HP A8800 Configuration Manual page 256

private network multicast packets transmitted in this VPN are forwarded along this share-MDT, no
matter at which PE device they entered the public network.
7. A share-group is assigned a unique switch-group-pool for MDT switching. When the rate of a
private network multicast stream that entered the public network at a PE device exceeds the
switching threshold, the PE chooses an idle address (namely, switch-group) from the
switch-group-pool, and encapsulates the multicast packets for that VPN sing that address.
8. All the ingress PE devices in the network monitor the forwarding rate on the share-MDT. When the
multicast traffic meets the switchover conditions, the PE device initiates a switchover message to
the downstream along the share-MDT, so that a switch-MDT is built using the switch-group between
that PE device and the remote PE devices with receivers downstream. Then, after a switch-delay
period has passed, an MDT switching takes place: all private network multicast packets that have
entered the public network at that PE device are encapsulated into public network multicast
packets using the switch-group, instead of using the share-group, so that they are switched from the
share-MDT to the switch-MDT.
For more information about switch-MDT, see
NOTE:
A VPN uniquely corresponds to an MD and an MD serves only one VPN, which is called a one-to-one
relationship. Such a relationship exists between VPN, MD, MTI, share-group, and switch-group-pool.
PIM neighboring relationships MD-VPN
Figure 67 PIM neighboring relationships MD-VPN
PIM neighboring relationships are established between two or more directly interconnected devices on
the same subnet. As shown in
MD-VPN, as follows:
• PE-P neighboring relationship—PIM neighboring relationship established between the public
instance interface on a PE device and an interface on the P device across the link.
PE-PE neighboring relationship—PIM neighboring relationship established after a VPN instance on
•
a PE device receives a PIM hello from a VPN instance on a remote PE device through an MTI.
"MDT switchover."
Figure 67, there are three types of PIM neighboring relationships in
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