TCP with sender-based delay control

This paper describes a congestion control method for TCP that adjusts the transmission rate of a TCP connection not only by changing the congestion window size as in normal TCP, but also by delaying the transmission of packets at the sender. We refer to this mechanism as TCP with sender-based delay control, or simply SDC. SDC can keep the window size of a TCP connection above a certain threshold even when its fair share of bandwidth is arbitrarily small. Since TCP fast retransmit and recovery is likely to work when the window size of the connection is sufficiently large, the new scheme can result in reduced-frequency of TCP timeouts for the connection. In particular, SDC allows many TCP flows to share a link without experiencing many timeouts. In addition, SDC reduces a well-known TCP bias against connections with large round trip times. The paper presents the principle behind SDC and simulation results demonstrating its properties and advantages.