White Paper: An introduction to thin client computing

The once simple PC has grown in complexity and its use in manipulating corporate data has brought a whole new set of problems to...

The once simple PC has grown in complexity and its use in manipulating corporate data has brought a whole new set of problems to Enterprise Computing

System configurations, data management, upgrades and user support has become increasingly difficult and expensive with the widespread deployment of PCs. However, going back from the Windows graphical user interface to text based terminals is not an acceptable solution to the problem. What is needed is a method to deliver PC functionality and compatibility with legacy systems while maintaining a centrally managed environment.

The key to this solution was delivered initially by Citrix Systems with a product called WinFrame. WinFrame was an adaptation of the Microsoft NT operating system that allowed a single NT system to support multiple users in a centrally managed Windows environment. The most important component of Citrix' WinFrame is the Independent Computing Architecture (ICA). As an application is run, the Citrix server intercepts the application's user interface data (display, keyboard and mouse) and transmits this data between the Citrix server and the ICA Client program running on the user's desktop device using the ICA protocol. Distributing the presentation of an application is not a new concept. It is much like traditional multi-user systems, like mainframes and UNIX, and is similar to X-Windows.

The WinFrame solution offers the multi-user application support that was missing in PC based implementations. A single WinFrame system can be centrally located and managed while still providing users with the graphical Windows interface and the Windows applications users demand. The desktop device required to access this new WinFrame system is no longer tied to the PC architecture, since all processing is actually performed on the centralised WinFrame server. This provided the opening for thin clients at the desktop and the birth of the Network Computer (NC).

Based on the success Citrix was having with the WinFrame product, Microsoft has decided to become involved in the multi-user NT system market. Now, after licensing some of the Citrix technology, Microsoft has introduced Windows Terminal Server NT 4.0 Terminal Server Edition (TSE) as the next generation product. Microsoft did not license Citrix' ICA technology though, and ICA is not included with Windows Terminal Server Edition. ICA can still be used in a TSE environment, but it must be obtained as an add-on product from Citrix.

Microsoft products defined

TSE is made up of three components: the multi-user server core, the Remote Desktop Protocol (RDP) and the TSE client software. The multi-user server core provides the basic ability to host multiple, simultaneous client sessions and includes administration tools for management of both the server and the client sessions. RDP is a display protocol allowing communication between the server and the TSE client software. TSE allows for connection to Windows 3.11, Windows 95/98 and Windows NT devices using the RDP protocol as well as the newly defined (by Microsoft) Windows CE based Terminals or WBTs.

WBT and NC thin client devices

The NC and the Windows based terminal were both spawned by the need to simplify the desktop environment, maintain functionality and centralise control. Both products succeed in this primary goal while each offers a unique set of advantages and disadvantages.

The Windows based terminal is the simpler of the two devices. The Windows based terminal uses Windows CE as the operating system (OS), although in many cases the OS is transparent to the user. Microsoft defines the Windows based terminal as a simple access device providing only the Graphical User Interface (GUI) to the Windows NT Server. A true Windows based terminal performs no application tasks at the desktop as all applications reside on the server.

Microsoft Windows CE is a 32-bit, multi-tasking, multi-threaded operating system (OS) that has an open architecture design that enables a variety of devices. Windows CE is compact, providing high performance with low memory conditions and is scaleable, allowing for future support of a range of embedded, mobile or multimedia product lines. Using a protocol named RDP (Remote Desktop Protocol) the Windows based terminal passes keystroke and mouse movement information across the network to the Windows server. This information is input to the application running on the server and all processing of the information is performed on the server. The resulting changes to the display are then transmitted back to the Windows based terminal, using the same protocol, to be displayed on the Windows based terminal screen.

The user experiences the same look and feel as when operating Windows applications on a local desktop PC. Windows based terminals can also have other interfaces allowing them to attach to different host systems and this is where manufacturers will probably differentiate their product offerings. Terminal emulation interfaces can be provided to communicate with legacy systems such as IBM(r) midrange and mainframe systems as well as UNIX systems. Many Windows based terminals will also offer the Citrix ICA, Independent Computing Architecture, interface to the Windows Terminal Server. Window based terminals can be considered a graphical version of the fixed function terminal and make a logical replacement for these devices in most applications, especially where access to two separate systems is needed. This fixed functionality makes the Windows based terminal simple to deploy but makes it totally dependent on network servers to perform its tasks.

