Tuesday, November 4, 2008

DNS Performance and the Effectiveness of Caching

DNS is an important part of the Internet and this paper tries to analyze its performance and the repercussions of its design parameters. Traces were collected at two universities - MIT and Korea - and were analyzed. Focus was on the latency and failures of DNS clients, and effect of cache sharing and TTL on caching effectiveness.

Over a third of all DNS lookups were not answered successfully. 23% of the client lookups in the MIT trace failed to elicit any answer while 13% lookups gave errors in the answer. This seems a fairly high number...wonder what it would be today. What does "not elicit any answer" mean? Packet loss?

As expected, the name popularity is Zipf-distributed. Hence aggressive caching does not necessarily buy us much. That said, I wonder if traces from a university are generic enough to make this comment. Maybe corporations have a different trend? Definitely caching should be useful in scenarios when the number of clients is more varied and large (e.g., ISPs) .

This paper does seem to point out some interesting results about DNS performance and I would vote for keeping it in the reading list.

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