Question: In a 3GPP network, where can interception functions for outgoing IMS-based VoIP calls be optionally provided in a non-roaming scenario, aside from the S-CSCF or P-CSCF?
Option 1: Only at the UE (User Equipment)
Option 2: At the Access Network's Radio Base Station
Option 3: At the Egress IBCF (Interconnection Border Control Function) or Egress MGCF (Media Gateway Control Function)
Option 4: Exclusively at the MME (Mobility Management Entity)
Explanation: In the context of lawful interception for outgoing IMS-based VoIP calls in a non-roaming scenario, aside from the Serving-Call Session Control Function (S-CSCF) or Proxy-Call Session Control Function (P-CSCF), the interception functions can also be provided by network elements responsible for interconnection and media control. The Egress IBCF, which handles interoperability with external networks, and the Egress MGCF, involved in controlling media gateways, are specified as alternative points for implementing these functions, ensuring flexibility in network architecture design without mandating a single approach across all CSPs (Communication Service Providers).