Analyzing Caching Gain in Small Geographical Areas in IP Access Networks

Abstract: Since its emergence, user generated content (UGC) has become the driving force in the growth of Internet traffic. As one of the most successful and popular UGC systems, YouTube contributes a great share of Internet traffic volume and has attracted a lot of academic interest. The continuously increasing amount of IP traffic motivates the need for better network design, more efficient content distribution mechanisms, and more sustainable system development. Web caching is one of the widely used techniques to reduce the inter Internet Service Provider (ISP) traffic. Web caching is considered an important part in the design of a content distribution infrastructure. This master’s thesis utilizes a one month trace of YouTube traffic in two residential networks in Sweden. Based upon a systematic and in-depth measurement we focus on analyzing the geographic locality of traffic patterns within small areas for these two networks. We summarize the YouTube traffic characteristics and user replay patterns, and then discuss why caching can be useful for YouTube-like systems. We present the optimal caching gain on a per area basis and also divide users into two groups: PC and mobile device users to show the caching gain for these two groups. Overall, an infinite capacity proxy cache for each small area could reduce the YouTube streaming data traffic by 30% to 45%. The result presented in this paper help us to understand YouTube traffic and user behaviors and provides valuable information for the ISPs to enable them to design more efficient caching mechanisms. When this work began we thought that a reduction of backhaul traffic (especially for mobile operators) may delay the need to make investments in upgrading their network capacity. However, an important conclusion from this thesis project is that the cache efficiency depends on the terminal type. For mobile terminals (smart phones, iPads, etc) a terminal cache solution is found to be the most efficient. For PCs in fixed networks, a network cache would be more efficient. It should be noted that the mobile terminals covered in the project are connected through home Wi-Fi, so further research is needed in order to draw definite conclusions for caching solutions for cellular networks.