Disable Exponential Backoff (retry) on Ethernet?

[Harti Brandt]

On Sat, 20 Oct 2007, Peter Jeremy wrote:

PJ>On Wed, Oct 17, 2007 at 08:51:34PM -0700, Len Gross wrote:
PJ>>I'm doing some protocol development and it is convenient to start it on
PJ>>Ethernet.  I will need to send a packet to the Ethernet device and only have
PJ>>it be sent once, even if there is a colision.
PJ>
PJ>I know we've still got some hubs lying around in a backroom at work
PJ>but I don't know of anything that will let you disable the retry-on-CD.
PJ>
PJ>Have you considered simulating the network at a slightly higher lever:
PJ>Use ipfw pipes or similar to simulate packet loss (either set a queue
PJ>length of 1 or probabilistically).  This could be done either as a
PJ>bridge or by tunneling your protocol over IP or UDP.

Some years ago I wrote a netgraph node that connected to ethernet nodes 
and simulated a wireless broadcast channel including collisions, 
timevariable delay, loss and shaping. Can be done in a couple of hundreds 
of lines and easily allows >100MBit/sec with gigabit ethernet. The 
ethernet is just the physical transport medium for the packets and does 
not take part in the emulation. All that was controlled by bsnmpd and a 
remote command line tool and/or Java-GUI. Unfortunately I cannot release 
this (yet) due to licensing...

harti