Citrix Presentation Server
Encyclopedia
Citrix XenApp is a thin client
product that allows users to connect to their corporate applications. XenApp can host applications on central servers and allow users to interact with them remotely or stream and deliver them to user devices for local execution.
' proprietary presentation layer protocol or thin client
protocol called Independent Computing Architecture
(ICA).
Unlike framebuffer
ed protocols like VNC
, ICA transmits high-level window display information, much like the X11
protocol, as opposed to purely graphical information. The Citrix Display Driver is installed in Session Space and captures high level GDI
draw commands, which can be replayed on GDI-capable clients, for example Windows-based clients. Clients are available for several operating system
s, including Microsoft Windows
(CE, 16-bit
, 32-bit
and 64-bit
platforms), Mac OS
, Linux
, and other Unix-like
systems.
Citrix MetaFrame version 3.x and 4.x servers listen for client connections on TCP
port
2598, by default. If the Session Reliability feature is disabled, then the server will listen on port 1494. Older MetaFrame servers (those running MetaFrame version 2.x or earlier) do not have the Session Reliability feature, and therefore always default to port 1494.remotely.
Both local and hosted application delivery methods in XenApp use existing network transmission protocols including TCP
, HTTP, HTTPS
, SMB and CIFS
.
XenApp components, including application hosting servers, if any, reside on a Microsoft Windows
computer, which can be either standalone or part of a larger cluster (farm) of Citrix servers. It is important to note that in addition to concurrent user Citrix licensing, there must exist a Terminal Server Client Access License (CAL
) and a Windows Server CAL from Microsoft for each client connection. Both products must be adequately licensed for the environment to function correctly.
over HTTPS when combined with Citrix Secure Gateway, both of which are included in the base XenApp product. XenApp also supports three UNIX
variants: HP-UX
, Solaris, and AIX which are included in Enterprise and Platinum editions of XenApp.
vWorkspace, Systancia
AppliDis Fusion, Spoon Server and Ericom Software
WebConnect. XenApp is built on top of the Windows Terminal Server platform which was originally developed by Citrix in the early-mid 90s. Win4Lin
Virtual Desktop Server provided similar functionality for serving sessions from Linux servers, while Sun's application virtualization offering, the Sun Secure Global Desktop
, serves to provide a complete solution allowing for the delivery of both Windows and Unix applications on all major platforms.
Thin client
A thin client is a computer or a computer program which depends heavily on some other computer to fulfill its traditional computational roles. This stands in contrast to the traditional fat client, a computer designed to take on these roles by itself...
product that allows users to connect to their corporate applications. XenApp can host applications on central servers and allow users to interact with them remotely or stream and deliver them to user devices for local execution.
Technical description
XenApp began life as an application hosting solution. Since 2007, XenApp has included application virtualization and streaming technologies that enable application delivery to user devices.Network protocol
The core XenApp application hosting technology utilizes Citrix SystemsCitrix Systems
Citrix Systems, Inc. is a multinational corporation founded in 1989, that provides server and desktop virtualization, networking, software-as-a-service , and cloud computing technologies, including Xen open source products....
' proprietary presentation layer protocol or thin client
Thin client
A thin client is a computer or a computer program which depends heavily on some other computer to fulfill its traditional computational roles. This stands in contrast to the traditional fat client, a computer designed to take on these roles by itself...
protocol called Independent Computing Architecture
Independent Computing Architecture
Independent Computing Architecture is a proprietary protocol for an application server system, designed by Citrix Systems. The protocol lays down a specification for passing data between server and clients, but is not bound to any one platform....
(ICA).
Unlike framebuffer
Framebuffer
A framebuffer is a video output device that drives a video display from a memory buffer containing a complete frame of data.The information in the memory buffer typically consists of color values for every pixel on the screen...
ed protocols like VNC
Virtual Network Computing
In computing, Virtual Network Computing is a graphical desktop sharing system that uses the RFB protocol to remotely control another computer...
, ICA transmits high-level window display information, much like the X11
X Window System
The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...
protocol, as opposed to purely graphical information. The Citrix Display Driver is installed in Session Space and captures high level GDI
Graphics Device Interface
The Graphics Device Interface is a Microsoft Windows application programming interface and core operating system component responsible for representing graphical objects and transmitting them to output devices such as monitors and printers....
draw commands, which can be replayed on GDI-capable clients, for example Windows-based clients. Clients are available for several operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
s, including Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
(CE, 16-bit
16-bit
-16-bit architecture:The HP BPC, introduced in 1975, was the world's first 16-bit microprocessor. Prominent 16-bit processors include the PDP-11, Intel 8086, Intel 80286 and the WDC 65C816. The Intel 8088 was program-compatible with the Intel 8086, and was 16-bit in that its registers were 16...
, 32-bit
32-bit
The range of integer values that can be stored in 32 bits is 0 through 4,294,967,295. Hence, a processor with 32-bit memory addresses can directly access 4 GB of byte-addressable memory....
and 64-bit
64-bit
64-bit is a word size that defines certain classes of computer architecture, buses, memory and CPUs, and by extension the software that runs on them. 64-bit CPUs have existed in supercomputers since the 1970s and in RISC-based workstations and servers since the early 1990s...
platforms), Mac OS
Mac OS
Mac OS is a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface...
, Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
, and other Unix-like
Unix-like
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
systems.
Citrix MetaFrame version 3.x and 4.x servers listen for client connections on TCP
Transmission Control Protocol
The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
port
TCP and UDP port
In computer networking, a port is an application-specific or process-specific software construct serving as a communications endpoint in a computer's host operating system. A port is associated with an IP address of the host, as well as the type of protocol used for communication...
2598, by default. If the Session Reliability feature is disabled, then the server will listen on port 1494. Older MetaFrame servers (those running MetaFrame version 2.x or earlier) do not have the Session Reliability feature, and therefore always default to port 1494.remotely.
Both local and hosted application delivery methods in XenApp use existing network transmission protocols including TCP
Transmission Control Protocol
The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
, HTTP, HTTPS
Https
Hypertext Transfer Protocol Secure is a combination of the Hypertext Transfer Protocol with SSL/TLS protocol to provide encrypted communication and secure identification of a network web server...
, SMB and CIFS
Server Message Block
In computer networking, Server Message Block , also known as Common Internet File System operates as an application-layer network protocol mainly used to provide shared access to files, printers, serial ports, and miscellaneous communications between nodes on a network. It also provides an...
.
Server components
The Citrix Developer Network contains a set of software development kits that enable custom development for XenApp. These SDKs include the following:- Citrix XenApp SDK
- Citrix Virtual Channel SDK
- Citrix ICA Client Object SDK
- Citrix Web Interface SDK
- Citrix Simulation API SDK
XenApp components, including application hosting servers, if any, reside on a Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
computer, which can be either standalone or part of a larger cluster (farm) of Citrix servers. It is important to note that in addition to concurrent user Citrix licensing, there must exist a Terminal Server Client Access License (CAL
Client Access License
A Client Access License is a proprietary software license distributed by software companies such as Microsoft to allow clients to connect to its server software and use the software's services.-Software licensing introduction:...
) and a Windows Server CAL from Microsoft for each client connection. Both products must be adequately licensed for the environment to function correctly.
Client components
There is a web-based Citrix client, freely available under the name Web Interface for XenApp. The Web Interface client may be used as a secure ICA proxyProxy server
In computer networks, a proxy server is a server that acts as an intermediary for requests from clients seeking resources from other servers. A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource available from a different server...
over HTTPS when combined with Citrix Secure Gateway, both of which are included in the base XenApp product. XenApp also supports three UNIX
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
variants: HP-UX
HP-UX
HP-UX is Hewlett-Packard's proprietary implementation of the Unix operating system, based on UNIX System V and first released in 1984...
, Solaris, and AIX which are included in Enterprise and Platinum editions of XenApp.
UNIX version
Presentation Server for UNIX is available for Solaris (SPARC and x86), AIX, and HP-UX. Patches typically come out first for the Solaris version. The product started as MetaFrame for Solaris 1.0 which was released in March 2000. MetaFrame for UNIX (MFU) 1.1 added support for AIX and HP-UX and came out in the fall of that year and Feature Release 1 came out about a year later. The next version came out in the first half of 2003. It was originally planned as MFU 1.1 Feature Release 2 but was rebranded MetaFrame Presentation Server for UNIX 1.2. However, references to MFU 1.1. FR2 can still be found (e.g. in the license key). Presentation Server for UNIX (PSU) 4.0 was released in the first half of 2005 and was the first version to be bundled with the Presentation Server suite. Existing customers paying for upgrades and new versions (known as Subscription Advantage) can however continue to get just the UNIX version. Existing MFU 1.x installs cannot be upgraded to PSU4; instead a clean install is required.Competition
Citrix XenApp competitors include Microsoft Terminal Services for Windows Server 2008, Quest SoftwareQuest Software
Quest Software is a computer software manufacturer headquartered in Aliso Viejo, California. Founded in 1987, Quest develops, manufactures and supports software used by Information Technology professionals in a variety of industries...
vWorkspace, Systancia
Systancia
Systancia, founded in 1998, is located in Sausheim and provides software specializing in desktop and application virtualization solutions.-History:...
AppliDis Fusion, Spoon Server and Ericom Software
Ericom Software
Ericom Software, Inc. , founded in 1993, is located in Closter, New Jersey, and provides software for enterprise-wide application access and application publishing for server-based computing environments, , Microsoft Windows Terminal Services management, Remote Desktop Services management, , Blade...
WebConnect. XenApp is built on top of the Windows Terminal Server platform which was originally developed by Citrix in the early-mid 90s. Win4Lin
Win4Lin
Win4Lin was a proprietary software application for Linux which allowed users to run a copy of Microsoft Windows 95, 98, Me, 2000 or XP applications on their Linux desktop.-Overview:...
Virtual Desktop Server provided similar functionality for serving sessions from Linux servers, while Sun's application virtualization offering, the Sun Secure Global Desktop
Sun Secure Global Desktop
Oracle Secure Global Desktop software provides secure access to both published applications and published desktops running on Microsoft Windows, Unix, mainframe and System i systems via a variety of clients ranging from fat PCs to thin clients such as Sun Rays.-History:In 1993 the Santa Cruz...
, serves to provide a complete solution allowing for the delivery of both Windows and Unix applications on all major platforms.