Revisiting Cacheability in Times of User Generated Content

Today´s Internet traffic is dominated by users´ demand for exchanging content. In particular, multi-media content, i. e., photos, music, and video, as well as software downloads and updates contribute substantially to today´s Internet traffic. One option for reducing network costs is to use caches-exploiting the observation that content popularity is consistent with Zipf´s law. Yet, Web caching became unprofitable due to the increase in popularity of dynamic Web content. However, since at this point rich content is not very dynamic caching appears to be worthwhile again. We base our analysis on anonymized traces from a large European ISP connecting more than 20,000 residential DSL customers to the Internet, collected in 2009. We focus on the most prominent protocols in this environment - HTTP, BitTorrent (BT), eDonkey, and NNTP - and estimate the potential of caching for traffic reduction. On the one hand, our results show that the potential for caching most client/server-based applications like HTTP and NNTP is small. On the other hand P2P-based applications such as BitTorrent and certain HTTP based applications have high content duplication ratios.