Friday, November 14, 2008

DNS Performance and the Effectiveness of Caching

This is a relatively modern study of how often DNS queries can be serviced from a cache based on snooping packets from the MIT Computer Science Laboratory, and from traces from KAST. Their most interesting result is that they claim reducing TTLs to as little as a few hundred seconds has almost no effect on hit rates. They further claim that sharing a cache between more then a few clients is not beneficial due to the long-tailed nature of DNS requests. These conclusions seem reasonable for the small number of users in each of their studies; they seem to claim that they will hold for larger groups as well because of the scaling properties of the hit rate in Fig 12. This figure is making a statement about the overlap in the set of domain names requested by a set of users. The result that NS records are well cached and so the actual request traffic has a nice pithy quality I admire; furthermore it makes sense and bodes well for things like DYNDns.

This paper has an interesting result, but other then the result I think reading the entire paper might be overkill for the class. I would rather we spend some time on security and discuss DNSSec, since our reading list has almost no papers considering security on it and I think that paper would spur an interesting discussion.

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