A rationale for web caching in consumer ISPs: the impact of DNS lookup times and HTTP session characteristics

Web caches are generally considered a useful tool because they reduce replication of network traffic flowing from original content sources. In this paper we experimentally characterise the network and transport layer consequences of web caching in the consumer ISP context. We instrumented a small number of Australian, broadband-attached homes to collect round-trip time (RTT) and hop count statistics for their HTTP/TCP sessions, and collect DNS lookup statistics associated with each HTTP exchange. We estimated the impact of DNS lookup delays on overall HTTP session times, and use our RTT and hop count statistics to show that consumer ISPs would benefit greatly from local caching, particularly in Australia where speed of light delays have a large impact on sessions times when retrieving international content.