rough an MPLS network, set up by a signaling protocol. Next Generation Mobile Communications Ecosystem 7.4.2.3.8 PBB-TE At this moment it is worthwhile looking into the building blocks for CE before diving into PBB-TE (Figures 7.18 and 7.19). The building blocks are some of the key previous IEEEs Ethernet and transport standards namely [12, 29]: IEEE 802. 1D The IEE 802. 1D [30] is the IEEE MAC Bridges standard and mainly includes Bridging and Spanning Tree Protocol (STP). Bridges were introduced in the IEEE 802. 1D standard to segregate LAN traffic thereby limiting the delay due to the increase in the number of users using CSMA/CD technology. STP was used to remove bridge loops in the network. STP provides loop-free forwarding with multicast support. While STP can provide for restoration, the time required for convergence of the algorithm is high, making it difficult to deploy in carrier networks. IEEE 802.1Q IEEE 802.1Q [31], or VLAN Tagging, is a networking standard written by the IEEE 802.1 work- group allowing multiple bridged networks to transparently share the same physical network link without leakage of information between networks. VLANs were proposed as a method to logically bifurcate a single LAN domain into multiple domains. By attaching a VLAN tag to an Ethernet frame, it is possible to differentiate traffic within a network by examining the 12-bit VLAN address within the VLAN tag. VLANs are a powerful tool in being able to differentiate traffic. However, they have a limitation - the address space is restricted by the number of bits in the address-field header - 12, which leads to an overall address space of 4096 of which two are reserved. The 4094 addresses are not sufficient for a carrier to denote all its customers and provide Layer-2 customer and service profiling. IEEE 802. lad (Provider Backbone) The IEEE 802. lad (Provider Bridges) [32], also known as QinQ or Stacked VLANs, provides separate instances of the MAC services to multiple independent users of a Bridged LAN in a manner that does not