Apple AirPort Networks - Manual (Page 59)

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Behind the Scenes
This chapter defines terms and concepts used to discuss
computer networks. Use it as a reference to help you
understand what is taking place behind the scenes of your
AirPort wireless network.
Basic Networking
Packets and Traffic
Information travels across a network in chunks called packets. Each packet has a
header that tells where the packet is from and where it’s going, like the address on
the envelope when you send a letter. The flow of all these packets on the network
is called traffic.
How Information Reaches Its Destination
Hardware Addresses
Your computer “listens” to all of the traffic on its local network and selects the
packets that belong to it by checking for its hardware address (also called the media
access control, or MAC address) in the packet header. This address is a number unique
to your computer.
Every hardware product used for networking is required to have a unique hardware
address permanently embedded in it. Your AirPort Card’s number is called the
AirPort ID.
IP Addresses
Since the Internet is a network of networks (connecting millions of computers),
hardware addresses alone are not enough to deliver information on the Internet. It
would be impossible for your computer to find its packets in all the world’s network
traffic, and impossible for the Internet to move all traffic to every network.