SSMP: Server Selection for Multipath TCP in CDN Environments

Nowadays, mobile devices are equipped with multiple interfaces connected to various networks, which makes it possible to aggregate bandwidth in actual application. Multipath TCP (MPTCP) is one of the transport protocols that uses multiple interfaces simultaneously and provides robust and efficient data transmission. In practice, MPTCP will interact with various network facilities. Among them, Content Delivery Network (CDN) is a popular one, which is a widely distributed network system deployed across the Internet. Using MPTCP in CDN could provide better performance for users, however, we find that CDN may not give full play to its functions when working with MPTCP. Because the Default Server Selection (DSS) mechanism in CDN only obtains servers optimal in single path connection scenarios, it may not provide the globally optimal server for MPTCP. In this paper, we propose a new algorithm called Server Selection for MPTCP (SSMP), which utilizes all available multi-homed sources to provide the globally optimal performance. SSMP modifies the DNS mechanism to return the optimal server for each available interface by the origin strategy and further selects the globally optimal server for both elephant and mice flows. We compare SSMP with DSS through experiments under video streaming and file download scenarios with both stable and variable environments. Our results show that SSMP consistently utilizes available paths more efficiently than DSS, particularly for servers with a great gap in server quality.