Simulation and Experimental Evaluation of Multipath Congestion Control Strategies

The need for service resilience is leading to a steadily growing number of multi-homed Internet sites. In consequence, this results in a growing demand for utilising multiple Internet accesses simultaneously, in order to improve application payload throughput during normal operation. Multi-path Transport Layer protocol extensions - like Multi-Path TCP (MPTCP) for TCP and Concurrent Multipath Transfer for SCTP (CMT-SCTP) - allow applications to make use of such network topologies. However, since TCP - which constitutes the basis of most Internet applications - and its congestion control procedures have been designed under the assumption of single-homed sites, fairness issues may arise by the usage of multipath transport. These issues are addressed by advanced congestion control approaches, which have already been examined by simulations. However, real-life network measurements are missing. In this paper, we perform an experimental proof-of-concept evaluation of several multipath congestion control strategies, which are currently under discussion within the IETF in the context of MPTCP as well as CMT-SCTP. Particularly, we validate effects that have been observed in simulations, in order to trigger further discussions on multipath congestion control. Also, our goal is to provide insight into the different approaches to support the ongoing IETF standardisation activities on multipath transport protocols.