Balancing Video on Demand Flows over Links with Heterogeneous Delays

The popularity of Video on Demand (VoD) services has recently grown to unprecedented levels. Even if UDP is often considered the standard transport protocol for video streaming, TCP is often used for VoD since its reliability, congestion control, and resilience to the presence of firewalls/NATs on the link. Unfortunately, poor video quality, frequent playback pauses, and delays due to slow frame buffering are still annoying users engaged in long RTT connections, both wired and wireless, with the server. This is due to the ack-based mechanism that increases the TCP’s congestion window, which leads to RTT-unfairness. As a practical consequence, if a VoD user is experiencing long RTTs while sharing the channel with another VoD user whose connection has small RTTs, the former will see a very slow progression of its video until the latter is done. In this paper, we propose the use of TCP Libra on VoD servers to resolve this RTT-unfairness issue, thus providing an efficient VoD service to any user, regardless of her/his RTTs.