Communications system and method with multilevel connection identification

A communication system comprising:

• at least two functional blocks, wherein a first functional block communicates with a second functional block by establishing a connection, wherein the connection is a logical state in which data may pass between the first functional block and the second functional block;
• and
• a communication medium configured to carry a plurality of signals between interface modules;
• an initiator interface module coupled to the communication medium, and coupled to an initiator functional block;
• a target interface module coupled to the communication medium to receive transfer requests having a connection identifier, said received connection identifier having been previously configured to be sent with a transfer request from the initiator interface module over the communication medium, the connection identifier comprising a multi-bit value that encodes information including a transfer priority, a transfer order, and a functional block that originated the transfer, the connection identifier is one of a plurality of connection identifiers associated with the initiator functional block, said target interface module mapping a received connection identifier to a thread identifier to indicate a transaction stream that a data transfer is part of;
• and
• a target functional block coupled to the target interface module to receive transfer requests having the thread identifier.