MPLS-Enabled Applications: Emerging Developments and New Technologies

10.4. THE ORIGINAL MULTICAST SOLUTION - PIM/GRE mVPN (DRAFT-ROSEN)

The original solution for multicast in BGP/MPLS VPNs is often referred to as 'draft-rosen', after the name of the IETF draft [DRAFT-ROSEN] that first described it, or PIM/GRE mVPN, after the technologies used for the exchange of routing information and traffic forwarding. Note that although implementations of this solution were deployed by some of the largest networks in the industry, the draft itself never gained working group status in the IETF. However, the working group draft describing the architectural solution for multicast [VPN-MCAST] is a superset of draft-rosen, allowing all the functionality available in the original draft.

Although targeted to multicast traffic in a BGP/MPLS VPN setup, the draft-rosen solution departs from the BGP/MPLS VPN model for unicast traffic described in previous chapters. Nevertheless, some of the elements of BGP/MPLS VPNs are reused: the interface between PE and CE in the multicast solution is still based on the VRF concept of BGP/MPLS VPNs, and customer traffic is still tunneled through the provider core between the PEs (the VPN tunnel concept of BGP/MPLS VPNs). Despite these high-level similarities, the PIM/GRE multicast solution is very different from the unicast one. Exactly how different we will see in the remainder of this section, by looking at the mechanisms used for carrying multicast mVPN routing information and data traffic. These will be discussed separately below. ...