Share-Mdt-Based Delivery Of Multicast Data Packets - 3Com MSR 50 Series Configuration Manual

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Share-MDT-Based
Delivery of Multicast
Data Packets
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share-group address as the multicast group address, to convert it into a normal,
public network multicast data packet (11.1.2.1, 239.1.1.1), and then passes the
packet to the public instance on PE 2 to have it forwarded to the public network.
4 The multicast data packet (11.1.2.1, 239.1.1.1) is forwarded to the public instance
on all the PE devices along the share-MDT. Upon receiving this packet, every PE
device decapsulates it to turn it back into a join message to be sent to the VPN RP.
Then, each PE device checks the join message. If any PE device finds that the VPN
RP is in the site it interfaces with, it passes the join message to the VPN instance on
it; otherwise, it discards the join message.
5 When receiving the join message, the VPN instance on PE 1 considers that it
received the message from the MTI. PE 1 creates a local (*, 225.1.1.1) state entry,
with the downstream interface being the MTI and the upstream interface being
the one that leads to CE 1. At the same time, it sends a join message to CE 1,
which is the VPN RP.
6 Upon receiving the join message from the VPN instance on PE 1, CE 1 creates a
local (*, 225.1.1.1) state entry or updates the entry if it already exists. By now, the
construction of a multicast distribution tree across the public network is
completed.
For details about GRE, refer to
After the share-MDT is established, the private network multicast data flows to the
receivers in each site along the distribution tree. The private network multicast
packets are encapsulated into normal public network multicast packets on the
local PE device, transmitted along the share-MDT, and then decapsulated on the
remote PE device to go into the normal protocol procedure.
1 If PIM-DM is running in the VPNs network, the customer multicast traffic flows
along the SPTs across the public network.
2 On a VPNs network running PIM-SM:
If the receivers and the VPN RP are in different sites, the customer multicast
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traffic flows along the RPT across the public network.
If the multicast source and the VPN RP are in different sites, the customer
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multicast traffic flows along the SPTs across the public network.
The following example explains how multicast data packets are transmitted based
on the share-MDT while PIM-DM is running in both the public network and the
VPNs network.
As shown in Figure 375, PIM-DM is running in both the public network and the
VPNs network, Receiver in Site 2 is attached to CE 2, and Source in Site 1 sends
multicast data to multicast group G (225.1.1.1).
"GRE Configuration" on page
How MD-VPN Works 1289
1589.