Terminal servers: de­f­i­n­i­tion, basics, and ad­van­tages

Computers have become an integral part of daily life for busi­ness­es, and many companies now have their own, in­dis­pens­able IT de­part­ments. Their most important tasks are not just in­stalling software programs and creating e-mail accounts, but also ensuring that all devices are optimally in­te­grat­ed into the company network. For example, employees should be able to access the central file server, check the corporate e-mail account, or use company software from both a company PC and their mobile device. Users should also have as many options as possible in terms of operating systems (Windows, Linux, macOS, etc.). Although re­quire­ments may vary from company to company, terminal servers have proven to be a powerful tool in an IT de­part­ment’s arsenal.

There are three necessary building blocks needed to create a terminal server:

1. Server hardware that supports a multi-user system
2. Network protocol for remote access
3. Client ap­pli­ca­tion for the terminal server

Like any server, a terminal server also needs the necessary hardware to fulfill its function properly. It is therefore important to ensure that suf­fi­cient computing power is available to host the in­di­vid­ual ap­pli­ca­tions and the server’s operating system. Pro­cess­ing per­for­mance is the most important element, and using multi-core proces­sors is rec­om­mend­ed. Work memory and disk space are equally important, with the re­quire­ments being heavily dependent on the resource intensity of managed ap­pli­ca­tions. An ad­di­tion­al factor is the number of terminal server clients that si­mul­ta­ne­ous­ly access the offered terminal services.

The second protocol then lays the foun­da­tion for com­mu­ni­ca­tion between terminal server and client. It es­tab­lish­es policies for data exchange to allow users to remotely access the terminal services. While the initial protocols, like the pre­vi­ous­ly mentioned X11, only had to regulate es­tab­lish­ing the con­nec­tion, newer proxies like the Citrix Protocol ICA (In­de­pen­dent Computing Ar­chi­tec­ture) or the pro­pri­etary Microsoft Protocol Remote Desktop Protocol (RDP) also allow com­pres­sion spec­i­fi­ca­tions, en­cryp­tion, and the caching of trans­mit­ted data and in­for­ma­tion.

Finally, each device must install client software that allows users to connect to the terminal server over the remote protocol and use the ap­pli­ca­tions provided. The software and hardware ar­chi­tec­ture is also often enhanced by a licensing server that manages the access licenses.

If software is made available through a terminal server, both the server and every accessing client must have the necessary licenses to use it. This plays an important role es­pe­cial­ly with pro­pri­etary programs, because they often require a license for the server itself and for each client. In this scenario, the licensing server will act as a central ad­min­is­tra­tive entity for the various licenses that Microsoft require, such as Client Access Licenses (CAL) for example. There are two licensing models:

• Device license: When equipped with a device license, the device can be used by multiple users to access the terminal service. This model is ideal for sit­u­a­tions where multiple users share a work PC, like a hotel reception.
• User license: If users need to access terminal server services from more than one device, users’ licenses are the best option. This means that just a single license is required even if a user accesses remote services from a work computer, as well as from a smart­phone on the go, or a PC at home.  

After the initial con­nec­tion is es­tab­lished, the licensing server forwards the desired licenses to the client. Each time they access it, they adjust it to determine that the device or user in question already has a valid license. Ad­min­is­tra­tors should always be aware of how licensing works on the pro­pri­etary terminal server to optimize costs.

The pre­vi­ous­ly mentioned license costs are one of the most important costs when it comes to running a terminal server. The amount depends on how many users are connected to the remote en­vi­ron­ment and use it si­mul­ta­ne­ous­ly. Fur­ther­more, which ap­pli­ca­tions should be cen­tral­ized plays a key role in whether pro­pri­etary products like a Windows operating system, or open source software like Linux dis­tri­b­u­tions and Li­bre­Of­fice, are more likely to be used. Next to the costs of the terminal services provided, the following expenses apply to terminal server operators:

