Thin Client

A thin client is a computer (client) in client-server architecture networks which depends primarily on the central server for processing activities. The word "thin" refers to the small boot image which such clients typically require - perhaps no more than required to connect to a network and start up a dedicated web browser or "Remote Desktop" connection such as X11, Citrix ICA, Microsoft RDP or Nomachine NX.

In contrast, a thick or fat client does as much processing as possible and passes only data required for communications and archival storage to the server.

Introduction

In designing a client-server application, there is a decision to be made as to which parts of the task should be done on the client, and which on the server. This decision can crucially affect the cost of clients and servers, the robustness and security of the application as a whole, and the flexibility of the design to later modification or porting.

One design question is how application-specific the client software should be. Using standardized client software such as a Web browser or X11 display can save on development costs, since one does not need to develop a custom client—but one must accept the limitations of the standard client.

Depending on the outcome of these decisions we might say that we use either a thin client or a thick/fat client (or a mixture of both).

Definitions

A thin client is a network computer without a hard disk drive, which, in client/server applications, is designed to be especially small so that the bulk of the data processing occurs on the server

Application program

A thin client as an application program communicates with an application server and relies for most significant elements of its business logic on a separate piece of software, an application server, typically running on a host computer located nearby in a LAN or at a distance on a WAN or MAN.

A thin client does most of its processing on a central server with as little hardware and software as possible at the user's location, and as much as possible at some centralized managed site.

The meaning of the words "significant elements", "core function", "most" and "as little" are arguable.

Other definitions of thin versus thick/fat client application program try to draw the line at whether the deployment of the application requires the installation of additional software at the user site or not. Unfortunately, this is also arguable, since e.g., a browser used for a client application might be part of one client platform, but not the other. So on one platform no additional software installation is required, while another client platform requires it. The only objective definition would seem to be whether the boot image that is normally used to start the user's computer needs to be modified in any way before the client can be used: if not, then, the client is probably thin. Another criterion is related to the management of the thin client device or program. If it can be centrally managed, it is probably thin.

However, a great deal of software is today typically included in a base boot image, specifically to support various user applications, so that it need not be reinstalled on every computer. Often, a departmental boot image is prepared to include applications specific to a department.

User-interface device

A thin client as a device is designed to provide just those functions which are useful for user-interface programs. Often such devices do not include hard disk drives, which may become corrupted by the installation of misbehaved or incompatible software, but instead, in the interests of low maintenance cost and increased mean-time between failures (MTBF) the thin client device will use read-only storage such as a CD-ROM, Network Virtual Drive or flash memory.

Ideally the user will have only a screen, keyboard, a pointing device (if needed) and enough computer to handle display and communications. Companies that develop and market these devices include Wyse, Chip PC, Sun Microsystems, WML (UK), BOSaNOVA, and Hewlett-Packard.

Device for running a thin client application program

"Thin client" has also been used as a marketing term for computer appliances designed to run thin client software. Chip PC Xtreme PC, Chip PC Jack PC, X terminal, Wyse Winterm, Neoware Appliance, Clearcube or Web kiosk might be considered thin clients in this sense.

The latest concept in this genre is 'Ultra Thin Client' technology - which takes the 'thin' concept one step further by running the connection client software (Citrix, Windows Terminal Services, telnet etc) directly from the appliance's hardware. This is a marked difference to legacy thin-client hardware architecture which ran an operating system, often Windows CE or Linux between the hardware and connection client software. There are many benefits in not requiring an operating system, lower cost, higher performance and non-vulnerablity to viruses.

Software thin client

Most thin clients are software-only however, and run on standard PC hardware. One example of this software-only thin client is PXES Universal Linux Thin Client and Pilotlinux. Knoppix is also actively pursuing this market, as is ThinStation. (See also Puppy Linux). An example on the Windows platform is the BeTwin program, which uses extra VGA/DVI graphics ports, or cards, in the host PC plus USB connected keyboards and mice to enable additional workstations.

