Mdt Switchover - HP A6600 Configuration Manual

Figure 70 Delivery of multicast data packets
The VPN multicast traffic is delivered across the public network as follows.
Source sends customer multicast data (192.1.1.1, 225.1.1.1) to CE 1.
1.
CE 1 forwards the VPN multicast data along an SPT to CE 1, and the VPN instance on PE 1 checks
2.
the MVRF. If the outgoing interface list of the forwarding entry contains an MTI, PE 1 processes the
VPN multicast data.. Now, the VPN instance on PE 1 considers that the VPN multicast data has
been sent out the MTI.
PE 1 encapsulates the multicast data by means of GRE, with its BGP interface address as the
3.
multicast source address and the share-group address as the multicast group address, to convert it
into a normal, public network multicast data packet (11.1.1.1, 239.1.1.1). PE 1 then forwards it to
the public network.
The multicast data packet (11.1.1.1, 239.1.1.1) is forwarded to the public network on all the PE
4.
devices along the share-MDT. After receiving this packet, every PE device decapsulates it to turn it
back into a VPN multicast data packet, and passes it to the corresponding VPN instance. If any PE
has a downstream interface for an SPT, it forwards the VPN multicast packet down the SPT.
Otherwise, it discards the packet.
The VPN instance on PE 2 searches the MVRF and finally delivers the VPN multicast data to
5.
Receiver. By now, the process of transmitting a VPN multicast packet across the public network is
completed.

MDT switchover

Switching from share-MDT to switch-MDT
When a multicast data packet of a VPN is transmitted through the share-MDT in the public network, the
packet is forwarded to all PE devices that support that VPN instance, no matter whether any active
receivers exist in the attached sites. When the rate of the customer multicast traffic of that VPN is high,
multicast data might get flooded in the public network, causing bandwidth waste and extra burden on the
PE devices.
To optimize multicast transmission, the MD solution establishes a dedicated switch-MDT between the PE
devices with VPN multicast receivers and multicast sources for any large-traffic VPN multicast stream
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