Verizon FIOS

[John Abreau]

On Dec 22, 2007 11:38 AM, Cole Tuininga <colet at code-energy.com> wrote:
> Actually, that's not entirely true.  Using a recursive DNS server that's
> on a fast backbone can sometimes noticeably increase the speed of
> lookups.  Keep in mind that a single recursive query causes a nameserver
> to have to go out and hit multiple different servers on the net.  If you
> have an "ok" connection, each request has to go across that.
>

That logic applies only to each request that is not already cached
in your local DNS.

In the special case of browsing the web with firefox, a typical web
page might require a dozen separate http fetches, and firefox will
do a separate DNS lookup for each. If www.foo.com isn't already
in the local DNS cache, then the first time firefox looks it up,
it will query a .com nameserver (as .com is likely already cached),
after which the authoritative nameservers for foo.com will be
cached locally.

For the subsequent 11 queries, if they all happen to be www.foo.com,
the local DNS responds without having to traverse
the cablemodem, whereas queries to the "fast backbone" are
delayed by a round trip through the cablemodem. And all further
queries of www.foo.com within its TTL (time-to-live) timespan
(typically 24 hours) will also be found quickly in the local cache.


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John Abreau / Executive Director, Boston Linux & Unix
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