From owner-freebsd-current Sat May 2 11:47:35 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id LAA03243 for freebsd-current-outgoing; Sat, 2 May 1998 11:47:35 -0700 (PDT) (envelope-from owner-freebsd-current@FreeBSD.ORG) Received: from jli.com (jli.com [199.2.111.1]) by hub.freebsd.org (8.8.8/8.8.8) with SMTP id LAA03215 for ; Sat, 2 May 1998 11:47:28 -0700 (PDT) (envelope-from trost@cloud.rain.com) Received: (qmail 6466 invoked by uid 4); 2 May 1998 18:46:51 -0000 Received: (qmail 4722 invoked from network); 2 May 1998 18:46:06 -0000 Received: from softdnserror (127.0.0.1) by softdnserror with SMTP; 2 May 1998 18:46:06 -0000 To: current@FreeBSD.ORG Subject: Re: Infrared ? (a simple experiment for laptop owners...) References: <9297.894130297@critter.freebsd.dk> In-reply-to: Your message of Sat, 02 May 1998 19:31:37 +0200. <9297.894130297@critter.freebsd.dk> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <4718.894134766.1@cloud.rain.com> Date: Sat, 02 May 1998 11:46:06 -0700 Message-ID: <4719.894134766@cloud.rain.com> From: Bill Trost Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG One concern I have (before getting into the nitty-gritty) is that anything "we" do (and I might go dig up an IR transceiver for my desktop just to help) be compatible with whatever else might be in use. Tekram (www.tekram.com) makes an IPX IR bridge, and Mac laptops run AppleTalk over their IrDA ports. I would expect the you might actually be able to get something out of Apple about what their machines do. Poul-Henning Kamp writes: >Example: one side (the 'client' ppp) acts as a master, the other >one as a slave. The protocol is governed by the master, and the >slave can only send a packet right after a pkt coming from the >master. On the other hand, IP isn't very well suited to half-duplex, and to get a decent performance you probably need to flip though Tanenbaums book and see if you can find some old stuff from Hawai to use... Slotted ALOHA is probably overkill for this task. You probably do not want to try more than two nodes in the infrared network. The reason is that IRdA ports have a fairly narrow beam width (30 degrees, as I recall), and not that great a range (3 feet +/- 3 feet). As soon as you add a third node, you will probably start running into hidden transmitter problems. ALOHA would deal with that in the simple case, but you more or less have to "know" that one node can reach all the other nodes in the network. Actually, in a two-node system, ALOHA more or less degenerates into the protocol Luigi described anyhow, so this seems like an on-track proposal. If you do try to go to three nodes, you may be better off with the PPP server acting as the master, as it is more likely to be the "fixed" system. Finally, I think cellphone systems like GSM use an ALOHA-like protocol as well, so that will provide a more recent literature reference. Note that cellphone systems have a known "master", however (the cell tower). To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message