Date: Thu, 16 Jul 2009 11:32:04 -0400 From: Lowell Gilbert <freebsd-questions-local@be-well.ilk.org> To: nightrecon@verizon.net Cc: freebsd-questions@freebsd.org Subject: Re: 5000' ethernet? Message-ID: <44ljmo7iff.fsf@be-well.ilk.org> In-Reply-To: <h3midk$ju2$1@ger.gmane.org> (Michael Powell's message of "Thu\, 16 Jul 2009 02\:49\:11 -0400") References: <20090715194718.GA16401@Grumpy.DynDNS.org> <h3llqc$rl9$1@ger.gmane.org> <41F6B586-E6A8-4FF8-95EB-E8A6C8E1F020@hiwaay.net> <h3midk$ju2$1@ger.gmane.org>
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Michael Powell <nightrecon@verizon.net> 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/
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