> 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.

For a great overview of switches go to http://www.techonline.com. TTYL

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