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
But most people think of the services provided on top of the
- Remote login
- File transfer (FTP)
- Bulletin boards / Usenet
- The World-Wide Web
Accessing the Internet
How do you "get on" the internet?
Type of provider:
- "Full service:" America Online, Compuserve, Microsoft Network,
- 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).
Type of connection:
- Modem: you dial into your service provider using your telephone.
- Speeds currently limited to about 5,000 bytes/sec or less (using 28.8kbps
- 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.