Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site deepthot.UUCP Path: utzoo!watmath!deepthot!julian From: julian@deepthot.UUCP (Julian Davies) Newsgroups: net.lan Subject: Re: Ethernet <=> Ethernet Link Message-ID: <340@deepthot.UUCP> Date: Tue, 31-Jul-84 21:44:56 EDT Article-I.D.: deepthot.340 Posted: Tue Jul 31 21:44:56 1984 Date-Received: Wed, 1-Aug-84 05:56:14 EDT References: <435@ittral.UUCP>, <708@CS-Arthur> Organization: UWO CS, London Canada Lines: 26 In the original request starting this line of discussion, I seem to remember that the two ethernets were several miles apart. In this case no kind of "repeater" is appropriate, no matter if it uses fibre optics, microwave or anything else. Ethernet has a maximum end-to-end propagation delay, which is assumed predictable for determining the length of time needed to listen for contention when trying to grab the ether. The geographical distance limit is usually quoted as 1500m (say 5000 feet) on thick ethernet cable, or one third of this on 'thin' cable. Fibre-optic links etc still have the same speed of light propagation speed limit for information pulses, so the lengths of any such links must be counted towards the 1500m limit. To go over about a mile, you MUST use a full-fledged gateway or bridge which buffers each packet being transferred and rebroadcasts it on the other cable as a separate activity. It seems that quite a few organizations are using broadband cable for networks over distances of a few miles; these can be set up to operate over longer distances than ethernet, by various means, and some organizations like the flexibility of combining video with several different carriers of data. The trade-offs depend on the particular needs though. PBXs in various flavours, and local packet-switched networks (X.25 type) are also possible solutions (though the latter is fairly unusual in N. America -- but is getting quite common in the UK and maybe in Europe.) Julian Davies {deepthot|uwo}!julian