Researchers contribute Multipath TCP code

Our Multipath TCP implementation in the Linux continues to attracts a lot of interest from both researchers and industry. Until now, most of the work on the implementation has been done by researchers at UCL are close collaborators who work with us in the framework of scientific projects with the few exceptions. During the last week, two research groups have contributed new patches to Multipath TCP.

The first patch, proposed last week by Enhuan Dong adds an implementation of a Multipath-aware Vegas congestion control scheme. Most TCP congestion control schemes rely on packet losses to detect congestion with one notable exception : TCP Vegas [1] . TCP Vegas measures the round-trip-time and uses increases in round-trip-times as an indication of congestion and adapts its congestion window accordingly. In 2012, several researchers proposed to adapt TCP Vegas for Multipath TCP [2] . This patch is a first step in implementing this extension of TCP Vegas in the Linux kernel. It has already generated some discussion on the mailing list.

The second patch is an extension to the Multipath TCP path manager. The path manager is a recent addition to the Linux Multipath TCP implementation. It acts as a control plane for Multipath TCP since it includes the logic that decides when and how subflows are created. The default path manager creates a full-mesh of subflows, but this is not always the best solution. The path manager was designed to be flexible and extensible. The patch sent by Duncan Eastoe and Luca Boccassi supports the Binder system described in [3] . It also includes some support for using the IPv6 Routing header with Multipath TCP. Given that this header has been deprecated, it is unlikely that this will end up in the standard Multipath TCP implementation, but it could be useful for research experiments.

[1]Lawrence S. Brakmo, S. W. O’Malley, and L. L. Peterson, TCP Vegas: new techniques for congestion detection and avoidance presented at the SIGCOMM‘94: Proceedings of the conference on Communications architectures, protocols and applications, New York, New York, USA, 1994, pp. 24-35.
[2]Yu Cao, M. Xu, and X. Fu, Delay-based congestion control for multipath TCP , presented at the Network Protocols (ICNP), 2012 20th IEEE International Conference on, 2012, pp. 1-10.
[3]Luca Boccassi, M. M. Fayed, and M. K. Marina, Binder: a system to aggregate multiple internet gateways in community networks presented at the LCDNet‘13: Proceedings of the 2013 ACM MobiCom workshop on Lowest cost denominator networking for universal access, New York, New York, USA, 2013, p. 3.