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Combining DJB’s dnscache and Google’s Public DNS

December 6, 2009

Most of the comments which I’m reading about Google Public DNS (GPD) performance centers around round trip latency from an end-users location to GPD’s resolvers vis-a-vis their network location and comparing the round trip time to their local ISP DNS cache. Ping time is only one part of the time taken for DNS resolution, one needs to factor in DNS resolution time also which can be affected by cache locality and sizing as well as how connected the requested authorative nameserver for the query is relative to the DNS resolver. IMHO, an effective way for setting up an office DNS cache is to setup a local caching nameserver such as Dan Bernstein’s dnscache and use GPD as an upstream forwarder.

Thus domains which are repeatedly asked are answered from your local dnscache and the long tail of domains can be answered by GPD which may have its in its cache because what may be infrequent for your organisation is frequent for someone else who is using GPD thus giving you the best of both worlds. Fast local caching, and a fast recursive resolver when you have no locally cached results.

I’m assuming that in the coming weeks, Google will reach out to a number of organisations who use anycast DNS such as Content Delivery Network operators (Akamai, Limelight, CDNetworks etc) and authorative DNS servers operators (Dynect,UltraDNS,DNSMadeEasy etc) and work out better network routing amongst them.

These instructions assume that you have setup dnscache as an external forwarding cache for your organisation.
Then run the following commands (asssumes that you have installed dnscache as per DJB’s setup. Ubuntu/Debian users may have to adjust paths if they use packages from these distributions

echo 1 > /service/dnscache/env/FORWARDONLY
echo '' > /service/dnscache/root/servers/@
svc -t /service/dnscache
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  1. December 6, 2009 at 5:52 am
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