An SMS flow entry point can be either an Application Phone or a Start iSMS depending on the way that is initiated:
By the End-user: in this situation the end-user contacts the application, sending a command to a specific phone number. How?
By another flow: in this situation, the application starts the dialog, sending a screen to the end-user. How?
In both situations, Platform Server creates a session to keep context for the end-user; the session is stored for a pre-defined period of time.
The session consists of user MSISDN and the application phone number. Platform Server uses this pair to identify the end.-user.
iSMS Initiated by the End-user | iSMS Initiated in Another Flow