Thin clients connected to their server via a computer network
A public thin-client computer terminal inside a public library
An Aleutia E3 thin client, with flash memory
A thin client is a lightweight computer that has been optimized for establishing a remote connection
with a server-based computing environment. The server does most of the
work, which can include launching software programs, performing
calculations, and storing data. This contrasts with a fat client or a conventional personal computer; the former is also intended for working in a client–server model but has significant local processing power, while the latter aims to perform its function mostly locally.
Thin clients occur as components of a broader computing
infrastructure, where many clients share their computations with a
server or server farm. The server-side infrastructure uses cloud computing software such as application virtualization, hosted shared desktop (HSD) or desktop virtualization (VDI). This combination forms what is known as a cloud-based system where desktop resources are centralized at one or more data centers. The benefits of centralization are hardware resource optimization, reduced software maintenance, and improved security.
- Example of hardware resource optimization: Cabling, busing and I/O can be minimized while idle memory and processing power can be applied to user sessions that most need it.
- Example of reduced software maintenance: Software patching and operating system (OS) migrations can be applied, tested and activated for all users in one instance to accelerate roll-out and improve administrative efficiency.
- Example of improved security: Software assets are centralized and easily fire-walled, monitored and protected. Sensitive data is uncompromised in cases of desktop loss or theft.
Thin client hardware generally supports a keyboard, mouse, monitor, jacks for sound peripherals, and open ports for USB
devices (e.g., printer, flash drive, webcam). Some thin clients include
legacy serial or parallel ports to support older devices such as
receipt printers, scales or time clocks. Thin client software typically
consists of a graphical user interface (GUI), cloud access agents (e.g., RDP, ICA, PCoIP), a local web browser, terminal emulators (in some cases), and a basic set of local utilities.
Characteristics
Architecture
In
using cloud-based architecture, the server takes on the processing load
of several client sessions, acting as a host for each endpoint device.
The client software is narrowly purposed and lightweight; therefore,
only the host server or server farm needs to be secured, rather than
securing software installed on every endpoint device (although thin
clients may still require basic security and strong authentication to
prevent unauthorized access). One of the combined benefits of using
cloud architecture with thin client desktops is that critical IT assets
are centralized for better utilization of resources. Unused memory,
bussing lanes, and processor cores within an individual user session,
for example, can be leveraged for other active user sessions.
The simplicity of thin client hardware and software results in a very low total cost of ownership,
but some of these initial savings can be offset by the need for a more
robust cloud infrastructure required on the server side.
An alternative to traditional server deployment which spreads out
infrastructure costs over time is a cloud-based subscription model
known as desktop as a service, which allows IT organizations to outsource the cloud infrastructure to a third party.
Simplicity
TA7 thin client by Gigabyte
Thin client computing is known to simplify the desktop endpoints by
reducing the client-side software footprint. With a lightweight,
read-only operating system
(OS), client-side setup and administration is greatly reduced. Cloud
access is the primary role of a thin client which eliminates the need
for a large suite of local user applications, data storage, and
utilities. This architecture shifts most of the software execution
burden from the endpoint to the data center. User assets are centralized
for greater visibility. Data recovery and desktop repurposing tasks are
also centralized for faster service and greater scalability.
Hardware
While
the server must be robust enough to handle several client sessions at
once, thin client hardware requirements are minimal compared to that of a
traditional PC desktop. Most thin clients have low energy processors, flash storage,
memory, and no moving parts. This reduces the cost and power
consumption, making them affordable to own and easy to replace or
deploy. Since thin clients consist of fewer hardware components than a
traditional desktop PC, they can operate in more hostile environments.
And because they typically don't store critical data locally, risk of
theft is minimized because there is little or no user data to be
compromised.
Graphics
Modern
thin clients have come a long way to meet the demands of today's
graphical computing needs. New generations of low energy chipset and CPU
(Central Processing Unit)
combinations improve processing power and graphical capabilities. To
minimize latency of high resolution video sent across the network, some
host software stacks leverage multimedia redirection (MMR) techniques to
offload video rendering to the desktop device. Video codecs are often
embedded on the thin client to support these various multimedia formats.
