A guide to thin client computing

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This guide is a work in progress by Ric_... please check back soon for updates!

What is thin client computing?

True thin client computing uses a 'dumb' access device without its own processing and storage capabilities to connect to a remote computer where the actual work is done. Nowadays, the term is also used when talking about slightly 'less-thin' client devices that may have access to local storage but very little processing power. We can extend the usage further to the use of 'regular' fat clients to connect to remote desktops.

Various protocols can be used (with Microsoft's Remote Despktop Protocol - RDP - and Citrix's ICA being two of the more popular). Many of these protocols can be run across platforms, for example allowing a Linux system to access applications on a Windows server.

What are the benefits of using thin clients?

Thin clients require very little processing power, so can use low power hardware. This gives several benefits:

  • Reduced power consumption reduces running costs, lowering the TCO (Total Cost of Ownership)
  • Since the machines don't need to be very powerful, it is possible to use them for longer than your normal 3-year refresh cycle (a conservative 10 years+) reducing TCO again
  • Low power CPUs allow for passive cooling and solid state storage means that there is little to go wrong... increasing the life expectencey and therefore further reducing TCO
  • The low power CPUs, etc. mean that the heat output of a terminal is very low providing the benefits of not needing air conditioning in computer suites and zero noise - therefore reducing TCO and providing a more pleasent learning environment
  • Most terminals have a very small footprint, in fact some can be attached to (or even integrated into) TFT monitors which frees up desk space and provides a nicer working environment

As well as these benefits from utilising specialist hardware, it is possible to 'recycle' old computers which extends the lifespan beyond that of a fat client. In doing this, it offers an excellent path for the adoption of a thin client infrastructure.

The benefits are not simply limited to the above cost savings. The server-based computing model means that management overheads are significantly reduced - indirectly leading to further cost savings.

  • Configuration of the clients is very basic and many manufacturers provide a means of zero touch configuration
  • Terminal servers do not require much more attention than a 'normal' PC meaning that only one computer must be looked after instead of 30 (the approximate number of clients that a server will support)
  • The centralised location of the terminal servers also makes maintenance considerably easier because there is no need to travel around site to perform common tasks

An added benefit of thin client computing is that the infrastructure provides a ready-made remote access solution, giving access to whatever applications you have, after hours.

What are the disadvantages of using thin clients?

After reading about all the cost savings and other benefits, you are probably wondering why thin client computing isn't more common.

There are obvious limitations about just how much data can be sent back and forth. As a result of this, it's innevitable that graphically intensive applications aren't going to work as well as if you had dedicated graphics hardware in front of you. Likewise, music and video editing is going to suffer. It is possible to perform some of these actions but performance will suffer.

There are also some problems with certain software titles that have a tendency to grab as many resources as possible. This normally isn't a problem on a single user system but when you are sharing the resources with 30 or so other users, everybody will experience a performance hit.

Of course the problems above are also considerations when specifying fat clients. For instance, a PC for music production might require additional hard disk space and a specialist sound card. By utilising thin clients for general use machines, you will have made sufficient cost savings to install specialist computer suites of a higher specification.

The other major downside to using thin client computing is the initial cost. Items such as terminal servers and licenses add to the initial cost but ongoing costs are cheaper... hence th elower TCO.


Native Windows Terminal Services

Native Terminal Services is an excellent way to begin looking at thin client technologies and is perfect for small scale deployments. Server 2008 has also added several of the features that were only previously found in Citrix products such as the ability to publish applications rather than just desktops.

What you need

  1. Terminal Services CAL for each device of user
  2. Windows Server CAL for each device or user
  3. Windows Server license for each terminal server
  4. A decent spec server for roughly every 30 concurrent connections

Advantages/Disadvantages (assuming Server 2003)

  1. Cost effetive way of implementing thin clients
  2. Clients available for most common operating systems (although many clients have been reverse engineered by open source projects)
  3. Limited load balancing support
  4. No concept of a farm (group of servers) which means you have to specify which server to connect to

Windows and Citrix

Citrix XenApp (formerly Presentation Server) gives the most features and possibilities for managing your implementation by far. Of course, it is not the perfect fit for all implementations - particularly small scale ones - and is one of the more expensive solutions.

