Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!unmvax!nmt.edu!nraoaoc
From: rmilner@zia.aoc.nrao.edu (Ruth Milner)
Newsgroups: comp.dcom.lans
Subject: Re: how to connect thin wire segements to thick wire backbone
Message-ID: <1991May20.174447.2310@nmt.edu>
Date: 20 May 91 17:44:47 GMT
References: <3021@kirk.nmg.bu.oz.au> <1991May15.195831.16169@nmt.edu> <1991May18.231445.18574@bitcave.in-berlin.de>
Reply-To: rmilner@zia.aoc.nrao.edu (Ruth Milner)
Organization: National Radio Astronomy Observatory, Socorro NM
Lines: 56

In article <1991May18.231445.18574@bitcave.in-berlin.de> cosheff@bitcave.in-berlin.de (Charles O. Shefflette) writes:
>rmilner@zia.aoc.nrao.edu (Ruth Milner) writes:
>
>>In article <3021@kirk.nmg.bu.oz.au> bambi@kirk.nmg.bu.oz.au (David J. Hughes) writes:
>>>From article <1991May13.170657.4786@zoo.toronto.edu>, by henry@zoo.toronto.edu (Henry Spencer):
>>>> The only way to hook cables
>>>> together at other than their ends is with a repeater of some flavor.
>>>
>>>Correct yet not correct.  
>>>The Star configuration is maintained by a Multi-Port repeater 
>>                                           ^^^^^^^^^^^^^^^^^^^
>>How does this differ from what Henry said?
>>The point is, you can't hook all the cables together without a box somewhere 
>>in between. 
>
>Well, that isn't exactly true, either.  According to the 3COM and to the
>Cabletron manuals we have, the only thing you really have to do to
>connect thin- and thick-wire ethernet together is to use the appropriate
>adapter connector between them.

Sure - *at the ends of the cable*. Not in the middle.

That's precisely what was said to start with (see above - note the phrase
"at other than their ends"). 

>#=======#=============#    #==============#========#========#=====
>|       |             |    |              |        |        |
>Server  |             Fiber             Repeater Repeater  Repeater
>     Repeater                             |        |        |
>        |                                 |        |        |
>========#===-------                    ===#==    ==#===   ==#===
           ^^^^^

The only piece of thinwire shown here is connected at the *end* of a piece 
of thickwire.

Summary: At each end of the cable, you can connect a single cable with the
         appropriate adapter - provided you don't exceed length/connection
         specs.

         If, however, you need to make a connection in the middle of the
         thick cable, or you need to connect more than one piece of the other
         cable (like a Y or a star), or you will be exceeding specs, you 
         *have* to have a box in between. 

This is all dictated by the fact that Ethernet is a multidrop topology, not a 
star or branch. Pure cable can only be linear.

From what I recall of the original poster's situation, he has several floors 
spanned by a vertical thickwire. So it stands to reason that he is not going 
to be able to connect all of those floors by thinwire at the ends of the 
thickwire. Therefore, he *must* put something in between. Period.
-- 
Ruth Milner
Systems Manager                     NRAO/VLA                    Socorro NM
Computing Division Head      rmilner@zia.aoc.nrao.edu