TCP and Buffer Management Adjustments for Improved HTTP Adaptive Streaming Performance

HTTP adaptive streaming (HAS), which relies on TCP for end-to-end transport, is increasingly being adopted for streaming video over the Internet.. Recent research has shown the inability of HAS to sustain the highest video quality level that is compatible with the capacity of the bottleneck link. We investigate the impact on HAS performance using a variety of adjustments of TCP at he source, most of which are compatible with existing standards. The adjustments concern the control of the congestion window size at the beginning of a video chunk transmission. We compare the performance of the TCP configuration options under study both in isolation, with only one HAS stream flowing through the bottleneck link, and in mixed traffic scenarios with multiple HAS streams and non-HAS TCP traffic (from long-lived FTP transfers). Given the sensitivity of TCP performance to the buffer management policy that regulates the admission of packets to the queue in front of the bottleneck link, we also evaluate the benefits of active queue management techniques versus the traditional tail-drop policy. We show that using larger initial windows and ssthresh values at the beginning of each chunk, a HAS client can increase its sustained VQ levels as well a higher level of fairness can be accomplished for clients sharing a bottleneck link.