From owner-freebsd-net@FreeBSD.ORG Sat Oct 20 00:00:18 2007 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id CE01F16A421 for ; Sat, 20 Oct 2007 00:00:18 +0000 (UTC) (envelope-from julian@elischer.org) Received: from outA.internet-mail-service.net (outA.internet-mail-service.net [216.240.47.224]) by mx1.freebsd.org (Postfix) with ESMTP id 9585C13C459 for ; Sat, 20 Oct 2007 00:00:17 +0000 (UTC) (envelope-from julian@elischer.org) Received: from mx0.idiom.com (HELO idiom.com) (216.240.32.160) by out.internet-mail-service.net (qpsmtpd/0.40) with ESMTP; Fri, 19 Oct 2007 17:00:17 -0700 X-Client-Authorized: MaGic Cook1e X-Client-Authorized: MaGic Cook1e X-Client-Authorized: MaGic Cook1e X-Client-Authorized: MaGic Cook1e Received: from julian-mac.elischer.org (nat.ironport.com [63.251.108.100]) by idiom.com (Postfix) with ESMTP id 9F70E12673F; Fri, 19 Oct 2007 17:00:16 -0700 (PDT) Message-ID: <47194526.7080200@elischer.org> Date: Fri, 19 Oct 2007 17:00:38 -0700 From: Julian Elischer User-Agent: Thunderbird 2.0.0.6 (Macintosh/20070728) MIME-Version: 1.0 To: Sten Daniel Soersdal References: <27cb3ada0710172051t536a4d11pfdfdb079ebd98932@mail.gmail.com> <20071018082056.GW39759@funkthat.com> <27cb3ada0710181842x4d214d31ob4f474ff790355b8@mail.gmail.com> <47193112.4030701@gmail.com> In-Reply-To: <47193112.4030701@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Len Gross , John-Mark Gurney , freebsd-net@freebsd.org Subject: Re: Disable Exponential Backoff (retry) on Ethernet? X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 20 Oct 2007 00:00:18 -0000 Sten Daniel Soersdal wrote: > 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 :) one thing I'd like, that is related, is that if you disconnect a link for 3 hours it shouldn't sit there using 3000 Mbufs in its output queue.. how about discarding them.... currently they sit in the queue forwever as far as I can see. certainly in the em or bce drivers they do.. >