Adaptive HTTP Video Streaming Over Multipath TCP: Measurement, Analysis, and Optimization

HTTP-based adaptive video streaming has become a key contributor to the Internet traffic. The streaming quality however is heavily affected by the throughput and stability of the underlying TCP. Being compatible and fair, multipath TCP (MPTCP) has recently been suggested as a promising enhancement to the conventional TCP, particularly considering that multi-home is becoming ubiquitous for modern networked devices. The opportunities and challenges of adaptive streaming over MPTCP however remain largely unclear to the research community. This paper presents a systematic study on adaptive streaming over MPTCP. We start from realworld experiments with Dynamic Adaptive Streaming over HTTP (DASH) and analysis on its performance over MPTCP. We show that DASH can greatly benefit from the improved aggregated throughput by MPTCP; yet the inter-path throughput difference and the intra-path throughput fluctuation have noticeable (negative) impact, too. Without a proper design of path selection and adaptation in MPTCP, they can easily confuse the adaptation logic of DASH, resulting in low bitrates or frequent rebuffering even if high-bandwidth paths are available. We present MPTCP+, an extended multipath TCP solution to offer high quality and smooth playback for adaptive HTTP streaming. MPTCP+ incorporates a path use decision algorithm that smartly disables/enables a path to minimize the inter-path difference, and a novel congestion control algorithm that smooths congestion window evolution with multiple paths. We have implemented MPTCP+ in the MPTCP Linux kernel, with minimum change on the server-side MPTCP module only. It is fully compatible with the existing MPTCP clients and requires no change on the upper-layer protocols, too. Our experiments suggest that MPTCP+ increases the quality of experience (QoE) of DASH by up to 50%.