Question: In an IMS network, which entities may check SDP offer/answer information to determine the need for media transcoding in a session?
Option 1: Only User Equipment (UE) and Media Resource Function Processor (MRFP)
Option 2: Only Application Servers and Media Gateway Control Function (MGCF)
Option 3: Only Serving Call Session Control Function (S-CSCF) and Home Subscriber Server (HSS)
Option 4: IMS control plane entities including P-CSCF, Application Servers, or Interconnection Border Control Function (IBCF) for inter-domain sessions
Explanation: In the context of IP Multimedia Subsystem (IMS), determining the need for transcoding based on SDP offer/answer information is crucial for ensuring seamless media communication. This task falls under the responsibilities of IMS control plane entities that are directly involved in session setup and management across different domains or networks, which includes the P-CSCF for initial filtering and routing, Application Servers for service logic, and the IBCF for inter-domain sessions to ensure compatibility and compliance with various network policies or SLAs.