Optimizing real-time transport protocols

A real-time transport protocol must trade delay against loss. Here we consider the problem of minimizing the mean transport delay subject to a given maximum acceptable loss rate. This form of the trade-off is appropriate for many voice, video and graphics applications. Yechiam Yemini has shown that for this problem, and for a particular model of the transport mechanism, the optimal protocol is a combination of send and wait for ack with send and discard, where the decision to wait for ack or to discard is made by comparing the number of packets currently awaiting ack with a threshold value, which is itself calculated from the arrival and permitted loss rates. In this paper we generalize Yemini's result, and give an elementary proof.