Introduction to the Structure and Organization of the Internet

What is the Internet?

Networks
Servers
Clients
FTP, Telnet, Email, IRC, Newsgroups, etc.

What is an Intranet?

The same as above, but restricted to a certain area or group. Thus, a bank might have a corporate Intranet, where employees can use their Web browsers to look up internal information. The rest of us non-bankers cannot access that private network. Usually, corporate Intranets are supported by LANs and WANs- Large and Wide Area Networks, not the Internet at large.

IP Addresses

IP = "Internet Protocol"

a set of rules that everyone follows so that email and Web pages get sent and received without communications breakdowns / failures.
every computer must be running a copy of IP to be connected to the Net.
every computer, or host, connected to the Net has a unique IP address. For example: 206.246.150.10
no two computers may be using the same IP address at the same time.

DNS- The Domain Name Service

IP addresses are the only way to specify a host. Because those number sets are so hard to remember, we use DNS- a mechanism that maps host names to IP addresses.

So, instead of http://206.246.150.10, we type in http://www.sony.com

when you specify a destination address of www.sony.com, your browser sends and address resolution request to a DNS server asking for the IP address of that host.
Therefore, DNS is never necessary.

But,

IP addresses are hard to remember, and-
IP addresses are subject to change- for example, when you switch your Web pages to another ISP (Internet Service Provider), but your host name of www.mememe.com stays the same
a single host, with a single IP address can have several DNS names- usually referred to as Virtual Hosting

The World Wide Web

The graphical "layer" of the Internet, the Web is built on HTTP- another Internet protocol. This one stands for HyperText Transfer Protocol. It is well suited for distributing multimedia and for hypertext jumps between sites. The Web is essentially a distributed multimedia system.

So, what is Hypertext?

Distributed Multimedia? Like... graphics, sound, and video?

The Web as a system does not require the Internet. Why not?

On to the WEB!