Last updated on March 31, 2023
Parallels RAS 19.2 Session Optimization: RDP Shortpath for Azure Virtual Desktop
Minimizing latency improves the user experience.
When accessing virtual applications and desktops, the user experience is highly dependent upon network communications, including latency. Latency refers to the time gap between requesting data and receiving a response from the server or resource.
When latency is high, it can lead to slow application performance, thereby impacting users’ productivity and compromising their overall experience. Users find that delays in keystrokes and mouse movements are frustrating. When mouse clicks and keystrokes don’t immediately reflect the user activity, this is most often due to latency.
RDP over UDP significantly boosts the overall user experience. This is especially the case for applications that are latency sensitive, as well as graphics-intensive applications. These use cases are mostly found in industries that use CAD/CAM applications such as manufacturing and engineering but can also apply to other industries.
For these use cases, there’s a new feature we are excited to introduce in Parallels RAS 19.2: the support for RDP Shortpath. In this article, we will delve into the benefits, requirements, and configuration of RDP Shortpath for Azure Virtual Desktop integrated in Parallels® RAS.
What is RDP Shortpath?
RDP Shortpath minimizes latency for Azure Virtual Desktop workloads by allowing the remote desktop client take make UDP based transport to access an Azure Virtual Desktop Session host (previously terminal server). First, let’s take a step back and look at the network protocol.
Connections to Azure Virtual Desktop can use Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) for transport. RDP Shortpath extends UDP functionality by establishing a direct UDP-based connection between the client and the remote desktop session hosts.
RDP Shortpath adds a UDP connection once the connection is established, which improves performance and reduces latency. This is especially beneficial for users who work with graphics-intensive applications or need to access large files, but also increases the perceived end user experience for any Azure Virtual Desktop session.
Benefits of Parallels RAS support for RDP Shortpath
Parallels RAS has a direct integration with Azure Virtual Desktop. When combining both solutions, you can manage RDP Shortpath to optimize user sessions from within the Parallels RAS console. To get a glimpse of how to manage RDP Shortpath using Parallels RAS, please take a look at this video:
Easy configuration of RDP Shortpath with Parallels RAS
It is easy to configure RDP Shortpath from the Parallels RAS Console. From the Parallels RAS Console, go to Farm > Azure Virtual Desktop > Host Pools, and open the Host Pools Settings tab. Now select “Manage RDP Shortpath” and click configure. This will get you to the dialog as shown below. 
Select “Use RDP Shortpath” to enable RDP Shortpath for all remote desktop session host servers as part of this Azure Virtual Desktop Host pool. You can, if needed, also disable RDP shortpath using the same dialog.
By default, RDP Shortpath uses a fairly large port range. To limit the port range select “Use a smaller default range of ports” and provide the ports you want to use. The default range is 49152-65535.
This port range only applies to RDP Shortpath for Public networks. RDP Shortpath for public networks does not require any inbound ports, as it uses outbound udp connectivity. From the Parallels RAS Console in the sessions area, you can confirm that the UDP protocol is being used for the user connection, by looking at the “User Experience” metric.
RDP Shortpath modes
RDP Shortpath for Azure Virtual Desktop can be used in two modes, depending on your infrastructure and requirements.
RDP Shortpath for Managed networks
When using RDP shortpath for managed networks, direct connectivity is established between the client and the session host when using a private connection, such as a virtual private network (VPN). This mode relies on inbound ports.
To allow access to the RDP Shortpath listener between client and session host across network security boundaries, an Azure Network Security Group or Azure Firewall must be configured to allow inbound UDP connection over port 3390.
Furthermore, a Virtual Private network (VPN) or ExpressRoute is also required to allow the UDP flow, or all session host servers should have public IP addresses assigned.
RDP Shortpath for Public networks
When using RDP shortpath for Public networks, direct connectivity is established between the remote desktop client and the session host when using a public connection. This mode relies on outbound ports with a predictable port range based on the Azure Virtual Desktop agent running on the session host. To allow access to the RDP Shortpath listener, no inbound ports are required because outbound ports are being used.
Both RDP Shortpath methods enabled
When both RDP Shortpath for public networks and managed networks are enabled, a first-found algorithm kicks in, meaning whichever connection gets established first for that session is used.
In most scenarios, when you have configured RDP Shortpath for managed networks you will want to have that take precedence, and that is usually the case because building the session for RDP Shortpath for public networks takes a little longer.
Integrated management of RDP Shortpath in Parallels RAS
When Azure Virtual Desktop workloads are deployed via Parallels RAS, RDP Shortpath can improve the user experience by minimizing latency by leveraging UDP based transport.
Using Parallels RAS, RDP Shortpath is easy to configure and maintain, and the usage can be verified within the user experience metrics.
Discover how support RDP Shortpath improves your Azure Virtual Desktop + Parallels RAS integration!
