Question: In an IP Multimedia Subsystem (IMS), when a user requests an anonymous session, what is expected of the terminating network regarding the originator's identity information?
Option 1: The terminating network may reveal the originator's identity to the destination endpoint if it deems necessary for security purposes.
Option 2: The terminating network should only protect the originator's identity but can share signalling routing information with the destination endpoint.
Option 3: The terminating network is not required to distinguish between intentional anonymity and identity deletion by a transit network.
Option 4: The terminating network must not reveal any identity or signalling routing information to the destination endpoint and should differentiate between intentional anonymity and transit network alterations.
Explanation: This option correctly reflects the requirements for anonymous session establishment in IMS. By choosing anonymity, the user expects privacy, which includes both their identity and how they were routed (signalling routing information). The terminating network's ability to distinguish between the originator intending anonymity versus a transit network deleting the identity ensures it can appropriately handle different scenarios while maintaining the requested level of privacy.