From owner-freebsd-net@FreeBSD.ORG Sun Oct 21 19:34:34 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 9342F16A46D for ; Sun, 21 Oct 2007 19:34:34 +0000 (UTC) (envelope-from julian@elischer.org) Received: from outJ.internet-mail-service.net (outJ.internet-mail-service.net [216.240.47.233]) by mx1.freebsd.org (Postfix) with ESMTP id 89C1F13C494 for ; Sun, 21 Oct 2007 19:34:34 +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; Sat, 20 Oct 2007 13:55:57 -0700 X-Client-Authorized: MaGic Cook1e X-Client-Authorized: MaGic Cook1e X-Client-Authorized: MaGic Cook1e Received: from julian-mac.elischer.org (home.elischer.org [216.240.48.38]) by idiom.com (Postfix) with ESMTP id 9F0CD126747; Sat, 20 Oct 2007 13:55:56 -0700 (PDT) Message-ID: <471A6B72.2030305@elischer.org> Date: Sat, 20 Oct 2007 13:56:18 -0700 From: Julian Elischer User-Agent: Thunderbird 2.0.0.6 (Macintosh/20070728) MIME-Version: 1.0 To: Len Gross References: <27cb3ada0710172051t536a4d11pfdfdb079ebd98932@mail.gmail.com> <20071019224155.GI20308@server.vk2pj.dyndns.org> <20071020183000.E8153@knop-beagle.kn.op.dlr.de> <27cb3ada0710201108l5e717fdbhc9fab610cb2a047c@mail.gmail.com> In-Reply-To: <27cb3ada0710201108l5e717fdbhc9fab610cb2a047c@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: freebsd-net@freebsd.org, Harti Brandt 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: Sun, 21 Oct 2007 19:34:34 -0000 Len Gross wrote: > If I have to, I will employ some form of simulation of collisions, but that > will have to be done carefully in order to get the effect of collsions > beteen multiple stations without messing up timing. > > I REALLY wanted to have the PHY handle it. Usng half duplex and some old > hubs (if I can find one) would get collisions, but the retry would create > other problems. > > So, looks like "simulated" collisions will be the way to go. > > BTW: I'm using Netgraph - very cool stuff. > > --Len > thankyou :-) > > > > On 10/20/07, Harti Brandt wrote: >> 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 >> > _______________________________________________ > freebsd-net@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org"