which the destination is unknown (and therefore must be learned) is disabled. If the destination MAC address has not already been configured in the filtering database, as dictated by tools with additional intelligence, the frame has been received in error and should not be forwarded since learning is neither required nor desirable [34]. The primary technical leap witnessed with PBB-TE is the ability to continue to use the Ethernet forwarding plane, while enabling carrier-centric tunnels can be set up resulting in deterministic service parameters. 7.4.2.3.8.1 PBB-TE Ethernet Frame Structure PBB-TE defined as IEEE 802. Qay has added T-DA, T-SA and T-IID fields to the existing PBB frame format as shown in Figure 7.19. T-DA/T-SA is TE-Service MAC (T-MAC) addresses which identify the TE-Service (Traffic Engineering) endpoints. T-IID (TE-Service Instance Identifier) is a 12-bit identifier and part of a TE-Service Instance Tag. PBB-TE adds an explicit path feature to PBB, and the forwarding tables are configured by a management system or a control plane (still to be defined). PBB encapsulates the client MAC-header in a service provider MAC-header at the ingress of the backbone network. The outer header contains backbone destination address (B-DA), backbone source address (B-SA) and backbone VLAN-ID (B-VID) fields that are used for forwarding the frames in the backbone network. This complete encapsulation allows the service provider to separate the topologies used by different customers, or aggregation of customers, by controlling the mapping of Service IDs (I-SID) to different B-VLANs (B-VID). Many customers can be supported on a single B-VLAN, and this considerably increases the scalability when compared to traditional VLAN services. B-Service instances are identified within a B-VLAN or TE-Service instance by their I-SID while B- VLAN instances are identified within an 802.3 Link by their B-VID. TE-Service instances are identified within an 802.3 Link by their 3-tuple <T-DA, T-SA, T-IID> 7.4.2.3.8.2 PBB-TE Control Plan