In case you don't know why you're reading this book, Citrix MetaFrame XP for Windows allows real Windows applications to be remotely accessed by many different types of client platforms, including Windows, Macintosh, UNIX, and Linux workstations, as well as wireless devices, laptops, set top boxes, mobile handheld devices, the X-Box, and network appliances. This access is provided via the Internet, LAN, WAN, dial-up or wireless connections, via TCP/IP, IPX, SPX, NetBIOS, or SLIP/PPP protocols.
When MetaFrame XP is used, Windows applications are executed on MetaFrame XP servers, and users access the applications from their client devices via "remote Windows" sessions. Even though applications are running on the servers, the applications' screen images are transmitted to the users, so the users feel that the applications are running locally on their own client devices. One single MetaFrame XP server can support dozens or even hundreds of simultaneous users.
Applications running on MetaFrame XP servers can have complete access to users' local system devices, including disk drives, ports, printers, audio, and the Windows clipboard. Users can resize remote application Windows and "Alt-Tab" through the application list. A single user may have several MetaFrame XP application sessions open in addition to their local applications. This means that from a user's standpoint, all applications look and feel the same. The users probably (and ideally) don't even realize that some applications are actually executing on centrally controlled and managed MetaFrame XP servers while others are local. Because MetaFrame XP allows users to use their regular Windows applications, their productivity remains high. This computing model is known as "Server-Based Computing."
MetaFrame XP Server-Based Computing Components
In order to understand how Citrix server-based computing works, you need to understand its components. There are three main components that make up MetaFrame XP server-based computing environments:
- A multi-user operating system.
- Citrix MetaFrame XP application server software.
- Citrix client software and devices.
- Let's examine each of these components.
Component 1. A Multi-user Operating System
The foundation for the servers that run Windows server-based computing environments (and therefore MetaFrame XP) is a "special" version of the Microsoft Windows Server operating system that allows multiple simultaneous users to connect and run applications independently of each other. This is different from a standard Windows server. Standard Windows servers allow multiple users to simultaneously connect to resources (such as files, printers, and applications), but only one user can be interactively logged onto the console at a time. A multi-user operating system allows multiple users to connect and run interactive sessions (like remote control sessions) on the server, independently of what any other user is doing.
For MetaFrame XP server-based computing environments, valid multi-user operating systems include Microsoft Windows NT Server 4.0 Terminal Server Edition and Windows 2000 Server with the Terminal Services network service installed in "application mode." (Citrix also makes derivative versions of MetaFrame for UNIX-based servers, but they are not the topic of this book.)
Component 2. MetaFrame XP Server Software
The Citrix MetaFrame XP server software installs as an application on top of the multi-user operating system. MetaFrame XP is the middleware that allows users to connect to the server to run applications. In addition to providing the client connection, MetaFrame XP increases the manageability and scalability of the default Microsoft Windows server-based computing environments.
Component 3. Citrix ICA Clients
In order to use applications running on MetaFrame XP server-based computing servers, end users need to have client software loaded on their client devices. This client software is known as the "Citrix ICA client." The exact meaning of this will become apparent as you read more of this book. For now, it's important to know that in order for users to access applications on a MetaFrame XP server, they need to have the "Citrix ICA client" software installed on their client devices. Fortunately, there are versions of the Citrix ICA client software for almost every operating system and type of device, including Windows, Linux, UNIX, Macintosh, Windows CE / Pocket PC, JAVA, and Psion.