12
Figure 10 VPN networking diagram
•
The provider (P) device belongs to the public network. The customer edge (CE) devices belong
to their respective VPNs. Each CE device serves its own VPN and maintains only one set of
forwarding mechanisms.
•
The provider edge (PE) devices connect to the public network and the VPNs. Each PE device
must strictly distinguish the information for different networks, and maintain a separate
forwarding mechanism for each network. On a PE device, a set of software and hardware that
serve the same network forms an instance. Multiple instances can exist on the same PE device,
and an instance can reside on different PE devices. On a PE device, the instance for the public
network is called the public network instance, and those for VPNs are called VPN instances.
Multicast application in VPNs
A PE device that supports multicast for VPNs does the following operations:
•
Maintains an independent set of multicast forwarding mechanisms for each VPN, including the
multicast protocols, PIM neighbor information, and multicast routing table. In a VPN, the device
forwards multicast data based on the forwarding table or routing table for that VPN.
•
Implements the isolation between different VPNs.
•
Implements information exchange and data conversion between the public network and VPN
instances.
Multicast VPN implements multicast on MPLS L3VPN networks. As shown in
, when a
multicast source in VPN A sends a multicast stream to a multicast group, only the receivers that
belong to both the multicast group and VPN A can receive the multicast stream. The multicast data is
multicast both in VPN A and on the public network.
VPN A
VPN A
VPN A
VPN B
VPN B
Public network
P
PE 1
PE 2
PE 3
CE b3
CE a2
CE a3
CE b1
CE a1
CE b2
