DNS Connection Question

[invalid at pizzashack.org (Derek Martin)]

On Wed, Oct 20, 2004 at 11:24:23AM -0400, trlists at clayst.com wrote:
> OK, this all makes perfect sense.  But I was assuming -- again 
> definitely not an assumption I tested, it was a casual thought at the 
> time and not an analysis -- that exchanging packets is typically 
> relatively fast while waiting for the nameserver to do a lookup is 
> typically relatively slow.  So is making a TCP connection really 
> "9/10", or not?  It depends on the relative speed of the lookup in the 
> nameserver vs. the packet transit times.

Well, I guess it depends.  If you look up hosts for which the server is
authoritative, then the look-up time will be almost infinitessimally
small.  That lookup will be done from the server's hash tables, i.e.
the server will in most cases be serving the data from its own memory.
If, on the other hand, you are waiting for it to query other name
servers on the internet, then yeah, that would probably be slow.

But if you have control over all this, just use a host for which you
know the server should be answering authoritatively.  A good choice is
localhost, since as someone else pointed out, virtually all
properly-configured DNS servers should have an authoritative record
for it.  The look-up time is negligible in this case -- it's the
network I/O that takes all the time.

-- 
Derek D. Martin    http://www.pizzashack.org/   GPG Key ID: 0xDFBEAD02
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