Date: Sat, 20 Oct 2007 00:34:58 +0200 From: Sten Daniel Soersdal <netslists@gmail.com> To: Len Gross <sandiegobiker@gmail.com> Cc: freebsd-net@freebsd.org, John-Mark Gurney <gurney_j@resnet.uoregon.edu> Subject: Re: Disable Exponential Backoff (retry) on Ethernet? Message-ID: <47193112.4030701@gmail.com> In-Reply-To: <27cb3ada0710181842x4d214d31ob4f474ff790355b8@mail.gmail.com> References: <27cb3ada0710172051t536a4d11pfdfdb079ebd98932@mail.gmail.com> <20071018082056.GW39759@funkthat.com> <27cb3ada0710181842x4d214d31ob4f474ff790355b8@mail.gmail.com>
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Len Gross wrote: > 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? That would be very NIC specific. Retries are done in NIC hardware as far as i know. All you need to do to get some collisions is to set the rates to half-duplex on both sides (hubs were half-duplex). Hubs with lot's of traffic between other hosts would definitely produce more collisions. Modern hardware didn't eliminate them. Full-Duplex medium did. There is a broad range of full-duplex RF systems too :) -- Sten Daniel Soersdal
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