Question: In an IMS network, when a CSCF (Call Session Control Function) interoperates with a proxy located in a non-IMS network using SIP signaling protected by TLS, how is the TLS connection typically initiated for security?
Option 1: Automatically upon detection of foreign network presence
Option 2: Manually by network administrators on both ends
Option 3: Through the CSCF publishing a `sips:` URI in a DNS server, resolvable via NAPTR/SRV mechanism
Option 4: By the proxy in the non-IMS network sending an unsolicited TLS request
Explanation: This is the correct answer because publishing a `sips:` URI in a DNS server allows the other network to discover and initiate a secure TLS connection using NAPTR/SRV mechanisms, enabling automated discovery and setup of secure connections without requiring manual intervention or relying on unsolicited requests.