Abstract
With the proliferation of the internet, voice over IP has penetrated in both terrestrial and satellite networks. One of the popular protocols responsible for its widespread usage is SIP. SIP is the signalling protocol responsible for the session establishment and termination. By default, it uses UDP as the transport layer protocol. As UDP is an unreliable protocol, the retransmission of the SIP messages is managed by the application layer, using exponential backoff algorithm. In this paper, this retransmission algorithm is studied in satellite environment. Based on the shortcomings of this algorithm, a new algorithm is proposed. The performance of the new algorithm is tested and evaluated on the satellite network testbed at Centre for Communication Systems Research (CCSR), University of Surrey. The results show that the performance of the new algorithm is better than the basic one, in terms of number of retransmissions of SIP messages and their bandwidth consumption, in addition to reduction in call setup time.