RobE: Robust Connection Establishment for Multipath TCP.

Over the past decade, the way that devices connect to the Internet has changed drastically. The introduction of high-speed mobile networks and the omnipresence of wireless access points led to a situation where most devices offer multiple network interfaces, such as cellular and WiFi radios. However the most prevalent Layer 4 protocol, TCP, is not multipath capable and thus limited to using one interface at a time [4]. Multipath TCP [6], which is based on the classic TCP, resolves this problem by spreading the data flow across multiple paths. When a new connection is established, an initial subflow is created for backwards compatibility to TCP; afterwards, additional subflows can be created and MPTCP offers resilience against link failures [1]. Depending on the first flow to create a new connection prevents MPTCP from exploiting multi-link capabilities during the establishment phase. Therefore, if the initial subflow is not successful, a connection cannot be established. In this paper an extension to the existing MPTCP standard is proposed: MPTCP RobE. This solution extends the inherent resiliency of MPTCP against link failures to the establishment phase by introducing the concept of several potentially initial subflows, which tremendously increases the chance to build a successful initial subflow, and at the same time improves end-to-end latency during the establishment phase significantly. In this paper, three different concepts for MPTCP RobE are proposed and discussed with regard to technical aspects and MPTCP standard integration. Finally, a protoype is used to verify the performance of MPTCP RobE with respect to robustness and latency gains in different scenarios.