B-MAC, B-VLAN
Backbone MAC addresses (B-MACs) are bridge MAC addresses associated with SPBM bridges. Backbone VLANs (B-VLANs) are VLANs assigned by the service provider for transmitting customer traffic on the SPBM network.
For customer frames to be transmitted across an SPBM network, the ingress BEB encapsulates them in MAC-in-MAC format. In the outer frame header, the source MAC address is a B-MAC of the ingress BEB, and the destination MAC is a B-MAC of the egress BEB. All devices in the SPBM network forward the MAC-in-MAC frames based on the destination B-MAC and B-VLAN.