The Internet

Think of it as the phone system for computers.

• Every computer has an address (phone number).
• The network infrastructure connects one computer to another, given its address (like dialing the phone).
• You don't have to worry about how the connection is made, nor about the physical location of the other computer. (You can call your neighbor, or you can call Japan.)
• If two computers don't agree on the communication protocol , nothing useful will happen. (You can call Japan, but if you don't speak Japanese...)

But most people think of the services provided on top of the basic infrastructure.

• E-mail
• Remote login
• File transfer (FTP)
• Bulletin boards / Usenet
• The World-Wide Web

Accessing the Internet

How do you "get on" the internet?

Via an Internet provider.

Type of provider:

• "Full service:" America Online, Compuserve, Microsoft Network, etc.
• You use connection and user-interface software provided by them.
• Easy, but lacks flexibility.
• Also have their own services.
• "Self service:" Independent service provider
• They may provide connection software.
• You can use any user-interface software (e.g., Netscape web browser).
• May or may not provide services other than connection and e-mail.
• Usually takes some work to set up.
• Harder, but more flexible.
• May be cheaper (e.g., flat-rate vs per-hour).

• Modem: you dial into your service provider using your telephone.
• Speeds currently limited to about 5,000 bytes/sec or less (using 28.8kbps modem).
• Relatively cheap
• No special wiring needed
• Supported by all service providers
• ISDN: high-speed digital connection over a special phone line.
• Speeds can be up to about 20,000 bytes/sec.
• Expensive to install, requires special "modem" costing hundreds of $. About $30/mo in Ann Arbor.
• Can use it as a voice line, too.
• Your service provider must support it.
• T1 and higher: very high speed connection over a dedicated line.
• Very high speeds: T1 up to about 120,000 bytes/sec, T3 is 40x that.
• Very expensive.
• Permanently connected.
• Your service provider probably has this sort of connection to the internet. T3 links form the "backbone" of the internet.