Efficiency of caches for content distribution on the Internet

Traffic engineering and an economical provisioning of bandwidth is crucial for network providers in times of high competition in broadband access networks. We investigate the efficiency of caching as an option to shorten end-to-end paths and delays while at the same time reducing traffic loads. The portion of HTTP based distribution of cacheable content on the Internet is increasing in recent time. In addition, the favourable effect of Zipf-like access pattern on caches is also confirmed for currently most popular Web sites with user generated content. Content delivery (CDN) and peer-to-peer (P2P) networks are distributing a major portion of IP traffic with different impact on caching. P2P traffic is subject to long transport paths although appropriate for caching in principle. CDNs are based on server infrastructures allowing for shorter paths on a global scale on top of network provider platforms. We give a brief overview of the options for deploying caches by content and network providers at different points in the interconnection, backbone or aggregation. The main part of the work focuses on the analysis of replacement strategies with regard to Zipf-like and fixed or slowly varying access pattern. A comparative evaluation shows that least recently used (LRU) essentially differs from caching strategies based on access statistics in terms of the achievable hit rates.