H3C Technologies H3C S12500 Series Switches - Manual (Page 14)

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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.
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
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 performs the following tasks, as shown in Figure 4 :
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.
Customer
network
BEB 1 BEB 2
SPBM network
BCB
GE1/0/1 GE1/0/1 GE1/0/2 GE1/0/1
CNP CNP
B-DA
BEB2
Data
B-SA
BEB1
B-VLAN
100
I-SID
300
Encapsulate frame
with B-MACs, B-
VLAN, and I-SID
Forward based on
destination B-MAC
and B-VLAN
Remove outer header
(B-MACs, B-VLAN,
and I-SID)
B-MAC
BEB2
B-VLAN
100 GE1/0/1
Port
BEB2
BEB1 100
100
GE1/0/1
GE1/0/2
B-MAC B-VLAN Port B-MAC
BEB1
B-VLAN
100 GE1/0/1
Port
Data Data
Customer
network
B-DA
BEB2
Data
B-SA
BEB1
B-VLAN
100
I-SID
300