Question: In an IP Multimedia Subsystem (IMS), what is the primary purpose of sending pre-alerting or alerting indications to the originating User Equipment (UE) before receiving incoming media?
Option 1: To authenticate the calling user's identity
Option 2: To enable the UE to inform the calling user of session progress, allowing for local synthesis of ringing or similar indicators
Option 3: To negotiate media codecs between the originating and terminating UEs
Option 4: To bill the calling user for the attempted connection
Explanation: The correct answer is Option 2 because, as per IMS session management principles, pre-alerting or alerting indications are used to update the calling user on the status of their outgoing session (e.g., that the call is being processed or that the called party is being alerted). This allows the originating UE to provide feedback (like synthesizing a ringing tone) to the user before the actual media stream (e.g., voice, video) is established, enhancing the user experience by providing timely updates on the session’s progress.