A Study of Partially Reliable Transport Protocols for Soft Real-Time Applications

Abstract: The profileration of multimedia applications, such as streaming video, teleconferencing,and interactive gaming has created a tremendous challenge for the traditional transportprotocols of the Internet – UDP and TCP. Specifically, many multimedia applicationsare examples of soft real-time applications. They have often relatively stringent requirementsin terms of delay and delay jitter, but typically tolerate a limited packet loss rate.In recognition of the transport service requirements of soft real-time applications,this thesis studies the feasibility of using retransmission based, partially reliable transportprotocols for these applications. The thesis studies ways of designing retransmissionbased, partially reliable transport protocols that are congestion aware and TCP compatible.Furthermore, the transport protocols should provide a service that, in terms ofperformance metrics such as throughput, delay, and delay jitter, are suitable for soft realtimeapplications. The thesis work comprises the design, analysis, and evaluation oftwo retransmission based, partially reliable transport protocols: PRTP and PRTP-ECN.Extensive simulations have been carried out on PRTP as well as PRTP-ECN. These simulationshave in part been complemented by some theoretical analysis. The results ofthe simulations and the analysis suggest that substantial reductions in delay jitter andimprovements in throughput can indeed be obtained with both PRTP and PRTP-ECN ascompared to TCP. While PRTP reacted too slowly to congestion to be TCP-friendly andaltogether fair, PRTP-ECN was found to be both TCP-friendly and reasonably fair.The thesis work also comprises an extensive survey on retransmission based, partiallyreliable transport protocols. Based on this survey, we have proposed a taxonomyfor these protocols. The taxonomy considers two dimensions of retransmission based,partially reliable transport protocols: the transport service, and the error control scheme.