Switch Avoids Collisions by Buffering the Frames

So, the litany of switch logic now reads like this:

• When receiving a frame, examine the destination Ethernet address. Forward the frame out the one portand only that portthrough which that address can be reached.

• If multiple frames need to be sent out the same port, send one frame and buffer the rest, sending them when the port becomes available.

By buffering frames, switches do not create collisions. The original frames make it across the LAN with minimal buffering delay. For instance, if those three frames were each 1250 bytes long, it would only take 3 milliseconds (.003 seconds) for all three to be sent over the cable from the switch to Fred. If collisions had occurred, each frame would have taken longer to reach Fred, and both the collision and the time taken to resend the frames could have prevented other user traffic from crossing the LAN. So, the buffering of frames definitely improves LAN performance.