + The ASBR constructs an IP-based Route Target extended community by placing the IP address carried in the next hop of the received Inter-AS I-PMSI A-D route 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 the Leaf A-D route to that community. Note that this Route Target is the same as the ASBR Import RT of the EBGP neighbor from which the ASBR received the Inter-AS I-PMSI 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. + To constrain the distribution scope of this route the route MUST carry the NO_ADVERTISE BGP community ([RFC1997]). Handling of this Leaf A-D route by the EBGP neighbor is described in Section "Leaf A-D route received via EBGP". The ASBR MUST set up its forwarding state such that packets that arrive on the one-hop ASBR-ASBR LSP, as specified in the PMSI Tunnel Attribute of the Leaf A-D route, are transmitted on the intra-AS segment, as specified in the PMSI Tunnel Attribute of the inter-AS I- PMSI A-D route that the ASBR re-advertises in its own AS. However, the packets MAY be filtered before forwarding, as specified in Section "Optimizing Bandwidth by IP filtering on ASBRs". 9.2.3.3. Leaf A-D route received via EBGP When an ASBR receives via EBGP a Leaf A-D route originated by its neighbor ASBR, if the Route Target carried in the Extended Communities attribute of the route matches one of the ASBR Import RT (auto)configured on the ASBR, the ASBR performs the following. The ASBR finds an Inter-AS I-PMSI A-D route whose MCAST-VPN NLRI has the same value as the Route Key field of the the Leaf A-D route. If the found Inter-AS I-PMSI A-D route was originated by ASBR itself, then the ASBR sets up its forwarding state such that packets received on the intra-AS tunnels originating in the ASBR's own AS are transmitted on the one hop ASBR-ASBR LSP specified by the MPLS label carried in the PMSI Tunnel attribute of the received Leaf A-D route. (However the packets MAY be filtered before transmission as specified in Section "Optimizing Bandwidth by IP filtering on ASBRs"). The intra-AS tunnels are specified in the PMSI Tunnel attribute of all the Intra-AS I-PMSI A-D routes received by the ASBR that the ASBR aggregated into the Inter-AS I-PMSI A-D route. For each of these Raggarwa [Page 26] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 intra-AS tunnels, if a non-zero MPLS label is carried in the PMSI Tunnel attribute (i.e aggregation is used) then only packets received on the inner LSP corresponding to that label MUST be forwarded, not the packets received on the outer LSP, as the outer LSP possibly carries the traffic of other VPNs. If the found Inter-AS I-PMSI A-D route was originated by some other ASBR, then the ASBR sets up its forwarding state such that packets received on the intra-AS tunnel segment, as specified in the PMSI Tunnel attribute of the found Inter-AS I-PMSI A-D route, are transmitted on the one hop ASBR-ASBR LSP, as specified by the MPLS label carried in the PMSI Tunnel attribute of the Leaf A-D route. 9.2.3.4. Inter-AS I-PMSI A-D route received via IBGP In the context of this section we use the term "PE/ASBR router" to denote either a PE or an ASBR router. If a given Inter-AS I-PMSI A-D route is received via IBGP by a BGP Route Reflector, the BGP Route Reflector MUST NOT modify the Next Hop field of the MP_REACH_NLRI attribute when re-advertising the route into IBGP (this is because the information carried in the Next Hop is used for controling flow of C-multicast routes, as specified in Section "Propagating C-multicast routes by an ASBR"). If a given Inter-AS I-PMSI A-D route is advertised within an AS by multiple ASBRs of that AS, the BGP best route selection performed by other PE/ASBR routers within the AS does not require all these PE/ASBR routers to select the route advertised by the same ASBR - to the contrary different PE/ASBR routers may select routes advertised by different ASBRs. When a PE/ASBR router receives from one of its IBGP neighbors a BGP Update message that carries an Inter-AS I-PMSI A-D route, if (a) at least one of the Route Targets carried in the message matches one of the import Route Targets configured on the PE/ASBR, and (b) the PE/ASBR determines that the received route is the best route to the destination carried in the NLRI of the route, the PE/ASBR performs the following operations. If the router is a PE, then the router imports the route into the VRF(s) that have the matching import Route Targets. If the router is an ASBR then the ASBR propagates the route to its EBGP neighbors. When propagating the route to the EBGP neighbors the ASBR MUST set the Next Hop field of the MP_REACH_NLRI attribute to a routable IP address of the ASBR. If the received Inter-AS I-PMSI A-D Raggarwa [Page 27] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 route carries the PMSI Tunnel attribute, then the propagated route MUST carry the PMSI Tunnel attribute with the Tunnel Type set to Ingress Replication; the attribute carries no MPLS labels. If the received Inter-AS I-PMSI A-D route carries the PMSI Tunnel attribute with the Tunnel Type set to mLDP P2MP LSP, or PIM-SSM tree, or PIM-SM tree, or PIM-Bidir tree, the PE/ASBR SHOULD join as soon as possible the P-Multicast tree whose identity is carried in the Tunnel Identifier. If the received Inter-AS I-PMSI A-D route carries the PMSI Tunnel attribute with the Tunnel Identifier set to RSVP-TE P2MP LSP, then the ASBR that originated the route MUST establish an RSVP-TE P2MP LSP with the local PE/ASBR as a leaf. This LSP MAY have been established before the local PE/ASBR receives the route, or MAY be established after the local PE receives the route. If the received Inter-AS I-PMSI A-D route carries the PMSI Tunnel attribute with the Tunnel Type set to mLDP P2MP LSP, or RSVP-TE P2MP LSP, or PIM-SSM, or PIM-SM tree, or PIM-Bidir tree, but the attribute does not carry a label, then the P-Multicast tree, as identified by the PMSI Tunnel Attribute, is an intra-AS LSP segment that is part of the inter-AS Tunnel for the MVPN advertised by the Inter-AS I-PMSI A- D route and rooted at the AS that originated the Inter-AS I-PMSI A-D route. If the PMSI Tunnel attribute carries a (upstream assigned) label, then a combination of this tree and the label identifies the intra-AS segment. If the receiving router is an ASBR, this intra-AS segment may further be stitched to the ASBR-ASBR inter-AS segment of the inter-AS tunnel. If the PE/ASBR has local receivers in the MVPN, packets received over the intra-AS segment must be forwarded to the local receivers using the local VRF. 9.2.3.4.1. Originating Leaf A-D route into IBGP If the Leaf Information Required flag in the PMSI Tunnel attribute of the received Inter-AS I-PMSI A-D route is set to 1, then the PE/ASBR MUST originate a new Leaf A-D route as follows. + The route carries a single MCAST-VPN NLRI with the Route Key field set to the MCAST-VPN NLRI of the Inter-AS I-PMSI A-D route received from that neighbor, and the Originating Router's IP address set to the IP address of the ASBR (this MUST be a routable IP address). Raggarwa [Page 28] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 + If the received Inter-AS I-PMSI A-D route carries the PMSI Tunnel attribute with the Tunnel Type set to Ingress Replication, then the Leaf A-D route MUST carry the PMSI Tunnel attribute with the Tunnel Type set to Ingress Replication. The Tunnel Identifier MUST carry a routable address of the PE/ASBR. The PMSI Tunnel attribute MUST carry a downstream assigned MPLS label that is used to demultiplex the MVPN traffic received over a unicast tunnel by the PE/ASBR. + The PE/ASBR constructs an IP-based Route Target community by placing the IP address carried in the next hop of the received Inter-AS I-PMSI A-D route 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 the Leaf A-D route to that community. + 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 the distribution scope of this route the route MUST carry the NO_EXPORT BGP community ([RFC1997]). + Once the Leaf A-D route