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 definedTSE 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 devicesThe 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 modelPicture 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
communicationsThin 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
configurationWith 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 ownershipThe 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
maintenanceOther 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 directionOver 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 marketToday'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