A large amount of data needs to be transferred from one site to another as fast as possible in the computational science fields. To achieve high-speed data transfer, many applications utilize multiple TCP streams. However, since multiple TCP streams of applications are usually routed according to the default IP routing protocol, only a single shortest path among the multiple paths can be utilized for the data transfer. This research proposes a multipath controller that increases the performance of data transfer by leveraging multiple paths simultaneously for parallel TCP streams. For this purpose, we utilize the Software-Defined Networking (SDN) technology and its implementation, OpenFlow. Furthermore, we proposed a method to determine optimal numbers of parallel TCP streams to be assigned for each path according to its own network condition. This paper presents the design and implementation of the proposed system. As a case study, we applied our proposed system on GridFTP and evaluated the performance improvement. The results demonstrate that our proposed system accelerates the data transfer of GridFTP in both a virtual and a real global-scale environment.
