| Internet is a packet switched network which provided Best-effort service at the beginning. It supports the FTP protocol, E-mail, HTTP, etc. These traditional data services do not ask for higher performance of the network delay. Today, more web applications, such as VOIP and video services which have higher bandwidth and less time delay requirements are added to the network services. And with the development of the terminal equipments, more and more terminals, such as computers and mobile-phones, have more than one network interface:alongside the ubiquitous digital subscriber line (DSL) and Ethernet ports, wireless and3G interfaces are becoming a basic feature. These make the transport layer protocol TCP and UDP cannot be well meet the increasing requirements of transmission. At this time, the transport layer protocol SCTP has become a research focus, especially the characteristics multi-stream and multi-homed have been proposed. SCTP has become a broad applicability transport-layer protocol.This thesis analyzes the disorder of packets at the receiving side of concurrent multipath communication of SCTP (SCTP-CMT), and the reordering at the receiving side and the unnecessary fast-rtx which affect the throughput of the entire transmission system. And the thesis also provides appropriate strategies of path selecting and packet scheduling.Firstly, a strategy of SCTP-CMT transmission and retransmission based on bandwidth estimation are provided from the point of view of path selecting. By analyzing the disorder of packets at the receiving side and unnecessary fast-rtx at the sending side due to the difference between paths and estimating bandwidth of paths, we divide paths into two groups used for transmission of data and retransmission. With the strategy provide in the thesis, throughput of the system is enhanced, retransmission packets are reduced and the performance of the communication is enhanced.Secondly, we provide RTT based forward prediction scheduling strategy with the analysis of the arrival and the transmission time of the packets. The strategy estimates arrival time of data packets to be sent through available paths in an association, and decides which packets are to be sent through each path. By scheduling of the packets, the strategy reduces possible occurrence of out-of-order and unnecessary retransmission.Finally, the thesis evaluates the performance of the strategy by simulation over Network Simulator2, and shows the simulation results with the throughput, arriving time of TSN, the number of transmit data packets and lost packets. The results show that the strategies effectively improve the transmission performance. |
