Question: What is the primary purpose of Public Service Identities (PSIs) in the IP Multimedia Subsystem (IMS), as opposed to Public User Identities?
Option 1: To identify individual users across different Application Servers.
Option 2: To identify services hosted by Application Servers, such as groups, chat-type services, or local services.
Option 3: To provide an alternative form of numbering for IMS-enabled devices.
Option 4: To enhance security for IMS messages transmitted over the internet.
Explanation: Public Service Identities (PSIs) are utilized to identify specific services, such as conferencing, messaging, or group services, that are hosted by Application Servers within the IM CN subsystem. This differentiation is crucial for routing IMS messages correctly and enabling users to access these services seamlessly. In contrast, Public User Identities are associated with individual users rather than services.