Fast SACK Scheme Based On Multi-homed SCTP

SCTP is a new transport layer protocol, it will be replace TCP in the future. SCTP is a protocol acting on multiple ports, but according to the latest requirements of RFC. SCTP use only one port for data transmission, and can not take advantage of the multi-port communication, however, we proposed an idea of SCTP-CMT.SCTP-CMT can take more advantage of the multi-port data transmission, but can not adapt to the algorithms and strategies, such as redundant retransmission, overly conservation congestion window update and large number of SACK packets.Upon these questions, lyengar propose new algorithm and strategy, SFR algorithm, CUC algorithm and DAC algorithm solve the problem of redundant retransmission, the problem of overly conservation congestion window update and the problem of large number of SACK packets respectively. SFR algorithm, CUC algorithm and DAC algorithm was used at the side of the data sender, however data transmission needs the both sides'effort, so this paper focus on the side of the data receiver. When need to send data, the data receiver always choose the path who received data last, and if this path is at worse situation, the overall throughout will be affect.In this paper, we analysis the problem above deeply, and we propose two strategies: positive fast SACK(FSACK1) and passive fast SACK(FSACK2). Both strategies are aimed to detect the real-time SACK transmission path. FSACK1 need to develop new packet format, and detect the fastest path by the timer just like the heartbeat timer.FSACK2 need to monitor the special DATA packet and the special SACK packet.Through simulation experiments, we confirm the rationality and effectiveness of FSACK algorithm. After the comparison of five kinds of experiments, we draw the conclusion:both FSACK can improve overall system throughput greatly, especially when the multi-path has large difference of time delay.