Avoiding spurious TCP timeouts in wireless networks by delay injection

The Transmission Control Protocol (TCP) has been designed to provide reliable transport of packets by adjusting the transmission rate to the network congestion level. While TCP can adapt to small fluctuations in the delay between the sender and the receiver, adverse affects (most importantly, spurious timeouts) have been observed under large delay variability. We exhibit the presence of such delay spikes in wireless networks and discuss their possible origins. We then investigate a new methodology for avoiding spurious TCP timeouts by appropriately injecting additional random delay along the communication path. Different algorithms for the delay injection are presented and we assess their relative performances and merits through simulations. In particular, we show, by numerical examples, that the delay injection methodology can significantly decrease the number of timeouts and increase the achieved TCP throughput by about 8% in the network scenario considered. One of the attractive features of the new methodology is that it does not require any changes to the TCP and can be applied independently of the TCP version used.