This is my second post in a short series about presentations I delivered at BriForums. In my previous post I discussed my presentation about Web Interfaces – how they work and their limitations. In this post I’ll discuss my presentation about the architecture of Server Based Computing / Terminal Services solutions.
A key difference between Ericom PowerTerm WebConnect and Citrix XenApp (Presentation Server / MetaFrame) is that XenApp was originally designed for Windows NT 3.51 where as PowerTerm WebConnect was originally designed for Windows Server 2000 / 2003. This is an important distinction because NT 3.51 was a single-user operating system and did not include Terminal Services. As a result, Citrix was required to implement this functionality itself, making XenApp a large and complex package that replaced various internal Microsoft components. Windows Server 2000, 2003 and 2008 are multi-user operating systems, and provide Terminal Services as a built in feature, however XenApp remains large and complex, and still replaces internal Windows components instead of utilizing them. PowerTerm WebConnect leverages modern Windows capabilities, and does not replace or modify any system components.
Another key distinction is that the original MetaFrame (WinFrame) was designed as a single server solution. When Citrix enhanced it for clusters (farms) they did this by elevating a specific server to a controller status (Zone Data Collector). However, the architecture remained that the entire software package must be installed on each server, so that the controller and all the other servers in the clusters are identical in terms of the components installed on them. Conversely, PowerTerm WebConnect was designed for Terminal Servers clusters from the get-go. A single PowerTerm WebConnect server (or a cluster of servers) can manage hundreds of Terminal Servers. On the Terminal Servers themselves only a small (2MB) agent needs to be installed.
In this session I delved into the consequences of these design distinctions, in terms of how the solutions are architected, and described the resulting capabilities and limitations. I also predicted that VDI solutions will utilize the same architecture as PowerTerm WebConnect, which I termed “three-tier architecture” – a prediction that has proven to be correct. You can find the presentation here.