kent@tfd.UUCP (Kent Hauser) (10/24/89)
Beginners question: How do you physically hook up a thinnet?
Specifically, how do you handle multiple BNC `T' connections.
1) Is it a bad idea to use a, say, 5-foot drop cable from the `T' to
the host?
2) Can you hang multiple hosts off in all directions from a `T'?
3) Does the cabling have to be a multiple of some magic length?
4) How can you test your network to see if you screwed something up?
5) Or, if you've only got 6 hosts & a couple of hundred feet of RG-58,
does it really not matter to much?
Now the $64k question: Is there a good reference for this kind of
info.
Thanks much in advance.
Kent
--
Kent Hauser UUCP: {uunet!cucstud, sun!sundc}!tfd!kent
Twenty-First Designs INET: sundc!tfd!kent@sun.comstev@VAX.FTP.COM (Stev Knowles) (10/24/89)
*Beginners question: How do you physically hook up a thinnet?
*Specifically, how do you handle multiple BNC `T' connections.
*
*1) Is it a bad idea to use a, say, 5-foot drop cable from the `T' to
*the host?
yes.
*2) Can you hang multiple hosts off in all directions from a `T'?
no. a T connector is intended to connect one "device" to the
network. this device can be a tranciever fan out box, though
(i am refering to qa DELNI type device here.)
*3) Does the cabling have to be a multiple of some magic length?
idealy. it is sold in pre made magic lengths. we wired some thin net
into the walls here, and did not worry abotu magic lenghts.
*4) How can you test your network to see if you screwed something up?
as you construct each run, test the cable with an ohm meter. you can
also place a machine at one end, and ping it from each drop as you add them.
*
*5) Or, if you've only got 6 hosts & a couple of hundred feet of RG-58,
*does it really not matter to much?
it does not matter that much, but remember, few LANS stay that trival.
it is worth investing in doing it correctly now so you dont have to
fix it later, when it may not be as convienent.
*
*Now the $64k question: Is there a good reference for this kind of
*info.
not that i have found, although most vendors of fan out boxes and
bridges take a shot at it. most of the information conflicts though .
. .
*
*Kent Hauser UUCP: {uunet!cucstud, sun!sundc}!tfd!kent
*Twenty-First Designs INET: sundc!tfd!kent@sun.com
stev knowles
ftp software
stev@ftp.comMAP@LCS.MIT.EDU (Michael A. Patton) (10/25/89)
Date: 23 Oct 89 20:08:55 GMT From: cucstud!tfd!kent@uunet.uu.net (Kent Hauser) Beginners question: How do you physically hook up a thinnet? Specifically, how do you handle multiple BNC `T' connections. 1) Is it a bad idea to use a, say, 5-foot drop cable from the `T' to the host? Extremely bad! There should be NO drop cable, the T connector goes right on the machine. Ethernet is a bus network, any stubs from the main run need to be as small as possible, much more than an inch (including what's inside the machine, typically around 3/4 of an inch) is probably pushing it for thin-wire Ethernet, the thick-wire spec is a little more sensitive which is why it allows longer runs and more hosts. 2) Can you hang multiple hosts off in all directions from a `T'? No, for the same reasons, there should be a T on each host and they should be connected end-to-end, no T except at a host. 3) Does the cabling have to be a multiple of some magic length? No, but there is a minimum spacing which I can't recall right now (the people who we have making cables just don't make any shorter than this). In practice this seldom comes into play on a thin-wire, you probably don't want two machines that close anyway. On thick-wire the cable is marked with stripes at this spacing the idea being that if you only insert transceivers at the stripes they can't be closer than the minimum spacing. Some people have extrapolated from this technique to deduce that they need to be on a regular pattern, this is not true. 4) How can you test your network to see if you screwed something up? Try operating it and see if it works :-). I don't think there is any way, after the fact, to determine that some entire installation meets the specs. The only way to determine this is by carefully observing the installation and seeing that it's done right. The technique I use is to continually remind the people who install our cable about the things not to do. Whenever someone posts a message to any list I read with rights and wrongs of Ethernet installation, I forward them a copy (and they'll probably get this one when it comes back). The one technology that might be useful for after the fact testing is a TDR, but for small installation (like you seem to be talking about below), this might increase the cost of your network by an unacceptable amount. 