Cap on network speed in CURRENT?

Brooks Davis brooks at
Tue Jun 1 18:20:23 PDT 2004

On Tue, Jun 01, 2004 at 05:29:44PM -0700, Luke wrote:
> >>I've got a 100Mbps LAN with ethernet cards that should be capable of using
> >>it, yet the highest transfer rates I seem to be able to get out of my
> >>FreeBSD box are 260KB/s receiving and 341KB/s sending with around 200KB/s
> >>being more normal.
> >>
> >
> >On a LAN, buffer size has minimal effect except at very high speeds.
> >Without tuning, two 5.x boxes with gigabit interfaces connected to a
> >Cisco 6513 switch (one 5/10/04 and one 2/20/04) reached 187Mbps in
> >iperf.  You're problems symptoms sound like duplex mismatch or bad
> >hardware to me.
> I've forced both full and half duplexing and gotten the same results both 
> ways.  I certainly won't rule out bad hardware.  I just don't know how to 
> troubleshoot this.
> Would disabling "witness" help?  I've read that "witness" can slow down 
> some things, but I don't know if network speed is one of them.

WITNESS definatly slows things down, but not that much.  The machines I
gave results from are running with WITNESS enabled.  How are you testing
your bandwidth?  If you aren't you should be using netperf, iperf, ttcp,
or similar.  Not that any other method I can think of would account for
this much slowness unless you've got really slow hosts.

-- Brooks

Any statement of the form "X is the one, true Y" is FALSE.
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