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On a typical network switch each port runs at a designed maximum speed, eg: 100Mb/s
But is there a limit to the maximum transfer rate between all ports of the switch at a given time?
I am guessing that all the data has to go through a single processor, and probably some kind of physical data bus inside the switch (connecting each interface to the processor).

Consider the following scenario:
Say i have an 8-port 100Mb/s switch, ie: each port has a maximum speed of 100Mbits / second.
I am transferring between ports 1 and 2 a negligibly large amount of data.
At the same time i am transferring between ports 3 and 4 a large amount of data.
And likewise between ports 5-6, and 7-8. So each transfer is essentially independent and does not share ports or cables with another transfer - the only common feature is that they are running through different ports on the same switch.

Will all of these transfers each be able to run simultaneously at the full 100Mb/s?
Or will the total transfer rate through the switch be limited to 100Mb/s (ie: each transfer would be limited to roughly 25Mb/s)? Or is the total limited to some other figure determined by the design? And what is this figure/specification called?

Thanks :)

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PS: I happen to have used (mega)bits in my example rather than (mega)bytes - i am aware of the difference. I am concerned with the maximum capacity of the switch as a whole. –  samjetski Jul 2 '11 at 13:35
    
A Router is not a Switch. –  Turbo J Jul 3 '11 at 9:58
    
Sorry, typo. Fixed –  samjetski Jul 7 '11 at 2:37
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1 Answer

up vote 1 down vote accepted

You want to look at the Backplane Speed in the datasheets of the switch. If its 100MBps, from this century and has <=8 Ports, then it will have fully meshed capability - all ports can run at full speed simultanously.

With more Ports or Gigabit speed there might be a limit in the back plane of the switch.

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Backplane Speed - thanks :) –  samjetski Jul 7 '11 at 2:38
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