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Draft-Rosen Multicast VPNs Overview

The Junos OS provides two types of draft-rosen multicast VPNs:

  • Draft-rosen multicast VPNs with service provider tunnels operating in any-source multicast (ASM) mode (also referred to as rosen 6 Layer 3 VPN multicast)—Described in RFC 4364, BGP/MPLS IP Virtual Private Networks (VPNs) and based on Section 2 of the IETF Internet draft draft-rosen-vpn-mcast-06.txt, Multicast in MPLS/BGP VPNs (expired April 2004).

  • Draft-rosen multicast VPNs with service provider tunnels operating in source-specific multicast (SSM) mode (also referred to as rosen 7 Layer 3 VPN multicast)—Described in RFC 4364, BGP/MPLS IP Virtual Private Networks (VPNs) and based on the IETF Internet draft draft-rosen-vpn-mcast-07.txt, Multicast in MPLS/BGP IP VPNs. Draft-rosen multicast VPNs with service provider tunnels operating in SSM mode do not require that the provider (P) routers maintain any VPN-specific Protocol-Independent Multicast (PIM) information.

Note:

Draft-rosen multicast VPNs are not supported in a logical system environment even though the configuration statements can be configured under the logical-systems hierarchy.

In a draft-rosen Layer 3 multicast virtual private network (MVPN) configured with service provider tunnels, the VPN is multicast-enabled and configured to use the Protocol Independent Multicast (PIM) protocol within the VPN and within the service provider (SP) network. A multicast-enabled VPN routing and forwarding (VRF) instance corresponds to a multicast domain (MD), and a PE router attached to a particular VRF instance is said to belong to the corresponding MD. For each MD there is a default multicast distribution tree (MDT) through the SP backbone, which connects all of the PE routers belonging to that MD. Any PE router configured with a default MDT group address can be the multicast source of one default MDT.

Draft-rosen MVPNs with service provider tunnels start by sending all multicast traffic over a default MDT, as described in section 2 of the IETF Internet draft draft-rosen-vpn-mcast-06.txt and section 7 of the IETF Internet draft draft-rosen-vpn-mcast-07.txt. This default mapping results in the delivery of packets to each provider edge (PE) router attached to the provider router even if the PE router has no receivers for the multicast group in that VPN. Each PE router processes the encapsulated VPN traffic even if the multicast packets are then discarded.

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