RE: RE: Sniffing out a firewall problem

["Robert McMahon" <rwm () mcmahoncpa com>]

Related to this is that hubs (which by their nature share a collision
domain), operate at only half-duplex.  I agree with Ryan, in that you have
to compare with total traffic.  I use to raise a flag (and look at
segmenting) when collision rate > 3-5 % in the days I use to run a hub
architecture.  I recall an O'Reilly book on "performance tuning" (has a
swordfish on cover), which is a great book that addresses these concerns.

Switches are not subject to having "polite" converstations, therefore, can
listen and reveive at same time - full duplex.

/rm

-----Original Message-----
From: firewall-wizards-admin () nfr com
[mailto:firewall-wizards-admin () nfr com]On Behalf Of Ryan Russell
Sent: Saturday, November 03, 2001 8:39 PM
To: Peter Lukas
Cc: ayoung () veros com; firewall-wizards () nfr com
Subject: Re: [fw-wiz] RE: Sniffing out a firewall problem


On Sat, 3 Nov 2001, Peter Lukas wrote:

> You'll get some pretty useful stats. Typically, any system with Ierrs,
> Oerrs or Collis will be experiencing a problem. Check caples, duplex
> settings and of course, the card /switch port itself.

Please be careful about making blanket statements about collisions
automatically meaning problems.  On any connection that is supposed to be
half-duplex Ethernet-style, collisions are perfectly normal, and you have
to measure collisions against total traffic to even have a rudimentary
problem measurement.

Sorry, it's a pet peeve of mine.  When I used to be primarily a network
engineer, I would have systems administrators come to me and report that
the system was reporting collisions, please fix the network.  I'd reply
that it was running half-duplex.  <blank stare>

                                        Ryan

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