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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 share-MDT. This causes a switch-MDT to be
built by using the switch-group between that PE device and the remote PE devices with
downstream receivers.
b.
After a data-delay period has passed, an MDT switchover process starts. All VPN multicast
packets that have entered the public network through that PE device are not encapsulated
with the share-group. They are encapsulated into public network multicast packets with the
switch-group. Then they are switched from the share-MDT to the switch-MDT.
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, and share-group.
PIM neighboring relationships in MD-VPN
Figure 70 PIM neighboring relationships in MD-VPN
PIM neighboring relationships are established between two or more directly interconnected devices
on the same subnet. As shown in
, the following types of PIM neighboring relationships
exist in MD-VPN, as follows:
•
PE-P neighboring relationship
—PIM neighboring relationship established between the public
network 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.
•
PE-CE neighboring relationship
—PIM neighboring relationship established between a
VPN-instance-associated interface on a PE device and an interface on a peer CE device.
Multicast across VPNs
MD VPN implements multicasting between the multicast source and the receivers when they are in
the same VPN. However, multicast data in different VPNs are isolated. If the multicast source and