is constructed, the PE/ASBR advertises this route into IBGP. 9.2.3.5. Leaf A-D route received via IBGP When an ASBR receives via IBGP a Leaf A-D route, if the Route Target carried in the Extended Communities attribute of the route matches one of the ASBR Import RT (auto)configured on the ASBR, the ASBR performs the following. The ASBR finds an Inter-AS I-PMSI A-D route whose MCAST-VPN NLRI has the same value as the Route Key field of the the Leaf A-D route. The received route may carry either (a) no PMSI Tunnel attribute, or (b) the PMSI Tunnel attribute, but only with the Tunnel Type set to Ingress Replication. If the received route does not carry the PMSI Tunnel attribute, the ASBR uses the information from the received route to determine the leaves of the P-Multicast tree rooted at the ASBR that would be used for the intra-AS segment associated with the found Inter-AS I-PMSI A- D route. The IP address of a leaf is the IP address carried in the Originating Router's IP address field of the received Leaf A-D route. Raggarwa [Page 29] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 If the received route carries the PMSI Tunnel attribute with the Tunnel Type set to Ingress Replication the ASBR uses the information carried by the route to construct the intra-AS segment with ingress replication. 9.2.3.6. Optimizing Bandwidth by IP filtering on ASBRs An ASBR that has a given Inter-AS I-PMSI A-D route MAY discard some of the traffic carried in the tunnel specified in the PMSI Tunnel attribute of this route if the ASBR determines that there are no downstream receivers for that traffic. When BGP is being used to distribute C-multicast routes, an ASBR that has a given Inter-AS I-PMSI A-D route MAY discard traffic from a particular customer multicast source C-S and destined to a particular customer multicast group address C-G that is carried over the tunnel specified in the PMSI Tunnel attribute of the route, if none of the C-multicast routes on the ASBR with RD and Source AS being the same as the RD and Source AS of the Inter-AS I-PMSI A-D route matches the (C-S,C-G) tuple. A C-multicast route is said to match a (C-S,C-G) tuple, if it is a Source Tree Join route with Multicast Source set to C-S and Multicast Group set to C-G, or a Shared Tree Join route with Multicast Group set to C-G. The above procedures MAY also apply to an ASBR that originates a given Inter-AS I-PMSI A-D route. In this case the ASBR applies them to the traffic carried over the tunnels specified in the PMSI Tunnel attribute of the Intra-AS I-PMSI A-D routes that the ASBR aggregates into the Inter-AS I-PMSI A-D route, and whose tails are stiched to the one-hop ASBR-ASBR tunnel specified in the Inter-AS I-PMSI A-D route. 10. Non-congruent Unicast and Multicast Connectivity It is possible to deploy MVPN such the multicast routing and the unicast routing are "non-congruent". For instance, the CEs may be distributing to the PEs a special set of unicast routes that are to be used exclusively for the purpose of upstream multicast hop selection, and not used for unicast routing at all. (For example, when BGP is the CE-PE unicast routing protocol, the CEs may be using SAFI 2 ("Network Layer Reachability Information used for multicast forwarding" [IANA-SAFI]), and either IPv4 or IPv6 AFI to distribute a special set of routes that are to be used for, and only for, upstream multicast hop selection.) In such a situation, we will speak of the MVPN as having two VRFs on a given PE, one containing the routes that are used for unicast, the other containing the unicast routes that Raggarwa [Page 30] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 are used for upstream multicast hop (UMH) selection. We will call the former the "unicast routing VRF", and the latter the "UMH VRF" (upstream multicast hop VRF). In this document, when we speak without qualification of the MVPN's VRF, then if the MVPN has both a unicast VRF and a UMH VRF, we are speaking of the UMH VRF. (Of course, if there is no separate UMH VRF, then we are speaking of the unicast VRF.) If there is a separate UMH VRF, it MAY have its own import and export Route Targets, different from the ones used by the unicast VRF. These Route Targets MUST be used to control distribution of auto-discovery routes. In addition, the export Route Targets of the UMH VRF are added to the Route Targets used by the unicast VRF when originating (unicast) VPN-IP routes. The import Route Targets associated with a given UMH VRF are used to determine which of the received (unicast) VPN-IP routes should be accepted into the UMH VRF. If a PE maintains an UMH VRF for that MVPN, then it is RECOMMENDED that the UMH VRF should use the same RD as the one used by the unicast VRF of that MVPN. If an MVPN site is multi-homed to several PEs, then to support non- congruent unicast and multicast connectivity, on each of these PEs the UMH VRF of the MVPN MUST use its own distinct RD (although on a given PE the RD used by the UMH VRF SHOULD be the same as the one used by the unicast VRF). If an MVPN has a UMH VRF distinct from its unicast VRF, then one option to support non-congruency is by exchanging the routes from/to that UMH VRF by using the same AFI/SAFI as used by the routes from the unicast VRF. Another option is to exchange the routes from/to the UMH VRF using the IPv4 or IPv6 AFI (as appropriate), but with the SAFI set to "Multicast for BGP/MPLS IP Virtual Private Networks (VPNs)" [IANA- SAFI]. The NLRI carried by these routes is defined as follows: +---------------------------+ | Length (1 octet) | +---------------------------+ | Prefix (variable) | +---------------------------+ The use and the meaning of these fields are as follows: a) Length: Raggarwa [Page 31] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 The Length field indicates the length in bits of the address prefix plus the label(s). b) Prefix: The Prefix field contains a Route Distinguisher as defined in [RFC4364] prepended to an IPv4 or IPv6 address prefix, followed by enough trailing bits to make the end of the field fall on an octet boundary. Note that the value of trailing bits is irrelevant. These routes MUST carry the VRF Route Import Extended Community. If for a given MVPN BGP is used for exchanging C-multicast routes, or if segmented inter-AS tunnels are used, then these routes also MUST carry the Source AS extended community. The detailed procedures for selecting forwarder PE in the presence of such routes are outside the scope of this document. However, this document requires these procedures to preserve the constrains imposed by the single forwarder PE selection procedures, as specified in [MVPN]. 11. Exchange of C-Multicast Routing Information among PEs VPN C-Multicast Routing Information is exchanged among PEs by using C-multicast routes that are carried using MCAST-VPN NLRI. These routes are originated and propagated as follows. 11.1. Originating C-multicast routes by a PE Part of the procedures for constructing MCAST-VPN NLRI depend on the multicast routing protocol between CE and PE (C-multicast protocol). 11.1.1. Originating routes: PIM as the C-Multicast protocol The following specifies construction of MCAST-VPN NLRI of C-multicast routes for the case where the C-multicast protocol is PIM. These C- multicast routes are originated as a result of updates in , or state learnt by a PE via the C-multicast protocol. Note that creation and deletion of (C-S, C-G, RPTbit) states on a PE when the C-multicast protocol is PIM do not result in any BGP actions. Raggarwa [Page 32] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 11.1.1.1. Originating Source Tree Join C-multicast route Whenever (a) a C-PIM instance on a particular PE creates a new state, and (b) the selected upstream PE for C-S (see [MVPN]) is not the local PE, then the local PE MUST originate a a C-multicast route of a type Source Tree Join. The Multicast Source field in the MCAST-VPN NLRI of the route is set to C-S, the Multicast Group field is set of C-G. This C-multicast route is said to "correspond" to the C-PIM state. The semantics of the route is that the PE has one or more receivers for in the sites connected to the PE (the route has the Join semantics). Whenever a C-PIM instance on a particular PE deletes a state, the corresponding C-multicast route MUST be withdrawn. (The withdrawal of the route has the Prune semantics). The MCAST-VPN NLRI of the withdrawn route is carried in the MP_UNREACH_NLRI attribute. 