For a network server (35) communicating with a wireless unit (10) via a Session Initiation Protocol, a retransmission method (50) first sets a timer based upon a time likely for a mobile unit to respond (54). Then the network server waits for a response (56). When the timer set for the kind of mobile unit being used expires (64), a retransmit of the original SIP request takes place (68). Optionally, modes for waiting may include a linear mode (72) and an exponential mode (74).
