From owner-freebsd-questions@FreeBSD.ORG Thu Jul 16 15:32:07 2009 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 16E4E106566B for ; Thu, 16 Jul 2009 15:32:07 +0000 (UTC) (envelope-from freebsd-questions-local@be-well.ilk.org) Received: from mail3.sea5.speakeasy.net (mail3.sea5.speakeasy.net [69.17.117.5]) by mx1.freebsd.org (Postfix) with ESMTP id E36CC8FC17 for ; Thu, 16 Jul 2009 15:32:06 +0000 (UTC) (envelope-from freebsd-questions-local@be-well.ilk.org) Received: (qmail 3985 invoked from network); 16 Jul 2009 15:32:06 -0000 Received: from dsl092-078-145.bos1.dsl.speakeasy.net (HELO be-well.ilk.org) ([66.92.78.145]) (envelope-sender ) by mail3.sea5.speakeasy.net (qmail-ldap-1.03) with SMTP for ; 16 Jul 2009 15:32:06 -0000 Received: by be-well.ilk.org (Postfix, from userid 1147) id 2AB1450822; Thu, 16 Jul 2009 11:32:05 -0400 (EDT) To: nightrecon@verizon.net References: <20090715194718.GA16401@Grumpy.DynDNS.org> <41F6B586-E6A8-4FF8-95EB-E8A6C8E1F020@hiwaay.net> From: Lowell Gilbert Date: Thu, 16 Jul 2009 11:32:04 -0400 In-Reply-To: (Michael Powell's message of "Thu\, 16 Jul 2009 02\:49\:11 -0400") Message-ID: <44ljmo7iff.fsf@be-well.ilk.org> User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.3 (berkeley-unix) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: freebsd-questions@freebsd.org Subject: Re: 5000' ethernet? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: freebsd-questions@freebsd.org List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 16 Jul 2009 15:32:07 -0000 Michael Powell writes: > You are running Ethernet, right? CSMA/CD is part of the Ethernet framing > protocol. It is present in the protocol independent of simplex/duplex, etc. > As such the timing windows contain non-infinite discreet value ranges. It is > integral to Ethernet and does not get 'switched off' or disappear just > because a link is full-duplex. I call your attention to the specification (IEEE 802.3) for Ethernet: 1.1.1 Basic concepts This standard provides for two distinct modes of operation: half duplex and full duplex. A given IEEE 802.3 instantiation operates in either half or full duplex mode at any one time. The term CSMA/CD MAC is used throughout this standard synonymously with 802.3 MAC, and may represent an instance of either a half duplex or full duplex mode data terminal equipment (DTE), even though full duplex mode DTEs do not implement the CSMA/CD algorithms traditionally used to arbitrate access to shared-media LANs. -- Lowell Gilbert, embedded/networking software engineer, Boston area http://be-well.ilk.org/~lowell/