Enhancing fairness and congestion control in multipath TCP

With the advancement in technology, today most of the end-host devices are equipped with multiple wired/wireless interfaces and capable of using them in parallel. This has led to research in taking advantage of utilizing additional available network resources simultaneously such as multiple paths between the multi-homed end devices to achieve better performance. In this regard, new multipath transport protocols such as Multipath TCP and Concurrent Multipath Transfer SCTP are being designed and developed. On one hand these new protocols need to optimize the usage of the available multiple paths efficiently with a suitable scheduler while on the other hand they should be also fair to the existing transport protocols like TCP and SCTP, especially in a congested environment. This paper illustrates and compares the solutions that have been proposed to ascertain that Multipath TCP can yield an improved performance while being fair to standard TCP. In addition, this paper highlights improvements to two of the proposed congestion control solutions-Dynamic Window Coupling and Opportunistic Linked Increases Algorithm. A brief look into hybrid scheduling mechanisms is also provided with a special interest in minimizing the overall reordering delay and to capture the dependency on the receiver buffer size. It is shown that the proposed solutions give good performance in most of the different bottleneck scenarios while staying friendly to legacy transport protocols.