Citrix Virtual Apps (formerly Citrix XenApp) is an application delivery solution that enables access to Windows-based applications to any device compatible with Citrix Receiver. What exactly is the difference between Citrix and VDI?
VDI stands for virtual desktop infrastructure. A VDI desktop is a desktop running on a server in the datacenter that a user can access from virtually any device. To use VDI with Citrix, you need to purchase Citrix Virtual Apps and Desktop (formerly Citrix XenDesktop). Citrix Virtual Apps and Desktop (formerly Citrix XenDesktop) and VMware Horizon are two well-known solutions to implement and deploy virtual desktop infrastructures.
What is VDI?
VDI comprises host servers for desktop operating systems and application software residing inside guest virtual machines. The VMs are accessible from devices of any kind, e.g. desktops, tablets PCs, and mobile devices, within the network.
Users connect to VMs, or their virtual desktops, using their preferred devices. Virtual desktops can be assigned to either a single user or multiple users:

Single-use desktops are configurable by their assigned users
Multiple-user desktops go back to their default configuration once a user completes their session
What makes the above possible is an abstraction layer known as a hypervisor, which allows guest VMs to be installed on a single server. It’s possible to scale the IT infrastructure up or down according to demand by adding more servers with more VMs. Hypervisors manage the VMs and broker the connections to the VMs.

What Are the Different Types of VDI?
While there is a standard definition of VDI, there are various methodologies to deliver virtual desktops, classified into three main categories:

Desktop-Based VDI – A desktop running in a virtual machine that is hosted on a server in the datacenter.
Server-Based VDI – A desktop running in a server operating system that is available only for a single user at a time (Remote PC).
Session-Based VDI – An individual session running inside a server OS on either a virtual machine or a physical server.
What Are the Limitations for Citrix and VDI?
Deploying and maintaining VDI with Citrix is complicated due to different licenses offering different features. For example, to support desktop-based VDI and server-based VDI, organizations need to upgrade from Citrix Virtual Apps to Citrix Virtual Apps and Desktop. In essence, even in its Platinum Edition, Citrix Virtual Apps does not support a full VDI.

How to Deploy VDI with Citrix
To deploy VDI with Citrix, organizations must consider what kind of VDI they need for their infrastructures (desktop, server, or session-based). They also need to be aware that publishing applications require either Citrix Virtual Apps or Citrix Virtual Apps and Desktop Enterprise/Platinum version.
Citrix’s VDI solution, Citrix Virtual Apps and Desktop, works in small environments and large ones, but it’s geared toward the medium and big enterprise. Citrix Virtual Apps and Citrix XenDesktop is available in three versions.
Virtual Desktops Standard
This version provides only the basic Citrix virtualization technology, restricting the delivery options to VDI for both pooled and dedicated services on Windows 7 and Windows 10. However, the app lacks basic security configurations, including FIPS compliance, Common Criteria certification, SmartAccess, Intelligent session recording, and provisions for SSL VPN.
In terms of productivity, the Virtual Desktop Standard does not provide optimized Skype and Microsoft Teams for business. Also, the app doesn’t allow for Citrix casting (transitioning applications and desktops from a mobile device to any display-connected device in a Citrix Ready hub) and Workspace Environment Management.
Virtual Apps and Desktops Advanced
This version offers more virtualization features including, server-based hosted apps, server-based virtual desktops, VDI (for both pooled and dedicated services), Windows Cloud PC access, and VM hosted applications.
The main benefit of this version is the inclusion of extra features to boost employee’s productivity, such as optimized Skype and Microsoft Teams for businesses that are not available in Virtual Desktop Standard. However, it still lacks Citrix casting and Citrix SD-WAN for WAN optimization that could boost efficiency in an organization.
In terms of security, Virtual Apps and Desktop Advanced lacks standard security configurations including FIPS compliance, Common Criteria certification, SmartAccess, Intelligent session recording, and provisions for SSL VPN just like its Virtual Desktops Standard counterpart.
Virtual Apps and Desktops Premium Edition
This version includes all VDI features, plus an enhanced version of Citrix Virtual Apps called Virtual Apps Premium (formerly XenApp Platinum). It also includes a couple of additional features such as seamless local applications, self-service password reset, and a UX network analysis.
Note: To deploy a fully-featured application and desktop delivery infrastructure with Citrix, you also need to purchase Citrix add-ons such as Citrix ADC (previously NetScaler).
Printing issues with Citrix Solutions
Printing is often a problematic area in Citrix. Among the pain points are:

Slow printing: Citrix uses a virtual channel for printing. As a result, latency, packet loss, and lack of bandwidth may slow down printing across networks. Proper configuration with the use of the correct protocol and PCL6-based drivers may help address this issue.
Not printing: Worse than slow printing are jobs that do not print at all. For example, while connected to a VPN, printing across a network may lead to jobs not being received on the other end. When this happens, check to see that your devices can connect to your printers, as network configuration may be the underlying cause.
Printer misconfiguration: Citrix provides printer drivers for just about any possible printing scenario. However, if these drivers are not properly configured, users cannot utilize their advanced features, making them unsuitable for their needs. In this case, printer redirection may be needed.
The printer is missing: Sometimes, connected printers may not appear at all when you try to use them for printing. When this happens, faulty policies and missing drivers may be to blame. The problem goes away when the correct policy is set, or the correct driver is installed.
Printer stops working: When errors appear during printing or the printer stops working altogether, this can be traced to problems in either the Citrix and/or Microsoft printer services. Restarting the services on the session hosts often resolves the problem.

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