Question: In MBMS, when constructing FEC source packets from original data packets (e.g., RTP, RTCP, MIKEY), how is the identity of the original packet's flow maintained in the FEC source packet?
Option 1: Through a unique Source FEC Payload ID embedded within each FEC source packet.
Option 2: By utilizing the same destination UDP port number and IP address as the original flow, advertised via SDP.
Option 3: Incorporating the Flow ID directly into the FEC repair packets for reverse mapping.
Option 4: Embedding the original protocol type (e.g., RTP, RTCP) within a custom FEC header.
Explanation: Maintaining the identity of the original flow is crucial for proper reassembly and processing at the receiver. According to the principles outlined in telecom standards for MBMS, utilizing the same destination UDP port number and IP address (previously advertised, for example, using SDP) ensures that the FEC source packets are correctly associated with their original stream (e.g., RTP, RTCP, SRTP, MIKEY), thereby preserving flow identity. This approach enables receivers to differentiate between various flows even after FEC encoding.