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List:       firewalls-gc
Subject:    Re: Harping on dynamic DNS, was RE: Two ISP's to one DMZ
From:       peter () baileynm ! com (Peter da Silva)
Date:       1997-07-09 8:15:43
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> Imagine the traffic increase at yahoo.com if dynamic DNS was widely
> adopted and their caching nameservers had to effectively re-fetch
> addresses for all active clients every 10-20 minutes, instead of once a
> week.

That would come to 100 extra bytes of data being transferred every 10 or 20
web pages, with the average "Yahoo" web page being 10-20k long and including
4-5k of GIFs.

Virtually every DNS lookup is associated with an actual connection, and the
connection is associated with at least two decimal orders of magnitude more
data than the lookup utself.

> 	20 minutes * (1 day/1440 min) =	0.0138 days
> 	period = 0.0139 days

> 	2GB / 0.0139 day period =	144G bytes/day

> This amounts to *30%* of Yahoo's available bandwidth just for DNS traffic. 
> UGH! 30% of a T3!

> I am pretty sure my math is correct.

If so, then you've got a broken assumption somewhere... because even a
"GET HEAD /" takes more bandwidth than a DNS lookup, and that's the smallest
request ever made from Yahoo. Or are you postulating people doing lookups
and never getting any data?

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