Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!mailrus!ames!uhccux!lee From: lee@uhccux.uhcc.hawaii.edu (Greg Lee) Newsgroups: comp.sys.next Subject: Re: Connecting a NeXT to twisted-pair Message-ID: <5719@uhccux.uhcc.hawaii.edu> Date: 13 Dec 89 14:54:55 GMT References: <341@egg-idINEL.GOV> Organization: University of Hawaii Lines: 233 From article <341@egg-idINEL.GOV>, by rhp@INEL.GOV (Robert Powell): " ... " Our biggest problem right now is connecting our cubes to our ethernet. It " is a problem because our building is only wired with twisted-pair thick-net " ethernet. Our networking people tell me that I need a thick-net to thin-net " bridge or repeater, at a cost of around $2,600! ... I thought thick-net and twisted-pair ethernet were different animals. There is a twisted-pair to thin-net converter in the DEC catalog for, I think I recall, $400 for a pack of 8. Something like that. I don't know whether that would be suitable. The subject of connecting thick-net to thin-net came up before in this newsgroup, and it was said that you can just stick them together directly with a connector. Following is some of that past discussion. Greg, lee@uhccux.uhcc.hawaii.edu >From: jbn@glacier.STANFORD.EDU (John B. Nagle) Newsgroups: comp.sys.next Subject: Re: My ramblings on the NeXT machine Message-ID: <17845@glacier.STANFORD.EDU> Date: 15 Nov 88 18:09:46 GMT References: <26812@ucbvax.BERKELEY.EDU> Reply-To: jbn@glacier.UUCP (John B. Nagle) In article <26812@ucbvax.BERKELEY.EDU> munson@renoir.Berkeley.EDU (Ethan V. Munson) writes: >3) Thin Ethernet -- NeXT has a Thin Ethernet connector. Here at Berkeley, > neither the EECS department or the academic computing service has > anything but thick ethernet. As of last week, even NeXT didn't > know where to find converters. Each converter will cost about > $200-300. Since these machines are targeted at professors, rather > than students, it may be hard to build short Thin Ethernets which > share one converter. Thick and thin Ethernet cable can simply be interconnected with coax adapters. Losses are higher in the thin sections, but the adapters themselves seem clean; I've looked at a mixed cable using a time-domain reflectometer, and I can see tranceivers and sharply bent cable, but not thick/thin adapters. Usually, you convert from thick to thin inside a wall, box, floor, or plenum, then bring two thin cables up to the machine, where they meet at a T connector attached to the back of the machine. Remember, the T connector must be directly on the back of the machine; any cable between the T and the computer causes reflections that trash data. If the entire cable is within the thin Ethernet length limit, everything should be safe. The appropriate adaptor is a constant-impedance UHF (female) to BNC (female) adapter. However, this is a hard-to-find adapter, and it may be necessary to combine a UHF (female) to BNC (male) adapter with a BNC-BNC barrel. Amphenol part 12025 is the adapter. John Nagle >From: jbn@glacier.STANFORD.EDU (John B. Nagle) Newsgroups: comp.sys.next Subject: Re: Followup to Who Has One? Message-ID: <17916@glacier.STANFORD.EDU> Date: 21 Dec 88 19:36:31 GMT References: <18496@agate.BERKELEY.EDU> Reply-To: jbn@glacier.UUCP (John B. Nagle) The simple, cheap solution to connecting thin to thick Ethernet is just to get the appropriate connector hardware. Thick Ethernet uses what are called "UHF" connectors, and thin Ethernet uses "BNC connectors." Adapters are available for under $10. See a Newark, Zack, or Arrow catalog for details. I've actually used such conversions, and couldn't see an impedance mismatch at the connector when examining the cabling with a TDR. Sharp bends (4" radius) in the thick Ethernet cable cause more reflections than a thick/thin transition. Remember how you hook it up. BNC T-connector on the back of the machine, two thin Ethernet cables to the place where you reach the big cable, two adapters to convert to thick Ethernet. Never put a section of thin Ethernet between the machine and the T-connector; the short arm of the T can't be more than a few inches before everything stops working due to reflections. John Nagle >From: kchen@Apple.COM (Kok Chen) Newsgroups: comp.sys.next Subject: Re: Followup to Who Has One? Message-ID: <22678@apple.Apple.COM> Date: 22 Dec 88 02:31:10 GMT References: <18496@agate.BERKELEY.EDU> <17916@glacier.STANFORD.EDU> Organization: Apple Computer Inc, Cupertino, CA In article <17916@glacier.STANFORD.EDU> jbn@glacier.UUCP (John B. Nagle) writes: > The simple, cheap solution to connecting thin to thick Ethernet is >just to get the appropriate connector hardware. Thick Ethernet uses what >are called "UHF" connectors, and thin Ethernet uses "BNC connectors." >Adapters are available for under $10. See a Newark, Zack, or Arrow >catalog for details. No, no. You want to use a "Type-N" connector, not a "UHF connector" for thick Ethernet. There IS such a thing called the "UHF connector," but that is NOT what you will find normally used on Ethernets. Those ancient enough may remember using the Tektronix 503 oscilloscope in undergrad labs (they