What is ICA – Independent Computing Architecture?

To start at the beginning, ICA stands for Independent Computing Architecture. It is a protocol used in Citrix XenApp / XenDesktop (or previously Presentation Server, MetaFrame, WinFrame) to separate the application logic (which runs on a remote system, usually in a datacenter) and the presentation (on the client).

In a nutshell what this protocols does is sending input from the client (like keyboard, mouse, audio, etc.) to the remote system and receive the output (like video, sound, etc.) from the remote system via the network. On the client (a workstation, laptop or thin client) a piece of software is used to handle this traffic. At the moment of this writing the Citrix Receiver is used.

Files with the extension .ICA contain information required  to connect to the remote system, including session properties and (optionally) authentication.

When are .ICA files used?

.ICA files are used in many applications that allow you to connect to a Citrix XenApp / XenDesktop environment. Most common used are the Citrix Web Interface and the Citrix CloudGateway, but third party applications like Denamik LoadGen use .ICA files as well. Usually the use of .ICA files is temporarily and hidden for the end user, which is a good thing.

Web portal default configuration

When you launch a published application / desktop via the web portal supplied by Citrix (WebInterface,  StoreFront or VDI in a box) a default configuration is applied. You can alter the default configuration to meet your needs, if it isn’t available in the management console (most settings are not configurable via the management console). The default configuration is stored in a default.ica file.

The location of the default.ica depends on the platform you’re using and the name of the site.

Since both WebInterface and StoreFront are integrated in Microsoft Internet Information Services (IIS) the configuration is stored in a directory in the %SystemRoot%\inetpub (default location). For each site a directory is created which you specified when you created the site.

Assuming you’ve used the default site name, these are the locations where the default configuration is stored:

Platform	Version	Type	Location
Web Interface	5.x	XenApp	\inetpub\wwwroot\Citrix\XenApp\conf
	4.5 / 4.6	XenApp	\inetpub\wwwroot\Citrix\AccessPlatform\conf
	4.0	XenApp	\inetpub\wwwroot\Citrix\MetaFrame\conf
	All	XenApp services / PNAgent	\inetpub\wwwroot\Citrix\PNAgent\conf
StoreFront	All	All	\inetpub\wwwroot\Citrix\Store\App_Data
VDI in a box	All	All	/home/kvm/install/servlet_container/webapps/ dt/WEB-INF/etc/proto.ica (not default.ica!)