Date: Fri, 14 Dec 2001 00:07:03 -0500 (EST) From: Garrett Wollman <wollman@khavrinen.lcs.mit.edu> To: juha@saarinen.org Cc: stable@FreeBSD.org Subject: Re: fxp half-duplex problemm Message-ID: <200112140507.fBE573Z89921@khavrinen.lcs.mit.edu> In-Reply-To: <20011214044937$6fe9@traf.lcs.mit.edu> References: <20011213202106.B78956@nexus.root.com>
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In article <20011214044937$6fe9@traf.lcs.mit.edu> you write: >It's a bit pendatic, really, but surely it should be "simplex" and not >"half-duplex"? No. ``Simplex'' means ``only one direction''. (The network interface flags get this wrong: IFF_SIMPLEX means ``can't hear myself talking''; this flag should have been called something different, as it is independent of the duplexity of a multiple-access medium.) ``Half-duplex'' is bidirectional communication where senders must take turns (e.g., all of the original IEEE 802 MAC layers), and obviously ``full-duplex'' is bidirectional communications without sender timing constraints.[1] We speak of TCP as being ``dual-simplex'', and not ``full-duplex'', because it provides two logically-independent one-way channels. Unfortunately, the designers of some protocols that sit on top of TCP did not understand this. (IIRC, TP, OSI's transport layer, is duplex.) -GAWollman [1] At least, I don't think a slotted bus could ever be full duplex. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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