From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-out.tiscali.be (spoolo1.tiscali.be [62.235.13.210]) by dsl2.external.hp.com (Postfix) with ESMTP id 2EC4A4841 for ; Sun, 16 Nov 2003 10:00:33 -0700 (MST) Message-ID: <3FB7AD39.9010305@tiscali.be> Date: Sun, 16 Nov 2003 17:00:41 +0000 From: Joel Soete MIME-Version: 1.0 To: "M. Grabert" Cc: parisc-linux@lists.parisc-linux.org Subject: Re: [parisc-linux] C110 builtin nic slow? References: <3F969FFE00009EA4@ocpmta2.freegates.net> <3F969FFE00009F73@ocpmta2.freegates.net> <20031110173525.GC24664@colo.lackof.org> <3FB0DC01.6070701@tiscali.be> <20031112032230.GB12000@colo.lackof.org> <3FB68167.10106@tiscali.be> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Sender: parisc-linux-admin@lists.parisc-linux.org Errors-To: parisc-linux-admin@lists.parisc-linux.org List-Help: List-Post: List-Subscribe: , List-Id: parisc-linux developers list List-Unsubscribe: , List-Archive: M. Grabert wrote: > Sorry to reply myself, Don't worry, I do it also frequently (tired or not i need some more time to test more stuff or find back more info ;) ) > but think I might need to clarify some points > (I'm a little bit tired, so I have missed some things in my previous post) > > On Sat, 15 Nov 2003, M. Grabert wrote: > > [...] > > >>>So i will continue to see how to set it up in half-duplex (would it not >>>be the default in 10BT?) > > > Yes, usually it defaults to 10Mbit half-duplex and then (if the cards > support it) it tries to negotiate better connections (full-duplex, 100Mbit ...) > > >>Actually if one end point uses Full-Duplex and the other end uses >>Half-Duplex, there should be no connection possible. > > > This is true if the (forced full-duplex) network card test for full-duplex > capable connection and doesn't find it. However most (cheap?) cards will > skip the test for full-duplex if it was 'forced', and you can still connect. > > Light traffic will work, but you will have problems with large traffic. > The explanation: > > The half-duplex side will send a packet, and assumes the other end stops > sending if a collision occurs, ie. if the other side was sending something > at the same time (CSMA/CD). > The full-duplex side will however will always send/receive as fast as it > can as it doesn't do CSMA/CD, ie. it doesn't care about collisions. > > The effect is that there will be a massive amount of collisions if both > sides want to send data, and only the half-duplex card will try to resend > the packets (causing even more collisions). > You will see slow traffic when sending from half-duplex, and dropped > packets when sending from full-duplex when both cards are sending. > > This will be most likely your problem, since it fits your description > perfectly (forced full-duplex mode). Sorry, I overlooked that in > my first post. > That explain perfectly the pb I encounter; thanks :) > > > >>The same for the situation when one side uses 10Mbit and the other is >>set to explicitly use 100MBit. > > > This will definitely never work. > > >>The only situation where such a decreased network performance occurs >>is IMHO that your have a cheap network equipment. >>IE. a dodgy network cable that isn't properly shielded or doesn't use all >>8 wires, > > > I mean in the context for 10BaseT, ie. all 4 wires (1/2,3/6) are connected, > but not the rest. There will be noise/crosstalk that will lead to > collisions. > I check: all 8 wires are connected > [...] > > >>In this (worst case) scenario there will be a lot of packet drop on >>the physical layer and the network cards will re-send the ethernet >>packets autmatically (usually) without notifying you. You will see >>decreased network performace as you mentioned it. > > > The network card (only in half-duplex) will think it detects collisions > due to noise/crosstalk and will automatically resend the packets without > notification. > > > Slan, > Max > > Thanks again, Joel