Ethernet
and 802.3 LANs are broadcast networks. All
stations see all frames. Each station must examine every frame to
determine whether that station is a destination.
On an Ethernet network, when one device wants to send data to
another device, it can open a communication pathway to the other device by using its MAC
address. When a source device sends data out on a network, the data carries the MAC
address of its intended destination. As this data propagates along the
network media, the NIC in each device on the network checks to see if
its MAC address matches the physical destination address carried by
the data frame. If there is no match, the NIC discards the data frame.
As data travels along the wire, the NIC in each station
checks it. The NIC verifies the destination address in the frame header to determine if the packet is properly addressed.
When the data passes its destination station, the NIC
for that station makes a copy, takes the data out of the envelope and gives it to the
computer.
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