Abstract: A multi-path channel interface for computer input-output systems includes the ability to define and activate unbalanced groups of unidirectional communications sub-channels for a user application. Protocol independent exchange identifications permit not only unbalanced transmission groups but also allow user-controlled extensions for negotiating the values of transmission parameters at the time the transmission group is activated. When error correcting re-transmissions force the re-segmenting of data blocks, second level sub-segment indexing assure the proper order of delivery of the various segments and sub-segments. The exchange identifications include an identification of the user protocol being supported and thus permit interfacing with any user protocol.