On Minimizing TCP Retransmission Delay in Softwarized Networks

Today's Internet mainly relies on TCP protocol to ensure reliable communications between two endpoints. Unfortunately, this widely-used protocol may incur significant delay when transmitting lost packets. Indeed, with TCP, the source of the data detects lost packets using a timeout or duplicated acknowledgements before retransmitting them. As a result, the delay needed for a packet to reach the destination may become significant. This delay is estimated to be at least three times the end-to-end delay when the packet is lost once and could be even worse when the same packet is lost several times. As a matter of fact, this high delay cannot be tolerated by critical applications. To address this problem, in this paper, we focus on minimizing TCP retransmission delays and we introduce a novel network function called Transport Assistant that could be deployed within the network in order to cache, detect and retransmit lost packets. Thanks to this function, there is no need to wait for the source to detect and retransmit lost packets as the TA ensures packet retransmission from the network itself and thereby minimize retransmission delays. Through extensive experiments, we show that the TA allows to outperform the standard TCP by minimizing the average packet transmission time, the flow completion time, the packet loss and the number of retransmitted packets from the source.