The emerging Ethernet bridging technologies have been hyped to an extent where the lines between them completely blurred, resulting in statements like “we need DCB and TRILL for FCoE”. Actually, none of that is true, but let’s focus on DCB and TRILL first.
TRILL and 802.1aq are Shortest Path Bridging (SPB) technologies. They replace the venerable Spanning Tree Protocol (STP) and all its variants and modify the frame forwarding rules. Replacing STP with TRILL is like replacing truly-stupid RIP (with maximum-paths set to one) with OSPF or IS-IS: you get faster convergence and better network utilization. The forwarding paradigm in network core is changed, so you could say a better analogy would be replacing RIP with IS-IS+MPLS.
DCB is a Quality-of-Service solution. Introducing DCB in your bridged network is like introducing IP QoS in your routed network.
SPB and DCB are completely independent, like OSPF and QoS are. You can use one or the other as needed in your network: DCB to give you standardized QoS behavior and lossless transport, SPB to give you faster rerouting and multipath forwarding.