What you need

  1. Terminal services CAL for each device or user
  2. Citrix CAL for each concurrent connection
  3. Windows Server license for each terminal server
  4. A decent spec server for roughly every 30 concurrent connections (pref. an additional server for a little redundancy)

Advantages/Disadvantages (assuming Enterprise or greater licenses)

  1. Load balancing across servers based on any number of metrics (e.g. number of connections, CPU load, memory utilisation, etc.)
  2. Clever installation management
  3. Client software for most OSs (e.g. Windows, Mac, Linux, Unix, PocketPC, Java Webclient - all supported by Citrix)
  4. Secure Gateway allows publishing of the farm to the Internet through a reverse proxy
  5. Too many management and monitoring tools to mention
  6. Licensing is relatively expensive (upwards of £120 per concurrent license)

Windows and 2x


Windows and Ericom


Windows and Jetro


Sun Secure Global Desktop (aka SGD)

Info to come

Sun Ray

Sun Ray are really really thin clients. Sun like to call them Ultra Thin Client or Virtual Display Clients.

The Sun Ray has no embedded OS, they are controlled fully by a small firmware download and instructions passed fron either Solaris or Linux based control servers.

The beauty is that they are platform agnostic, effectively clever picture painters. Due to this you can have a mix of operating systems "painted" on the same Sun Ray.

Traditional "windows" deployments of Sun Ray have been to Windows Terminal Server. However as virtualisation gathers momentum they have the abilty to provide individual users XP/Vista desktop using Virtual Desktop Infrastructure.

Additionally the latest Sun Ray 2 and 270 models have the ability to have VPN info stored in the firmware. The allows with the correct networking equipment Sun Ray to be deployed at home connecting back to the school datacentre. There are currently 2 large implementations of this under way under Computers for Pupils which will see by the end over 2000 Sun Ray deployed into Students homes.

Linux Terminal Servers

Linux Terminal Server Project (LTSP) is an add-on package for Linux that allows many people to simultaneously use the same computer. Applications run on the server with a terminal known as a thin client handling input and output. These thin clients are also known as X terminals. Generally, they are low-powered, lack a hard disk and are quieter than desktop computers. This is because they do not have any moving parts. LTSP is distributed under the terms of the GNU General Public License[1] and is thus free software.

This technology is becoming popular in schools as it allows the school to provide pupils access to computers without purchasing or upgrading expensive desktop machines. If the school does not have enough computers, new thin client machines are less costly than standard computers. If the school does have enough computers but they are a few years old, they may be able to extend the useful life of obsolescent computers by converting them into thin clients, since even a relatively slow CPU can deliver excellent performance as a thin client. Some examples of distributions using LTSP are AbulÉdu, the Cutter project, Deworks, Edubuntu, K12LTSP and Skolelinux.

In addition to the possibility of getting more performance for less money by getting one high-end server and turning their existing computers into thin clients, an educational institution may also gain more control over how their students are using computing resources by switching to a thin client configuration. http://en.wikipedia.org/wiki/Linux_Terminal_Server_Project

HP t5725 Clients

Although not a true thin client (the client boots from onboard flash and you can run local applications) these terminal are great as thin clients. With no moving parts and low power consumption you get many of the cost savings and other benefits of thin client computing.

With the terminals you get a license for Altiris Deployment Solution which allows you to centrally manage the terminals (including scheduled powering off and on). It is very easy to script settings changes, etc. and the full-blown Debian installation means you can run 'proper' apps.

Prior to the t5725, the best terminal was the t5125 which ran a slimmer version of Debian but offered the essential features still, including Altiris configuration. Steer clear of the t5135... why bundle an Altiris license if all you can do is set the time and startup/shutdown the terminal???


Thinstation is an opensource project that turns any old PC into a thin client device to allow you to access terminal services offered by a server. Thinstation can be installed locally or can be PXE booted from the network and you are presented with either a basic Windows-style interface or a simple RDP/ICA session.

What you need

  1. Some old PCs (preferably with PXE-capable network adapters)
  2. A TFTP server
  3. The necessary licenses for your clients


  1. Very cheap - a good option for initial migrations to reduce the startup costs or to run thin client on your existing fat client PCs either as a trial/pilot or a backup for if the fat client OS fails. (Using a PXE menu system allows the user to choose at boot time.)
  2. True thin clients take less space, make less noise, use less power.
  3. The full TCO savings are not realised due to the usage of more power-hungry hardware and moving parts such as CPU fans and actively cooled PSUs

Development on this projcet has slowed. Some experience problems with USB support (its mounted under teh thinstation linux so the folder structure on the device shows the partition as well as the folders which confuses some users).

CULT Thin Client

  1. Fast booting RDP thin client software similar to Thinstation
  2. http://cult-thinclient.sourceforge.net/
  3. Designed to be modular to make additions easy to add. EG add firefox so that users can easily access email/vle without having to take up a TS license. Security provided by the email server or VLE login.
  4. Can have ICA support compiled in.

Licensing Notes

There are a few important notes on licensing (particularly MS licensing)

  • MS Office requires each access device to have its own license
  • MS Exchange requires each access device plus each terminal server to have its own CAL