On making SCTP robust to spurious retransmissions

Abstract

Network anomalies such as packet reordering and delay spikes can result in spurious retransmissions and degrade performance of reliable transport protocols such as TCP and SCTP. Past research showed that in certain networks or paths, such anomalies were fairly common. The result was a series of proposals (Eifel, DSACK-based, F-RTO) targeted towards making a transport robust to such events. Most of the proposals focused on TCP and assumed applicability to SCTP. This paper focuses on SCTP and makes three contributions. First, the effect of spurious retransmissions in SCTP is shown to be more aggravated than in TCP, leading to a problem of congestion window overgrowth. Second, it is shown that most but not all of the solution space is shared between TCP and SCTP. An extension to the Eifel algorithm is proposed. Third, a microscopic as well as macroscopic comparison of the Eifel algorithm and the DSACK-based algorithm is presented. Such a comparison will provide implementers and vendors a clearer view of the applicability and tradeoffs involved in different algorithms.