How your computer accesses resources on the Internet

This diagram shows a simplified version of the computer connections that you are likely to deal with at Cal Poly Pomona. All the light magenta lines represent Internet connections. Each computer graphic represents an actual computer, either a server of services such as email, PPPconnection, or databases, or a client for such services, such as a computer you might have at home or in your office or lab. There are other computers, such as routers and gateways, that are intentionally left off this diagram.

Cal Poly Pomona internet connections When you check your email from a computer at Cal Poly that is hooked up through a network card, the computer on your desk communicates directly (the connection marked 1) with the computer that gets your email, usually one of the OpenVMS systems ("Vaxes"). You can also connect to any other computer on the Internet (2), including the Library databases (3), where you have full access, since the computer you are using is part of the same domain (in this case,

When you dial in to Cal Poly using the PPP connection (4), you are connected to the PPP server, a computer that translates between your modem and phone line and the rest of the Internet. You can check your mail (5), access the rest of the Internet (6), and connect to the Library databases (7). This latter is possible because the PPP server is part of, as is your home computer when you connect through the Cal Poly PPP.

You may also have in independent Internet Service Provider (ISP) such as Cyberg8t or Earthlink. You can dial up and connect (8) just as you would to the Cal Poly PPP. When you are connected, you can get email from your ISP email account, or connect to any computer on the Internet (10). Although it is not widely known, you can also connect to your Cal Poly email through an independent ISP (9). (The method differs, depending on your email program.)

The problem comes when you try to connect to the Library databases (11), specifically the ones that are restricted to computers in the domain. Because you are connected through your ISP, your home computer is now part of,, or some other ISP domain, and you can no longer get access. Every other computer outside has the same problem (12).

You can also connect to the OpenVMS cluster by direct dialup (13), using a terminal program such as Kermit or Hyperterm. This is not a PPP connection; rather, your computer at home is acting as if it were a terminal for the OpenVMS cluster. You can use this connection to check your email using Pine or Mail, and you can connect to the World Wide Web (14) with Lynx, a non-graphic web browser. Since the OpenVMS cluster is part of (and your computer at home is merely a terminal for it), you can access the Library databases.

You can connect to the OpenVMS cluster in the same way through your ISP, using a telnet program: In essence, you are connecting to the Internet to pretend that you are a terminal so that you can connect to the Internet to use a Library database.

Copyright © 1998 by Curtis Clark. May be copied in its entirety freely for nonprofit educational use.

Space for this page is provided by California State Polytechnic University, Pomona. Although it is intended to further the educational mission of the University, the opinions expressed here are those of Curtis Clark, and do not represent official policy of the University.