Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site well.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!think!harvard!seismo!lll-crg!well!drk From: drk@well.UUCP (Doug Kaye) Newsgroups: net.lan,net.dcom Subject: Re: Thin Ethernet - (Any Specifications?) Message-ID: <247@well.UUCP> Date: Thu, 31-Oct-85 00:12:28 EST Article-I.D.: well.247 Posted: Thu Oct 31 00:12:28 1985 Date-Received: Sat, 2-Nov-85 05:25:00 EST References: <943@unmvax.UUCP> Distribution: net Organization: Whole Earth Lectronic Link, Sausalito, CA Lines: 46 Xref: watmath net.lan:1113 net.dcom:1421 Summary: Thin Ethernet - Specifications! In article <943@unmvax.UUCP>, eric@unmvax.UUCP writes: > ... Is there a standard for this "thin ethernet" > or a group that backs it with published specs, such as DEC-INTEL-XEROX > group that backed the standard Ethernet? As this is probably of interest to many, I've posted this article. To the best of my knowledge, there is no published spec for RG-58. However, after months of research, here's what we've come up with: A "segment" (Thick or RG-58) can support a mximum of 100 nodes of MAUs. A segment may be composed of one or more lengths of cable. Using thick cable, each segment has a maximum length of 500 meters (1640 feet). With RG-58 this maximum is reduced to 152 meters (500 feet[!]). The difference is capacitance and signal loss. The formula to use is: T * 3.28 + E = 500 meters where T= length ofhin and E= length of thernet (thick). Transceivers are ALWAYS required, it's just that using RG-58 it is reasonable to use on-board transceivers such as 3Com, etc. It is just as legal to connect thick cable to a thick-to-thin adaptor, through the T, and back to thick cable again...but the big yellow stuff would probably bust the T! Likewise, you can use a transceiver with BNC connectors and run a transceiver cable from the RG-58 net to the standard 15-pin IEEE 802.3 connector. (Another difference between Thick and RG-58 is the velocity, of course. Thick cable is 0.77c while RG-58 is somewhat slower, perhaps 0.65c or less.) Now, how come some folks (3Com in particular say "run 1000' with RG-58"? They cheat! As best we can tell, their transceviers put out a signal level greater than that of the IEEE802.3 standard. This means that a network with ALL 3Com can be 1000' per segment. BUT (!) if you put any other transceiver on the net, look out! We never go beyond the 802.3 specs in our installations. Anyone needing more info can reach me through the net. Doug Kaye Rational Data Systems 5725 Paradise Drive Corte Madera, CA 94925 ihnp4!hplabs!well!drk