3Com S7906E Configuration Manual page 1144

For details about the concepts of Protocol Independent Multicast (PIM), bootstrap router (BSR),
candidate-BSR (C-BSR), rendezvous point (RP), candidate RP (C-RP), shortest path tree (SPT) and
rendezvous point tree (RPT), refer to PIM Configuration in the IP Multicast Volume.
Comware implements multicast VPN by means of the multicast domain (MD) method. This multicast
VPN implementation is referred to as MD-VPN.
The most significant advantage of MD-VPN is that it requires only the PE devices to support multiple
instances. Multicast VPN can be implemented without upgrading any CE devices and P devices, and
without changing the original PIM configuration of the CE devices and the P devices. In other words, the
MD-VPN solution is transparent to the CE devices and the P devices.
Basic concepts in MD-VPN
The basic concepts involved in MD-VPN are described in
Table 1-1 Basic concepts in MD-VPN
Concept
Multicast domain (MD)
Multicast distribution tree (MDT)
Multicast tunnel (MT)
Multicast tunnel interface (MTI)
Share-group
Share-multicast distribution tree
(Share-MDT)
Introduction to MD-VPN
Main points in the implementation of MD-VPN are as follows:
1) The public network of the service provider supports multicast. The PE devices need to support the
public instance and multiple VPN instances, each instance running PIM independently. Private
network multicast traffic between the PE devices and the CE devices is transmitted on a
Table
An MD is a set of VPN instances running on PE routers that
can send multicast traffic to each other. Each MD uniquely
corresponds to the same set of VPN instances.
An MDT is a multicast distribution tree between all PE devices
in the same VPN, such as share-MDT.
An MT is a tunnel that interconnects all PEs in an MD for
delivering private network traffic within the MD.
An MTI is the entrance to or exit of an MT, equivalent to an
entrance to or exit of an MD. PE devices use the MTI to access
the MD. An MTI handles only multicast packets but not unicast
packets. An MTI is automatically created with the configuration
of a share-group and MTI binding for a VPN instance.
In the public network, each MD is assigned an independent
multicast address, called share-group. A share-group is the
unique identifier of an MD in the public network. It is used to
build a share-MDT corresponding to the MD in the public
network.
A share-MDT is an MDT that uses a share-group as its group
address. In a VPN, the share-MDT is uniquely identified by the
share-group. A share-MDT is automatically created after
configuration and will always exist in the public network,
regardless of the presence of any actual multicast services in
the public network or the VPN.
1-4
1-1.
Description