To understand how the different XenApp/XenDesktop components interact, it is important to first understand the XenDesktop FlexCast Management Architecture (FMA) and the easiest way to do this is to highlight the main steps taken when starting a published application or desktop.
The following steps assume XenDesktop 7.5/7.6 is used together with Citrix StoreFront and/or NetScaler Gateway. The scenario where web interface is used instead of StoreFront is not taken into account:
The user initiates the connection using Citrix Receiver or a browser; ports 80 or 443 are used for the communication. The connection is made to the StoreFront or to the NetScaler Gateway if the user is external.
If the user is authenticating against a NetScaler Gateway (an external user), then the NetScaler validates the user against Active Directory using port 389 and forwards the validated user credentials to the Citrix StoreFront on port 443.
