[K12OSN] 100Mbit switch vs. 100Mbit hub

Rob Owens rowens at ptd.net
Mon Mar 19 22:47:18 UTC 2007

Thanks Olivier and Les.  I didn't know about the need for the receiver
to constantly send acknowlegments.


On Mon, Mar 19, 2007 at 10:24:13PM +0100, Olivier Mugnier wrote:
> On heavy traffic, the server talk a lot....
> But:
> There communication from the client to the server as well...
> Imagine that all your 20 client ask 1 questions to the servers...
> You are (with a Hub) saying to them: Wait a second to the first....
> Wait 2 second to the other one... and then wait 3,4,5,...
> And, 1 second latter, the first one try again... you're again telling him 
> wait
> a second....
> 1 Second latter, you have both 1 and 2 asking you... Since there are 2 at
> the same time, collision appear... And they will try again a bit latter....
> With a switch... You said nothing to them... you just take the packet in, 
> wait
> for the server to listen... and send it to the server (queuing)
> Much more efficient... (as in classroom, the first to ask, the first to 
> answers
> the second one wait until the first have finish his question, than the 
> third one...)
> So has the server on it side.... It will send data as much as he can... but 
> the switch
> will wait until he as finished talking to ask him something new...
> Slowing down the fill by queuing is more efficient than making all of them 
> talking as
> the same time...
> (As for car jame... better slowing down speed and be regular than going 
> fast on 30 feet
> then stop)
> ----- Original Message ----- 
> From: "Rob Owens" <rowens at ptd.net>
> To: <k12osn at redhat.com>
> Sent: Monday, March 19, 2007 10:06 PM
> Subject: [K12OSN] 100Mbit switch vs. 100Mbit hub
> >I've been on this list long enough that I've heard "use a switch, not a
> >hub" about a hundred times.  But I have a question about the reasoning:
> >
> >The server has the most traffic going to/from it.  So if you were using
> >a switch, the server port of the switch would be saturated first--as
> >soon as 100Mbit/sec is going to/from the server.  If
> >you instead used a hub, the only difference I see is that *all* of the
> >ports would saturate at the same time--as soon as 100Mbit/sec is going
> >to/from the server.
> >
> >Since there is no traffic going from one terminal
> >to another, it seems like a 100Mbit/sec hub would become a bottleneck at
> >the same time that a 100Mbit/sec switch would.  What am I missing?
> >
> >-Rob
> >
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> >
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