Introduction

OVERVIEW

The complexity of information systems is driving the cost of enterprise computing out of control, frequently offsetting the business benefits derived from information technology. Consequently, in spite of continuing and rapid advances in IT, it is more difficult than ever before for IT organizations to provide consistency of service to all the places and people they must serve. What's driving all this? Heterogeneity. Each successive wave of computingmainframe, minicomputer, PC, client-server, the Web, Web serviceshas not superseded previous waves but rather has been piled on top of what came before. Moreover, the diversity and proliferation of access devices, computing platforms, software languages, networks, standards and application infrastructures have further complicated the picture, making the cost of computing more variable and more expensive than ever.

IT organizations are coping with these technical, economic and business challenges through consolidation. They are reducing the number of moving parts by centralizing and consolidating as much of the heterogeneity and complexity as possible to fewer data centers, servers and networks. Their goal is to migrate to a model that allows them to improve the level of service they provide to the business. To accomplish this, many are moving the complexity of computing to a central place where it can best be managed, controlled, and evolved over time. This makes everything outside the data center simpler to manage and more cost-effective to operate . It also dramatically improves information security and resilience to technological and business interruptions.

The On-Demand Enterprise is an infrastructure providing a consistent user experience and instant access to IT services from anywhere . It allows heterogeneity to be managed centrally , and shields the user from the complexity of accessing heterogeneous information systems. It includes a trusted connection that knows the user's identity and dynamically adjusts to the specific user's device, location and preferences.

Access infrastructure for the on-demand enterprise provides a consistent user experience across a wide variety of access devices and easy, secure, and instant access to IT servicesfrom anywhere. It allows heterogeneity to be managed centrally, and shields the user from the complexity of accessing heterogeneous information systems. It knows the user's identity and presents an interface that dynamically adjusts to the specific user's device, location, and preferences.

The Citrix Access Suite provides access infrastructure for the on-demand enterprise; applications are executed on central server farms running Microsoft Windows Server 2003 Terminal Server and Citrix Presentation Server 4. Users see only screen prints of their applications displayed on a wide variety of devices, including handheld PDAs, PC tablet devices, Windows-based terminals, Macs, smart phones, Linux workstations, and traditional PCs.

By providing organizations with the ability to quickly deploy a wide range of applications to users, regardless of their location, bandwidth constraints, or device, on-demand access has changed the way many organizations work today. And by reducing eliminating the requirements for PC upgrades and remote office servers, organizations also can minimize their ongoing capital expenditures and dramatically slash their administration costs.

This computing paradigm also goes by several other names (with some variations in meaning), including server-based computing, server-centric computing, application serving, thin-client computing, ASP services, and simply Terminal Services. While on-demand access covers a much broader range of capabilities than server-based computing, in respect to the Citrix Access Suite, we utilize these terms as synonyms to refer to the concept of a centrally hosted application environment for a majority of applications and a majority of users. Another way to think about this concept is application virtualization, which is discussed in Chapter 1.