critical data over low-cost, widely available Internet links. Over the long term, the Internet will be the best transport for an organization's com- munications with its partners. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. X.25, Internets, Intranets, and Extranets X.25, Internets, Intranets, and Extranets An internal network is comprised of one or more LANs interconnected with one or more routers running the IP protocol. (So far, this is only an Internet with a lowercase i.) The bulk of our traffic on this Net is Web based. That is, we have one or more Web servers and all of the clients are running a browser. Our primary means of communicating is using the Web. (Technically, mail is a different set of application protocols, but most browsers also provide a mail capability.) Perhaps we should say that the primary interface that our users have to their data is via their browser. This network may be geographically far flung where dedicated lines (or Frame Relay) are used to connect our routers. No connection exists to the Internet. This is where things get touchy. If we were to use Virtual Private Network (VPN) technology between our corporate locations, one could argue it is still an intranet. Extranet By using an external server sitting outside the firewall, the organization has an extranet. Business partners can access the extranet server, and pass or retrieve data from the server. As a query or data request is generated, the server can then spawn a request to the intranet and retrieve that data as needed. By doing so, the server is protected on the inside, but accessible by a limited few from the outside. The World Wide Web The proliferation of much of the Internet frenzy occurred when the old UNIX command-line interface was replaced with a graphical user interface (GUI) called a browser. As soon as the Internet became friendlier to th