Marooned magic numbers - An adaptive congestion control architecture

TCP and other Internet transport protocols rely on series of hard-coded initial values for their connection state, particularly for the congestion control parameters. For example, recently the initial value of congestion window has been under much debate, as there is a desire to make TCP more efficient for common use cases, while not endangering its performance on scenarios with limited network bandwidth. Our take on this discussion is that there is no clear single set of initial values that would work for all cases. Earlier research has proposed sharing connection and congestion control state among multiple connections over time, but that approach is limited to sharing connections to a particular host, which is not sufficient, because services are often distributed across multiple hosts, and opening multiple connections to the same host is a rather rare use case. We aim to solve this problem by proposing the Pathlet Transport Architecture that models the network paths as a series of pathlets, and uses those as the basis of initializing and maintaining the various transport parameters, particularly those related to congestion control. We analyze our initial instantiation of the PTA architecture using ns-3 simulations for TCP congestion control parameters, and show how it improves the communication performance in various different network scenarios, where single common set of magic values would fail.