were popular in the '60's). THOSE animals used UHF connectors. A "type-N" is VERY different, and definitely will not mate with a UHF type. Kok Chen {decwrl,sun}!apple!kchen Apple Computer, Inc. P.S. Someone (a Harvard prof., no less [but Physics, not EE :-) ] ) once claimed to me that BNC (the connector used in thin-Ethernets) stood for "Baby N-Connector." Said person is also author of the "The Art of Electronics" book you see in bookstores and once (40+ years ago :-) held the record for being the youngest amateur radio operator in W-land, so he may be right. (I doubt it, Paul :-) :-)) >From: gore@eecs.nwu.edu (Jacob Gore) Newsgroups: comp.sys.next Subject: Re: Followup to Who Has One? Message-ID: <12670010@eecs.nwu.edu> Date: 22 Dec 88 04:02:26 GMT Organization: Northwestern U, Evanston IL, USA / comp.sys.next / jbn@glacier.STANFORD.EDU (John B. Nagle) / Dec 21, 1988 / >BNC T-connector on the back of the >machine, two thin Ethernet cables to the place where you reach the big >cable, two adapters to convert to thick Ethernet. Just to make sure I understand you correctly: are you actually splicing a piece of thin Ethernet into a thick Ethernet? Jacob Gore Gore@EECS.NWU.Edu Northwestern Univ., EECS Dept. {oddjob,gargoyle,att}!nucsrl!gore >From: jbn@glacier.STANFORD.EDU (John B. Nagle) Newsgroups: comp.sys.next Subject: Re: thin/thick Ethernet Message-ID: <17925@glacier.STANFORD.EDU> Date: 22 Dec 88 18:08:22 GMT References: <18496@agate.BERKELEY.EDU> <12670010@eecs.nwu.edu> Reply-To: jbn@glacier.UUCP (John B. Nagle) Organization: Stanford University Lines: 26 In article <12670010@eecs.nwu.edu> gore@eecs.nwu.edu (Jacob Gore) writes: >Just to make sure I understand you correctly: are you actually splicing >a piece of thin Ethernet into a thick Ethernet? Yes. It works. Loss per unit length is higher in the thin cable, but unless you are pushing the length limits of the Ethernet cable, adding a few feet of thin cable isn't that important. You might think that the transition would produce reflections, but my experience is that it doesn't. Find a TDR and check for yourself. If you have a farm of NeXT machines or other small machines with thin Ethernet connectors, it might be better to tie them all together on thin cable and only have one thick/thin transition. But this is not mandatory. Always check the machines at the ends of the cable for high retransmit rates. This is the first symptom of excessive losses, and indicates that collisions are being undetected due to cumulative loss in the cable. This means the cable is too long, or too lossy; time to get out a TDR or put a repeater in the middle. If your thick/thin mixed cable falls within the length limitations for thin Ethernets, everything should work fine. Only beyond that length should it be necessary to worry much about the electrical properties of the cabling. John Nagle >From: gore@eecs.nwu.edu (Jacob Gore) Newsgroups: comp.sys.next Subject: Re: Re: thin/thick Ethernet Message-ID: <12670012@eecs.nwu.edu> Date: 22 Dec 88 21:29:25 GMT References: <17925@glacier.STANFORD.EDU> Organization: Northwestern U, Evanston IL, USA Lines: 23 / comp.sys.next / jbn@glacier.STANFORD.EDU (John B. Nagle) / Dec 22, 1988 / > In article <12670010@eecs.nwu.edu> gore@eecs.nwu.edu (Jacob Gore) writes: > >Just to make sure I understand you correctly: are you actually splicing > >a piece of thin Ethernet into a thick Ethernet? > > Yes. It works. Oh, I'm not surprised that it works. It just struck me as a rather inconvenient thing to do. When we have several thin-connector machines near each other, we do connect them all with thin-net, as you suggested. Except that our thick-cable networks are usually large-spread nets, with multi-user hosts on them as well as scattered workstations. We just don't like splicing into that net, even for inline transceivers. We use thick/thin repeaters for this kind of stuff. A repeater with one thick port and one thin port plus its transceiver and drop cable (for the think side) cost us about $1,000. If you are putting 5 or more stations on the thin side, the cost is quite reasonable. But for a single workstation, it's rather steep... Jacob Gore Gore@EECS.NWU.Edu Northwestern Univ., EECS Dept. {oddjob,gargoyle,att}!nucsrl!gore >From: jbn@glacier.STANFORD.EDU (John B. Nagle) Newsgroups: comp.sys.next Subject: Re: Re: thin/thick Ethernet Message-ID: <17934@glacier.STANFORD.EDU> Date: 23 Dec 88 17:01:57 GMT References: <17925@glacier.STANFORD.EDU> <12670012@eecs.nwu.edu> Reply-To: jbn@glacier.UUCP (John B. Nagle) Organization: Stanford University Lines: 12 I certaintly agree that a repeater to isolate important multi-user systems and servers from farms of little machines where the cables are accessable to many people is a valuable addition to a network. I was merely pointing out that thich/thin Ethernet transitions are not difficult to accomplish, should one wish to do so. Some people have found repeaters, as an active device and a single point of failure, to cause more trouble than they prevent. But that information is a few years old, and repeaters may be more reliable now. John Nagle