A client access license (CAL) is a license that provides a user or a computer access to a server service. Device CALs give a computer with several users (e.g., working in shifts) access to a server. User licenses give users access to a server from their devices (e.g., PCs, laptops, tablets, or smartphones). To find the best approach for an enterprise, you always need to do the math. Licenses are available for both the operating system and for server applications such as Exchange and SharePoint.

Licensing with Windows Server 2012 R2

Companies can purchase server licenses for Windows Server 2012 R2 and use CALs for user licensing, which is the easiest approach in most cases. In this special case, CALs for servers with Windows Server 2012 are also valid for Windows Server 2012 R2, as well as Remote Desktop Services (RDS) or Active Directory rights management CALs – something that is normally not allowed.

The Foundation and Essentials editions of Windows Server 2012 R2 are the exceptions to this rule because you do not need any CALs here. This means you can only connect 25 (Essentials) or 15 users (Foundation). Furthermore, the servers are only allowed a maximum of two processors (Essentials) or one processor (Foundation). This is, however, only an exception in Windows Server 2012 R2, because CALs for Windows Server 2008 R2 are valid in neither Windows Server 2012 nor Windows Server 2012 R2. Conversely, it is always possible to access the previous version of the product with a CAL. In other words, you can use Windows Server 2012 CALs to access servers with Windows Server 2008 R2.

As soon as the successor to Windows Server 2012 R2 is released, enterprises are thus well advised to choose the successor version CALs with new licensing and use them with Windows Server 2012 R2. This step can save a large sum of money during a later migration because the CALs are already in place.

If you use other Microsoft products, such as SharePoint or Exchange, on your servers, you will also need another CAL for the corresponding server application in addition to the operating system CAL. That also applies to the use of the Remote Desktop Services and Active Directory rights management. In the case of RDS CALs, the server stops working if you have not licensed the product (Figure 1). As with conventional CALs, you can purchase user and device licenses for RDS CALs. Administrators using remote desktop services in the enterprise need to come to grips with the topic of licensing.

Figure 1: For Remote Desktop Services, you need to manage the licensing actively; otherwise, users cannot work with the system.

Cheaper by the Dozen: CAL Suites

If you use Windows Server 2012 R2 with Exchange Server 2013 on the network, you need to purchase a CAL for Windows and a CAL for Exchange for each user or device. If users also use Enterprise functions in Exchange, an Enterprise CAL is also required. Microsoft offers CAL suites to simplify licensing. Suites bundle the required CALs and are naturally cheaper than individually licensing all the products. Like normal CALs, you can assign CAL suites to users and devices. If you assign a CAL suite for Exchange to a user, that user can access their mailbox via the Internet from all their PCs, notebooks, and devices. However, you are not allowed to split CAL suites. In other words, you cannot spread a suite's individual licenses over multiple computers or users.

Another advantage of CAL suites is their comprehensive version support. If you opt for a CAL suite, you can access the latest versions of the licensed products without having to purchase additional licenses. For example, if you migrate from Windows Server 2008 R2/Exchange Server 2010 to Exchange Server 2013 with a CAL suite, the CAL suite remains valid. In this case, too, you need to be mindful of the suitability of the license for Enterprise. If you have a CAL Standard suite for Exchange, advanced features such as archive and journal are not included. You need a CAL Enterprise suite for these.

Microsoft offers a Core CAL suite and an Enterprise CAL suite for the major products. The Core CAL suite provides access to core components, such as Exchange mailboxes or calendars. The typical components are Windows Server CALs, Exchange Server Standard CALs, SharePoint Server Standard CALs, Lync Server Standard CALs, as well as a System Center Management license and System Center Endpoint Protection. The two suites are only available in the scope of software assurance agreements.

Licensing External Users and Server-Based Services

If external users need to access server services via the Internet, these users need to be licensed. This requirement also applies to server-based services such as printers or multifunction devices. If a printer communicates with the server in any way and uses server-based software (e.g., to email scanned documents), the printer needs a CAL. However, if the user accessing the device has a user CAL, you do not need to license the device.

If you have assigned CALs for accessing internal server services to users in the company, these users with external access to other servers must also be considered in terms of licensing. The user might be allowed to access your own servers via the Internet, but not the servers of your clients or partners. A CAL is not valid for all Windows servers, but rather just for your own company's servers. If, for example, you have assigned a CAL to a sales employee that allows that employee to access your own server on the network, this employee is not permitted to access partner company or client servers. This kind of access is not covered by the conventional CALs. This also applies to accessing services in Windows Azure and others, but more on that later.

In this context, Microsoft offers the External Connector license. This allows external users who have not been assigned a CAL in the company and who do not belong to your company to access public, server-based services such as Lync or a web server via the Internet. External Connector licenses are assigned directly to the servers and cover all external user access rights to this server and its services. In this way, it is possible, for example, for partners and clients to access the server without you having to purchase licenses for all users. The External Connector license thus replaces CALs for external access.