From: Peter da Silva <peter @
Subject: Re: Harping on dynamic DNS, was RE: Two ISP's to one DMZ
Date: Wed, 9 Jul 1997 08:15:43 -0500 (CDT)
To: aajpeter @
Cc: mikech @
net, Firewalls @
> > 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?
---------------End of Original Message-----------------
The one thing I negelcted to add to my previous post is the fact that we do
updates every ten minutes. So DNS servers within an ISP would still need to
pull down the new addresses every ten minutes. This is not the same thing as
every ISP *client* pulling down the new IPs every ten minutes. It is still
neglible bandwidth (for the benefits received) in the great Internet scheme of
Michael W. Chalkley Tel: +1.770.823.7846
ZapNet! Inc. Fax: +1.770.475.7640
Suite 400-120 E-mail: mikech @
10945 State Bridge Road mikech @
Alpharetta, GA 30202 (wireless) mikech @