[ On Saturday, July 5, 2003 at 19:00:13 (-0700), Avleen Vig wrote: ]
> Subject: Re: [Exim] Brain Dead ISP's?
>
> Your idea is noble
There's nothing "noble" about it. Remember the "good network neighbour"
part is merely gravy for free. The primary purpose of error response
rate limiting is to reduce the overhead on the server caused by
misbehaving clients (including, but not exclusively, spammers -- ineed
most of the serious problems I've seen were not caused by spammers but
rather by extremely badly programmed but otherwise normal SMTP clients).
> and works on a small scale, but on the scale of
> accepting 300+ new connections, per machine, per second, they just don't
> work unless you at least quadrouple your hoursepower.
I don't think you understand queuing and operational theory very well.
I'm no expert either, but I've had enough basic training and lots of
real-world experience in these issues and I can assure you that you
don't know what you're talking about.
The actual factor depends on how many of those connections you're
ultimately rejecting with a 4xx or 5xx response.
I'll bet you can get by with only about 25% more system capacity, at
most, even if 99% of those connections result in successful message
deliveries (since of course 99% of the time there would be no delay
introduced by error rate response limiting).
Indeed if any significant number of those connections are caused by
misbehaving clients that have just a moment ago been sent a 5xx reply
then I'll bet you a pint of beer or even two that you'll actually reduce
your system load significantly by introducing error reponse rate
limiting. Spend a little, save a _LOT_!
Have you got actual stats for any such machine or group of machines?
--
Greg A. Woods
+1 416 218-0098; <g.a.woods@???>; <woods@???>
Planix, Inc. <woods@???>; VE3TCP; Secrets of the Weird <woods@???>
