Question: In a 3GPP network, where can interception functions for incoming IMS-based VoIP calls (Non-Local ID) be optionally provided in a non-roaming scenario, aside from the S-CSCF or P-CSCF?
Option 1: Only at the Serving Gateway (S-GW)
Option 2: Exclusively at the PDN Gateway (P-GW)
Option 3: Solely at the Mobile Management Entity (MME)
Option 4: At the Ingress IBCF or Ingress MGCF
Explanation: For non-roaming cases, aside from the Serving-Call Session Control Function (S-CSCF) and Proxy-Call Session Control Function (P-CSCF), interception functions for incoming IMS-based VoIP calls can also be provided at the Ingress Interconnection Border Control Function (IBCF) or the Ingress Media Gateway Control Function (MGCF). This is an alternative implementation approach within a Communication Service Provider's (CSP's) network, highlighting flexibility in architectural design for lawful interception.