Several presentation virtualization solution providers, including Ericom, are touting improvements to multimedia performance over remote presentation protocols. These improvements are implemented either as enhancements to the standard Remote Desktop Protocol (RDP) or using proprietary protocols, such as ICA and Teradici (Ericom does both: enhancements to RDP as well as support for the Teradici PC-over-IP protocol). With all these 3rd-party extensions and enhancements it’s easy to forget that Microsoft itself has already enhanced RDP performance in the new version 6, especially when used with Windows Server 2008 Terminal Services. In this post I will describe some of the Microsoft enhancements to RDP and explain how to enable them.
Back in November of 2007, Nelly Porter, senior program manager lead for the Terminal Service Product Development team, presented a TechNet Webcast entitled “Remote Desktop Protocol as a Presentation Remoting Platform“. In this Webcast Nelly described various enhancements to RDP in version 6 (RDP6). For example, in previous versions of RDP its performance improved when color depth is reduced. As a result, sysadmins often publish desktops and applications using the lowest acceptable color depth (or lower ). Turns out that in RDP6 this is not necesarily the case. Nelly presented a graph which showed that the new 32bpp color mode consumes less bandwidth than 24bpp color mode, and is more-or-less on par with 16bpp color mode. This means that RDP6 can provide improved end-user experience without adversely impacting network performance. Note that the new 32bpp color mode requires both an RDP6 client and a Windows Server 2008 Terminal Server, or Vista host if you are implementing VDI.
Another significant RDP6 enhancement which Nelly also discussed is its new compression mechanism. By default Windows Server 2008 Terminal Server and Vista utilize a new bulk compression algorithm, codenamed NCrush, which can reduce RDP network bandwidth usage by 15%. Windows Server 2008 Terminal Services also introduces a newer compression algorithm (which is not available on Vista) codenamed XCrush, which can reduce bandwidth by 35%! Note that XCrush consumes more memory per-session so enabling it may reduce the number of sessions which can be hosted on a single Terminal Server. By default Windows Server 2008 Terminal Services utilizes NCrush, which is labeled “Balance use of memory and bandwidth”. To enable XCrush select “Optimize to use less network bandwidth” in the Computer Configuration / Administrative Templates / Windows Components / Terminal Services / Terminal Server / Remote Session Environment group policy.
Some RDP6 enhancements may actually increase bandwidth consumption. One such enhancement is ClearType remoting, also known as Font smoothing. Helge Klein measured the impact of enabling ClearType remoting and posted the results on his blog. Helge concluded that “Enabling font smoothing dramatically increases the bandwidth required for displaying text over RDP”. So this is a feature better left disabled if bandwidth is limited.
Since Ericom PowerTerm WebConnect supports RDP6 and is certified for Windows Server 2008 – PowerTerm WebConnect is, in fact, the only presentation virtualization solution that supports this platform – you can use it to gain the benefits of Microsoft’s RDP improvements. You will then be able to combine the Windows Server 2008 improvements with Ericom’s own enhancements for even more significant bandwidth savings.