Received: by oss.sgi.com id ; Mon, 3 Apr 2000 05:00:32 -0700 Received: from adsl-151-196-244-92.bellatlantic.net ([151.196.244.92]:20722 "EHLO vaio.greennet") by oss.sgi.com with ESMTP id ; Mon, 3 Apr 2000 05:00:09 -0700 Received: from localhost (becker@localhost) by vaio.greennet (8.9.3/8.8.7) with ESMTP id HAA19297; Mon, 3 Apr 2000 07:59:05 -0400 Date: Mon, 3 Apr 2000 07:59:05 -0400 (EDT) From: Donald Becker X-Sender: becker@vaio.greennet To: Andrew Morton cc: kuznet@ms2.inr.ac.ru, netdev@oss.sgi.com Subject: Re: coverage In-Reply-To: <38E8695B.E99D0D6A@uow.edu.au> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-netdev@oss.sgi.com Precedence: bulk Return-Path: X-Orcpt: rfc822;netdev-outgoing On Mon, 3 Apr 2000, Andrew Morton wrote: > kuznet@ms2.inr.ac.ru wrote: > > > > It is easy. "ping -f" does not create any real load on the network, > > it is pure latency test, when there is always only one packet in flight. > > I use 'ping -l 100000' > -l preload And, as you found out, most of the preloaded packets are discarded, at least with most versions of 'ping' and the kernel. The discard is done by the queue layer, before the device driver gets to see the packets. > > > - Tx stuck, invoke tx_timeout > > > > I think any man working with network has in his table some broken hub, > > which generates only collisions. 8) Mmm... what will occur if to plug > > crossed pair to two hub slots? Will it simulate broken hub then? > > (I did not advise you to do this! 8)) This won't accomplish what you expect. Most chips won't transmit on twisted pair without having link beat, producing a different type of error. Coax transceivers always get a collision when no cable is connected, resulting in a 16 collision error, not a Tx timeout. You can sometimes simulate the same effect on 10baseT with a mispaired cable, although not with 100baseTx. Donald Becker Scyld Computing Corporation, becker@scyld.com