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Comparing app streaming to thin clients: Pros and cons

When is application virtualization the way to go instead of thin-client computing? The two sound like they're trying to accomplish the same goal -- but naturally, they are far different approaches.

With the emergence of virtualization as an option for application delivery to user desktops, IT shops have something new to weigh when considering the consolidation of application resources.

When most technical experts refer to application virtualization, they are talking about products such as SoftGrid technology from Microsoft's recent acquisition of Softricity, Altiris Inc.'s Software Virtualization Solution and Project Tarpon, currently in beta from Citrix Systems Inc. All have different techniques for approaching the same job.

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This contrasts with server-based computing and thin client computing, which is also occasionally referred to in marketing parlance as an application virtualization technology. Here the term virtualization is used in a more comprehensive manner. The products widely used for thin client computing come from Citrix, based in Fort Lauderdale, Fla., and Microsoft.

Application streaming

The big difference between application streaming and server-based computing is that in the former, the application executes on the desktop, running as if it were on the client. In the latter, applications are physically installed and are executing on back-end servers.

"[In application streaming], instead of being installed, however, [the application is] being downloaded on demand," said Brian Madden, a Washington, D.C.-based analyst. "If you have an application like Office, it will copy your application down even as you are using the application."

The term virtualization comes into the picture when, in order for the technology to work, there must be a client agent running on the workstation. This client agent provides a virtual sandbox in which the application can run.

There is also the streaming component itself -- a packaged application that resides on the server and is streamed to the workstation. The technology is helpful for administrators who are managing remote desktops using tools such as System Management Server and who now don't need to necessarily care what is running on those workstations.

And because the applications run locally, desktop virtualization products can work when the client devices are not connected to the network. With applications running locally, it also means that thousands of users can receive streamed applications without requiring big servers.

Because application streaming technology is so new, there is still a lot about it that is unknown, such as its ability to scale, said Mark Margevicius, a research director and vice president at Gartner Inc. in Stamford, Conn.

"There's not a lot of traction yet in the marketplace and not a lot of third-party tools to manage the environment," Margevicius said. "There's a lot of work that needs to be done."

Server-based computing

Microsoft's Terminal Services and Citrix Presentation Server (which is derived from Terminal Services technology) are another way to deliver applications without installing software on an end point.

Thin client computing has some key advantages. First, in the case of the Citrix software, applications can be accessed from any platform. Streaming technology from Softricity and Altiris are for Windows-only clients, whereas Presentation Server connects any application to any device.

Also, there is no major bandwidth requirement. "I can walk up to any kiosk and within 15 seconds use an application from behind my corporate firewall," Madden said.

The downside is that it requires a network connection and a substantial back-end architecture to support the applications. If there are thousands of end users to support, an IT shop needs to buy a lot of hardware.

Shared beginnings

The Citrix server and Terminal Services share the same beginnings. In the early 1990s, Citrix licensed the Windows Server operating system and built the foundation of Citrix Presentation Server. Today, customers who buy a Citrix license must also buy a Windows Server and Terminal Services license from Microsoft.

"It's not an either/or situation," said Mike Schutz, group product manager for the security and access product management team at Microsoft. "You either use Terminal Services or you use Citrix and Terminal Services."

Terminal Services offers basic technology. As such, it is aimed mainly at small to medium-sized corporations with less complex deployments than are required with Citrix Presentation Server, Schutz said.

Citrix software offers features such as farm management -- which is the ability to manage large numbers of servers -- and load balancing, and it provides clients for the vast array of non-Windows devices. Presentation Server has synchronized audio and video, too, and smooth roaming, which lets users go from one device to another or one location or another and keep their same workspaces.

When the next version of Windows Server arrives in late 2007, Terminal Services will add the ability to access a Terminal Services application without a VPN.

Both streaming and server computing are right for different scenarios. Madden said Citrix is in a good position with Presentation Server and the Tarpon technology to eventually provide both a management and an application framework.

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