11.1.1.2. Originating Shared Tree Join C-multicast route Whenever (a) a C-PIM instance on a particular PE creates a new state, and (b) the selected upstream PE for the C-RP corresponding to the C-G (see [MVPN]) is not the local PE, then the local PE MUST originate a a C-multicast route of a type Shared Tree Join. The Multicast Source field in the MCAST-VPN NLRI of the route is set to the C-RP address. The Multicast Group field in the MCAST- VPN NLRI is set to the C-G address. This C-multicast route is said to "correspond" to the C-PIM state. The semantics of the route is that the PE has one or more receivers for in the sites connected to the PE (the route has the Join semantics). Whenever a C-PIM instance on a particular PE deletes a state, the corresponding C-multicast route MUST be withdrawn. (The withdrawal of the route has the Prune semantics). The MCAST-VPN NLRI of the withdrawn route is carried in the MP_UNREACH_NLRI attribute. Raggarwa [Page 33] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 11.1.2. Originating routes: mLDP as the C-Multicast protocol The following specifies construction of MCAST-VPN NLRI of C-multicast routes for the case where the C-multicast protocol is mLDP [mLDP]. Whenever a PE receives from one of its CEs a P2MP Label Map over interface I, where X is the Root Node Address, Y is the Opaque Value, and L is an MPLS label, the PE checks whether it already has state for in the VRF associated with the CE. If yes, then all the PE needs to do in this case is to update its forwarding state by adding to the forwarding state associated with . If the PE does not have state for in the VRF associated with the CE, then the PE constructs a Source Tree Join C-multicast route whose MCAST-VPN NLRI contains X as the Multicast Source field, and Y as the Multicast Group field. Whenever a PE deletes a previously created state that had resulted in originating a C-multicast route, the PE withdraws the C- multicast route. The MCAST-VPN NLRI of the withdrawn route is carried in the MP_UNREACH_NLRI attribute. 11.1.3. Constructing the rest of the C-multicast route The rest of the C-multicast route is constructed as follows (the same procedures apply to both PIM and mLDP as the C-Multicast protocol). The local PE executes the procedures of [MVPN] to find the selected Upstream Multicast Hop (UMH) route and the selected upstream PE for the address carries in the Multicast Source field of MCAST-VPN NLRI. From the selected UMH route the local PE extracts (a) the autonomous system number of the upstream PE (as carried in the Source AS extended community of the route), and (b) the C-multicast Import RT of the VRF on the upstream PE (the value of this C-multicast Import RT is the value of the VRF Route Import Extended Community carried by the route). The Source AS field in the C-multicast route is set to that autonomous system. The Route Target Extended Community of the C- multicast route is set to that C-multicast Import RT. If there is more than one (remote) PE that originates the (unicast) route to the address carried in the Multicast Source field of the MCAST-VPN NLRI, then the procedures for selecting the UMH route and the upstream PE to reach that address are as specified in [MVPN]. If the local and the upstream PEs are in the same AS, then the RD of the advertised MCAST-VPN NLRI is set to the RD of the VPN-IP route that contains the address carried in the Multicast Source field. Raggarwa [Page 34] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 The C-multicast route is then advertised into IBGP. If the local and the upstream PEs are in different ASes, then the local PE finds in its VRF an Inter-AS I-PMSI A-D route whose Source AS field carries the autonomous system number of the upstream PE. The RD of the found Inter-AS I-PMSI A-D route is used as the RD of the advertised C-multicast route. The local PE constructs an IP-based Route Target community by placing the next hop of the found Inter-AS I-PMSI A-D route in the Global Administrator field of this community, with the Local Administrator field of this community set to 0, and adds this community to the Extended Communities attribute of the C- multicast route. (Note that this Route Target is the same as the ASBR Import RT of the ASBR identified by the next hop of the found Inter- AS I-PMSI A-D route.) Inter-AS I-PMSI A-D routes are not used to support non-segmented inter-AS tunnels. To support non-segmented inter-AS tunnels, if the local and the upstream PEs are in different ASes, the local system finds in its VRF an Intra-AS I-PMSI A-D route from the upstream PE (the Originating Router's IP Address field of that route has the same value as the one carried in the VRF Route Import of the (unicast) route to the address carried in the Multicast Source field). The RD of the found Intra-AS I-PMSI A-D route is used as the RD of the advertised C-multicast route. The Source AS field in the C-multicast route is set to value of the Originating Router's IP Address field of the found Intra-AS I-PMSI A-D route. The Next Hop field of the MP_REACH_NLRI attribute MUST be set to a routable IP address of the local PE. If the next hop of the found (Inter-AS or Intra-AS) I-PMSI A-D route is an EBGP neighbor of the local PE, then the PE advertises the C- multicast route to that neighbor. If the next hop of the found (Inter-AS or Intra-AS) I-PMSI A-D route is within the same AS as the local PE, then the PE advertises the C-multicast route into IBGP. 11.1.4. Unicast Route Changes The particular UMH route that is selected by a given PE for a given C-S may be influenced by the network's unicast routing. In that case, a change in the unicast routing may invalidate prior choices of the UMH route for some C-S. If this happens, the local PE MUST execute the UMH route selection procedures for C-S again. If the result is that a different UMH route is selected, then for all C-G, any previously originated C-multicast routes for (C-S,C-G) MUST be re-originated. Raggarwa [Page 35] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 Similarly, if a unicast routing change results in a change of the UMH route for a C-RP, then for all C-G such that C-RP is the RP associated with C-G, any previously originated C-multicast routes for (C-*,C-G) MUST be re-originated. 11.2. Propagating C-multicast routes by an ASBR When an ASBR receives a BGP Update message that carries a C-multicast route, if at least one of the Route Targets of the route matches one of the ASBR Import RTs (auto)configured on the ASBR, the ASBR finds an Inter-AS I-PMSI A-D route whose RD and Source AS matches the RD and Source AS carried in the C-multicast route. If no matching route is found, the ASBR takes no further actions. If a matching route is found, the ASBR proceeds as follows. To support non-segmented inter-AS tunnels, instead of matching the RD and Source AS carried in the C-multicast route against the RD and Source AS of an Inter-AS I-PMSI A-D route, the ASBR should match it against the RD and the Originating Router's IP Addr of the Intra-AS I-PMSI A-D routes. The ASBR first checks if it already has one or more C-multicast routes that have the same MCAST-VPN NLRI as the newly received route. If such route(s) already exists, the ASBR keeps the newly received route, but SHALL NOT re-advertise the newly received route. Otherwise, the ASBR re-advertises the route, as described further down. When an ASBR receives a BGP Update message that carries a withdraw of a previously advertised C-multicast route, the ASBR first checks if it already has at least one