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dns-prefetch. Anyone familiar?
02-25-2010, 08:00 AM
Post: #5
RE: dns-prefetch. Anyone familiar?
DNS pre fetch is something i have been looking into, and so far as in browser dns pre fetch tags go, its still a dream...

Meanwhile Google have re invented the DNS server with one that incorporates DNS pre fetch.

Normaly when the ISPs DNS server goes back to the authoritative host to get the DNS record it just caches it without inspecting the TTL on the record. For our site that is 300 seconds, which is deliberately quite short. The next time a user requests the DNS record from their ISPs DNS server, only then does it inspect the TTL and if its expired then it will go back to the authoritative host.

Google found that their googlebot was spending more time looking up DNS records, than it was spidering pages. So they made their DNS server inspect the TTL of the record and before it expired fetch it again so the cache is kept hot.

If you give yourself a tight target like a "1 second homepage" then you may see 700ms wasted in DNS resolving. If thats the case give the google DNS server a go. its available on and its quite shocking the difference it can make.

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Messages In This Thread
dns-prefetch. Anyone familiar? - p83822 - 02-15-2010, 08:25 PM
RE: dns-prefetch. Anyone familiar? - hsiboy - 02-25-2010 08:00 AM
RE: dns-prefetch. Anyone familiar? - pqdbr - 04-17-2012, 02:59 PM

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