a transfer request bus and transfer request bus node is described which is suitable for use in a data transfer controller processing multiple concurrent transfer requests despite the attendant collisions which result when conflicting transfer requests occur . transfer requests are passed from an upstream transfer request node to downstream transfer request node and then to a transfer request controller with queue . at each node a local transfer request can also be inserted to be passed on to the transfer controller queue . collisions at each transfer request node are resolved using a token passing scheme wherein a transfer request node possessing the token allows a local request to be inserted in preference to the upstream request .