other C-multicast route that has the same MCAST-VPN NLRI. If such a route already exists, the ASBR processes the withdrawn route, but SHALL NOT re-advertise the withdraw. Otherwise, the ASBR re-advertises the withdrawal of the previously advertised C-multicast route, as described below. If the ASBR is the ASBR that originated the found Inter-AS I-PMSI A-D route, then before re-advertising the C-multicast route into IBGP the ASBR removes from the route the Route Target that matches one of the ASBR Import RTs (auto)configured on the ASBR. If the ASBR is not the ASBR that originated the found Inter-AS I-PMSI A-D route, then before re-advertising the C-multicast route, the ASBR modifies the Extended Communities attribute of the C-multicast route by replacing the Route Target of the route that matches one of the ASBR Import RTs (auto)configured on the ASBR with a new Route Target constructed as follows. The new Route Target is an IP-based Route Raggarwa [Page 36] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 Target that has the Global Administrator field set to the Next Hop of the found Inter-AS I-PMSI A-D route, and Local Administrator field of this community set to 0. Note that this newly constructed Route Target is the same as the ASBR Import RT of the ASBR identified by the next hop of the found Inter-AS I-PMSI A-D route. The rest of the Extended Communities attribute of the route SHOULD be passed unmodified. The Next Hop field of the MP_REACH_NLRI attribute SHOULD be set to an IP address of the ASBR. If the Next Hop field of the MP_REACH_NLRI of the found (Inter-AS or Intra-AS) I-PMSI A-D route is an EBGP neighbor of the ASBR, then the ASBR re-advertises the C-multicast route to that neighbor. If the Next Hop field of the MP_REACH_NLRI of the found (Inter-AS or Intra- AS) I-PMSI A-D route is an IBGP neighbor of the ASBR, the ASBR re- advertises the C-multicast route into IBGP. If it is the ASBR that originated the found Inter-AS I-PMSI A-D route in the first place, then the ASBR just re-advertises the C-multicast route into IBGP. 11.3. Receiving C-multicast routes by a PE When a PE receives a C-multicast route the PE checks if any of the Route Target communities carried in the Extended Communities attribute of the route match any of the C-multicast Import RTs associated with the VRFs of any MVPN maintained by the PE. If no match is found the PE SHOULD discard the route. Otherwise, (if a match is found), the PE checks if the address carried in the Multicast Source field of the C-multicast route matches one of the (unicast) VPN-IP routes advertised by PE from the VRF. If no match is found the PE SHOULD discard the route. Otherwise, (if a match is found), the PE proceeds as follows, depending on the multicast routing protocol between CE and PE (C-multicast protocol). 11.3.1. Receiving routes: PIM as the C-Multicast protocol The following described procedures when PIM is used as the multicast routing protocol between CE and PE (C-multicast protocol). 11.3.1.1. Receiving Source Tree Join C-multicast route If the received route has the route type set to Source Tree Join, then the PE creates a new state in its MVPN-TIB from the Multicast Source and Multicast Group fields in the MCAST-VPN NLRI of Raggarwa [Page 37] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 the route, if such a state does not already exist. If there is no S- PMSI for then the PE adds an I-PMSI to the outgoing interface list of the state if it is not already there. If there is an S-PMSI for then the PE add S-PMSI to the outgoing interface list of the state if it is not already there. 11.3.1.2. Receiving Shared Tree Join C-multicast route If the received route has the route type set to Shared Tree Join, then the PE creates a new state in its MVPN-TIB with the RP address for that state taken from the Multicast Source, and C-G for that state taken from the Multicast Group fields of the MCAST-VPN NLRI of the route, if such a state does not already exist. If there is no S-PMSI for (C-*, C-G), then the PE adds I-PMSI to the outgoing interface list of the state if it is not already there. If there is an S-PMSI for , then the PE adds S-PMSI to the outgoing interface list of the state if it is not already there. 11.3.2. Receiving routes: mLDP as the C-Multicast protocol The following described procedures when mLDP is used as the multicast routing protocol between CE and PE (C-multicast protocol). When mLDP is used as a C-multicast protocol, the only valid type of a C-multicast route that a PE could receive is a Source Tree Join C- multicast route. When the PE receives a Source Tree Join C-multicast route, the PE applies, in the scope of this VRF, the P2MP mLDP procedures for a transit node using the value carried in the Multicast Source field of the route as the C-Root Node Identifier, and the value carried in the Multicast Group of the route as the C-Generic LSP Identifier Value. If there is no S-PMSI for then the PE creates and advertises an S-PMSI as described in Section "Using S-PMSI A-D routes to Bind C-trees to P- tunnels" using C-Root Node Identifier as the value for the Multicast Source field of the S-PMSI A-D route and C-Generic LSP Identifier Value as the value for the Multicast Group field of the route. To improve scalability when mLDP is used as the C-Multicast protocol for a given MVPN, within each AS that has sites of that MVPN connected to the PEs of that AS, all the S-PMSIs of that MVPN MAY be aggregated into a single P-Multicast tree (by using upstream assigned labels). Raggarwa [Page 38] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 11.4. C-multicast routes aggregation Note that C-multicast routes are "de facto" aggregated by BGP. This is because the MCAST-VPN NLRIs advertised by multiple PEs, for a C- multicast route for a particular C-S and C-G (or a particular C-* and C-G) of a given MVPN are identical. Hence a BGP Route Reflector or ASBR that receives multiple such routes with the same NLRI will re-advertise only one of these routes to other BGP speakers. This implies that C-multicast routes for a given (S,G) of a given MVPN originated by PEs that are clients of a given Route Reflector are aggregated by the Route Reflector. For instance, if multiple PEs that are clients of a Route Reflector, have receivers for a specific SSM channel of a MVPN, they will all advertise an identical NLRI for the "Source Tree Join" C-multicast route. However only one C- multicast route will be advertised by the Route Reflector for this specific SSM channel of that MVPN, to other PEs and Route Reflectors that are clients of the Route Reflector. This also implies that an ASBR aggregates all the received C- multicast routes for a given (S,G) (or a given (*,G)) of a given MVPN into a single C-multicast route. To further reduce the routing churn due to C-multicast routes changes a Route Reflector that re-advertises a C-multicast route SHOULD set the Next Hop field of the MP_REACH_NLRI attribute of the route to an IP address of the Route Reflector. Likewise, an ASBR that re- advertises a C-multicast route SHOULD set the Next Hop field of the MP_REACH_NLRI attribute of the route to an IP address of the ASBR. Further a BGP receiver, that receives multiple such routes with the same NLRI for the same C-multicast route, will potentially create forwarding state based on a single C-multicast route. As per the procedures described in Section "Receiving C-Multicast Routes by a PE", this forwarding state will be the same as the state that would have been created based an other route with same NLRI. Raggarwa [Page 39] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 12. Using S-PMSI A-D routes to Bind C-trees to P-tunnels This section describes BGP-based procedures for using S-PMSIs A-D routes to bind (C-S, C-G) trees to P-tunnels. 