NCs use a variety of operating systems and typically load their OS over the network. The devices can vary significantly from vendor to vendor with some devices offering functionality similar to the Windows based terminals while others use Java to promise ongoing advancements rivaling PC capability. NCs are promoted as a seamless extension of the Internet/intranet communications boom with many devices offering the ability to run a browser on the desktop NC.

The NC typically has its own user interface and many vendors have chosen to simulate the look and feel of Windows to reduce the user training time. NCs use the Citrix ICA protocol and as such require the Citrix extensions to Microsoft's Terminal Server product. NCs can also utilise terminal emulation programs to provide access to other systems on the network.

Since Windows based terminals have their operating system stored internally, the time to boot such a system is significantly less than that of a NC and produces less loading on the network. Should an update to the operating system be required, the Window based terminal can download the new version from the network. This will occur only when needed and only once, as the new version simply replaces the old version in the flash ROM. The very nature of the Windows based terminal's defined functionality will help reduce the rapid obsolescence that has become common in the PC industry.

NCs benefit somewhat from their network boot model resulting in, at first glance, easy updates to the desktop device and easy deployment of applications that can operate on the NC platform. Serious consideration to increased demand on network traffic levels should be taken, especially if a number of NCs are booting at the same time.

The thin client computing model

Picture connecting a PC to a network then borrowing as many of the network's functions as possible to make that PC work. All the application programs and data that were stored on that PC's hard drive now come from a centralised network memory. Now, throw away the components no longer needed - the PC's hard drive, floppy drive, CD-ROM drive and the interface hardware, including the fan that keeps all that hardware cool. Keep the keyboard and a mouse. Add a simpler operating system to reduce CPU and memory requirements. What do you have? About the lowest cost "computer" available. Of course, you still need the network server. The cost of implementing a total Web based terminal or NC solution, with a server, will not save significantly on the total cost per user, initially. The savings are in the cost of managing and maintaining the thin client computing environment over a period of time.

Thin client communications

Thin client computing environments use a Microsoft NT-based application server to centrally run (deploy) programs to users and to centrally store data. The thin client makes use of an efficient protocol to communicate with the PC or server executing the applications. The multi-user server side software that permits access to desktop applications is Microsoft's Windows Terminal Server NT 4.0 Terminal Server Edition or the WinFrame server and ICA protocol from Citrix Systems Inc. This software executes the personal productivity applications on the Windows NT Server but deploys the presentation screens remotely on the thin client. The Microsoft or Citrix Windows Server software allows concurrent users to log on and run applications in separate, protected and secure virtual sessions on a single server.

In this new computing architecture, a thin layer of software in the desktop device establishes a communications link between the Windows Server and the client desktop. The communications protocol only redirects the local screen, keyboard and mouse actions and posts the information received from the server to the client. Thin client devices offering connections to other servers or hosts usually provide Telnet terminal emulation. These terminal emulations allow the thin client to connect to the other servers and emulate the standard terminal device used in that environment. Terminal emulation allows the thin client user to access all the host-based applications they accessed through their green screen terminal or through terminal emulation on a PC.

User based configuration

With all application software and data residing on the server or host system, a thin client only needs network access to be operational. Initial configuration is usually accomplished in several minutes as opposed to the many hours required to load and configure a standard PC. If the network is set up for automatic address assignment, configuration is almost as easy as plugging in a telephone. Server based configurations and data storage also makes thin clients user independent. Any user can access their applications and data from any thin client on the network. After logging on, a user will be presented with his/her specific desktop configuration, regardless of which thin client in the enterprise he/she logged in on. Users are tied to a profile not their desktop PC.

Thin clients equipped with Terminal Emulation provide access to traditional host and server based applications including 5250, 3270 and UNIX server functions. Internet and Intranet access is provided through the host, Windows Server or locally, if supported by the thin c lient. Access to PC applications is provided by Windows NT Servers offering multi-user environments to support a large number of thin client users. These applications run directly on the server and send out only their display output over network links or serial connections to thin clients using a display protocol such as ICA or X. ICA is similar to the X protocol used with UNIX and was designed for Windows applications such as Windows 3.1, Windows 95 and Windows NT. Java-based applications, which can run directly on a NC with the Java Virtual Machine, are also being developed at a rapid rate to augment the NCs.

