Application Streaming is a new feature of Citrix Presentation Server™ 4.5
Is a set of technologies that are used to package and “stream” applications from a central server to individual client machines. The applications are then executed locally on the client. The cool thing is that the applications are not “technically” installed on the client; instead, their files, DLLs, and registry settings are packaged up and sent down to the client where they’re executed in a Citrix Application Isolation Environment (AIE).
How it works:
1. Administrator must create a Citrix Streaming application package. This is done by running a packager utility on a standard computer. The utility watches an application’s installation procedure and makes a list of everything the installation process did (which files were installed, registry keys that were modified, etc.). Once the installation process is complete, the Streaming packager gathers up all of the bits needed to install the application and creates a package file that sits out on a network share. The package file is then advertised to users or groups like any other Citrix published application.
2. Application Stream requires a client-side agent installation where it basically adds the application isolation environment capability to the client device.
3. Once the streaming application is published, the user clicks on the application icon in PN Agent. The client retrieves the application’s information from the server. The client sets up an isolation environment and copies the application’s main executable into it. Then the executable is launched.
4. There are some file systems and registry filter drivers as part of the isolation environment that watch for resources the application calls for. If the app needs a specific DLL, the filter driver intercepts that call, copies the needed DLL down from the Tarpon share to the client and then makes that DLL available to the executable within the isolation environment. This process is repeated for every file that’s part of the application package.
The idea is that a laptop user could use their laptop without a network connection and the application could be executed from the cache—the user wouldn’t even know it wasn’t a “normally” installed application (except for the fact that it wouldn’t show up in the Add/Remove Programs list).
1. Citrix’s Application Isolation Environments (both in PS4 and PS4.5) are NOT application virtualization. Citrix’s AIE are simply file system and registry redirection.
2. Citrix’s “Application Streaming” is NOT “real” application streaming. Citrix’s Application Streaming, on the other hand, simply copies complete files down to the client one-by-one as they are needed.
What does this mean for Softricity?
Softricity offers streaming capabilities where individual function calls from individual files are cut apart and sent down to the client on an as-needed basis. Softricity has application virtualization capabilities.
Citrix did try to buy Softricity a few years ago, but a deal could never be completed. No one is really talking about what exactly happened (because these discussions never “really” happened <wink>), but the general consensus is that Citrix wanted to buy the Softricity sequencing and streaming environment right as Softricity was entering the desktop market, and the two companies couldn’t really agree on which components would be bought and for how much.
How will Microsoft fit into all of this?
It’s no surprise that Microsoft is looking at streaming technology and that this capability will play some role in some future version of Windows.