Cutting Internet Access Costs Through HTTPS Caching: A Measurement Study

Abstract

In this paper, we look at web caching as a means to cut Internet access costs. We specifically look at caching of HTTPS traffic which has thus far not received much attention. We first look at client side caching on smartphones in mobile web scenarios to evaluate the potential for bandwidth savings. Our analysis based on user logs reveals that app traffic dominates browser traffic at 82.7% and HTTPS traffic dominates HTTP traffic at 82.3%. There is around 15% redundancy in this traffic, however much of this redundancy does not lend itself to practical savings since app logic or server cache configurations cannot be controlled.

Given the negative result of above approach, we shifted our attention to infrastructure side caching (wired) in an organizational setting. Analysis of our logs indicate that HTTPS accounts for 91.6% of all considered traffic and YouTube accounts for 82% of this HTTPS traffic. We found that there is some amount of redundancy in this traffic and hence potential for bandwidth savings. However proxying HTTPS traffic is challenging given that the proxy has to act as a man in the middle of a secure transaction. To circumvent this problem, we propose a new architecture that serves only insensitive HTTPS traffic from the proxy. We validate the feasibility of this approach via an implementation. A trace driven simulation shows that one can realize bandwidth savings of between 13–17% with our architecture.