12.1. Originating S-PMSI A-D routes The following describes procedures for originating S-PMSI A-D routes by a PE. The PE constructs the MCAST-VPN NLRI of an S-PMSI A-D route for a given as follows. + The RD in this NLRI is set to the RD of the MVPN's VRF associated with . + The Multicast Source field MUST contain the source address associated with the C-multicast stream, and the Multicast Source Length field is set appropriately to reflect this. + The Multicast Group field MUST contain the group address associated with the C-multicast stream, and the Multicast Group Length field is set appropriately to reflect this. + The Originating Router's IP Address field MUST be set to the IP address that the (local) PE places in the Global Administrator field of the VRF Route Import extended community of the VPN-IP routes advertised by the PE. Note that the tuple uniquely identifies a given multicast VRF. The PE constructs the rest of the S-PMSI A-D route as follows. Depending on the type of a P-Multicast tree used for the P-tunnel, the PMSI tunnel attribute of the S-PMSI A-D route is constructed as follows: + The PMSI tunnel attribute MUST contain the identity of the P- Multicast tree (note that the PE could create the identity of the tree prior to the actual instantiation of the tree). + If in order to establish the P-Multicast tree the PE needs to know the leaves of the tree within its own AS, then the PE obtains this information from the Leaf A-D routes received from other PEs/ASBRs within its own AS (as other PEs/ASBRs originate Leaf A-D routes in response to receiving the S-PMSI A-D route) by setting the Leaf Information Required flag in the PMSI Tunnel Raggarwa [Page 40] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 attribute to 1. + If a PE originates S-PMSI A-D routes with the Leaf Information Required flag in the PMSI Tunnel attribute set to 1, then the PE MUST be (auto)configured with an import Route Target, which controls acceptance of Leaf A-D routes by the PE. This Route Target is IP address specific. The Global Administrator field of this Route Target MUST be set to the IP address carried in the Next Hop of all the S-PMSI A-D routes advertised by this PE (if the PE uses different Next Hops, then the PE MUST be (auto)configured with multiple import RTs, one per each such Next Hop). The Local Administrator field of this Route Target MUST be set to 0. If the PE supports Route Target Constrain [RT-CONSTRAIN], the PE SHOULD advertise this import Route Target within its own AS using Route Target Constrains. To constrain distribution of the Route Target Constrain routes to the AS of the advertising PE these routes SHOULD carry the NO_EXPORT Community ([RFC1997]). + A PE MAY aggregate two or more S-PMSIs originated by the PE onto the same P-Multicast tree. If the PE already advertises S-PMSI A- D routes for these S-PMSIs, then aggregation requires the PE to re-advertise these routes. The re-advertised routes MUST be the same as the original ones, except for the PMSI tunnel attribute. If the PE has not previously advertised S-PMSI A-D routes for these S-PMSIs, then the aggregation requires the PE to advertise (new) S-PMSI A-D routes for these S-PMSIs. The PMSI Tunnel attribute in the newly advertised/re-advertised routes MUST carry the identity of the P-Multicast tree that aggregates the S-PMSIs. If at least some of the S-PMSIs aggregated onto the same P- Multicast tree belong to different MVPNs, then all these routes MUST carry an MPLS upstream assigned label [MPLS-UPSTREAM]. If all these aggregated S-PMSIs belong to the same MVPN, then the routes MAY carry an MPLS upstream assigned label [MPLS-UPSTREAM]. The labels MUST be distinct on a per MVPN basis, and MAY be distinct on a per route basis. 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. By default the set of Route Targets carried by the route MUST be a set intersection between the set of Route Targets carried in the intra-AS I-PMSI A-D route originated from the VRF, and the set of Route Targets carried by the (unicast) VPN-IP route to C-S originated originated from the VRF. The default could be modified via Raggarwa [Page 41] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 configuration. 12.2. Handling S-PMSI A-D routes by ASBRs Procedures for handling an S-PMSI A-D route by ASBRs (both within and outside of the AS of the PE that originates the route) are the same as specified in Section "Propagating Inter-AS Auto-Discovery Information", except that instead of Inter-AS I-PMSI A-D routes the procedures apply to S-PMSI A-D routes. 12.2.1. Merging S-PMSI into an I-PMSI Consider the situation where: + An ASBR is receiving (or expecting to receive) inter-AS (C-S, C- G) data from upstream via an S-PMSI. + The ASBR is sending (or expecting to send) the inter-AS (C-S, C-G) data downstream via an I-PMSI. This situation may obtain if the upstream providers have a policy of using S-PMSIs but the downstream providers have a policy of using I- PMSIs. To support this situation, an ASBR MAY, under certain conditions, merge one or more upstream S-PMSIs into a downstream I- PMSI. An S-PMSI (corresponding to a particular S-PMSI A-D route) MAY be merged by a particular ASBR into an I-PMSI (corresponding to a particular Inter-AS I-PMSI A-D route) if and only if the following conditions all hold: + BGP is used to exchange C-multicast routes. + The S-PMSI A-D route and the Inter-AS I-PMSI A-D route originate in the same AS. The Inter-AS I-PMSI A-D route carries the originating AS in the Source AS field of the NLRI of the route, and also in the AS_PATH attribute of the route. The S-PMSI A-D route carries the originating AS in the AS_PATH attribute of the route. + The S-PMSI A-D route and the Inter-AS I-PMSI A-D route have exactly the same set of RTs. Raggarwa [Page 42] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 + For each (C-S,C-G) mentioned in the S-PMSI route, if the ASBR has installed a Source Tree Join (C-S, C-G) C-multicast route, then the S-PMSI route was originated by the upstream PE of the C- multicast route. The address of the upstream PE is carried in the RT of the C-multicast route. The address of the PE that originated the S-PMSI route is carried in the Originating Router's IP Addr field of the MCAST-VPN NLRI of the route. + The ASBR supports the optional capability to discard (C-S, C-G) traffic received on an I-PMSI. An ASBR performs merging by stitching the tail end of the P-tunnel, as specified in the the PMSI Tunnel Attribute of the S-PMSI A-D route received by the ASBR, to the to the head of the P-tunnel, as specified in the PMSI Tunnel Attribute of the Inter-AS I-PMSI A-D route re-advertised by the ASBR. IP processing during merge: If an ASBR merges an (C-S, C-G) S-PMSI A- D route into an Inter-AS I-PMSI A-D route, the ASBR MUST discard all (C-S, C-G) traffic it receives on the tunnel advertised in the I-PMSI A-D route. An ASBR that merges an S-PMSI A-D route into an Inter-AS I-PMSI A-D route MUST NOT re-advertise the S-PMSI A-D route. 12.3. Receiving S-PMSI A-D routes by PEs Consider a PE that receives an S-PMSI A-D route. If one or more of the VRFs on the PE have their import Route Targets that contain one or more of the Route Targets carried by the received S-PMSI A-D route, then for each such VRF (and associated with it MVPN-TIB) the PE performs the following. Procedures for receiving an S-PMSI A-D route by a PE (both within and outside of the AS of the PE that originates the route) are the same as specified in Section "Inter-AS I-PMSI A-D route received via IBGP" except that (a) instead of Inter-AS I-PMSI A-D routes the procedures apply to S-PMSI A-D routes, and (b) a PE performs procedures specified in that section only if in addition to the criteria specified in that section all of the following is true: + The PE has in its MVPN-TIB the state for either (C-*, C-G) or (C- S, C-G), where C-S is the Multicast Source and C-G is the Multicast Group carried in the S-PMSI A-D route, and the oif (outgoing interfaces) for this state contains one or more interfaces to the locally attached CEs. Raggarwa [Page 43] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 + Either (a) the PE originates a Source Tree Join (C-S, C-G) C- multicast route, and the upstream PE of that route is the PE that originates the S-PMSI A-D route, or (b) the PE does not originate a Source Tree Join (C-S, C-G) C-multicast route, and the best (as determined by the BGP route selection procedures) Source Active A-D route for (C-S, C-G) selected by the PE is originated by the same PE as the one that originates the S-PMSI A-D route. Note that if the received S-PMSI A-D route has a PMSI Tunnel attribute with the Leaf Information bit set, then the above procedures may cause the origination of a Leaf A-D route whose Route Key is set to the NLRI of the S-PMSI A-D route. In addition to the procedures specified in Section "Inter-AS I-PMSI A-D route received via IBGP" the PE MUST set up its forwarding path to receive (C-S, C-G) traffic from the tunnel advertised by the S- PMSI A-D route (the PE MUST switch to the S-PMSI). 