Will a 60-foot run of CAT-5 ethernet cable work?

[James Knott]

Lennart Sorensen wrote:
> On Wed, May 12, 2010 at 07:36:45AM -0400, James Knott wrote:
>    
>> Dave Cramer wrote:
>>      
>>> Ethernet is spec'd well past 60 feet, something in the neighourhood of
>>> 1000 feet, so 60 should not bother it.
>>>        
>> It's 100M or 330' max over CAT 5 or 6.  The original 10base5, 10 Mbit
>> ethernet would go about 500M over coaxial cable (Thicknet).  Much
>> greater distances are possible with fibre.
>>      
> And 10base2 (the coax everyone actually used) was allowed 200m.  The base#
> indicated how long the cable run could be in hundreds of meters.
>
>    
Now, do you know the maximum distance allowed?  Many people confuse this 
with cable length.

Back in the days of coax or hubs, collisions were likely.  To properly 
handle collisions, they had to occur within 64 bytes or 512 bits.  This 
works out to about 50 uS (actually, 51.2).  That is also round trip 
time.  In 50 uS, light will travel 15 Km.  Divide by 2 for round trip = 
7.5 Km.  After allowing for cable velocity factor, you're down to about 
5 Km end to end.  Of course, repeaters etc. also consume time and reduce 
that distance, but it is reachable with fibre.  However all those 
concerns disappeared with full duplex switches, as collisions do not 
occur with them.
--
The Toronto Linux Users Group.      Meetings: http://gtalug.org/
TLUG requests: Linux topics, No HTML, wrap text below 80 columns
How to UNSUBSCRIBE: http://gtalug.org/wiki/Mailing_lists