Split-TCP based acceleration gateway over packet lossy networks

The conservative Additive Increase Multiplicative Decrease mechanism of traditional TCP causes the link under-utilization in the Wide Area Networks (WANs) due to the WANs´ intrinsic nature of high latency and high packet loss. To alleviate the problem, we present the design and implantation of STAG, an Acceleration Gateway with Split-TCP in the paper. STAG is built on embedded network equipment and acts as a transparent proxy. In STAG, a new improved congestion control method named Rapid TCP is adopted, which determines whether or not to decrease the congestion window based on the packet loss trend. In particular, in the fast recovery phase, it chooses different window adjustment strategies based on the current size of congestion window to achieve higher utilization. The performance validation of STAG is done on both our emulation testbed and the real wide area network. The results show that STAG with Rapid TCP effectively adapts to the high loss network environment and significantly speeds up the applications without loss of fairness.