Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S272426AbTHFVNw (ORCPT ); Wed, 6 Aug 2003 17:13:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S272387AbTHFVNv (ORCPT ); Wed, 6 Aug 2003 17:13:51 -0400 Received: from mail.webmaster.com ([216.152.64.131]:24031 "EHLO shell.webmaster.com") by vger.kernel.org with ESMTP id S272426AbTHFVNu (ORCPT ); Wed, 6 Aug 2003 17:13:50 -0400 From: "David Schwartz" To: "Andy Isaacson" , "Jesse Pollard" Cc: , Subject: RE: TOE brain dump Date: Wed, 6 Aug 2003 14:13:47 -0700 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.6604 (9.0.2911.0) In-Reply-To: <20030806143956.B15543@hexapodia.org> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Importance: Normal Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1521 Lines: 38 > This statement is completely false. Ethernet switches *do* read the > packet into memory before starting transmission. Some do. Some don't. Some are configurable. > This must be so, > because an Ethernet switch does not propagate runts, jabber frames, or > frames with an incorrect ethernet crc. If they use cut-through switching, they do. Some use adaptive switching, which means they use cut-through switching but change to store and forward if there are too many runts, jabber frames, bad CRCs, and so on. Obviously, you can't always do a cut-through. If the target port is busy, cut-through is impossible. If the ports are different speeds, cut-through is impossible. The Intel 510T switch for my home network does adaptive switching with configurable error thresholds. In fact, it's even smarter than that, with an intermediate mode that suppresses runts without doing a full store and forward. See: http://www.intel.com/support/express/switches/23188.htm > If the switch starts > transmission before it's received the last bit, it is provably > impossible for it to avoid propagating crc-failing-frames; ergo, > switches must have the entire packet on hand before starting > transmission. Except not all switches always avoid propogating bad frames. DS - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/