RDS — Remote Desktop Services
Category: server
Last reviewed by the MSLicenseHub Licensing Desk.
Remote Desktop Services (RDS) is a server role in Windows Server that allows users to access graphical desktops and Windows applications hosted on a centralized server. Unlike a standard PC environment where processing happens locally, RDS executes workloads on the server while streaming the user interface to a remote client device, such as a thin client, laptop, or smartphone.
Technical and Licensing Architecture
RDS operates by facilitating multiple concurrent sessions on a single instance of Windows Server. To utilize this functionality, the environment requires three distinct licensing layers:
- Windows Server Base License: The physical server cores must be licensed (typically via the Per Core model).
- Windows Server CALs: Every user or device accessing the server for any purpose requires a standard Windows Server Client Access License (CAL).
- RDS CALs: Accessing the specific RDS functionality requires an additional "additive" CAL. You cannot use RDS legally without both the base CAL and the RDS CAL.
How RDS Appears on Quotes and Agreements
When reviewing a Microsoft Volume Licensing quote (such as an Enterprise Agreement, MPSA, or CSP), RDS is typically listed as a separate line item under the Windows Server family. It is categorized by its "Tracking Type":
| Licensing Model | Description |
|---|---|
| RDS User CAL | Best for users who access the RDS environment from multiple devices (e.g., a home PC, a mobile phone, and an office laptop). |
| RDS Device CAL | Best for shared workstations, such as those used by shift workers or in kiosks, where multiple people use the same hardware. |
| External Connector | A specialized license for high-volume external (non-employee) access, removing the need to count individual CALs for non-staff. |
Common Misunderstandings
A frequent point of confusion is the "Two-User Limit." Windows Server allows for two concurrent administrative sessions for server management purposes without RDS CALs. However, using these sessions for general business tasks or application hosting without proper RDS licensing is a breach of the licensing agreement. Additionally, users often mistake RDS for Virtual Desktop Infrastructure (VDI); while related, RDS shares a single OS instance among many users, whereas VDI provides each user with their own dedicated Virtual Machine (VM) running a client OS like Windows 11.
Related Terms
- RD Session Host: The specific server role that hosts the applications or desktops.
- RD Gateway: A role that allows secure, encrypted access to the RDS environment over the internet.
- Azure Virtual Desktop (AVD): The cloud-native evolution of RDS, which often includes the RDS access rights within specific Microsoft 365 subscriptions.
- Extended Rights: If you have Software Assurance on your RDS CALs, you may have rights to use them in cloud environments via License Mobility.
Practical Buying Advice
When purchasing, remember that RDS CALs must match or exceed the version of the Windows Server OS they are accessing. For example, a Windows Server 2019 RDS CAL cannot be used to access a Windows Server 2022 Session Host. If you are buying new hardware, note that while the base Windows Server OS might be provided via an OEM license (pre-installed by the manufacturer), RDS CALs are almost exclusively purchased through Volume Licensing or CSP channels. Always verify if your existing Microsoft 365 E3 or E5 licenses already provide the necessary access rights for cloud-hosted environments before purchasing standalone RDS CALs.
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