Disable Exponential Backoff (retry) on Ethernet?

[Len Gross]

Thanks so much for the response.  Here is some additional information.

I'm trying to emulate an RF network where there are colisions (e.g. "Aloha"
type protocol) so I actually need collisions!  I had forgotten that modern
hardware
essentially eliminated them.  So, lets say I can find/use an "old hub",
can I control the number of retries?  Maybe I have to find some old NICs and
old drivers?

-- Len


On 10/18/07, John-Mark Gurney <gurney_j at resnet.uoregon.edu> wrote:
>
> Len Gross wrote this message on Wed, Oct 17, 2007 at 20:51 -0700:
> > I'm doing some protocol development and it is convenient to start it on
> > Ethernet.  I will need to send a packet to the Ethernet device and only
> have
> > it be sent once, even if there is a colision.  (Higher levels in the
> > protocol will detect the failure.)  I've searched quite a bit, and
> haven't
> > found any place that talks about this.   Are there any hardware cards,
> or
> > drivers, that let me turn off the backoff/retry behavior?
>
> Are you even using hardware that does collisions?  Collisions pretty
> much went out w/ 10Mbit ethernet...  Not completely as there are older
> 10/100mbit "switches" that only switched between the two segments (and
> each of 10/100 segments was hubbed)...  All modern switches are
> full-duplex and don't suffer from the old CD part of CDMA that was part
> of the original ethernet specification..
>
> For Gige, you can't even do half-duplex, as each side is transmitting
> on all four pairs at the same time...  The physical layer handles the
> fact that both sides may transmit at the same time, and knows how to
> cancel their own interference out so they can hear the other side...
>
> --
> John-Mark Gurney                              Voice: +1 415 225 5579
>
>     "All that I will do, has been done, All that I have, has not."
>