Communication flow during the different stages of the Citrix XenApp/XenDesktop logon process

1. The user device submits credentials to the Web Interface
(WI) or StoreFront (SF) web server.

2. For StoreFront, the credentials are verified directly to
a Domain Controller (Similar to Step 3 below). The
SF then passes the validation over to the Citrix Delivery
Controller (DDC) to begin resource enumeration
(Step 4). For Web Interface, the username and password
is passed to the DDC.

3. The DDC then queries a Domain Controller with the
end user’s credentials to verify user authorization.

4. Next, the DDC then queries the site SQL database
for the end user’s assigned Delivery Groups. The resources
defined by the Delivery Groups are sent to
the WI or SF server and presented to the user (enumeration).

5. When the User clicks on one of the resource icons
to start a desktop or application session, using the
Delivery Group obtained from the database, the DDC
queries the hypervisor about the status of resources
within that group.

6. The DDC identifies to Web Interface/StoreFront the
virtual machine it assigned for this particular session
(in the case of XenDesktop).

7. The Web Interface/StoreFront creates and sends an
ICA file to the Citrix Receiver pointing to the virtual
machine that hypervisor identified.

8. The Citrix Receiver establishes an ICA connection to
the specific virtual machine that the DDC allocated
for this session.

9. The Virtual Delivery Agent (VDA) verifies the license
file with the DDC.

10. The DDC queries the Citrix License server to verify
that the end user has a valid ticket.

11. The DDC then passes session policies to the VDA,
which in turn applies session policies to the virtual
machine. Profile loading, GPO processing, loading of
scripts, drivers, printers, etc. all occur at this stage.

12. The Citrix Receiver displays the selected resource to
the end user.