Other host software stacks makes use of User Datagram Protocol
(UDP) in order to accelerate fast changing pixel updates required by
modern video content. Thin clients typically support local software
agents capable of accepting and decoding UDP.
Some of the more graphically intense use cases, remain a
challenge for thin clients. These use cases might include the
applications like photo editors, 3D drawing programs, and animation
tools. This can be addressed at the host server using dedicated GPU cards, allocation of vGPUs
(virtual GPU), workstation cards, and hardware acceleration cards.
These solutions allow IT administrators to provide power-user
performance where it is needed, to a relatively generic endpoint device
such as a thin client.
Limitations
To
achieve such simplicity, thin clients sometimes lag behind desktop PCs
in terms of extensibility. For example, if a local software utility or
set of device drivers are needed in order to support a locally attached
peripheral device (e.g. printer, scanner, biometric security device),
the thin client operating system may lack the resources needed to fully
integrate the required dependencies (although dependencies can
sometimes be added if they can be identified). Modern thin clients
address this limitation via port mapping or USB redirection software.
However, these methods cannot address all scenarios. Therefore, it is
good practice to perform validation tests of locally attached
peripherals in advance to ensure compatibility. Further, in large
distributed desktop environments, printers are often networked, negating
the need for device drivers on every desktop.
While running local productivity applications goes beyond the
normal scope of a thin client, it is sometimes needed in rare use cases.
License restrictions that apply to thin clients can sometimes prevent
them from supporting these applications. Local storage constraints may
also limit the space required to install large applications or
application suites.
It is also important to acknowledge that network bandwidth and
performance is more critical in any type of cloud-based computing model.
IT organizations must ensure that their network can accommodate the
number of users that they need to serve. If demand for bandwidth exceeds
network limits, it could result in a major loss of end user
productivity.
A similar risk exists inside the data center. Servers must be
sized correctly in order to deliver adequate performance to end users.
In a cloud-based computing model, the servers can also represent a
single point of failure risk. If a server fails, end users lose access
to all of the resources supported by that server. This risk can be
mitigated by building redundancies, fail-over processes, backups, and
load balancing utilities into the system. Redundancy provides reliable
host availability but it can add cost to smaller user populations that
lack scale.
Providers
Popular providers of thin clients include Wyse Technology, NComputing, Dell (acquired Wyse in 2012), HP, IGEL Technology, LG and Samsung Electronics.
History
Thin clients have their roots in multi-user systems, traditionally mainframes accessed by some sort of computer terminal. As computer graphics matured, these terminals transitioned from providing a command-line interface to a full graphical user interface, as is common on modern advanced thin clients. The prototypical multi-user environment along these lines, Unix, began to support fully graphical X terminals, i.e., devices running display server
software, from about 1984. X terminals remained relatively popular even
after the arrival of other thin clients in the mid-late 1990s. Modern Unix derivatives like BSD and Linux
continue the tradition of the multi-user, remote display/input session.
Typically, X software is not made available on non-X-based thin
clients, although no technical reason for this exclusion would prevent
it.
Windows NT became capable of multi-user operations primarily through the efforts of Citrix Systems, which repackaged Windows NT 3.51 as the multi-user operating system WinFrame in 1995, launched in coordination with Wyse Technology's Winterm thin client. Microsoft licensed this technology back from Citrix and implemented it into Windows NT 4.0
Terminal Server Edition, under a project codenamed 'Hydra'. Windows NT
then became the basis of Windows 2000 and Windows XP. As of 2011 Microsoft Windows systems support graphical terminals via the Remote Desktop Services
component. The Wyse Winterm was the first Windows-display-focused thin
client (AKA Windows Terminal) to access this environment.
The term thin client was coined in 1993 by Tim Negris, VP of Server Marketing at Oracle Corporation, while working with company founder Larry Ellison on the launch of Oracle 7.
