Communications system and method with multilevel connection identification

A method for communicating between functional blocks in a computer system, the method comprising the steps of:

• establishing a plurality of connection identifiers, wherein each connection identifier associates a particular data transfer with a particular connection, wherein a connection is a logical state in which data may pass between an initiator functional block of the plurality of functional blocks and a target functional block of the plurality of functional blocks, and wherein a connection is established when a particular data transfer is initiated;
• and
• allowing an initiator functional block to issue a first transfer “Y” if the transfer “Y” is an oldest, non-issued, non-retired transfer among a set of transfer requests with a same connection identifier as the transfer “Y”.