Examples of thin client and thick client usage

The advocates of both architectures tend to have contentious relationships. In practice, there seems to be little to choose between the two approaches for many applications. A few situations may clearly call for one or the other. Distributed computing projects such as the SETI@home project (whose whole point is to pass off computationally intensive analysis to a large collection of remote computers) are applications that require thick clients. On the other hand multicasting entertainment or educational material to a number of clients might best be done with thin clients since exactly the same material is to be presented at each.

Some technologies such as Network Virtual Disks or Disk Drive Images are aimed to provide central management and security/reliability/affordability comparable to what is found in Thin Client devices: the OS that operates the client is stored on a shared virtual disk image (a disk image file) that is housed on a server in the clients' LAN. This virtual disk drive is "write protected" and shared by several clients at the same time. The content of this virtual disk drive is streamed on demand to the clients. Yet, all the computing is done by the client itself. Instead of centralizing a complete computer (centralize the storage, CPU, memory, devices etc) this approach centralizes only the hard disk drives. Because the virtual disk drives can be shared and protected, the aim to reduce TCO is also achieved with this technology. This technology can be used to run typical Embedded Operating Systems such as Embedded Linux and Windows XP Embedded, but also to run desktop operating systems such as Microsoft Windows XP Pro, FreeBSD or Linux.

Organizations that develop and market Network Virtual Disks include Linux Terminal Server Project, IBM (iBoot technology) and Ardence. Network Block Device support is another kind of Network Virtual Disk embedded in Unix and Linux.

Advantages of thin clients

Obviously, boot image control is much simpler when only thin clients are used - typically a single boot image can accommodate a very wide range of user needs, and be managed centrally, resulting in:

1. Lower IT admin costs. Thin clients are managed almost entirely at the server. The hardware has fewer points of failure and the local environment is highly restricted (and often stateless), providing protection from malware.
2. Easier to secure. Thin clients can be designed so that no application data ever resides on the client (it is entirely rendered), centralizing malware protection.
3. Lower hardware costs. Thin client hardware is generally cheaper because it does not contain a disk, application memory, or a powerful processor. They also generally have a longer period before requiring an upgrade or becoming obsolete. The total hardware requirements for a thin client system (including both servers and clients) are usually much lower compared to a system with fat clients. One reason for this is that the hardware is better utilized. A CPU in a fat workstation is idle most of the time. With thin clients, memory can be shared. If several users are running the same application, it only needs to be loaded into RAM once with a central server. With fat clients, each workstation must have its own copy of the program in memory.
4. Lower Energy Consumption. Dedicated thin client hardware has much lower energy consumption than thick client PCs. This not only reduces energy costs but may mean that in some cases air-conditioning systems are not required or need not be upgraded which can be a significant cost saving and contribute to achieving energy saving targets.
5. Worthless to most thieves. Thin client hardware, whether dedicated or simply older hardware that has been repurposed via cascading, is useless outside a client-server environment. Burglars interested in computer equipment have a much harder time fencing thin client hardware (and it is less valuable).
6. Hostile Environments. Most devices have no moving parts so can be used in dusty environments without the worry of PC fans clogging up and overheating and burning out the PC.
7. Less network bandwidth. Since terminal servers typically reside on the same high-speed network backbone as file servers, most network traffic is confined to the server room. In a fat client environment if you open a 10MB document that's 10MB transferred from the file server to your PC. When you save it that's another 10MB from your PC to the server. When you print it the same happens again - another 10MB over the network to your file server and another 10MB back to the printer. This is highly inefficient. In a thin client environment only mouse movements, keystrokes and screen updates are transmitted from/to the end user. Over efficient protocols such as ICA or NX this can consume as little as 5Kbps bandwidth.

Advantages of thick clients

1. Fewer server requirements. A thick client server does not require as high a level of performance as a thin client server (since the thick clients themselves do much of the application processing). This results in drastically cheaper servers.

