Aggregate TCP congestion control using multiple network probing

Extensive research in TCP's congestion control mechanism has resulted in an effective algorithm that gives fairly precise estimates on the available bandwidth on a given network path (J. Postel, 1981; V. Jacobson, 1988). However, most past efforts focused on enhancing the accuracy and robustness of the path bandwidth estimation algorithms for individual TCP connections. Relatively fewer attempts have been made to further improve data transport efficiency by sharing path bandwidth information among concurrent TCP connections with the same sources and destinations. The paper proposes an aggregate TCP-based congestion control algorithm (ATCP) that allows individual TCP connections to reach their fair shares of the available network path bandwidth more quickly, while still observing TCP's congestion control semantics. In addition, the proposed algorithm is guaranteed to perform no worse than current TCP congestion control algorithm in all cases, and is designed to be implemented in a way that is completely transparent to both ends of a TCP connection. ATCP is particularly useful for TCP connections that are short-lived and yet have a long round-trip delay, such as Web page transfers using HTTP 1.0. Our trace-driven simulation study shows that the aggregate congestion control algorithm can reduce the normalized transaction latency by a factor of up to 2, compared to standard TCP.