Apple AirPort Networks User Manual

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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.