2. Better multimedia performance. Thick clients have advantages in multimedia-rich applications that would be bandwidth intensive if fully served. For example, thick clients are well suited for video gaming.

3. More flexibility. On some operating systems (such as Microsoft Windows) software products are designed for personal computers that have their own local resources. Trying to run this software in a thin client environment can be difficult.

Advantages of Network Virtual Disks clients

Disadvantages of Network Virtual Disks clients

100Base-T LAN required. Because of the amount of data streamed to the clients, it is usually difficult to have a Network Virtual Disk client connected through a WAN link to the server that houses

What is a thin client?

What is a thin client?

A thin client is a computer without a hard drive. It operates on the mainframe paradigm. All instructions and sessions take place on a central, secure server. Each thin client has its own session and operates independently from others. As thin clients have no hard drives, there is no loss of data if a thin client is damaged or has a local power failure.

Why use a thin client instead of a regular PC?

The main reason thin clients are better than PCs is because they offer ‘lower Total Cost of Ownership (TCO)’. By reducing maintenance and installation time, thin clients keep downtime to an absolute minimum. Take the example of a business that has a server and five PCs. Assume that this business needs to apply a security patch for an application that’s installed on all the PCs; it would need to install and configure all five PCs, one at a time.

With a thin client an update on the server ensures that all thin clients are running the latest software. Client management and maintenance is centralised. It attempts to address staffing shortages, data privacy and security issues, and the quest for value from technology purchases. Centralising core functions of processing, disk storage, memory, applications and operating systems shifts the requirement for performance significantly, with the entire burden being placed on one or more back-end servers.

What are the advantages of a thin client?

Thin clients can be used anywhere you would normally have a PC. With thin clients being less expensive on a per-seat basis, more seats can be made available. Since servers usually have large hard drives, the user hard drive space is considerable, and data backup is simple. Most thin clients come with displays that work at up to 1600 x 1200 resolution, and top-end models come with flat panel displays.

Thin client computing is secure as there are no removable drives and users cannot insert disks that may contain viruses. They permit rapid, system-wide application or operating system upgrades. Since applications are stored on a centralised server, it is possible to upgrade thin client servers within four hours or less.

When should one use a thin client?

Thin clients are useful when a company needs several workstations with substantially lower TCO, and the workload isn’t very heavy (CAD/animation and other heavy-duty tasks require an engineering workstation.) Thin clients can be handy in harsh factory conditions or when a company doesn’t have the time or money to hire IT staff to keep its industrial or office systems up and running.

What is a thin client computing environment?

A thin client is similar to a traditional PC, except that it has minimal hardware as the computing and data storage takes place on the server. Thin clients have low-power, high-performance CPUs and decent graphics capabilities. The power requirements for thin clients tend to be on the lower side. They are usually compact with many present-day thin clients built within the display device, or externally mounted behind or beneath a flat panel or CRT.

The thin client operating system is usually loaded on the thin client flash memory or other programmable memory. The typical operating systems on these machines are Windows CE or Linux. Some browser applications may be available. Having a resident browser shifts the computing load from the host to the client to some extent. This is acceptable as long as the client has flash or similar non-volatile memory to maintain user settings, bookmarks, cache, etc.

Who are the major vendors for thin clients in India?

Wyse, HP and Neoware are the top three vendors in the thin client space.

India shows how to cut IT costs with open-source thin clients

India shows how to cut IT costs with open-source thin clients

What does a developing country like India do when plans to accelerate the adoption of computers by businesses and consumers have to overcome the high price of computing hardware and software?

It builds a computer that doesn't use costly products from Microsoft Corp. or Intel Corp., and seeks out cheaper alternatives that can get the job done, said Deepak Phatak, a professor at the Indian Institute of Technology Bombay.

"Affordability is the key to making IT happen in developing countries," Phatak said.

