From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: Re: Ethernet CRC questions Date: Wed, 30 Dec 2009 11:37:13 +0100 Message-ID: <1262169433.2247.15.camel@localhost> References: <1262108376.5941.5.camel@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: thomas yang Return-path: Received: from mail.solarflare.com ([216.237.3.220]:31143 "EHLO exchange.solarflare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752530AbZL3KhS (ORCPT ); Wed, 30 Dec 2009 05:37:18 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 2009-12-30 at 13:53 +0800, thomas yang wrote: > 2009/12/30 Ben Hutchings : > > On Wed, 2009-12-30 at 01:17 +0800, thomas yang wrote: > >> How does Linux generate Ethernet CRC ? > >> by the hardware (Ethernet controller) or use crc32_le() / > >> crc32_be() ( lib/crc32.c ) ? > >> > >> P.S. my network card is rtl8139d , use 8139too driver > > > > The Ethernet frame CRC is normally generated and verified in hardware. > > These library functions are needed for the few MACs that don't, or where > > the same CRC function is used for some other purpose (e.g. as a hash > > function for multicast filtering). > > > > Does the Ethernet frame CRC (generate and verify in hardware) make > the TX / RX rate a little smaller , and a longer end-to-end delay ? Relative to what? > Could I disable CRC appending / verifying in the network card driver > on all of my nodes (machines) ? Maybe if you want switches to discard everything you send... Ben. -- Ben Hutchings, Senior Software Engineer, Solarflare Communications Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked.