TCP-in-UDP: Enabling gradually deployable TCP coupled congestion control using an efficient UDP encapsulation

Abstract

This thesis recalls the desirability of being able to apply congestion control coupling to concurrent TCP connections between the same end hosts. We identify challenges that must be overcome to provide practically deployable solutions to this end, chiefly the presence of multi-path routing mechanisms, such as Equal Cost Multi-Path Routing (ECMP) in the network. Additionally, we identify some inherent weaknesses in previous proposals for TCP congestion control coupling. We contribute a novel design for a TCP-in-UDP encapsulation scheme which is able to work around the problems created by multi-path routing, as well as delivering other advantages, which we implement in the FreeBSD kernel. In order to be able to test and evaluate this mechanism, we also present and implement a design for TCP congestion control coupling based on the Flow State Exchange architecture. Finally, we carry out an evaluation of the combinations of these two solutions, and find that they yield tangible performance benefits in terms of delay and packet loss reductions.