Name resolution latency is a significant component of the time required to access web services. Wills and Shang [41] have found, based on NLANR proxy logs, that DNS lookup time contributes more than one second to 20% of web object retrievals, Huitema et al. [16] report that 29% of queries take longer than two seconds, and Jung et al. [18] show that more than 10% of queries take longer than two seconds. The low performance is due mainly to low cache hit rates, stemming from the heavy-tailed, Zipf-like query distribution in DNS. It is well known from studies on Web caching [6] that heavy-tailed query distributions severely limit cache hit rates.
Wide-spread deployment of content distribution networks, which perform dynamic server selection, have further strained the performance of the legacy DNS. These services, such as Akamai and Digital Island, use the DNS in order to direct clients to closer servers of Web content. They typically use very short TTLs (on the order of 30 seconds) in order to perform fine grain load balancing and respond rapidly to changes in server or network load. But, this mechanism virtually eliminates the effectiveness of caching and imposes enormous overhead on DNS. A study on impact of short TTLs on caching [19] shows that cache hit rates decrease significantly for TTLs lower than fifteen minutes. Another study on the adverse effect of server selection [35] reports that name resolution latency can increase by two orders of magnitude.