13. Switching from Shared C-tree to Source C-tree The procedures defined in this section only apply when the C- multicast routing protocol is PIM [RFC4601], moreover only apply for the multicast ASM mode, and MUST NOT be applied to Multicast Group addresses belonging to the SSM range. The procedures also MUST NOT be applied when the C-multicast routing protocol is BIDIR-PIM [RFC5015]. The procedures of this section are applicable only to MVPNs that use both shared (i.e., rooted at a C-RP) and source (i.e., rooted at a C- S) inter-site C-trees. These procedures are not applicable to MVPNs that do not use shared inter-site C-trees and rely solely on source inter-site C-trees. See section ""Supporting PIM-SM without Inter-Site C-Shared Trees" for the procedures applicable to that scenario. Whether a given MPVN uses both inter-site shared and source C-trees or not must be known a priori (e.g., via provisioning). In the scenario where an MVPN customer switches from an C-RP based tree (RPT) to the shortest path tree (SPT), in order to avoid packet duplication choosing of a single consistent upstream PE, as described in [MVPN], may not suffice. To illustrate this consider a set of PEs {PE2, PE4, PE6} that are on the C-RP tree for and have chosen a consistent upstream PE, as described in [MVPN], for state. Further this upstream PE, say PE1, is using an MI-PMSI for . If a site attached to one of these PEs, say PE2, switches to the C-S tree for , PE2 generates a Source Tree Join C- Raggarwa [Page 44] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 multicast route towards the upstream PE that is on the path to C-S, say PE3. PE3 also uses the MI-PMSI for , as PE1 uses for . This results in {PE2, PE4, PE6} receiving duplicate traffic for - both on the C-RP tree (from PE1) and C-S tree (from PE3). If it is desirable to suppress receiving duplicate traffic then it is necessary to choose a single forwarder PE for . The following describes how this is achieved. 13.1. Source Within a Site - Source Active Advertisement Whenever a PE creates an state as a result of receiving a Source Tree Join C-multicast route for from some other PE, the PE that creates the state MUST originate a Source Active A-D route. The route carries a single MCAST-VPN NLRI constructed as follows: + The RD in this NLRI is set to the RD of the VRF of the MVPN on the PE. + The Multicast Source field MUST be set to C-S. The Multicast Source Length field is set appropriately to reflect this. + The Multicast Group field MUST be set to C-G. The Multicast Group Length field is set appropriately to reflect this. The Next Hop field of the MP_REACH_NLRI attribute MUST be set to the IP address that the PE places in the Global Administrator field of the VRF Route Import extended community of the VPN-IP routes advertised by the PE from the MVPN's VRF. The route SHOULD carry the same set of Route Targets as the Intra-AS I-PMSI A-D route of the MVPN originated by the PE. Using the normal BGP procedures the Source Active A-D route is propagated to all the PEs of the MVPN. Whenever the PE deletes the state that was previously created as a result of receiving a Source Tree Join C-multicast route for from some other PE, the PE that deletes the state MUST also withdraw the Source Active A-D route, if such a route was advertised when the state was created. Raggarwa [Page 45] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 13.2. Receiving Source Active A-D route When a PE receives a new Source Active A-D route, the PE finds a VRF whose import Route Targets match one or more of the Route Targets carried by the route. If the match is found, then the PE updates the VRF with the received route. We say that a given (C-S, C-G) Source Active A-D route stored in a given VRF matches a given entry present in the MVPN-TIB associated with the VRF if C-G carried by the route is the same as C- G of the entry. When (as a result of receiving PIM messages from one of its CEs) a PE creates in one of its MVPN-TIBs a (new) entry with a non- empty outgoing interface list that contains one or more PE-CE interfaces, the PE MUST check if it has any matching Source Active A- D routes. If there is one or more such matching route, such that the PE does not have (C-S, C-G) state in its MVPN-TIB for (C-S, C-G) carried in the route, then the PE selects one of them (using the BGP route selection procedures), and sets up its forwarding path to receive (C-S, C-G) traffic from the tunnel the originator of the selected Source Active A-D route uses for sending (C-S, C-G). When as a result of receiving a new Source Active A-D route a PE updates its VRF with the route, the PE MUST check if the newly received route matches any entries. If (a) there is a matching entry, (b) the PE does not have (C-S, C-G) state in its MVPN-TIB for (C-S, C-G) carried in the route, and (c) the received route is selected as the best(using the BGP route selection procedures), then the PE sets up its forwarding path to receive (C-S, C-G) traffic from the tunnel the originator of the selected Source Active A-D route uses for sending (C-S, C-G). 13.2.1. Pruning Sources off the Shared Tree If the incoming interface list (iif) for the found entry in the MVPN-TIB on the PE contains one of the PE-CE interfaces (interfaces from the PE to its directly connected CEs), then the PE MUST check to see if there is already a entry in the MVPN-TIB. If there is not, the PE SHOULD start a timer. The value of the timer MUST be configurable. Once the timer expires (or immediately if the timer is not used), the PE creates a entry. C-S of this entry is set to the address carried in the Multicast Source field of the received Source Active A-D route, and C-G of this entry is set to the address carried in the Multicast Group field of the route. Creating this entry results in pruning traffic off Raggarwa [Page 46] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 the shared (RPT) tree. As a result of creating the entry in the MVPN- TIB, the PE will use PIM to prune C-S off the tree. The purpose of this timer is to ensure that C-S is not pruned off the shared tree until all PEs have had time to receive the Source Active A-D route for . The timer is canceled if the PE no longer has at least one Source Active A-D route for . The PE maintains the entry for as long as it has at least one Source Active A-D route for . 14. Supporting PIM-SM without Inter-Site Shared C-trees The procedures defined in this section only apply when the C- multicast routing protocol is PIM [RFC4601], moreover only apply for the multicast ASM mode, and MUST NOT be applied to Multicast Group addresses belonging to the SSM range. The procedures also MUST NOT be applied when the C-multicast routing protocol is BIDIR-PIM [RFC5015]. The procedures of this section are applicable only to MVPNs that do not use inter-site shared (i.e., rooted at a C-RP) C-trees. These procedures are not applicable to MVPNs that use both shared and shortest path inter-site C-trees. See section "Switching from Shared C-trees to Source C-trees" for the procedures applicable to that scenario. Whether a given MPVN uses inter-site shared C-trees or not must be known a priori (e.g., via provisioning). 