Question: What is a required function of the P-CSCF for firewall traversal of IMS control plane, specifically regarding SIP communication?
Option 1: Supporting SIP over UDP on standard port 5060
Option 2: Implementing IPsec encryption for all IMS signaling
Option 3: Supporting SIP over TLS/TCP on non-standard port 443 (HTTPS)
Option 4: Enforcing Basic Authentication for all SIP requests
Explanation: For effective firewall traversal in the context of IMS control plane, utilizing a commonly allowed port like 443 (typically used for HTTPS) helps ensure that SIP signals can pass through firewalls that might block other ports. Supporting SIP over TLS/TCP on this non-standard port enhances the likelihood of successful communication across networks with strict firewall policies, thus maintaining service accessibility and security.