At the time, Oracle wished to differentiate their server oriented
software from Microsoft's desktop oriented products. Ellison
subsequently popularized Negris' buzzword
with frequent use in his speeches and interviews about Oracle products.
Ellison would go on to be a founding board member of thin client maker
Network Computer, Inc (NCI), later renamed Liberate.
Size comparison – traditional desktop PC vs Clientron U700
The term stuck for several reasons. The earlier term 'graphical
terminal' had been chosen to distinguish such terminals from text-based
terminals, and thus put the emphasis heavily on graphics – which
became obsolete as a distinguishing characteristic in the 1990s as
text-only physical terminals themselves became obsolete, and text-only
computer systems (a few of which existed in the 1980s) were no longer
manufactured. The term 'thin client' also conveys better what was then
viewed as the fundamental difference: thin clients can be designed with
less expensive hardware, because they have reduced computational
workloads.
By the 2010s, thin clients were not the only desktop devices for
general purpose computing that were 'thin' – in the sense of having a
small form factor and being relatively inexpensive. The nettop form factor for desktop PCs was introduced, and nettops could run full feature Windows or Linux; tablets and tablet-laptop hybridshad
also entered the market. However, while there was now little size
difference, thin clients retained some key advantages over these
competitors, such as not needing a local drive. However, 'thin client'
can be a misnomer for slim form factor computers using flash memory such as compactflash, SD card, or permanent flash memory as a hard disk substitute.
Variants
Zero client
Zero
client is also referred as ultra thin client, contains no moving parts
but centralizes all processing and storage to just what is running on
the server. As a result, it requires no local driver to install, no
patch management, and no local operating system licensing fees or
updates. The device consumes very little power and is tamper-resistant
and completely incapable of storing any data locally, providing a more
secure endpoint.
While a traditional thin client is streamlined for multi-protocol
client-server communication, a zero client has a highly tuned on board
processor specifically designed for one possible protocol (PCoIP, HDX, RemoteFX, DDP).
A zero client makes use of very lightweight firmware that merely
initializes network communication through a basic GUI (Graphical User
Interface), decodes display information received from the server, and
sends local input back to the host. A device with such simple
functionality has less demand for complex hardware or silicon, and
therefore becomes less prone to obsolescence. Another key benefit of the
zero client model is that its lightweight firmware represents an
ultra-small attack surface making it more secure than a thin client.
Further, the local firmware is so simple that it requires very little
setup or ongoing administration. It's the ultimate in desktop
simplification but the trade-off is flexibility. Most mainstream zero
clients are optimized for one communication protocol only. This limits
the number of host environments that a zero client can provide its users
with access to.
Providers
Popular providers of zero clients include Wyse (Xenith), IGEL Technology, 10ZiG, Teradici, vCloudPoint.
Web client
Web-centric thin client
Web clients only provide a web browser, and rely on web apps to provide general-purpose computing functionality. However, note that web applications may use web storage to store some data locally, e.g. for "offline mode", and they can perform significant processing tasks as well. Rich Internet Applications for instance may cross the boundary, and HTML5 web apps can leverage browsers as run-time environments through the use of a cache manifest or so-called "packaged apps" (in Firefox OS and Google Chrome).
Examples of web thin clients include Chromebooks and Chromeboxes (which run Chrome OS) and phones running Firefox OS.
O
Chromebooks and Chromeboxes also have the capability of remote desktop using the free Chrome Remote Desktop
browser extension, which means, other than being a web thin client,
they can also be used as an ultra-thin client (see above) to access PC
or Mac applications that do not run on the Chromebook directly. Indeed,
they can be used as a web thin client and an ultra-thin-client
simultaneously, with the user switching between web browser and PC or
Mac application windows with a click.
Chromebooks are also able to store user documents locally –
though, with the exception of media files (which have a dedicated player
application to play them), all such files can only be opened and
processed with web applications, since traditional desktop applications
cannot be installed in Chrome OS.
US$570 million 
