Microsoft licensing rules are the bane of many IT pros' existence. If you're using Remote Desktop Services, you need to get your licenses and policies straight.
Prior to the release of Windows Server 2008 R2 in 2009, Microsoft customers who used Terminal Services -- now Remote Desktop Services (RDS) -- had to purchase Terminal Services licenses for Windows Terminal Server to meet licensing requirements for their remote sessions. Since Windows Server 2008 R2 was released, however, customers have been required to comply with a licensing scheme based around the Remote Desktop (RD) Licensing role instead.
Make sure you understand the requirements of that licensing policy and the various methods to calculate the number of licenses required to comply with Remote Desktop Services licensing terms and conditions.
Building blocks of Remote Desktop Services licensing
Three building blocks come into play for remote desktop access in a Microsoft Remote Desktop Services environment:
RD Session Host role. For Windows Server 2008 R2 and later versions, the server role for Remote Desktop Services is called an RD Session Host. For clients to have a remote server with which to establish a session, at least one Internet-accessible host on your network must support the RD Session Host services role.
Licensing server. To use Remote Desktop Services, at least one license server must also be available on your network (usually as part of the domain or domain forest in which your remote users reside). It is possible for a single physical or virtual server to support both the RD Session Host and the RD Licensing role services (often called a licensing server) in smaller network environments.
Client Access Licenses. Each active remote session on a server that supports the RD Session Host services role requires a single RDS Client Access License (CAL). The Licensing role keeps track of CALs on a network and won't allow more active sessions at a given time than the total number of CALs under its control.
Any Standard Windows Server 2008 R2, Windows Server 2012 or Windows Server 2012 R2 license (or better) includes the two server-side building blocks needed to set up and use RD Session Host and Licensing services.
Calculating CAL needs
You should calculate the maximum number of simultaneous remote sessions needed to determine how many CALs you must purchase for the Licensing server to manage. CALs come in two forms:
- RDS per-device CALs: associates a license with a specific device (nontransferable to other devices)
- RDS per-user CALs: associates a license with a specific user account (nontransferable to other user accounts)
Choosing one type over another depends on whether users typically initiate remote sessions from the same device or not. If so, per device probably makes the most sense. On the other hand, if users log in remotely from two or more devices regularly, per user will keep costs down.
Microsoft sells its RDS CALs singly or in 5 and 25 license packages, and it will negotiate some set number of CALs as part of overall volume licensing agreements. Prices for CALs vary from around $100 (purchased one at a time) down to $65 or so (for 25-pack CALs; prices for a Volume Purchasing agreement are typically negotiated case by case).
Tips for implementing RDS licensing
When you set up one or more Windows 2008 R2 (or later version) servers for the RD Host and RD Licensing services roles, a grace period of 60 to 120 days applies to the initial usage timeframe for client access, during which interval CALs will not be checked. But once the grace period expires, numerous administrators have reported difficulties in recognizing the RD Licensing server, and remote clients get locked out of remote access.
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This is a well-known gotcha that can be repaired by deleting a specific registry key. Once that key is deleted, remote clients can then use the Licensing server to access remote desktop sessions using available CALs.
You should also know that Remote Desktop Services supports deployment of a virtual desktop infrastructure. In this kind of scenario, every device that connects to a Remote Desktop Services VDI deployment needs either an RDS CAL, a Microsoft VDI Standard Suite license or a Microsoft VDI Premium Suite license. This means that the VDI Standard Suite license or a VDI Premium Suite license is an acceptable alternative to an RDS CAL in such circumstances, though VDI licenses are only valid for RDS access into a virtual desktop infrastructure.
Additional reading on RDS licensing
The best online resources for further information on RDS licensing include:
- TechNet Overview of Remote Desktop Licensing
- TechNet Remote Desktop Services Client Access Licenses
- Windows Server forums: Fixing the Licensing Gotcha
About the authors:
Ed Tittel writes regularly on Windows topics, including a TechTarget blog called "Windows Enterprise Desktop," and has contributed to over 100 computing books. Earl Follis is a long-time Windows writer, trainer, consultant and co-author with Ed Tittel of three editions of Windows Server For Dummies.