5) Or, if you've only got 6 hosts & a couple of hundred feet of RG-58, does it really not matter to much? Well, when your net is that small it may not matter. But your net won't stay small, and if you don't obey the rules from the start you will find someday that you add something in a legal fashion and the net breaks. Then your only choice is to pull it all out and start over, doing it right. Let me tell you, this can be quite painful. Now the $64k question: Is there a good reference for this kind of info. Gee, you found one I don't have a good answer to. I use lots of references, the most important being my experience and what I've learned talking to others (in forums like this and just standing around in the corridors at conventions :-). I've been hacking Ethernet (and Ethernet-like technologies) since the late 70's and haven't found the need recently of an overview book specifically oriented at Ethernet and I don't seem to have such in my collection. Thanks much in advance. Your welcome. I'm sorry about missing on your last question, hopefully someone else will chime in with some references. __ /| /| /| \ Michael A. Patton, Network Manager / | / | /_|__/ Laboratory for Computer Science / |/ |/ |atton Massachusetts Institute of Technology Disclaimer: The opinions expressed above are a figment of the phosphor on your screen and do not represent the views of MIT, LCS, or MAP. :-)
cutter@cutsys.UUCP (Bernie Hoffstadt) (10/27/89)
-------- In article <8910241805.AA26176@gaak.LCS.MIT.EDU> Michael A. Patton writes: >> >> Now the $64k question: Is there a good reference for this kind of >> info. > >Gee, you found one I don't have a good answer to. I use lots of >references, the most important being my experience and what I've >learned talking to others (in forums like this and just standing >around in the corridors at conventions :-). I've been hacking >Ethernet (and Ethernet-like technologies) since the late 70's and >haven't found the need recently of an overview book specifically >oriented at Ethernet and I don't seem to have such in my collection. > Seeing that this seems to be the question that no one else has been able to answer, maybe you should write one yourself -- there may be some money in it! :-) We have an installation much like Kent's, And I have had a few of the questions that he asked, but fortunately had no real problems with them (I stuck with what I *was* able to read about here and there). That is, until I started thinking about extending our net- work to the Sales building. It's currently confined to our Service building. We already have a bunch of (presumably twisted-pair, though I wouldn't swear to it -- looks like a gob of 22 guage solid wire packed into a sheath) phone wiring installed between the two buildings, only half of which is in use for the phones. I wanted to use this to make the link. I thought that I should be able to put a balun on an end machine in each building, and run the twisted pair between these. I purchased a couple of baluns from Altex electronics which a salesman told me were for thinnet->twisted pair, but they didn't work, not even for replacing a short section of thinnet that I knew was working. I suspect that the baluns were really for IBM networks (RG62, I think -- I've seen lots of these for the ~$6 I paid Altex) and for obvious reasons wouldn't work anyway. But since I haven't seen any manufacturer explicitly explicitly list this scheme as a workable configuration, I'm not even sure it can be done. A guy I talked to at Black Box in CA seemed to think so, and they DO have thinnet->twisted pair baluns. But these things are $75 a pop (probably the same thing as 3-com's "pair-tamers" @ $119), and the catalog still doesn't say I can do what I want to with these. Says you use them with repeaters... Well, what do you think? Would it work? Or do I need to buy a bunch more expensive hardware? In which case I'd save us money by digging a trench and burying some RG58. BTW, the length of cabling in the Service building runs about 150-200' end-to-end, and in Sales it will be about 100'. The distance between the two is about 150'. Thanks in advance for any advice you might offer! Bernie. -- Bernie Hoffstadt (503) 752-5929 * Internet: cutter%cutsys.UUCP@CS.ORST.EDU 1437 N.W. 9th st. -or- 753-1646 * -or- cutter@jacobs.CS.ORST.EDU Corvallis, Oregon 97330 **** UUCP: {tektronix,hp-pcd}!orstcs!cutsys!cutter
smb@ulysses.homer.nj.att.com (Steven M. Bellovin) (10/27/89)
In article <431@cutsys.UUCP>, cutter@cutsys.UUCP (Bernie Hoffstadt) writes: > That is, until I started thinking about extending our net- > work to the Sales building. It's currently confined to our Service > building. We already have a bunch of (presumably twisted-pair, > though I wouldn't swear to it -- looks like a gob of 22 guage solid > wire packed into a sheath) phone wiring installed between the two > buildings, only half of which is in use for the phones. I wanted to > use this to make the link. Well, you could use any of the 10BaseT (draft) twisted pair stuff, but -- if you're going between buildings I *very* strongly suggest that you use fiber. It's worth it for a variety of reasons, especially during thunderstormseason.
