Slow transfer with 21140 card

[Robert G. Brown]

On Wed, 22 Jul 1998, Hannu Krosing wrote:

> >  The Rx process state is 'Waiting for packets'.
> >  The Tx process state is 'Idle'.
> > Transmit started, Receive started, full-duplex.
> 
> Are you sure that the hubs are full-duplex ?

I think that "hubs" are never full duplex (correct me if I'm wrong).
I thought only switches are full duplex and hubs are intrinsically
half duplex.  A hub, for novices, is a multiport device that echos the
traffic from any line to all of the lines without retiming -- all the
hosts are in the same collision domain, and the 100 Mbps bandwidth of
the hub is SHARED among all the connected hosts.  A switch, on the
other hand, listens for the ethernet address(es) on each line, builds
a table, and generally forwards packets only to the line on which the
destination lives.  The packets are retimed, and the hosts live in
distinct collision domains (although with most 100BT switches these
days there is just one host on each line and "collision domain" has
little meaning:-).  A (decent) switch typically has 100 Mbps of
bandwidth PER CONNECTION -- the bandwidth is NOT shared -- and can
support full duplex connections.

I believe that if you don't force the card to be ANYTHING, in most
cases it will correctly autodetect the kind of device it is connected
to (base frequency, duplex, and all that, via Nway) and set itself,
and one overrides this at one's peril in the few cases that it just
doesn't work.



   rgb

Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb@phy.duke.edu