when Host A on port 1 needs to transmit to Host B on port 2, the LAN switch forwards frames from port 1 to port 2, thus sparing other hosts on port 3 from responding to frames destined for Host B. If Host C needs to send data to Host D at the same time that Host A sends data to Host B, it can do so because the LAN switch forwards frames from port 3 to port 4 at the same time it forwards frames from port 1 to port 2.