mcneill@eplrx7.uucp (Keith McNeill) (10/27/89)
From article <431@cutsys.UUCP>, by cutter@cutsys.UUCP (Bernie Hoffstadt): > -------- > In article <8910241805.AA26176@gaak.LCS.MIT.EDU> Michael A. Patton writes: >>> >>> Now the $64k question: Is there a good reference for this kind of >>> info. >> >>Gee, you found one I don't have a good answer to. I use lots of >>references, the most important being my experience and what I've >>learned talking to others (in forums like this and just standing >>around in the corridors at conventions :-). I've been hacking >>Ethernet (and Ethernet-like technologies) since the late 70's and >>haven't found the need recently of an overview book specifically >>oriented at Ethernet and I don't seem to have such in my collection. >> I've found that "Unix System Administation Handbook" by Evi Nemeth (ISBN #0-13-933441-6) a really good reference. It's mostly based on BSD unix. There is a large chapter on networking. Keith -- Keith D. McNeill | E.I. Du Pont de Nemours & Co. eplrx7!mcneill@uunet.uu.net | Engineering Physics Laboratory (302) 695-9353/7395 | P.O. Box 80357 | Wilmington, Delaware 19880-0357 -- The UUCP Mailer
pat@hprnd.HP.COM (Pat Thaler) (11/14/89)
> / hprnd:comp.protocols.tcp-ip / mas@bridge2.ESD.3Com.COM (Mike Smith) / 11:13 am Nov 3, 1989 / > In article <8910301951.AA28831@gaak.LCS.MIT.EDU> MAP@LCS.MIT.EDU (Michael A. Patton) writes: > >Date: 27 Oct 89 12:56:14 GMT > >From: eplrx7!mcneill@louie.udel.edu (Keith McNeill) > >Subject: Re: How do you string a thinnet? > >To: tcp-ip@nic.ddn.mil > > > >Bernie Hoffstadt <cutter@cutsys.UUCP> asked: > >Now the $64k question: Is there a good reference for this kind of info. > >---------------- > > THE book - > > ANSI/IEEE Standards for Local Area Networks: > > Carrier Sense Multiple Access with Collision Detection (CSMA/CD) > Access Method and Physical Layer Specifications (with supplements) > ISBN 1-55937-0130, SH12351 (1989) > Actually, the correct title is "Supplements to Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications." It is also refered to as IEEE Supplements to ISO 8892-3:1989 (ANSI/IEEE Std 802.3-1988). It only contains the supplements which are IEEE standards and not yet through the ISO standards process. 10BASE2 (aka thinLAN or thinnet) is now an ISO standard and has moved to ISO 8802-3 : 1989 (E) (ANSI/IEEE Std 802.3-1988) ISBN 1-55937-005-X, SH11726 So order this if you want 10BASE2. Note that section 9 in this book has been replaced by a new section 9 which is in the supplement. Section 9 up to 9.8 has been approved by ISO, but 9.9 on Fiber Optic Inter Repeater Links (FOIRL) is still going through ISO and therefore the whole repeater section was kept together in the supplement. > This includes 10Base2. Anything else is second hand information. > ---------- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Exactly. It would be nice if someone would produce a more tutorial explaination which was technically correct. Apparently, some of those currently available contain serious factual errors. Pat Thaler
MLESSINS@WAYNEST1.BITNET (02/09/90)
Thanks Brain....I mean Brian.....