Total cost of ownership

The thin client revolution is really all about cost containment and control of the computing environment. Centralised system management insures that a common set of applications and consistent revision levels are used by everyone. Centralised management also allows better control of data with consistent back ups and enhanced security for sensitive information. The simplicity of the desktop device with little or no storage and minimal configuration greatly reduces the cost to maintain the desktop interface.

Thin clients are positioned between a terminal and a PC in purchase price and functionality but they offer many advantages other than the initial low price. These advantages are often measured in TCO or Total Cost of Ownership. Contributions to the TCO benefit are claimed in many areas. Centralised upgrades and support are two areas that allow the addition of new applications at the host or Windows Server without disruption to the user. This means no more weekends and late nights for the IT staff running from desk to desk to distribute and install software changes and upgrades. This feature alone will save thousands of dollars per desktop in maintenance costs. Standardisation and centralisation are key as everyone shares the same applications and the same data.

Enhanced security, lower maintenance

Other TCO benefits are not so obvious. Since the thin client device has no hard or floppy disk drives, games and favorite personal software cannot be loaded on it. The primary pluses of this seeming reduction in functionality are increased productivity and increased data security as company data cannot "walk away" and viruses cannot be introduced through the thin client. And, no one would want to steal a thin client. For without a network to connect to, the device imitates a bulky paperweight. Losing that library of computer games aside, the loss of data portability may prove to be totally unacceptable for some users and thin clients are not the solution for all desktop requirements.

Counterbalancing the resistance from users who want control of their desktops are the non-technical users who "just want something that works" and who abhor the idea of managing their computers - dealing with viruses, new software and disk fragmentation. The non-technical user is the perfect target for thin client computing. With fewer parts, Mean Time Between Failure is much higher for the new desktop devices than for the PC and a hot swap of a failed device takes only minutes. The shared nature of applications and data in thin client computing eases the Technical Support requirements. Often Technical Support can answer a user's cry for help by taking over via remote control of any session, more commonly known as mirroring or shadowing. All these features reduce maintenance, training cost and simplify the support/help personnel's job load, further enhancing the TCO benefits. TCO is estimated anywhere from $2,500 to $3,144 annually for thin clients versus an estimated $5,731 to $11,900 for a PC based on industry research studies from the Gartner Group, IDC and Zona Research Inc.

Product direction

Over the past few years, a number of thin client device types have been paraded across the landscape. Although different in name (Disk-less PC, Net PC, Network Computer, Information Appliance, X-Terminal, Windows Based Terminal), the common threads woven into this acronym laden tapestry, are Centralised Management and Reduced Cost of Ownership. The overall market outlook has changed from a perception that thin clients would replace all PCs, to a more realistic vision of "peaceful coexistence". The flexibility offered through a thin client solution is attractive in many, but not in all computing environments. Windows based terminals and NCs have emerged as the two thin client desktop devices of the future, with Web based terminals expected to capture a significantly larger share of the market over the next three years.

Endorsement and promotion of the thin client computing model by industry giants such as IBM, Microsoft, Sun and Intel certainly legitimise this emerging technology. Market leaders such as Development Concepts, Inc., NCD and Wyse have all introduced new products positioned to accelerate the desktop revolution.

Target market

Today's thin client devices answer the call for simple, low maintenance desktop devices and, as such, are ideal for terminal replacement applications. IT shops looking to upgrade from green screen applications will find these devices offer an excellent opportunity to provide increased functionality without the loss of control over applications and data. Enterprises that use PCs for data entry and routine/daily office tasks can also benefit from the low TCO of thin client devices. Typical market segments that fit well into the model are banking, health care, manufacturing, insurance and transportation, such as airline reservation counters. Anywhere that users rely on a standard set of applications can be ideal targets for this new generation of desktops.

(c) 1998, Development Concepts, Inc.

Compiled by Rachel Hodgkins

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