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8 NG MVPN: Overview and Configuration
Now that we know how to create LSPs that cross AS boundaries, we can configure and
deploy a so-called next-generation multicast VPN (NG MVPN) that uses these LSPs.
Let’s start with a look at the main components needed to deploy the service. Configuration is
required for two main aspects of the feature:
• The Provider–Customer (PE-CE) connection—This is where the multicast protocol,
in this case Protocol Independent Multicast (PIM), runs.
• The core network—There is no multicast routing protocol running here. We simply
use BGP to allow the routers to exchange information about VPN membership.
All forwarding uses MPLS LSP tunnels. These tunnels are actually point-to-multipoint LSPs
(P2MP LSPs), used to mimic a multicast tree. To create a P2MP LSP that crosses AS
boundaries, we use previously described techniques, such as BGP-TE.
8.1 The PIM Protocol
PIM is the most common multicast protocol. PIM is used to create a distribution tree over
which multicast packets travel to reach all the destinations interested in the multicast
(members of the multicast group).
There are two ways this distribution tree can be built:
• When the source is known, it is possible to build a sourced-tree (S,G). This kind of
tree has its root at the multicast source.
• When the source is initially unknown, it is possible to elect a node to act as a
rendezvous point (RP). The tree will be initially rooted at the RP. Later, when a
multicast source is discovered, the tree will change and will converge into a (S,G)
tree.
Both methods are shown in Figure 20.
Figure 20. Multicast Shared Tree and Sourced Tree Methods
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