Terminalserver

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Terminal servers provide a network terminals available that can be used by the core applications on other computers as input and output devices. Originally, the actual physical devices, the so-called over multiple RS232 ports "dumb" terminals could be connected as a workplace. The application could then communicate over the network with the user in such a terminal, with multi-user capability even with several.

Meanwhile, the role of the server and the terminal is completely imaged within a PC through applications such as PuTTY. On this PC any files. In this way, in conjunction with thin clients (minimal PC with a terminal server client) applications can be made very cost effective and low maintenance users.

This principle of only one centrally installed application that can be used over the network by several local computers, has remained, except that now full graphical user interfaces rather than simple command line functionality can be offered.

This approach followed by several software manufacturers. The most prominent representatives are the Remote Desktop Services on the Windows server 2008 R2 from Microsoft. Since Windows Server 2000 they are part of the operating system and can be activated when needed. For the management of multiple terminal servers and additional services, in practice, often the products of the company Citrix used.

Idea

With terminal servers, it is possible to make data and the required applications centrally and independently from the terminal available. An employee of a company can be accessed in this way worldwide to their data and applications from any device. The data and applications never leave here the internal network, only the screen output is transmitted to the terminal. In the other direction, only mouse movements and keystrokes are sent. So it is possible, even over a very limited performance WAN lines to work with complex programs. For several years, this principle is also known as cloud computing.

Operation

In a Microsoft Terminal Server applications, which are to be published will be installed in a classic on it. Later, individual applications or even the entire desktop can then be made available to users via a single management console. The latter is usually the use of thin clients is the case, since they themselves often have no desktop. The users can operate directly on the desktop of Windows server and start all required applications directly from the Start menu. You notice not that they do not use alone but with many other people the same Microsoft Excel or Internet Explorer. Even in the task manager they see only their own processes, they do not interfere with each other. The local disk of the terminal server is often hidden, so that users only have their network drives are available. The number of users per terminal server greatly depends on the applications and the underlying hardware used. Since switching to the 64 -bit technology and the associated loss of the 4 GB RAM limit the number of users on a terminal server is theoretically no upper limit.

Hardware

Very few servers are utilizing their hardware from even begin; this is also the reason why virtualization is very popular because they can use unused hardware resources useful. Is different with terminal servers, which can be very busy to very strongly on the number of users. In practice, space-saving hardware variants such as 1U rack servers or blades are used for terminal servers, as they have no data storage. Meanwhile, no system disk is necessary because modern servers can start a virtualization system directly from a USB stick. Due to the large number of parallel processes, terminal servers are ideal for the effective use of ( several ) multi-core processors (dual core, quad core, hexa core). However, this scaling of the hardware has its limits. Even if you can see the number of users continues to enlarge with many processor cores and very large amounts of memory, you come at some point to the limits of the network card or the hard disk subsystem. Right then and for reasons of reliability are several terminal servers are used, so-called terminal server farms.

Services in an operating system

On computers running Microsoft Windows XP or an operating system of Windows Server 2003 family, the client program for Terminal Services (Remote Desktop Connection ) by default (default ) is installed.

Microsoft Terminal Server system service uses a Remote Desktop Protocol (RDP ) to connect, this is the server component ( server role ) Terminal Services (Terminal Services). Since Windows Server 2008 R2 Terminal all role services have been renamed. The Terminal Server is now called Remote Desktop Session Host and Terminal Services Remote Desktop Services (Remote Desktop Services).

Areas of Terminal Servers

Terminal servers are mostly used in companies where a large number of employees working with identical applications, such as in large authorities or insurance companies. These applications are then installed on terminal servers and the users access via thin clients (possibly also on fat clients ) on this to.

Economy

When building with many workstations (clients) and a powerful central system (host) is the cost-effectiveness evaluated in a total model, which takes into account, for example:

  • Number of clients for simultaneous use ( licensing costs )
  • Server performance and redundancy (hardware costs)
  • Effort for the clients and local backup (maintenance cost of the hardware and operating costs)
  • Effort for changes to the application ( care costs of the application )
  • Interpretation of the network for the transfer ( hardware and management costs)
  • Security and protection of data resources ( default and abuse risks)
  • Summary of the access mechanisms in a common concept (authentication, authorization, and abuse risks)

Benefits

  • Since the data storage and processing of the data on the remote (remote) computer takes place, the local workstation (client ) with the use of thin clients be more cost effective and more robust than the use of full-fledged desktop computers with its own hard drive, etc.

The server can also function with a powerful server (host) for multiple server roles are virtualized and requires no proprietary hardware.

  • On failure, theft or virus attack of the local terminal (client) the data stored in the protected server data is not lost.
  • On the terminal server (host) can be accessed from the network. Thus, the user can log on from anywhere in the world via internet connection as a terminal and then has all applications and data installed on the Terminal Server.
  • The workplace costs ( Total Cost of Ownership, TCO ) decrease significantly for large installations.
  • The application software must be installed and maintained only once on the terminal server.
  • The maintenance required is shifting to the central system (host). A key change relates to each client.
  • At the local PC systems (clients), no adjustments need to be made, only the terminal access software must be available.
  • A redundant installation such failures can completely bridge (hot swap)

Disadvantages

  • Centralization: the plant system is basically depended on networking
  • A failure of a non-redundant server affects all clients that a failure in the network disabled all connected clients.
  • Hardware cost of a powerful terminal server that must be configured as a central interface according performant.
  • The software compatibility and the licensing model must fit: Not every standard software running on the terminal server.

Unchanged

  • The function of a permanently existing network connection between the client and the terminal server changes over a data server without the application does not.
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