Can ethernet use branched cable?

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4 total messages Started by Roy Smith Thu, 20 Feb 1986 01:09

#959

Author: Roy Smith
Date: Thu, 20 Feb 1986 01:09

23 lines
1741 bytes

        Is there any reason why an ethernet (thin or thick) cable can't be
branched?  All the diagrams I see only show linear layouts with taps off
the main line.  Will the following work?  We plan on some extra runs that
don't have anything on them (yet); thus the branch with just a terminator.
Assuming these branches are legal at all, should the ends have just dust
caps instead of terminators?

        *=======T========T===========T============X======X====*
                |        |           |            #      #
          3/50--+        *           +---3/50    etc     #
                |             3/50---+                   #
                +---3/50             +---3/50          3/180
                |                    |
                *                    *

   Key:  *  50-Ohm terminator            +  BNC-tee connector
         =  Thick cable                  |  Thin cable
         X  Ethernet tranceiver          T  N-tee connector with BNC adapter
-- 
Roy Smith, {allegra,philabs}!phri!roy
System Administrator, Public Health Research Institute
455 First Avenue, New York, NY 10016

Re: Can ethernet use branched cable?

#978

Author: carl
Date: Fri, 21 Feb 1986 17:16

11 lines
1009 bytes

>         Is there any reason why an ethernet (thin or thick) cable can't be
> branched?  All the diagrams I see only show linear layouts with taps off
> the main line.  Will the following work?

From my experience you will definitely get hosed if you try to tee a cable
without using a repeater.  It *might* work, but unreliably.  You definitely
want to use a repeater or other alternative.

Carl Dierschow
Hewlett-Packard Colorado Networks Division
{ihnp4|hplabs}!hpfcla!hpcnof!c_dierschow

Re: Can ethernet use branched cable?

#964

Author: Skip Addison Jr
Date: Fri, 21 Feb 1986 17:16

16 lines
1353 bytes

In article <2239@phri.UUCP> roy@phri.UUCP (Roy Smith) writes:
>
>        Is there any reason why an ethernet (thin or thick) cable can't be
>branched?  All the diagrams I see only show linear layouts with taps off
> ...

Yes, there is a reason why that won't work, in general.  Just about anything
can work, as those of the bubble-gum and bailing wire school of thought so
often discover.  But branching an Ethernet will not work reliably in general.

The reason has to do with transmission line theory, maxwell's equations, or
the law of parallel resistors :-), depending on your persuasion.  Basically,
the cable needs to appear to be one continuous length of cable.

-- Skip Addison
   {lll-crg, decwrl, ihnp4}!amdcad!cae780!ubvax!skip

Re: Can ethernet use branched cable?

#977

Author: Andre Hut
Date: Sat, 01 Mar 1986 23:23

28 lines
2061 bytes

In article <454@ubvax.UUCP> skip@ubvax.UUCP (Skip Addison Jr) writes:
>In article <2239@phri.UUCP> roy@phri.UUCP (Roy Smith) writes:
>>        Is there any reason why an ethernet (thin or thick) cable can't be
>>branched?  All the diagrams I see only show linear layouts with taps off
>> ...
>Yes, there is a reason why that won't work, in general.  Just about anything
>can work, as those of the bubble-gum and bailing wire school of thought so
>often discover.  But branching an Ethernet will not work reliably in general.
>
>The reason has to do with transmission line theory, maxwell's equations, or
>the law of parallel resistors :-), depending on your persuasion.  Basically,
>the cable needs to appear to be one continuous length of cable.

Sorry Skip, that is wrong.  The only rule is that there can not be more than
two paths between any two stations.  Each branch must also be terminated.
-- 
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