D&C GLug - Home Page

[ Date Index ] [ Thread Index ] [ <= Previous by date / thread ] [ Next by date / thread => ]

Re: [LUG] Ethernet hub recommendation

 

On Sat, 10 Mar 2007 15:07:41 +0000
"Richard Brown" wrote:

> Does it make a difference depending on connection speeds. There is a
> difference between a hub and a switch. What speeds are your network
> cards as well? 10/100 I wouldn't worry but if you have a 1000 then it
> could make a difference. Just thought I would add these thoughts and I
> don't suppose with two computers networked together it makes a whole
> lot of difference.

As a point of interest (well, to me)... you *cannot* have a gigabit
ethernet hub.  Gigabit over copper *must* use switches.  10mbps and
100mbps both support "half duplex" (why it's not called simplex, I do
not know) communication where they can either talk, or listen, but do
both simultaneously.  For "full duplex" communication, the network
devices are both talking and listening simultaneously, so in effect a
100mbps connection running at full duplex actually provides you with
200mbps bidirectional throughput.  Gigabit ethernet, however, *must*
operate at full duplex in order to reach the magic 1000mbps speed.
Indeed, where-as on 10/100 networks using Cat5(e) only 2 pairs of
cables are used, with 1000mbps networks all 4 pairs are being used
simultaneously, in both directions.  Each pair of cables on Cat5e has a
(current) maximum potential throughput of 125mbps (apparently); 4 pairs
of cables @ 125mbps/pair = 500mbps; 500mbps in both directions
simultaneously = 1000mbps.  Hubs do not support full duplex,
whereas switches do; gigabit must use full duplex therefore gigabit
cannot use hubs.

--Grant

-- 
The Mailing List for the Devon & Cornwall LUG
http://mailman.dclug.org.uk/listinfo/list
FAQ: http://www.dcglug.org.uk/linux_adm/list-faq.html