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How RDS licensing rules work and recommendations to follow

Microsoft's Remote Desktop Services licensing policies can be confusing if you don't know the Client Access Licenses and Remote Desktop Services roles.

As an IT professional, Microsoft licensing rules can be the bane of your 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, if you used Terminal Services -- now Remote Desktop Services (RDS) -- you had to purchase Terminal Services licenses for Windows Terminal Server to meet licensing requirements for your remote sessions. Since Microsoft released Windows Server 2008 R2, however, you must comply with an RDS licensing scheme based on the Remote Desktop (RD) Licensing role instead. This remains true through the most current preview of Windows Server 2019.

Make sure you understand the requirements of the RD Licensing policy and the various methods to calculate the number of licenses you will require to comply with RDS licensing terms and conditions.

How to determine roles for licenses

Three building blocks come into play with remote desktop access in a Microsoft RDS deployment.

Remote Desktop Session Host (RDSH). For Windows Server 2008 R2 and later versions, the server role for RDS is called RDSH. For clients to have a remote server with which to establish a session, at least one internet-accessible host on the network must support the Remote Desktop Session Host server role.

Licensing server. When it comes to RDS licensing, at least one RD Licensing 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 RDSH and the RD Licensing role services -- usually called an RD Licensing server -- in smaller network deployments.

RDS per device CALs
How Microsoft Remote Desktop Services per-device Client Access Licenses work.

Client Access Licenses. Each active remote session on a server that supports the RDSH 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 Windows Server 2008 R2, Windows Server 2012 or Windows Server 2012 R2 Standard license -- or better -- includes the two server-side building blocks you will need to set up and use RDSH and RD Licensing services.

Calculating CAL needs

You should calculate the maximum number of simultaneous remote sessions you need to determine how many CALs you must purchase for the RD Licensing server to manage. CALs come in two forms:

  • RDS per-device CALs, which associate a license with a specific device. They are nontransferable to other devices.
  • RDS per-user CALs, which associate a license with a specific user account. They are nontransferable to other user accounts.
If you have a Volume Licensing Program agreement, you will have to negotiate with Microsoft on a case-by-case basis.

Choosing one type of CAL over another depends on whether users typically initiate remote sessions from the same device or not. If they generally use the same device, then per device probably makes the most sense. On the other hand, if users log in remotely from two or more devices regularly, per user RDS licensing will keep costs down.

RDS per-user CALs
How Remote Desktop Services per-user Client Access Licenses work.

Microsoft sells its RDS CALs on an individual basis or in license packages of five and 25. The company 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 or in small lots -- down to $80 or so for 25-pack CALs. If you have a Volume Licensing Program agreement, you will have to negotiate with Microsoft on a case-by-case basis.

Tips for implementing RDS licensing

When you set up one or more Windows 2016 servers for the RD Host and RD Licensing services roles, a grace period of 60 days, renewable once for a total of 120 days, applies to the initial usage time frame for client access. During this time, Microsoft will not check interval CALs. But once the grace period expires, numerous IT administrators have reported difficulties recognizing the RD Licensing server, which locks remote clients out of remote access.

This is a well-known catch that you can repair by deleting a specific registry key. Once you delete that key, remote clients can then use the RD Licensing server to access remote desktop sessions using available CALs.

RDS supports VDI deployments. In a VDI deployment, every device that connects to RDS must have an RDS CAL, a Microsoft VDI Standard Suite license or a Microsoft VDI Premium Suite license. This means that a 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 through VDI.

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