17

This seems like a simple question, but I can't find a definitive answer for it. I have four devices connected to a Gigabit switch as in this diagram:

enter image description here

Can I get the full GBit bandwidth from A-B simultaneously as C-D are maxing out their link? Or, in general, do they "share" the bandwidth through the switch?

Kristian
  • 3,130
Sam
  • 173

1 Answers1

13

With a well-designed Ethernet switch, it's possible to get the full port speed into each port and the full port speed out each port, all simultaneously (switch ports are full-duplex).

A switch designed to guarantee it can do this will be marketed has having an aggregate throughput of:

2 * (#-of-ports) * (speed-per-port)

This is sort of double-counting because the data going out any given port must have come in some other port, but this double-counting has become a de facto industry standard marketing practice.

So in your example of a 4-port Gigabit Ethernet switch, it would be marketed as having 8Gbps of bandwidth.

Unfortunately, it wouldn't surprise me if most 4-8 port GigE switches are cheap consumer crap that can't do that and thus wouldn't be marketed as such.

Spiff
  • 110,156