• Hardware: As pre­vi­ous­ly mentioned, there must be enough computing power to run the server. When it comes to a local hardware solution, re­dun­dan­cy must be ensured to be able to replace defective com­po­nents as quickly as possible.
• Main­te­nance and operation: The chosen hardware solution not only results in purchase but also main­te­nance costs. In addition, expenses for cabling, elec­tric­i­ty etc. should be included in the budget.  
• Ap­pli­ca­tion main­te­nance: The in­di­vid­ual ap­pli­ca­tions that are available to terminal server users must also be main­tained regularly. Therefore, it is necessary to ensure that you update, make ad­just­ments, or install new terminal services if necessary.
• Backup and pro­tec­tion: Both the terminal services them­selves as well as the in­di­vid­ual databases should be secured in the best possible way. Pro­tec­tion software and backup solutions are therefore a must to be optimally prepared for technical problems (e.g. power outages) and unau­tho­rized access.  
• Rights man­age­ment: Funds should be set aside for the de­vel­op­ment of a com­pre­hen­sive access concept (au­then­ti­ca­tion, au­tho­riza­tion, etc.) to benefit in the long term from a well-con­sid­ered and regulated rights al­lo­ca­tion.

A terminal server is very ben­e­fi­cial to busi­ness­es as a central ap­pli­ca­tion man­age­ment unit for a variety of reasons. For example, ad­min­is­tra­tors benefit from the con­sid­er­able workload as­so­ci­at­ed with network ar­chi­tec­ture being eased: all ap­pli­ca­tion software just needs to be installed once (on the server), which saves a lot of time and effort. This pref­er­ence is also no­tice­able when the re­spec­tive ap­pli­ca­tions need to be main­tained and updated. It is only necessary to install the terminal server client software on all devices that should allow remote access to the services provided. In addition, a central dashboard makes it easy to monitor the in­fra­struc­ture of the network and all relevant user ac­tiv­i­ties.

As pre­vi­ous­ly mentioned, costs can be saved thanks to the specific terminal server licensing models. But the remote concept is also very cost-effective for other reasons: Since most of the pro­cess­ing and storage of data is done on the central server, expensive hardware does not have to be purchased for in­di­vid­ual work­sta­tions. In certain scenarios, even a return to the original terminal server concept with clients without their own hard disk space is con­ceiv­able. In this instance, we are also talking about so-called thin clients (“slim clients”). These slimmed-down desktop setups also have the advantage of being very energy efficient and have a longer lifespan than ordinary work­sta­tions.

The great ad­van­tages of a terminal server include the ability to access the services provided (including personal data) with almost no re­stric­tions. Users have the freedom to select their terminal and operating system. The chosen system only needs to support the re­spec­tive terminal server client software and the protocol needed for com­mu­ni­ca­tion. Remote access requires no physical con­nec­tion between server and the client, so resources can be used from anywhere.

Centrally hosting and managing ap­pli­ca­tions also has the advantage of providing less access to external users. Since the data does not leave the server en­vi­ron­ment, a com­pre­hen­sive security plan can be created with little effort. If a client ex­pe­ri­ences an un­fore­seen incident (power failure, virus attack, hack, etc.), the program and user data stored on the terminal server is never com­pro­mised. Meanwhile, backup solutions and pro­tec­tion programs ensure its security.

The ad­van­tages listed make terminal servers a worth­while in­vest­ment for numerous companies. The pre­req­ui­site is, however, that the ap­pli­ca­tion re­quire­ments of different clients are not too different. Namely, if the terminals place too broad a range of demands on hardware and software, a client terminal server network tends to be im­prac­ti­cal. In this case, the benefit of unified in­stal­la­tion and main­te­nance cannot be realized, while de­pen­den­cy on central man­age­ment still exists. However, this shows one of the few concrete dis­ad­van­tages of the model: Terminal service users are au­to­mat­i­cal­ly limited in their options (ad­min­is­tra­tion, etc.) and cannot use in­di­vid­ual ap­pli­ca­tions in the event of a server failure.

A second dis­ad­van­tage is that a terminal server does not always support all standard software. If the ap­pli­ca­tions that need to be centrally hosted are not com­pat­i­ble with the server, the remote model does not make much sense for a business. Similarly, the licensing models as­so­ci­at­ed with the server and its services can similarly become exclusion criteria if they are not cost-effective for the specific re­quire­ments.