Related Documentation
MBGP Multicast VPN Sites
There are two ways to implement Layer 3 VPNs using PIM, or multicast VPNs (MVPNs). There are no official names for the two methods: using dual PIM MVPNs (also known informally as “draft-rosen”) and multiprotocol BGP (MBGP)-based MVPNs (the “next generation” method of MVPN configuration). Both methods are supported and equally effective, but the MBGP-based MVPN method does not require multicast configuration on the service provider backbone. In other words, the PIM state information is maintained between the PE routers using the same architecture that is used for unicast VPNs. The main advantage of deploying MVPNs with MBGP is simplicity of configuration and operation because multicast is not needed on the service provider VPN backbone connecting the PE routers.
Multiprotocol BGP multicast VPNs employ the intra-autonomous system (AS) next-generation BGP control plane and PIM sparse mode as the data plane.
There are several multicast applications driving the deployment of next-generation Layer 3 MVPNs. Some of the key emerging applications include the following:
- Layer 3 VPN multicast service offered by service providers to enterprise customers
- Video transport applications for wholesale IPTV and multiple content providers attached to the same network
- Distribution of media-rich financial services or enterprise multicast services
- Multicast backhaul over a metro network
The main characteristics of MBGP MVPNs are:
- They extend Layer 3 VPN service (RFC 4364) to support IP multicast for Layer 3 VPN service providers.
- They follow the same architecture as specified by RFC 4364 for unicast VPNs. Specifically, BGP is used as the provider edge (PE) router-to-PE router control plane for multicast VPN.
- They eliminate the requirement for the virtual router (VR) model (as specified in Internet draft draft-rosen-vpn-mcast, Multicast in MPLS/BGP VPNs) for multicast VPNs and the RFC 4364 model for unicast VPNs.
- They rely on RFC 4364-based unicast with extensions for intra-AS and inter-AS communication.
An MBGP MVPN defines two types of site sets, a sender site set and a receiver site set. These sites have the following properties:
- Hosts within the sender site set can originate multicast traffic for receivers in the receiver site set.
- Receivers outside the receiver site set should not be able to receive this traffic.
- Hosts within the receiver site set can receive multicast traffic originated by any host in the sender site set.
- Hosts within the receiver site set should not be able to receive multicast traffic originated by any host that is not in the sender site set.
A site can be in both the sender site set and the receiver site set, so hosts within such a site can both originate and receive multicast traffic. For example, the sender site set could be the same as the receiver site set, in which case all sites could both originate and receive multicast traffic from one another.
Sites within a given MBGP MVPN might be within the same organization or in different organizations, which means that an MBGP MVPN can be either an intranet or an extranet. A given site can be in more than one MBGP MVPN, so MBGP MVPNs might overlap. Not all sites of a given MBGP MVPN have to be connected to the same service provider, meaning that an MBGP MVPN can span multiple service providers. Feature parity for the MVPN extranet functionality or overlapping MVPNs on the Junos Trio chipset is supported in Junos OS Releases 11.1R2, 11.2R2, and 11.4.
Another way to look at an MBGP MVPN is to say that an MBGP MVPN is defined by a set of administrative policies. These policies determine both the sender site set and the receiver site set. These policies are established by MBGP MVPN customers, but implemented by service providers using the existing BGP and MPLS VPN infrastructure.
