Apple AirPort Networks User Manual download pdf (Page 54)

54 Chapter 4

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.

So your computer also has an IP (Internet Protocol) address that deﬁnes exactly where and

in what network it’s located. IP addresses ensure that your local Ethernet network only

receives the trafﬁc intended for it. Like the hierarchical system used to deﬁne zip codes,

street names, and street numbers, IP addresses are created according to a set of rules, and

their assignment is carefully administered.

The hardware address is like your name; it uniquely and permanently identiﬁes you. But it

doesn’t offer any clues about your location, so it’s only helpful in a local setting. An IP

address is like your street address, which contains the information that helps letters and

packages ﬁnd your house.

Rules for Sending Information (Protocols)

A protocol is a set of rules that deﬁne how communication takes place. For instance, a

networking protocol may deﬁne how information is formatted and addressed, just as there’s

a standard way to address an envelope when you send a letter.

Important Networking Devices

Bridges

A bridge joins two networks at the hardware level. Other protocols see the two networks as

the same.

Routers

A router connects two IP networks. In contrast to a bridge, which joins networks at the

hardware level, a router directs network IP trafﬁc based on information stored in its routing

tables. A routing table matches IP addresses with hardware addresses. The router stamps

each incoming IP packet with the hardware address that corresponds to that IP address. As a

result, the packet can be picked up by the right computer on the hardware network.

DNS (Domain Name Server)

Networks (domains) on the Internet have names that correspond to their IP addresses. A

Domain Name Server maintains a list of domain names and their corresponding addresses. That

is why you can go to the Apple website by typing www.apple.com instead of the IP address.

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Apple AirPort Networks User Manual Page 54