Question: Which of the following statements about the Data Channel Signalling Function (DCSF) in the IP Multimedia Subsystem (IMS) is correct?
Option 1: The DCSF is primarily responsible for handling SIP signalling within the IMS.
Option 2: The DCSF manages data channel resources and supports HTTP web server functionality for downloading applications to the User Equipment (UE).
Option 3: The DCSF directly interacts with the User Equipment (UE) to retrieve subscription information.
Option 4: The primary function of the DCSF is to provide voice call services within the IMS.
Explanation: This option is correct because, according to the specifications, the DCSF is not involved in SIP signalling (contrary to Option 1) but is responsible for managing data channel resources and supports HTTP web server functionality for bootstrapping (downloading) data channel applications to the UE based on its subscription. Options 3 and 4 are incorrect as they misrepresent the DCSF's role, particularly in direct interaction with UE for subscription info (which is not mentioned) and providing voice call services (not a primary function of DCSF).