TCP/IP only understands routing along IP addresses.
"Message router" usually involves understanding higher level entities - In this case, it would understand that a given type of message with given information needs to be forwarded to X, Y, and Z.
DCE was "Distributed Computing Environment", and provided among other things RPC system that is still used by MS Windows NT and DCOM. In this case it was easier to make all parts of the system first talk TCP/IP, then use DCE to provide glue code between divergent environments.
"Message router" usually involves understanding higher level entities - In this case, it would understand that a given type of message with given information needs to be forwarded to X, Y, and Z.
DCE was "Distributed Computing Environment", and provided among other things RPC system that is still used by MS Windows NT and DCOM. In this case it was easier to make all parts of the system first talk TCP/IP, then use DCE to provide glue code between divergent environments.