Managing Connections by QUIC-TCP Racing: A First Look of Streaming Media Performance Over Popular HTTP/3 Browsers

With the push towards HTTP/3, most modern browsers have started supporting it. HTTP/3 uses QUIC, which runs on top of UDP. However, a few Internet middleboxes tend to block or rate-limit UDP traffic; therefore, the browsers ensure compatibility by enabling connection racing via simultaneously initiating a TCP connection with the QUIC one. Each time the QUIC protocol suffers, connection racing is activated, and whichever protocol wins the race is further used for the application. In this paper, we study how browsers implement this connection racing mechanism and analyze its impact on applications that require a long-lived Internet connection, such as video streaming. We perform a large-scale measurement study across different browsers (Chrome/Chromium and Firefox), which helps to analyze why and how the repeated connection racing between protocols affects adaptive streaming QoE over 6013 YouTube sessions covering 5474 hours of streaming. Interestingly, we observe that YouTube QoE over an HTTP/3 supported browser suffers many times, and repeated connection racing is one of the major reasons that hinder the performance. We modified the Chromium browser source code to disable the connection racing altogether and observed that it improves the QoE for YouTube streaming over this modified browser. We then design and implement a solution that dynamically decides when to enable connection racing. We observe that it improves the QoE compared to the original browser. The analysis presented in this paper highlights the requirement of revisiting how browsers handle and switch between protocols through connection racing to ensure compatibility with middleboxes.