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Chapter 1

Overview

Top The Basics

This section explores the basic parts of the system you need to set up to create a gateway between your private network and the Internet. Topics include:

What is the Internet?

The Internet is a worldwide network of computers tied together to share information. The Internet is not owned by any one business or organization. The Internet is the internetwork formed by all the businesses and organizations that choose to link their computers to the Internet. The Internet is now a universal carrier of electronic mail, text files, multimedia objects, and real-time audio. In the future, even more information will be available in these and other formats.

The basic protocol for the Internet is the Transmission Control Protocol (TCP). Information (such as an e-mail) is sent in chunks called packets. These packets reach your computer by using its Internet Protocol (IP) address. An IP address consists of four numbers between 0 and 255, separated by periods. Using TCP/IP, your computer can communicate with other computers on the Internet.

Another method of addressing is domain name. Domain names, which are easier to remember than IP addresses, are mapped to IP addresses. Domain names consist of a host name, a subdomain name, and a top-level domain name, separated by periods. The host name often indicates the protocol used by the Internet site. The subdomain name is usually the name of the organization that manages the site. Domain names are registered with InterNIC (Internet Network Information Center). The top-level domain which indicates the type of organization that runs the Web site, is assigned by InterNIC.

For example, www.microsoft.com is the domain name for the Microsoft World Wide Web site. The host name www. denotes a World Wide Web server. The subdomain microsoft, is the name registered with InterNIC by the owner of the site. In this case the owner is the Microsoft Corporation. The top-level domain, .com, means the Web site is operated by a commercial organization.

Some common Internet host protocols are:

Some Internet top-level domain names include:

The main trunks of the Internet, or backbones, are run by the major telecommunications carriers. These provide access to the Internet through smaller companies called Internet Service Providers (ISPs). Users can get access to the Internet through the ISP to browse the World Wide Web, to download files, and to send and receive e-mail.

What is the World Wide Web?

The World Wide Web (WWW or, simply, the Web) is an Internet service, based on the HTTP (Hypertext Transport Protocol), that delivers multimedia objects — text, sound, video, images, database access, and interactive applications — to your computer. These objects are grouped together into pages using a scripting language called HTML (Hypertext Markup Language). A Web page is viewed with a browser. A browser is an application, such as Microsoft Internet Explorer, that requests a page on the Web by using HTTP and then displays the page on your screen. HTML pages are text files that include special codes called tags. These tags control text formatting, the placement of objects on the page and hyperlinks. You click a hyperlink to jump from one Web page to another.

The content for the Web is created and maintained on computers that are configured to act as Web sites. A Web site responds to requests from browsers and returns HTML pages. Web sites are typically maintained by organizations. Individuals sometimes run their own Web sites, or they create HTML pages and load them onto public sites.

The content of the Web is dynamic. It changes daily, or even hourly. The number of Web sites and the scope and richness of content is growing astronomically. The Web offers business information, on-line shopping, and searchable databases.

What is an Intranet?

Intranet is another name for a private, internal, or corporate network. An intranet is an organization’s internal network of computers based on the Internet model. This internal network may be as small as a local area network (LAN) that connects two PCs over a serial link, or as large as a wide area network (WAN) that connects a mainframe computer to hundreds of remote sites worldwide. An intranet can be thought of as any network whose computers and network hardware are under the responsibility of an organization. Many organizations use intranets to publish information for their network users.

An intranet consists of workstations, which are also called clients, and servers connected by a LAN or WAN. The workstations run operating systems such as Windows NT Workstation or Windows 95. The intranet can be connected to the Internet with a gateway, such as Catapult Server.

Throughout this guide, the term “private network” is used to indicate the “intranet,” “corporate network,” or “internal network.”

What is a Gateway?

A gateway refers to software or a computer running software that enables two different networks to communicate. Catapult Server connects your private network to the Internet. You configure Catapult Server to enable your workstations to communicate with remote services on the Internet. You select the appropriate hardware for a gateway computer, adequate bandwidth for the Internet connection, and choose the level of security for protecting your private network.

By using a Catapult Server gateway, you are able to secure your network against intrusion. The gateway acts as a barrier that allows you to make requests to the Internet and receive information, but does not allow access to your network by unauthorized users.

What is a Client?

A client is a computer that sends a request for data over a network to a server computer. For example, a computer on an private network running Internet Explorer that makes a request to an Internet Information Server Web site is a client. In this example, Internet Information Server responds by sending out HTTP objects addressed to the private network. Catapult Server receives these objects and passes them to the computer running Internet Explorer, which displays the objects in a Web page.

Internet-based client software includes:

Many Microsoft applications are able to act as Internet clients. Each application is able to receive objects from the Internet into its own file format.

Top What is Catapult Server?

When a client application makes a request for an object on the Internet, Catapult Server responds by translating the request and passing it to the Internet. When a computer on the Internet responds, Catapult Server passes that response back to the client application on the computer that made the request.

To run Catapult Server, the gateway computer must have Windows NT Server version 4.0 or later. You set up your computer with two network adapter cards. One card connects the gateway computer running Catapult Server to your private network. The other card connects your computer to the Internet.

Catapult Server has two services: Proxy and Remote Windows Sockets (RWS).

Top What Does Setup Install?

Catapult Server Setup installs the following on your computer:

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