Microsoft, trying to gain a larger footprint in desktop virtualization, has applied a protocol acceleration technique to its lagging remote user protocol, RDP, and is widening its partnership with Citrix Systems.

The desktop acceleration technology was acquired from Calista in 2008 and is now called RemoteFX into Microsoft Remote Desktop Services, its former terminal services.

Remote Desktop Services includes the RDP protocol, which feeds the desktop display to either a terminal, or more frequently today, a virtualized desktop device, such as a laptop or thin client. RemoteFX will act as an accelerator for RDP but it will do so only for the clients of a server running Windows 7 Service Pack 1 server.

The slowness and limited capabilities of RDP have made if useful in departmental settings for handfuls of virtualized desktops but it lagged the capabilities of new protocols offered by VMware and Citrix Systems in their desktop virtualization architectures.

The speed of a remote desktop protocol is one of the biggest factors in determining how organizations go about implementing desktop virtualization. The protocol in some cases need to be able to perceive the capabilities of the end user device and move video or other high bandwidth display traffic to it at an acceptable rate.

Implementers want to be able to assure end users that their PC and laptops are being replaced with virtual machines that match their existing desktop experience.

RDP was an inhibitor to virtual desktop performance in the cases where it was the only available protocol. Until yesterday's announcement, Microsoft tended to rely on its partner, Citrix Systems, to provide high end terminal services, application virtualization and virtual desktop infrastructure through its high speed ICA protocol, its application virtualization software XenApp (the former Presentation Server) and its virtual desktop generator and manager, XenDesktop.

XenDesktop includes Flexcast, the capability to determine the network bandwidth needed to appropriately deliver Flash animation or other multimedia to an end user device. ICA includes High Definition Experience or HDX to move Flash, 60-frames a second video or other multi-media to the end user.

Microsoft said Thursday that it's also simplifying and lowering the price it charges for virtualized desktops to run Windows.

The software giant previously offered licensing to run virtual Windows desktops under a complex Virtual Enterprise Centralized Desktop scheme, charging customers signed up for its Software Assurance Program and addition $23 per desktop per year. For customers not signed up, the charge was $110 a year. Effective July 1, it will drop the $23 charge for Software Assurance customers and reduce non-Software Assurance customers to a charge of $100 a year, the company said in an announcement Mar. 18.

Microsoft and Citrix Thursday signed an agreement to extend Microsoft's RemoteFX with Citrix' HDX.