Re: Why was the hub faster than the switch?

In article <2jPkf.1311$Of1.142@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Reed <reedh@xxxxxxx> wrote:

> f/fgeorge wrote:
> > On Sun, 04 Dec 2005 23:11:47 GMT, "RobW" <robwl-no-spam@xxxxxxxxx>
> > wrote:
> >
> >
> >>Could someone give me a technical reason why, when I connected a cable
> >>modem
> >>and three computers to a hub, it was faster than connecting a cable modem
> >>and three computers with a switch?
> >>
> >>I know that routers are the solution, but I am in a debate and am drawing
> >>on
> >>my past experience. For example, when using a packet sniffer, you want to
> >>be a part of the same collision an broadcast domain. You can do that with
> >>a
> >>hub, but you can't with a switch.
> >>
> >>It must be the same principle when you only have 2 or 3 computers on the
> >>same network and collisions are not a problem. Am I right and if I am,
> >>could someone explain why?
> >>
> >>TIA
> >>
> >
> > The switch should be faster. The switch directs the data to a specific
> > port while a hub makes all the lights blink when a data transfer is
> > underway because it is broadcasting to all of the ports. This slows
> > down data transfers.
> > go here for more info: http://www.darron.net/network/secondpage.html
> >
> What f/fgeorge says is true but not the whole story. All switches
> introduce some amount of throughput delay into the data transfer from
> input port to output port. The delay can be more or less depending on
> which class of switch; "store and forward", or "cut-through" is used.
>
> SF is worst because the complete incoming frame has to be received and
> "stored" in the switch before it is allowed to start being sent out the
> output port. This is primarily for error checking purposes.
>
> CT is faster because data starts being output as soon as switch has
> enough data to know which output port to send it to.

Does that mean that switches which support speed switching (e.g. 10/100
Mbps) will always store and forward when moving data between a 10 Mbps
port and a 100 Mbps port?

>
> The most common mis-understanding about switches vs hubs is that
> switches are not faster in all applications. The worst application is
> where several PCs are trying to access the same one target ( ie DSL
> modem) (many to one network). Hubs are actually faster here because they
> have no delay as above.
>
> Switches work best in applications where the PCs can access many targets
> in the local network(ie, DSL, file servers, networked printers, PC-PC
> transfer, etc) (any to any network)
>
> --reed

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