Java Network Programming, Second Edition

The Internet

The Internet is the world’s largest IP-based network. It is an amorphous group of computers in many different countries on all seven continents (Antarctica included) that talk to each other using the IP protocol. Each computer on the Internet has at least one unique IP address by which it can be identified. Most of them also have at least one name that maps to that IP address. The Internet is not owned by anyone, though pieces of it are. It is not governed by anyone, which is not to say that some governments don’t try. It is simply a very large collection of computers that have agreed to talk to each other in a standard way.

The Internet is not the only IP-based network, but it is the largest one. Other IP networks are called internets with a little i: for example, a corporate IP network that is not connected to the Internet. Intranet is a current buzzword that loosely describes corporate practices of putting lots of data on internal web servers. Since web browsers use IP, most intranets do too (though a few tunnel it through existing AppleTalk or IPX installations).

Almost certainly the internet that you’ll be using is the Internet. To make sure that hosts on different networks on the Internet can communicate with each other, a few rules need to be followed that don’t apply to purely internal internets. The most important rules deal with the assignment of addresses to different organizations, companies, and individuals. If everyone picked the Internet addresses she ...