Multi-Instance Application In Multicast - 3Com S7906E Configuration Manual

Figure 1-10 Networking diagram for VPN
CE b2
VPN B
CE b1
CE a1
VPN A
The P device belongs to the public network. The CE devices belong to their respective VPNs. Each
CE device serves its own network and maintains only one set of forwarding mechanism.
The PE devices interface with the public network and the VPN networks, serving multiple networks
at the same time. On each PE device, the information for different networks must be strictly
distinguished and a separate forwarding mechanism must be maintained for each network. On a
PE device, a set of software and hardware that serves the same network forms an instance.
Multiple instances exist on a PE device at the same time, and an instance resides on different PE
devices.

Multi-Instance Application in Multicast

With multi-instance multicast enabled, a PE is able to:
Maintain a set of independent multicast forwarding mechanism for each instance, include various
multicast protocols, a list of PIM neighbors and a multicast routing table per instance. Each
instance searches its own forwarding table or routing table to forward multicast data.
Guarantee the isolation between different VPN instances.
Implement information exchange and data conversion between the public instance and VPN
instances.
Multi-instance multicast is the basis of multicast over a VPNs network. With multicast VPN, as shown in
Figure 1-10, when a multicast source in VPN A sends a multicast stream to a multicast group, of all
possible receivers on the network for that group, only those belong to VPN A can receive the multicast
stream. The multicast data is multicast both in VPN A and in the public network.
VPN A
CE a2
PE 2
P
PE 1
Public network
CE b3
VPN B
CE a3
PE 3
VPN A
1-14