Investigating Transparent Web Proxies in Cellular Networks

People increasingly use mobile devices as their primary means to access the Internet. While it is well known that cellular network operators employ middleboxes, the details of their behavior and their impact on Web performance are poorly understood. This paper presents an analysis of proxy behavior and how transparent Web proxies interact with HTTP traffic in four major US cell carriers. We find that all four carriers use these proxies to interpose on HTTP traffic, but they vary in terms of whether they perform object caching, traffic redirection, image compression, and connection reuse. For example, some transparent proxies unilaterally lower the quality of images, which improves object fetch time but may hurt user satisfaction. We also find that these proxies do not necessarily enhance performance for mobile Web workloads in terms of object fetch times; namely, we observe noticeable benefits only when flow sizes are large and the path between the server and proxy exhibits large latency and/or loss.