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List:       firewalls-gc
Subject:    Re: Harping on dynamic DNS, was RE: Two ISP's to one DMZ
From:       Neil Readwin <nreadwin () csksoftware ! com>
Date:       1997-07-09 21:15:04
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This has nothing to do with firewalls, I apologize in advance for that.

> While I don't know what the specific error is, I'm pretty certain that
> your logic is wrong.

It is. The logic Aaron used was:

	Yahoo talks to 10 million hosts a day. Looking up 10 million
	hosts requires 2 gigabytes of DNS traffic.

	If the TTL is a week then cacheing smoothes that traffic over
	7 days, so it requires .286 gigabytes of DNS traffic per day.

	If the TTL is 20 minutes, that traffic is spread over 20
	minutes so it requires 144 Gb per day.

The 3rd part is wrong. As soon as the TTL goes below one day the level
of traffic per day is constant (well, 2nd order effects would increase
it slightly, but nothing close to 1/TTL).

Aaron's logic indicates that if the TTL was 0 then Yahoo would require
an infinite amount of bandwidth. This is not so :-) Neil.

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