Switch
Like a hub, a switch connects multiple segments of a network together, with one important difference. Whereas a hub sends out anything it receives on one port to all the others, a switch recognizes frame boundaries and pays attention to the destination MAC address of the incoming frame as well as the port on which it was received. If the destination is known to be on a different
port than the port over which the frame was received, the switch will forward the frame out over only the port on which the destination exists. Otherwise, the frame is silently discarded.
If the location of the destination is unknown, then the switch acts much like a hub in that it floods the frame out every port, except for the port over which it was received, unlike a hub. The only way any party not involved in that communication will receive the transmission is if it shares a port with the transmitter or receiver of the frame. This can occur if a hub is attached to the switch port, instead of in a 1:1 relationship of end devices and switch ports. The
benefit of a switch over a hub is that the switch increases performance because it is able to support full wire speed on each and every port with a nonblocking backplane, meaning the electronics inside the switch are at least equivalent in speed to the sum of the speeds of all ports.
Example:
Switch
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