Question: In the IP Multimedia Core Network Subsystem (IMS), how is confidentiality and integrity protection for SIP-signalling provided between the User Equipment (UE) and the P-CSCF across the IMS access network?
Option 1: End-to-end encryption using NDS/IP security mechanisms
Option 2: Hop-by-hop protection using specified security mechanisms for this interface
Option 3: No protection is mandated for this leg of the communication
Option 4: Protection is solely the responsibility of the IMS core network's inherent security
Explanation: According to the IMS security architecture, the first hop (between the UE and the P-CSCF) utilizes specified security mechanisms for confidentiality and integrity protection in a hop-by-hop manner, rather than relying on end-to-end encryption or other methods for this specific segment.