On making TCP robust against spurious retransmissions

Despite the fact that Transmission Control Protocol (TCP) is a stable and mature protocol, and has been well tuned over years, changes in its congestion control are still in progress without altering the fundamental underlying dynamics of TCP congestion control. In today's Internet, the network environment is more complex than ever. TCP's loss detection methods may falsely invoke retransmission even when the original packet is actually not lost. Such behavior is called Spurious Retransmission, which damages the TCP throughput greatly. In this article, we describe Spurious Timeout and Spurious Fast Retransmit, the causes for their occurrences, and the impacts that they have on TCP performance. Then we discuss the various detection and mitigation techniques available. To make TCP robust to these spurious retransmissions, we also provide some results of our comparative performance study of these detection and mitigation techniques.