The problem is that existing notions of affordable prices for IT products, such as PCs and software applications, have been defined by the Western world and do not match what developing nations can afford, he said.

"This leaves only two choices. One, if you can't afford it, well, don't use IT: use paper and pencil and continue to lag behind. Or two, build your own affordable solutions," Phatak said.

For India, this means finding a cheaper alternative to the PC for local companies, he said.

The country currently has just seven PCs for every 1,000 people, far behind the 37 PCs per 1,000 people in China, Phatak said. And while India is on a drive to accelerate the adoption of computers by business and consumers, there is a lot of ground to cover before it can match China's PC penetration rates, let alone those of developed nations in the West.

Meanwhile, the gap between India and other countries continues to widen. Desktop PC sales in India are expected to reach 2.6 million in 2003, according to Kitty Fok, the director of personal systems research at IDC Asia-Pacific. That pales in comparison to China where desktop PC sales are predicted to reach 12.9 million this year, she said.

The problem, as Phatak sees it, is that PC prices are too high for Indian companies to afford.

"The PC costs are not coming down below 35,000 rupees ($763)," Phatak said.

To overcome this obstacle and spur the wider adoption of computers in India, Phatak is pushing for increased investment in IT and lower prices for hardware and software.

"I'm telling the government, the large companies, small companies, 'Quadruple your investments. Invest four times as much as you are investing.' And to IT companies I am saying, 'Give me solutions at one-quarter the total cost of ownership,'" Phatak said.

"They call me mad for that," he said.

To help bring down the cost of computers, Phatak is promoting the adoption of a low-cost thin client based on Via Technologies Inc.'s 800MHz C3 processor, rather than a more expensive chip from Intel, and Linux applications that run on a PC server.

Opting for a thin client instead of a desktop PC saves money in two ways. Thin clients don't require a hard disk and the 800MHz C3, which costs $22 in 1,000-unit quantities, is cheaper than processors from both Intel and Advanced Micro Devices Inc (AMD), he said. The cheapest desktop Celeron processor listed on Intel's Web site is a 2.1GHz version of the chip, which is priced at $69 in 1,000-unit quantities.

The lower price of the C3 helps bring down the cost of the thin client -- which includes a 15-inch CRT (cathode ray tube) monitor -- to 14,000 rupees, Phatak said. That price may fall to around 10,000 rupees next March if the Indian government follows through on an expected cut in tariffs on computer components, he said.

When it comes to software for the thin clients, Phatak has chosen Linux and other open-source software. This provides an alternative to software from companies like Microsoft, which require expensive software licenses, he said.

"We touched base with Microsoft in this regard. But Microsoft's pricing for the operating system and applications, and the application infrastructure, still proved to be too costly and that is why we have chosen the open-source route," Phatak said.

Linux and open-source software may currently be seen as the most affordable route for India's push to expand the use of IT by local businesses, but Phatak is no open-source ideologue. His goal is to see the price of building an IT infrastructure become affordable to IT companies, regardless of the specific software or hardware involved.

"We have picked up open-source software as the base today because it happens to be affordable. If something else becomes affordable, we ... do not play favorites with either technologies or products," he said. "We are innovators and we'll innovate on whatever is available."

Phatak's vision of thin clients running open-source applications is starting to take hold.

Life Insurance Corp. of India, the country's largest financing company, will roll out 10,000 of these thin clients in 2,000 offices across the country between now and the end of this year, said Tim Goldring, the chief executive officer of VXL Instruments Ltd., which is manufacturing the thin clients in Bangalore, India.

In addition, the Maharashtra State Police will put these thin clients in 900 offices in the Indian state of Maharashtra and the State Bank of India plans to deploy them at 10,000 branches across the country, Phatak said.

"I would expect the growth (in thin client shipments) to be exponential," Phatak said. "I believe in the first year the numbers could be as few as 100,000, but the fourth-year and fifth-year numbers should go up."

"My ambition is that we should sell 20 million PCs every year, for the next five years at least," he said.