Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84 SMI; site sun.uucp Path: utzoo!watmath!clyde!bonnie!akgua!sdcsvax!dcdwest!ittvax!decvax!decwrl!sun!sunny From: sunny@sun.uucp (Sunny Kirsten) Newsgroups: net.lan Subject: Re: Ethernet query Message-ID: <1841@sun.uucp> Date: Tue, 4-Dec-84 03:45:56 EST Article-I.D.: sun.1841 Posted: Tue Dec 4 03:45:56 1984 Date-Received: Thu, 6-Dec-84 05:17:25 EST References: <1286@hao.UUCP> Distribution: net Organization: Sun Microsystems, Inc. Lines: 43 > We are about to embark on a journey into the deepest jungles > of Ethernet, and we have a few questions. Hopefully the explorers > who have been there before us will provide us with the benefit > of their knowlege. > > > 1. We have been told that it is "Better" to install a single > length of cable, rather than join several smaller lengths with > barrel connectors. The benefits of using many smaller lengths > are obvious. The dangers of doing so are not so obvious. Why > is it better to use a single cable, and what kinds of problems > will we encounter if we use several smaller lengths? > > > 2. Has anybody tried to install "zero impedance bump" connectors? > Is this something that might help? If not, why not? > Every tap, connector, kink, etc. in a cable tends to introduce an impedance discontinuity, which causes signal reflection, standing waves, and some attenuation. Although these things in general are to be avoided, there are other considerations. For example, if you choose to go the 3Com route (connectorized transceivers), you'll find that their transceivers exceed the spec more than enough to compensate for the connectors. > > 4. Does the bit error rate increase as the cable length approaches > the specification maximum? Is there some problem other than > collision time that constrains the length? > Yes. Detection of collisions. Stations at opposite ends of the cable tend to not notice that they're participating in a collision, so go ahead and transmit anyway...producing garbled packets which get thrown out by the CRC logic. The net effect is not an increased BIT error rate, but an increased PACKET error rate. Bit error rate is seldom a problem. > > 5. Do repeaters work? Are they available? Do the board makers > suppy them? Are they expensive? Yes.Yes.No?Relative to what? Xerox makes a good one. That and a pair of 3Com transceivers, and you're all set. -- mail ucbvax\!sun\!sunny decvax\!sun\!sunny ihnp4\!sun\!sunny<