Microsoft has announced the public preview of Azure Virtual Desktop RDP Shortpath for public networks – a bit of a mouthful, but what this really means is a switch towards UDP as the first choice transport for remote desktop sessions on the Azure cloud.
“Long running TCP sessions are problematic” said Senior Program Manager Denis Gundarev. “UDP is more tolerant to the temporary network interruptions caused by wireless interference or by changes in dynamic routing.”
UDP in itself is not enough; for example, UDP “does not care about each individual packet’s packet order or delivery. It does not have built-in congestion or rate control,” explains Gundarev. The implementation for RDP (Remote Desktop Protocol) uses a thing called URCP (Universal Rate Control Protocol) which Microsoft developed back in 2013, for real-time communications.
AVD already supported UDP for private networks, but many users do not have a private connection to Azure like ExpressRoute, hence the introduction of the public network version. Microsoft says that the benefits include lower latency, better network utilization, and high tolerance to packet loss.
Implementing the preview is done by setting a registry key on the AVD session host, so this can be done experimentally for just a few hosts in order to try out the feature. That said, it will not always be possible. “RDP Shortpath may fail if you use double NAT setups,” said Gundarev. Users should not notice as the old TCP-based connection will be used automatically instead.