At 05:22 PM 07/27/2000 , you wrote:
> > Anyway...  switches are only necessary if you have PCs on the network with
> > different speed network cards, a hub will do fine if they all
> > have the same speed
> > card.
>
>         I was under the impression that a switch was more than just a speed sensor.
>A switch, as it is my understanding, gains knowledge of the physical address
>of the NICs on each port. On receipt of a packet a switch analyses the
>destination address and transfers the packet to the port where that NIC can
>be found. A hub on the other hand just transmits everything it hears to
>every port. A switch GREATLY reduces the number of collisions on a network.
>Basically there are two major types of switches, cut-through and 'store and
>forward'.
>
>Cut-through switches only look at the destination address and transfer the
>packet based on that address, they don't check the packet for correct size
>or CRC. However these types have very low latencies, barely slower than a
>dumb hub.
>
>Store and forward switches suck in the whole packet and make sure it is
>valid, they then forward the packet to the appropriate port. These types of
>switches have relatively high latencies but make up for it by reduced
>traffic and bandwidth needs.
>
>There are a few other types of switches but they are just combinations of
>the above two, a "best of both worlds" concept.


Yes, you are right that more goes on than I had originally stated, but
for the basis of explaining the difference, getting into the technicalities
of advanced networking only confuses the issue of deciding on the differences
for a basic network.  The same can be said for switching hubs vs. switches,
though actual switching hubs are seldom seen any more, there is a difference.
I was ably reminded by Mark Rode, that I was over simplifying again, especially
in this matter.  But, when you head out to buy something to connect between
PCs on a network today, you usually find Hubs, Switches and Routers...  hence
my simplification.

I know that we have a great many people here on PCBUILD that are professionals
in the PC industry, with advanced knowledge of all phases of PCs, which can
tend to turn our discussion deep into the technical aspects.  But, we should
also remember that the majority of our readers are either beginners to
intermediate users.  Often we become too deeply stressed on the technical
and lose them in the discussion.  Currently, we lose an average of about
30% of all new subscribers due to this...   hence, my usual attempt to keep
explanations basic and simple.  I try to allow everyone to keep track...

We are here to help...  if we lose our readers by dazzling them with our
knowledge...   are we really helping them???   This is not a criticism....  only
something to consider.

      Bob Wright
The NOSPIN Group

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