14.1. Discovering Active Multicast Sources A PE can obtain information about active multicast sources within a given MVPN in a variety of ways. One way is for the PE to act as a fully functional customer RP (C-RP) for that MVPN. Another way is to use PIM Anycast RP procedures [PIM-ANYCAST-RP] to convey information about active multicast sources from one or more of the MVPN C-RPs to the PE. Yet another way is to use MSDP [MSDP] to convey information about active multicast sources from the MVPN C-RPs to the PE. When a PE using any of the above methods first learns of a new (multicast) source within that MVPN, the PE constructs a Source Active A-D route, and sends this route to all other PEs that have one Raggarwa [Page 47] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 or more sites of that MVPN connected to them. The route carries a single MCAST-VPN NLRI constructed as follows: + The RD in this NLRI is set to the RD of the VRF of the MVPN on the PE. + The Multicast Source field MUST be set to the source IP address of the multicast data packet carried in the PIM-Register message. The Multicast Source Length field is set appropriately to reflect this. + The Multicast Group field MUST be set to the group address of the multicast data packet carried in the PIM-Register message. The Multicast Group Length field is set appropriately to reflect this. The Next Hop field of the MP_REACH_NLRI attribute MUST be set to the IP address that the PE places in the Global Administrator field of the VRF Route Import extended community of the VPN-IP routes advertised by the PE. The route SHOULD carry the same set of Route Targets as the Intra-AS I-PMSI A-D route of the MVPN originated by the PE. Using the normal BGP procedures the Source Active A-D route is propagated to all the PEs of the MVPN. When a PE that previously advertised a Source Active A-D route for a given (multicast) source learns that the source is no longer active (the PE learns this by using the same mechanism by which the PE learned that the source was active), the PE SHOULD withdraw the previously advertised Source Active route. 14.2. Receiver(s) Within a Site A PE follows the procedures specified in Section "Originating C- multicast routes by a PE", except that the procedures specified in Section "Originating Shared Tree Join C-multicast route" are replaced with the procedures specified in this Section below. When a PE receives a new Source Active A-D route, the PE finds a VRF whose import Route Targets match one or more of the Route Targets carried by the route. If the match is found, then the PE updates the VRF with the received route. We say that a given (C-S, C-G) Source Active A-D route stored in a given VRF matches a given entry present in the MVPN-TIB Raggarwa [Page 48] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 associated with the VRF if C-G carried by the route is the same as C- G of the entry. When (as a result of receiving PIM messages from one of its CEs) a PE creates in one of its MVPN-TIBs a (new) entry with a non- empty outgoing interface list that contains one or more PE-CE interfaces, the PE MUST check if it has any matching Source Active A- D routes. If there is one or more such matching routes, and the best path to C-S carried in the matching route(s) is reachable through some other PE, then for each such route the PE MUST originate a Source Tree Join C-multicast route. If there is one or more such matching routes, and the best path to C-S carried in the matching route(s) is reachable through a CE connected to the PE, then for each such route the PE MUST originate a PIM Join (C-S, C-G) towards the CE. When as a result of receiving a new Source Active A-D route a PE updates its VRF with the route, the PE MUST check if the newly received route matches any entries. If there is a matching entry, and the best path to C-S carried in the (A-D) route is reachable through some other PE, the PE MUST originate a Source Tree Join C-multicast route for the (C-S, C-G) carried by the route. If there is a matching entry, and the best path to C-S carried in the (A-D) route is reachable through a CE connected to the PE, the PE MUST originate a PIM Join (C-S, C-G) towards the CE. Construction and distribution of the Source Tree Join C-multicast route follows the procedures specified in Section "Originating Source Tree Join C-multicast route", except that the Multicast Source Length, Multicast Source, Multicast Group Length, and Multicast Group fields in the MCAST-VPN NLRI of the Source Tree Join C-multicast route are copied from the corresponding field in the Source Active A- D route. A PE MUST withdraw a Source Tree Join C-multicast route for (C-S, C- G) if, as a result of having received PIM messages from one of its CEs, the PE creates a Prune upstream state in one of its MVPN-TIBs, but has no Joined state in that MVPN- TIB, and had previously advertised the said route. (This is even if the VRF associated with the MVPN-TIB still has a (C-S, C-G) Source Active A-D route). A PE MUST withdraw a Source Tree Join C-multicast route for (C-S, C- G) if the Source Active A-D route that triggered the advertisement of the C-multicast route is withdrawn. Even though PIM is used as a C-multicast protocol, procedures described in Section "Originating Shared Tree Join C-multicast route" Raggarwa [Page 49] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 do not apply here, as only the Source Tree Join C-multicast routes are exchanged among PEs. 14.3. Receiving C-multicast routes by a PE In this model the only valid type of a C-multicast route that a PE could receive is a Source Tree Join C-multicast route. Processing of such a route follows the procedures specified in Section "Receiving Source Tree Join C-multicast route". 15. Carrier's Carrier A way to support the Carrier's Carrier model is provided by using mLDP as the CE-PE multicast routing and label distribution protocol, as specified in this document. To improve scalability it is RECOMMENDED that for the Carrier's Carrier scenario within an AS all the S-PMSIs of a given MVPN be aggregated into a single P-Multicast tree (by using upstream assigned labels). 16. Scalability Considerations A PE should use Route Target Constrain [RT-CONSTRAIN] to advertise the Route Targets that the PE uses for the VRF Route Imports extended community (note that doing this requires just a single Route Target Constraint advertisement by the PE). This allows each C-multicast route to reach only the relevant PE, rather than all the PEs participating the an MVPN. To keep the intra-AS membership/binding information within the AS of the advertising router the BGP Update message originated by the advertising router SHOULD carry the NO_EXPORT Community ([RFC1997]). An Inter-AS I-PMSI A-D route originated by an ASBR aggregates Intra- AS I-PMSI A-D routes originated within the ASBR's own AS. Thus while the Intra-AS I-PMSI A-D routes originated within an AS are at the granularity of within that AS, outside of that AS the (aggregated) Inter-AS I-PMSI A-D routes are at the granularity of . An Inter-AS I-PMSI A-D route for a given indicates the presence of or or more sites of the MVPN connected to the PEs of the AS. For a given inter-AS tunnel each of its intra-AS segments could be Raggarwa [Page 50] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 constructed by its own mechanism. Moreover, by using upstream assigned labels within a given AS multiple intra-AS segments of different inter-AS tunnels of either the same or different MVPNs may share the same P-Multicast tree. Since (aggregated) Inter-AS I-PMSI A-D routes may have granularity of , an MVPN that is present in N ASes would have total of N inter-AS tunnels. Thus for a given MVPN the number of inter-AS tunnels is independent of the number of PEs that have this MVPN. Within each Autonomous System BGP Route reflectors can be partitioned among MVPNs present in that Autonomous System so that each partition carries routes for only a subset of the MVPNs supported by the Service Provider. Thus no single Route Reflector is required to maintain routes for all MVPNs. Moreover, Route Reflectors used for MVPN do not have to be used for VPN-IP routes (although they may be used for VPN-IP routes as well). As described in Section "C-multicast routes aggregation", C-multicast routes for a given (S,G) of a given MVPN originated by PEs that are clients of a given Route Reflector are aggregated by the Route Reflector. Therefore, even if within a Route Reflector cluster there are multiple C-multicast routes for a given (S,G) of a given MVPN, outside of the cluster all these routes are aggregated into a single C-multicast route. Additional aggregation of C-multicast routes occurs at ASBRs, where an ASBR aggregates all the received C- multicast routes for a given (S,G) of a given MVPN into a single C- multicast route. Moreover, both Route Reflectors and ASBRs maintain C-multicast routes only in the control plane, but not in the data plane. 