Citrix: XenDesktop 5 Logon Process and Communication Flow

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Martijn Bosschaart just posted CTX128909 on twitter, this article contains the following information:


  1. The user device submits credentials to the Web Interface site.
  2. Web Interface passes the user credentials to the controller.
  3. Controller verifies user authorization by performing a Microsoft Active Directory query with the end user’s credentials.
  4. Controller queries the site database for the end user’s assigned desktop groups, named instance uses ports 1434 and 1433.
  5. Using the desktop group obtained from the database, controller queries the hypervisor about the status of desktops within that group.
  6. Controller identifies to Web Interface the desktop it assigned for this particular session.
  7. Web Interface sends an ICA file to the online plug-in, which points to the virtual desktop identified by the hypervisor.
  8. Online plug-in establishes an ICA connection to the specific virtual desktop that was allocated by the controller for this session.
  9. Virtual Desktop Agent verifies the license file with the controller.
  10. Controller queries Citrix license server to verify that the end user has a valid ticket.
  11. Controller passes session policies to the Virtual Desktop Agent (VDA), which then applies those policies to the virtual desktop.
  12. Online plug-in displays the virtual desktop to the end user.
  13. Administrator and helpdesk personnel use Desktop Director and Studio tools to manage the desktops from the management server.

Note: Source port will be random open port. This is for reference only and should not be used for security and/or architecture review.

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  1. Paul BergetzPaul Bergetz04-17-2011

    Very nicely done. Easy to read and understand. I have been using and setting up virtual systems since the first Citrix and MS Terminal servers and am amazed at all the mis-information out there. Hopefully you will continue and keep up with storing or linking well done information that is available. I just spent half a day researching licensing issues with xd5 only to find that there is a xd5 express and the technical rep I spoke with (when I installed 3 weeks ago) led me to the evaluation version which uses different licensing as a result my systems are timing out ( and I will need to re-install xd5 express version.

    • k.baggermank.baggerman04-19-2011

      Thanks Paul, I will try to keep this up to date and post as much as I can.



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