Many many years ago, I wrote a lot of blog posts around the different remoting protocols (HDX, Blast, PCOIP and RDP) (back in 2016! Remote protocols benchmarking, Citrix, VMware and RDP–Part One PCoIP vs Blast Extreme – msandbu.org) While there was continuous improvements in the Citrix and VMware protocols, there was little improvements in the RDP protocol (at least from how it handles bandwidth and video codecs it was using)
I think that the last improvement that we had in the RDP protocol was back in Windows Server 2016 with the introduction of Remote Desktop Protocol (RDP) 10 AVC/H.264 improvements in Windows 10 and Windows Server 2016 Technical Preview – Microsoft Community Hub AVC/H.264.
Then in 2019 Windows Virtual Desktop was released, which still used RDP but tunneled within another protocol called Secure Reverse Connect which means that it used a form of reverse TCP connection to establish a RDP session to a machine. The problem with this was that it used TCP as a transport protocol which both Citrix and Omnissa stopped used a while back.
Then now fast forward 5 years later. What have we gotten in terms of new protocol features?
If you have looked at the protocol specification –> [MS-RDPBCGR]: Remote Desktop Protocol: Basic Connectivity and Graphics Remoting | Microsoft Learn which AVD still uses much at its core, there is little news there. Only a couple of things..
1: Support for newer versions of Windows Server
2: Integration with Entra ID (Needed for AVD)
Even when I looked at one of the comments at an earlier blog post from Microsoft, like support for hardware encoding for iOS (Which is still not there yet)
However you could argue that Shortpath is a improvement to the protocol which uses UDP/3390 for communication, however this has been part of RDS using Gateway for a long time as well, it is just how Microsoft is combining this together with STUN/TURN to allow communication with the endpoints to allow faster communication using UDP.
While there is no denying that both Citrix and Omnissa have a better protocol with HDX and Blast which allows much more customization and is much more able to adjust according the bandwidth needs. I do not think that this has been the top priority of Microsoft. Given that that Internet Connectivity has gotten a lot better and more stable the last 10 years, maybe we didn’t need all this investment into the protocol?
However now comes the interesting part. Microsoft recently published this documentation regarding AVD and how the RDP protocol handles encoding in the protocol (Graphics encoding over the Remote Desktop Protocol – Azure Virtual Desktop | Microsoft Learn) and one thing stood out, namely (HEVC/H.265 support is in preview and requires a compatible GPU-enabled remote virtual machine)
As long as the remote machine is one of the supported virtual machines below (and you also need to buy the HEVC codec from the Microsoft Store LOL HEVC Video Extensions – Download and install on Windows | Microsoft Store to use it…)
And in terms of configuring H.265 it can only be done using Group Policy at the moment.
Encoders are components that process raw media, compressing it into a manageable format for efficient delivery to the endpoint. At the endpoint, a decoder then receives and decompresses the signal to display the media. There are several video codecs in use today, with popular examples being H.264 (released in 2003), H.265 (released in 2013), and the newer AV1 (released in 2018). Each codec has unique algorithms and hardware requirements. Encoding involves compressing digital images to reduce the video’s file size, minimizing the bandwidth needed to stream media. When it comes to remote applications, it’s essential to balance frame rate, bandwidth, and quality to optimize performance, as high frame rates and quality demand more bandwidth.
So when Microsoft now introduced h.265 support it means something that has not been supported before in the RDP protocol. Is this game-changing? not really. Both Citrix and Omnissa already support the newer protocol called AV1, you can even see here in this blogpost from 6 years ago to see the difference between H.264 and H.265 when it was introduced into Citrix Comparison between H.264 and H.265 with Citrix XD 7.16 – GRID4ALL.
So not new! but! I find it great that we now see “new” features supported in the RDP protocol (at least from AVD perspective) and I hope that they now invest more into the protocol stack to improve the RDP protocol so we can
1: Adjust it more for high-latency and high-packet loss scenarios
2: Better throughput where we have high bandwidth connections
3: Even support for AV1 codec.
So I hope that this is the start of more new innovation in the RDP protocol stack.