HP FlexNetwork 7500 Series Configuration Manual page 193

a. The local PE device encapsulates a VPN multicast packet into a public network multicast
packet.
b. The encapsulated multicast packet is sent by the PE device and travels over the public
network.
c. After receiving the multicast packet, the remote PE device decapsulates the multicast
packet to get the original VPN multicast packet.
•
The local PE device sends VPN data out of the MTI. The remote PE devices receive the private
data from their MTI interfaces.
As shown in Figure
as an entrance or exit of the pool. The local PE device puts the private data into the
transmission pool (MD) through the entrance (MTI). The transmission pool automatically
duplicates the private data and transmits the data to each exit (MTI) of the transmission pool.
Then, a remote PE device that needs the data can get it from its exit (MTI).
Figure 62 Relationship between PIM on the public network and an MD in a VPN instance
•
Each VPN instance is assigned a unique default-group address. The VPN data is transparent to
the public network.
A PE device encapsulates a VPN multicast packet (a multicast protocol packet or a multicast
data packet) into a public network multicast packet. The default-group address is used as the
public network multicast group. Then, the PE sends this multicast packet to the public network.
•
A default-group corresponds to a unique MD. For each default-group, a unique default-MDT is
constructed through the public network resources for multicast data forwarding. All the VPN
multicast packets transmitted in this VPN are forwarded along this default-MDT, regardless of
which PE device they used to enter the public network.
•
An MD is assigned a unique data-group address range for MDT switchover. When the rate of a
VPN multicast stream that entered the public network at a PE device reaches or exceeds the
switchover threshold, the PE does the following:
Selects an address that is least referenced from the data-group address range.
Uses the address to encapsulate the multicast packets for that VPN.
•
All the PE devices on the network monitor the forwarding rate on the default-MDT.
a. When the rate of a VPN multicast stream that entered the public network at a specific PE
device exceeds the threshold, the PE device creates an MDT switchover message. The
message travels to the downstream along the default-MDT. This causes a data-MDT to be
built by using the data-group between that PE device and the remote PE devices with
downstream receivers.
62, you can think of an MD as a private data transmission pool and an MTI
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