Transport Layer Protocol Sctp Performance Optimization Study

With the development of Internet and wireless technology, many new network services become available in recent years. The performance of transport layer protocol is a key issue because of its middle status in IP protocol stacks. Though more than 90 percent of Internet traffics are transmitted by the TCP protocol, there are still many disadvantages about TCP. IETF proposed a new transport protocol: Stream Control Transmission Protocol (SCTP) in 2000. SCTP has such novel characters as multi-homing, multi-streaming, partially reliable data transmission and "Cookie" mechanism. The topics related to these new features about SCTP are discussed in this thesis. The main contributions are as following:(1) The reason and influence of packet reordering, packet duplication and delay spike occurred in mobile network are studied. We found that SCTP is vulnerable to spurious timeout resulting from the delay spike. Moreover, the SCTP sender would increase the congestion window of the alternate path unnecessarily. With the introduction of Timestamp Chunk, we proposed the detection and response algorithms to make SCTP more robust to spurious timeout.(2) A novel approach to decide whether there is a bottleneck shared by the SCTP primary path and the alternate path is proposed. This algorithm is based on the cross-correlation of the delay experienced in both paths. To get more exact cross-correlation, wavelet denoising is used to eliminate the disturbance coming from other independent paths delay. Therefore, more accurate detection can be achieved.(3) A dynamic handover mechanism between the SCTP primary path and the alternate one according to their traffics and congestion status is proposed. To get the exact performance of both paths in time, a Precise Control Chunk (PCC) is introduced. By comparing the in-time congestion degree on both paths, the traffics would be switched to the better path.