Citrix XenApp and its Metaframe roots

Citrix XenApp (formerly Citrix WinFrame Server, Citrix MetaFrame Server and Citrix Presentation Server) is a thin client product that allows users to connect to their corporate applications. XenApp can either host applications on central servers and allow users to interact with them remotely or stream and deliver them to user devices for local execution. (from wikipedia definition)
The three main advantages of XenApp are:

reduces cost (you only deploy the application once, to the server)
Ensures secure access (you can specify the level of access the user can have to the application)
Improves Performance (It knows the type of client is requesting the access and identifies the most efficient deployment methodology); Also it allows flexibility delivering the application anywhere where users are located (home-office, office, mobile devices, etc.)

Citrix combined two very important early products (winframe and metaframe) on a proprietary OSI model presentation layer called Independent Computing Architecture (ICA) also knwon as thin-client protocol where the core XenApp application hosting technology resides

ICA traffic flows from the client device to the XenApp Server over TCP port 1494. Each ICA session then creates and uses a dynamically allocated TCP port for communications from the server to the client
device. The ICA protocol functions on the Presentation layer of the OSI model, which is Layer 6. Within the ICA protocol, virtual channels are used to designate the various functionalities, such as client drive mappings, video, keyboard strokes, etc. (Citrix pdf from

Layer 3 (IP) and Layer 4 (TCP) functionality of the ICA protocol can easily be viewed by using Microsoft Network Monitor or other network analysis tools such as Wireshark.

MetaFrame is the name for a thin client/server software application from Citrix that is used to provide Microsoft’s Windows Terminal Server product (WTS) with additional server and client functionality by allowing any client, no matter what operating system (OS) they are using, to connect to a Windows Terminal Server and run a Windows application through their browser. MetaFrame is useful for its ability to “load balance” by automatically directing a client to the server with the lightest load in a server farm, and its ability to allow publishing and application management from a single server in that farm. MetaFrame also features a secure encryption option through a distributed Windows presentation protocol developed by Citrix, called ICA (Independent Computing Architecture).

There is also a MetaFrame product for UNIX operating systems.

Citrix brings the application’s user interface, audio, and print jobs to the user’s computer in a way that is completely transparent or “seamless” (source:

Part of the text above was copied from the following


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