Research On Congestion Control Mechanism Of Stream Control Transmission Protocol

Stream Control Transmission Protocol(SCTP) is a new transport layer protocol proposed by IETF in 2000 . As with TCP and UDP incomparable advantages, it attracts researchers'attention.SCTP congestion control algorithm is inherited from TCP, so there are also TCP-like problems that packet loss rate is too large and the throughput is relatively small. This thesis aims at overcoming the shortcomings of SCTP congestion control algorithm. Based on TCP Vegas algorithm idea,an improved algorithm SCTP Vegas-A is proposed.The improvements are mainly in the phases of slow start and congestion avoidance. In the phase of slow start , control of r,ssthresh factors is adjusted dynamically, adaptive strategy of gradually approaching the congestion window is adopted, and the problem of stopping increasing of congestion window too early for large BDP network is solved. In the phase of congestion avoidance, the algorithm is divided into three phases.The different congestion window growth strategies in defferent stages are adopted. Referring to the change of throughput and actual network conditions, the parametersαandβare set to increase scale of congestion window properly. As a result, the increase of congestion window become more reasonable.Besides proposing SCTP Vegas-A congestion control algorith, The works of the thesis include analysis of SCTP protocol, comparison of SCTP with TCP and UDP, analysis and comparison the congestion control mechanisms of TCP Reno, TCP Vegas and SCTP, description and validation of SCTP Vegas-A algorithm. The co-existance SCTP Vegas-A and TCP Reno is emulated. The improved algorithm SCTP Vegas-A is emulated to show that it has better performance in term of throughput, packet loss rate, delay jitter and delay. It has shown that the improved algorithm SCTP Vegas-A is suitable for WEB applications.