XenDesktop Communication Process

Source: CTX128909

The following is the pictorial representation of the same:

The following list explains the basic  Logon Process and the flow of communication for XenDesktop 5.x and XenDesktop/XenApp 7.x:
1. The user device submits credentials to the Citrix web site hosted on either a Web Interface (WI) or StoreFront(SF) web server. 
2. a For StoreFront, the credentials are verified directly to a Domain Controller (Similar to Step 3). SF then passes the validation over to the DDC to begin resource enumeration (Step 4).
2.b For Web Interface, the username and password is passed to the Desktop Delivery Controller (DDC).
3. The DDC then queries a Domain Controller with the end user’s credentials to verify user authorization. 
4. DDC then queries the site SQL database for the end user’s assigned Delivery Groups (SQL named instance uses default ports 1434 and 1433). ​    The resources defined by the Delivery Groups are sent to the WI or SF server and presented to the user (enumeration).
5. User clicks on one of the resource icons to start a desktop or application session. Using the Delivery Group obtained from the database, DDC queries the hypervisor about the status of resources within that group.
6. DDC identifies to Web Interface/StoreFront the virtual machine it assigned for this particular session.
7. Web Interface/StoreFront creates and sends an ICA file to the Citrix Receiver pointing to the virtual machine that hypervisor identified.
8. Citrix Receiver establishes an ICA connection to the specific virtual machine that the DDC allocated for this session.
9. Virtual Delivery Agent (VDA) verifies the license file with the DDC.
10. DDC queries Citrix License server to verify that the end user has a valid ticket.
11. DDC passes session policies to the VDA, which then applies session policies to the virtual machine.
12. Citrix Receiver displays the selected resource to the end user.13. Administrator and help desk personnel use Desktop Director and Desktop Studio tools to manage the desktops from the management server.