[Sussex] Re: Sourcing list of hardware

[Steven Dobson]

Fay

On Tue, 2006-10-24 at 20:36 +0100, Fay Zee wrote:
> Hi Dave,
> 
> On 20/10/06, David Chapman <dokterdave at ntlworld.com> wrote:
> > I have patch cables about 1m
> > And 2x 16 port 10bit hubs, not switches.
> > Think I have a router ?
> 
> Thanks for replying. I'm not yet totally clear about the difference
> between a hub and a switch, or which is best for this situation.

Hubs are dumb devices.  When one computer on a hub starts to "talk" a
hub echo that chatter to all the other computers connected to it.  As a
result, on a hub, only one computer can talk at any one time.

A switch is more intelligent.  If computer A wants to talk to computer B
then the switch will only send that message down the wire that computer
B is on.  This leaves the other wires free to allow computer C to talk
to computer D, E to F and so one.  All at the same time.

> It's a training courseroom with 12 student PCs, the tutor's two laptops, a
> firewall machine and a couple of servers. However, there are also 12
> free positions which need Internet connection occasionally.

As a rule of thumb switches are better than hubs and that is the case
here.  As you have two servers and a router a switch will allow
workstation 1 to talk with server A while workstation 2 talks with
servers B and workstation 3 talks to the router.

However, you will only notices slow network performance if you have a
lot of network traffic.  I can remember the old days (before switches
and hubs) when computers where networked using coaxial cable at 10Mbit
speeds - this is simular in characteristics to Dave's offer.  We ran
networks bigger than yours without a problem.  Of course the computers
were much slower than the ones available today, but it should work okay
for you.

The really cool think about hubs and switches is that you can mix and
match.  If you deploy Dave's network but find it too slow then you will
get an improvement if you just add a small (5 port) switch.  You plug
the the router, the servers and both hubs to the switch.  The
workstations divide between the two hubs.

The switch will then isolate the workstations pluged into one hub from
those pluged into the other.  Thus, a workstation of one hub can talk to
one server while a workstaion on the other hub talks to the other server
or the router - much better network utilisation.

Remember that the network usage of the machines is going to be very
different.  A workstation will only need to use the network when a slow
human's asks it to do something (like open/save a file on a server or
surf the Net).  The servers and router, however, have to use the network
as a responce to any of the requests from the workstation on the
network.  So it makes sence to plug higher network users into expensive
switches and lower use machines into the cheaper hubs.

When switches and hubs took over from coaxial cable the prices
difference between the two types ment that you did thinks like this.
These days switches are so cheap getting hold of hubs is rare. 

Hope this is clear.

See you Thursday
Steve

P.S.

Looking on dabs.com I see (all prices rounded up to the nearest pound):

   Edimax 5 port switch £9
   Edimax 8 port switch £11  <-- The one we bought a while back
   Dynamode 8  port hub £18
   Belkin 5 port switch £19
   Belkin 8 port switch £24
   Edimax 16 port switch £25
   Edimax 24 port switch £45

So a full switch configureation could cost as little as £34 + cable
costs.  Although I would pay the extra and get the 24 port switch.

Ready made patch cables are not going to be cheap [dabs 25 meter are £15
each].  It would probably be cheaper to buy a 100m box of cat5e cable
[dabs £19] and the connectors [maplin £2.36 pack of ten] (you will need
spare connectors as you WILL make mistakes - I have the crimp tool).