There has been a lot of interest in the past decade in using timed Petri nets to model computer systems. In this paper we show how such timed Petri nets can be used to great advantage in describing and algebraically specifying communication system performance. We make use of the time parameter of timed Petri nets to model the delay in performing certain operations of a communication protocol. The specification is borrowed from the recently reported AFFIRM language, and the protocol chosen for illustration is the ECMA transfer protocol, proposed for the ISO reference model. However, the methodology can be used with other protocols as well. We also show how liveness properties can be specified, easily using timed Petri nets.