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Date:      Fri, 18 Aug 2000 12:32:44 -0400 (EDT)
From:      Jim Sander <jim@federation.addy.com>
Cc:        freebsd-security@FreeBSD.ORG
Subject:   Re: [Q] why does my firewall degrade Web performance? 
Message-ID:  <Pine.BSF.4.10.10008181211590.3414-100000@federation.addy.com>
In-Reply-To: <Pine.BSF.4.10.10008180932120.25370-100000@bsdie.rwsystems.net>

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   Personally, I think we're straying a bit from 'security' - but it's
close enough that I guess I can chime in with something that may help
improve someone's "gut feel" sense. (which is why I liked reading the
other messages in this thread- thanks all)

   We run a firewall with about 3000 rules- used mainly for bandwidth
tracking purposes. The highest load average I ever see is about .1 (when
the bandwidth tracking scripts update our database) but the telling
numbers are this line from "top" but also available in other utilities
like iostat, etc.

> CPU states: 0.0% user, 0.0% nice, 0.0% system, 40.5% interrupt, 59.5%idle

   The interrupt load on that machine is about 10 or 20 times higher than
on any of the machines behind the wall. (which of course makes perfect
sense) The hardware is a 400MHz Celeron- slowest thing we could find at
the time, 64MB RAM, 100MB NIC, connected to a dual T1 through an etinc
interface. (in other words it's a router-firewall in one box) The software
is FreeBSD 3.3R and ipfw.

   I've never had trouble with slow browsing from the outside, even during
heavy use periods. (although to be honest we've never fully maxxed our
connection out) YMMV, but I'd say that the problems described would be a
duplex-mismatch or other oddball thing. Firwalling just isn't that hard on
the CPU, a Cisco 2500 is like a 68030- right?

   Anyway, hope this helps a little.

-=Jim=-



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