Cacheability of bulk content for ISPs

The application considered responsible for most of the Internet traffic volume is file-sharing. Among the popular file-sharing applications are P2P-based ones, using e. g., the BitTorrent protocol, Web based offers by direct download services (DDS), e. g., rapidshare.com, and NNTP based services, e. g., giganews.com. To cope with the ever growing bandwidth demands ISPs are exploring various options ranging from exploiting locality for peer/server selection, e. g., via CDNs or P2P neighbor selection strategies [11, 2, 4], to taking advantage of caching [1]. In this paper, we reexamine the feasibility of caching filesharing content. In the early days of the InternetWeb caches were very popular. But, the efficiency of Web caches decreased dramatically [7] with the introduction of advanced HTTP features, such as cookies, dynamicWeb pages, AJAXbased applications, etc. However, recent studies of caching efficiency within Gnutella [9], Fasttrack [10], or YouTube [12] indicate that it is time to revisit the potential of caching. We base our analysis on anonymized traces from a site that connects more than 20, 000 DSL customers of a large commercial ISP in Europe to the Internet. We focus on the most prominent file-sharing applications in our environment: (i) BitTorrent (BT), the most used P2P system, (ii) DDS1, the most popular DDS provider, and (iii) NNTP. We find that caching looks like a promising option for BitTorrent but not for DDS and NNTP.