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Date:      Sun, 16 Mar 2003 12:47:40 -0500
From:      Bill Moran <wmoran@potentialtech.com>
To:        Olivier Dony <odony@student.info.ucl.ac.be>
Cc:        Simon Barner <barner@in.tum.de>, freebsd-questions@freebsd.org
Subject:   Re: Too many collisions on network?
Message-ID:  <3E74B8BC.4030009@potentialtech.com>
In-Reply-To: <002201c2ebd3$92d0a7d0$1502a8c0@blacktrap.net>
References:  <005d01c2ebcb$82b343b0$1502a8c0@blacktrap.net> <20030316152335.GA1434@zi025.glhnet.mhn.de> <002201c2ebd3$92d0a7d0$1502a8c0@blacktrap.net>

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Olivier Dony wrote:
> On Sunday, 16 March, 2003 16:23, Simon Barner wrote:
> 
>>Are you running your network adaptor in full-duplex mode? Perhaps the device on
>>the other end of the wire does only support half-duplex. Changing this increased
>>the throughput from 20kb/s to almost 1mb/s on our internal network here
>>(10baseT/UTP).
> 
> 
> I'm not really sure about this, here is the output of ifconfig related
> to the external interface :
> 
> root@charon:/root# ifconfig -m fxp0
> fxp0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>         inet xxx.xxx.191.100 netmask 0xfffffff0 broadcast xxx.xxx.191.111
>         inet xxx.xxx.191.101 netmask 0xffffffff broadcast xxx.xxx.191.101
>         ether 00:e0:81:23:c5:32
>         media: Ethernet autoselect (10baseT/UTP)
>         status: active
>         supported media:
>                 media autoselect
>                 media 100baseTX mediaopt full-duplex
>                 media 100baseTX
>                 media 10baseT/UTP mediaopt full-duplex
>                 media 10baseT/UTP
>                 media 100baseTX mediaopt hw-loopback
> 
> It seems that fxp(4) supports full-duplex but that it is currently 
> disabled, and I guess this is because the other end of the wire doesn't
> support it, since the media has been autoselected? Please correct me
> as I have never played a lot with ifconfig except for basic configutarion.
> I wouldn't be too eager to do tests with this setting since this is a
> production server and I have no direct physical access to it, so shutting
> down the only interface by mistake is *not* an option ;-)
> But if I was to change it, how would I go about this without shutting down
> fxp0? 'ifconfig fxp0 media 10baseT/UTP mediaopt full-duplex' ??

I have seen cases where the media type was auto-negiotiated wrong.  I think
this was due to crappy wiring, but the circumstances didn't allow for a lot
of experimenting.

I would suggest talking to your ISP and verifying what the connection _should_
be.  Then work towards getting it there.  When the two ends see something
different, performance blows.

Going to full-duplex should reduce collisions to 0, and give you the max
performance available.  I just did some experimenting with turning duplex
from half to full and back on my computer here, and if there's any interruption,
it was less than I could easily measure.  Don't know if that'll be the same
with all switches or not.

-- 
Bill Moran
Potential Technologies
http://www.potentialtech.com


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