16.1. Dampening C-multicast routes The rate of C-multicast routing changes advertised by a PE is not necessarily directly proportional to the rate of multicast routing changes within the MVPN sites connected to the PE, as after the first Join originated within a site, all the subsequent Joins for same originated within the sites of the same MVPN connected to the PE do not cause origination of new C-multicast routes by the PE. Depending on how multicast VPN is engineered, dynamic addition and removal of P2MP RSVP-TE leaves through advertisement/withdrawal of Leaf A-D routes, will happen. Dampening techniques can be used to limit corresponding processing. To lessen the control plane overhead associated with processing of C- Raggarwa [Page 51] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 multicast routes, this document proposes OPTIONAL route dampening procedures similar to what is described in RFC2439. The following OPTIONAL procedures can be enabled on a PE, ASBR, or BGP Route Reflector advertising or receiving C-multicast routes. 16.1.1. Dampening withdrawals of C-multicast routes A PE/ASBR/Route Reflector can OPTIONALLY delay the advertisement of withdrawals of C-multicast routes. An implementation SHOULD provide the ability to control the delay via a configurable timer, possibly with some backoff algorithm to adapt the delay to multicast routing activity. Dampening of withdrawals of C-multicast routes does not impede the multicast join latency observed by MVPN customers, and also does not impede the multicast leave latency observed by a CE, as multicast forwarding from the VRF will stop as soon as C-multicast state is removed in the VRF. The potential drawbacks of dampening of withdrawals of C-multicast routes are: + Until the withdrawls are actually sent, multicast traffic for the C-multicast routes in question will be continued to be transmitted to the PE, which will just have to discard it. Note that the PE may receive useless (multicast) traffic anyway, irrespective of dampening of withdrawals of C-multicast routes due to the use of I-PMSIs. + Any state in the upstream PEs that would be removed as a result of processing the withdrawls will remain until the withdrawls are sent. Discussion on whether the potential drawbacks mentioned above are of any practical significance is outside the scope of this document. 16.1.2. Dampening Source/Shared Tree Join C-multicast routes A PE/ASBR/Route Reflector can OPTIONALLY delay the advertisement of Source/Shared Tree Join C-multicast routes. An implementation SHOULD provide the ability to control the delay via a configurable timer, possibly with some backoff algorithm to adapt the delay to multicast routing activity. Dampening Source/Shared Tree Join C-multicast routes will not impede multicast join latency observed by a given MVPN, except if the PE Raggarwa [Page 52] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 advertising the Source/Shared Tree Join C-multicast route for a particular C-S/C-RP is the first to do so for all the sites of the MVPN that share the same upstream PE with respect to the C-S/C-RP. 16.2. Dampening withdrawals of Leaf A-D routes Similarly to the procedures proposed above for withdrawal of C- multicast routes, dampening can be applied to the withdrawal of Leaf A-D routes. 17. IANA Consideration This document defines a new BGP Extended Community called Source AS. This community is 2-octet AS specific, of an extended type, and is transitive. This document defines a new BGP Extended Community called VRF Route Import. This community is IP address specific, of an extended type, and is transitive. This document defines a new NLRI, called MCAST-VPN, to be carried in BGP using multiprotocol extensions. It requires assignment of a new SAFI. This document defines a new BGP optional transitive attribute, called PMSI Tunnel. 18. Security Considerations The mechanisms described in this document could re-use the existing BGP security mechanisms. 19. Acknowledgement Some of the text in Section "Supporting PIM-SM without Inter-Site Shared C-trees" has been taken almost verbatim from RFC3618. Raggarwa [Page 53] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 20. References 20.1. Normative References [IANA-SAFI] http://www.iana.org/assignments/safi-namespace [MVPN] E. Rosen, R. Aggarwal [Editors], "Multicast in MPLS/BGP IP VPNs", draft-ietf-l3vpn-2547bis-mcast [RFC1997] R. Chandra, P. Traina, T. Li, "BGP Communities Attribute", RFC1997, August 1996. [RFC2119] "Key words for use in RFCs to Indicate Requirement Levels.", Bradner, RFC2119, March 1997. [RFC4271] Rekhter, Y., Li, T., Hares, S., "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006 [RFC4760] Bates, T., Rekhter, Y., Chandra, R., and D. Katz, "Multiprotocol Extensions for BGP-4", RFC 2858, January 2007. [RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended Communities Attribute", RFC 4360, February 2006. [RFC4364] E. Rosen, Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC4364, February 2006 [RFC4601] B. Fenner et. al., "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", RFC 4601, August 2006 20.2. Informative References [MPLS-UPSTREAM] R. Aggrwal, Y. Rekhter, E. Rosen, " MPLS Upstream Label Assignment and Context Specific Label Space", draft-ietf-mpls- upstream-label [RT-CONSTRAIN] P. Marques et. al., "Constrained Route Distribution for Border Gateway Protocol/MultiProtocol Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual Private Networks (VPNs)", RFC 4684, November 2006 [mLDP] I. Minei et. al., "Label Distribution Protocol Extensions for Point-to-Multipoint and Multipoint-to-Multipoint Label Switched Paths", draft-ietf-mpls-ldp-p2mp [RFC4607] H. Holbrook, B. Cain "Source-Specific Multicast for IP", Raggarwa [Page 54] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 RFC 4607, August 2006 [RFC5015] M. Handley et. al., "Bidirectional Protocol Independent Multicast (BIDIR-PIM)", RFC5015, October 2007 [RSVP-TE-P2MP] R. Aggarwal et. al., "Extensions to RSVP-TE for Point- to-Multipoint TE LSPs", draft-ietf-mpls-rsvp-te-p2mp [PIM-ANYCAST-RP] D. Farinacci, Y. Cai, "Anycast-RP using PIM" RFC 4610, August 2006 [MSDP] B. Fenner, D. Meyer, "Multicast Source Discovery Protocol (MSDP)", RFC3618, October 2003 21. Author's Address Rahul Aggarwal Juniper Networks 1194 North Mathilda Ave. Sunnyvale, CA 94089 Email: rahul@juniper.net Eric C. Rosen Cisco Systems, Inc. 1414 Massachusetts Avenue Boxborough, MA, 01719 E-mail: erosen@cisco.com Thomas Morin France Telecom R & D 2, avenue Pierre-Marzin 22307 Lannion Cedex France Email: thomas.morin@francetelecom.com Yakov Rekhter Juniper Networks 1194 North Mathilda Ave. Sunnyvale, CA 94089 Email: yakov@juniper.net Chaitanya Kodeboniya Raggarwa [Page 55] Internet Draft draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt June 2008 22. Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf- ipr@ietf.org. 23. Copyright Notice Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Raggarwa [Page 56]