HP 5920 series Configuration Manual page 10

Figure 3 MAC-in-MAC unicast traffic over an SPBM network
Multicast
SPBM floods unknown customer unicast, unknown customer multicast, and broadcast as multicast traffic.
SPBM supports the following replication methods for multicast:
Head-end replication—Replicates frames at the ingress BEB for frames to enter the SPBM network.
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This method is suitable for SPB VSIs that have sparse multicast traffic. It does not require BCBs to
maintain multicast FDB entries.
Tandem replication—Replicates frames only at the node where the shortest path tree forks. This
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method is suitable for SPB VSIs that have dense multicast traffic. It requires BCBs to maintain
multicast FDB entries.
In head-end replication, the ingress BEB does the following, as shown in
1. Replicates the customer frame for each destination BEB.
2. Encapsulates each replica in one unicast frame.
3. Sends the unicast frames to the destination BEBs.
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Figure 4: