XenApp – Beyond Application Virtualization

A couple of days ago, in the post entitled “What Is Application Virtualization?” I made the statement that, although application virtualization is a component of XenApp, and has been since the release of Presentation Server v4.5, XenApp is more than just application virtualization. To fully understand what I mean by that, you need to understand the Citrix vision of how applications should be delivered to users.

Over the years, there have been a lot of ways to connect client devices to server-based applications and desktops: Program Neighborhood, Program Neighborhood Agent, “Project Charlotte” which became Nfuse which became Web Interface, etc., etc. But if you look back over the last 15+ years, you will see an evolution toward the Citrix vision of “Any” – any application, to any device, anytime, anywhere, over any kind of connection – and you will see an ongoing effort to make it simple and easy for users to access the applications they need, as well as easier for the IT staff to deliver the right applications to the right users.

In Citrix’s view, the delivery of applications to users should be as simple as the delivery of broadcast content over your satellite TV network. Think about that model for a moment – you generally don’t have to worry about whether you have a big or small TV set, or whether it has a traditional picture tube (yes, there are still some of those around), an LCD screen, or a Plasma screen…because you have a receiver that conforms to an accepted standard, and that will connect to any TV. You bring the TV home, take it out of the carton, and connect it to your satellite receiver, and with little or no additional configuration, you can watch the channels you’ve subscribed to. And you get to decide what you watch and when. If you have a DVR built into your receiver (as most do these days), you can even cache the programming content and watch it later.

The current Citrix delivery method is darned close to this, and completely unique in the market, in my opinion. There are four basic components:

  • The Citrix Receiver, together with several plug-ins for the Receiver.
  • The Citrix Merchandising Server, which is a virtual appliance designed to run on either XenServer or VMware. My expectation is that it will also soon be ported to Hyper-V.
  • Citrix Dazzle, which is a mechanism for user self-service.
  • Citrix Update Service, which is an on-line service provided by Citrix that is responsible for notifying Merchandising Servers of available plug-in updates.

Let’s look at these in turn, then see how they all play together.

Citrix used to have a lot of separate clients, that all had to be installed separately. You had a client for XenApp. You had another client for XenDesktop. You had one for the Access Gateway, one for Single Sign On (a.k.a. Password Manager), one for Branch Repeater acceleration, one for receiving streamed apps – you get the picture. It was getting a little ridiculous, not to mention difficult to manage, and cluttered up your System tray with multiple little icons. By contrast, the Receiver is a sort of “universal client” that is responsible for managing a variety of plug-ins on the client desktop. Instead of multiple client icons in your System Tray, you’ll have just one – the Receiver. The plug-ins are modules of client functionality that are managed by the Receiver. At the moment, you have plug-ins for:

  • Secure Access (for Access Gateway Enterprise Edition)
  • Secure Access (for Access Gateway Standard Edition)
  • Online Plug-in (for XenApp hosted applications/desktops and connecting to XenDesktop-managed virtual PCs)
  • Offline Plug-in (for streamed applications)
  • App-V Plug-in (for Microsoft App-V streamed applications)
  • Communications Plug-in (for EasyCall)
  • Acceleration Plug-in (Branch repeater)
  • Service Monitoring Plug-in (enables Edgesight for Endpoints to gather data from the client)
  • Profile Management Plug-in (enables Citrix Profile Manager)
  • Dazzle Plug-in (enables application self-service via the Dazzle interface)

Merchandising Server
The Merchandising Server is the virtual appliance responsible for managing and delivering the Receiver and its various plug-ins to end users. The Merchandising Server can contact the Citrix Update Service via the Internet and download the latest versions of the Receiver and plug-ins. Once you have those, you create rules that stipulate what the Merchandising Server will push to different users as they authenticate, depending on such parameters as Machine Name, User Domain Membership, Machine Domain Membership, Operating System, and IP Address Range.

The first time the user connects, s/he will point a browser at a designated URL and enter login credentials, and the Merchandising Server will push down the specified package, which will be automatically installed. One installed, the Receiver will periodically check back with the Merchandising Server for updates, so you can dynamically add, remove, or update plug-ins as required.

Dazzle is a new variation on the old Program Neighborhood Agent theme that enables user self-service. Those who have worked with Citrix technology for a while will remember that the PN Agent communicated “behind the scenes” with a special Web Interface site to retrieve a list of the published applications available to the user. Icons for those applications could be pushed onto the Start Menu, or accessed by right-clicking on the PN Agent icon in the System Tray. The Dazzle plug-in also communicates with a special Web Interface site, but allows the user to open a window, view the available applications, and select the ones s/he wants to use (see below):

Dazzle User Experience

Dazzle User Experience

Applications can be organized into multiple “Stores” by the Administrator, and can be tagged to appear in a “Featured” list to draw the user’s attention. There’s a friendly description of each available application, and a column that indicates whether that application will work offline (i.e., whether it will be streamed to the client machine) – and, by the way, it doesn’t matter whether the app was packaged for streaming using the Citrix tools or using Microsoft’s App-V, so long as you’ve delivered the correct plug-in to them. Applications that are not tagged as working offline are, by implication, going to be executed on a XenApp server, and therefore will only be available when the client has connectivity to the XenApp server farm.

The user can browse through the list, or use a search function, which is extremely valuable in an enterprise that may have dozens – or even hundreds – of applications. To select an application, the user simply clicks on the “Add” button. The selected applications will appear in a “Dazzle Apps” folder on the Start Menu tree:

Dazzle Apps Folder

The Dazzle Apps Folder

So let’s summarize what we have with this system:

  • Administrators can easily publish applications, and organize them into “App Stores.” Applications from multiple server farms can be integrated into a single App Store, or multiple App Stores can be created as desired (e.g., one for Human Resources, one for Engineering, etc.).
  • Users no longer have to install or configure anything – all required client software is transparently pushed out to them and installed, and automatically updated, by the Merchandising Server.
  • Users can help themselves to the applications they need to be productive, and to only those applications. Just because an application is available to them doesn’t necessarily mean they will have an icon for that application cluttering up their desktop or Start Menu.

I don’t think that application delivery can get much easier than that.

And why, you may ask, is User Self-Service something you should be concerned about? Well, in addition to the obvious fact that is makes life easier for both your users and your IT staff, take a peek at the following video. Increasingly, these are the people you are going to want to attract and retain as employees. They’ve grown up with technology, and they have their own preferred ways of using it to be productive. Here’s what they had to say about corporate computing:

This is why I contend that XenApp is substantially more than just application virtualization, and substantially more than “something I add to my Remote Desktop Servers to make things run faster.” It is a new and unique way of delivering to your users the applications they want and need, and only those applications, with minimal muss and fuss on both ends of the transactions. Increasingly, your users are used to the self-service model (e.g., the Apple on-line store), they find it intuitive, and they like it. It enables BYOC (“Bring Your Own Computer”) policies. It makes life simpler for everyone. And no one else has anything like it at the moment.

If this has caught your interest and you’d like to see more detail, check out the video below. It’s a bit long (about 30 minutes), but does an excellent job of explaining how everything works:

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