Demystifying Citrix Excalibur Architecture

For all XenApp admins and consultants out there Project Avalon will bring a big change as we are used to having XenApp servers running on the (what seemed to be) everlasting Citrix Independent Management Architecture and we’re heading to Citrix FlexCast Management Architecture (already included in XenDesktop at this moment) and will be included in the Citrix Excalibur Architecture.


When looking up IMA in the eDocs you’ll find:

Independent Management Architecture (IMA) is the underlying architecture used in XenApp for configuring, monitoring, and operating all XenApp functions. The IMA data store stores all XenApp configurations.

Basically IMA exists to manage the XenApp or Presentation Server farms by enabling the communications between servers. As stated it transfers information about all XenApp functions like licenses, policies, sessions and server loads. All management tooling within these versions of Citrix’s PS/XA rely on this service for information.

According to Communication ports used by Citrix Technologies IMA uses the following ports:

Ports Source Prot. Comment
2512 Common Citrix Communication Ports TCP Independent Management Architecture (IMA)
2513 Access Gateway 5.0 Controller administration TCP IMA-based Communication

As we can see IMA uses 2512 (by default) to communicate with other servers and the Access Gateway Controller uses 2513 (by default) for IMA-based communication. The port IMA uses can be changed or queried via the commandline tool IMAPORT.

Brian Madden did a blogpost way back in 2007 but it’s definition of IMA is still current:

Independent Management Architecture is:

  • A data store, which is a database for storing MetaFrame XP server configuration information, such as published applications, total licenses, load balancing configuration, MetaFrame XP security rights, and printer configuration.
  • A protocol for transferring the ever-changing background information between MetaFrame XP servers, including server load, current users and connections, and licenses in use

With the introduction of XenDesktop we got a new architecture called Flexcast Management Architecture. This new architecture has got an agent-based setup where we can install the operating system including the basic applications that need to be installed and after that we can install an agent. This agent registers itself to a controller and is offered through StoreFront to the end user.

This will be delivered by two different types of agents, one to support Windows Server OS’s and one for Windows Desktop OS’s.

Andrew Wood did an article on Excalibur and used this diagram to explain the architecture:

Citrix FlexCast Management Architecture

Citrix FlexCast Management Architecture

  • Receiver provides users with self-service access to published resources.
  • StoreFront authenticates users to site(s) hosting resources and manages stores of desktops and applications that users access – Web Interface as a platform is essentially resting, but it will cease to be.
  • Studio is a single management console that enables you to configure and manage your deployment, a dramatic reduction over the 23 consoles you could well have today. Studio provides various wizards to guide you through the process of setting up an environment, creating workloads to host applications and desktops, and assigning applications and desktops to users.
  • Delivery Controller distributes applications and desktops, manages user access, and optimizes connections to applications. Each site will have one or more delivery controllers.
  • Server OS Machines are the “XenApp” replacement, VMs or physical machines based on the Windows Server operating system used for delivering applications or hosted shared desktops to users.
  • Desktop OS Machines are the “XenDesktop” replacement, VMs or physical machines based on the Windows Desktop operating system used for delivering personalized desktops to users, or applications from desktop operating systems.

Which explains a lot about the components and the future management of our XenApp/XenDesktop environments. At this moment we need to build seperate infrastructures to support both XenDesktop and XenApp but the next release will change this as there will be one infrastructure needed to support both server and desktop operating systems. The benefits of these delivery agents are explained in this post:

  • The Excalibur Delivery Agent for Windows Server Machines is designed from the ground up for dynamic provisioning with Machine Creation Services and Citrix Provisioning Services. Unlike XenApp, the Delivery Agent communicates only with the controllers in the site and does not need to access the site database or license server directly.
  • Delivery Agents do not need to run the same version or OS as the controllers. This simplifies the process of upgrading sites, and allows Excalibur to support six different Windows operating systems all within a single farm: Server 2008 R2, Server 2012, XP, Vista, 7, and 8.
  • While the XenApp session host-only mode disabled functionality and offered performance benefits over XenApp controllers, it consisted of the same installed services and same binaries as the controllers. The Excalibur Delivery Agent for Windows Server Machines is lighter weight, and only consists of the components needed for hosting sessions. It does not share any common installed components with the controllers.

So this new architecture offers more freedom to mix and mingle Operating Systems and deployment mechanisms (PVS/MCS) while removing the complexity from the former IMA.

By the way, Thomas Koetzing wrote a small blog about some noticeable facts about Excalibur here.

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Kees Baggerman

Kees Baggerman is a Staff Solutions Architect for End User Computing at Nutanix. Kees has driven numerous Microsoft and Citrix, and RES infrastructures functional/technical designs, migrations, implementations engagements over the years.


  1. Nice work and interesting read!

  2. Bas van kaam says:

    Good article, well written.



  3. Very useful and timely. Good work!

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