Deadlock-free packet switching networks

Deadlock is one of the most serious system failures that can occur in a computer system or a network. Deadlock states have been observed in existing computer networks emphasizing the need for carefully designed flow control procedures (controllers) to avoid deadlocks. Such a deadlock-free controller is readily found if we allow it global information about the overall network state. Generally, this assumption is not realistic, and we must resort to deadlock free local controllers using only packet and node information. We present here several types of such controllers, we study their relationship and give a proof of their optimality with respect to deadlock free controllers using the same set of local parameters.