Question: When an IMS-ALG/IMS-AGW supports both ECN Transparent and transcoding, what additional procedure must it also support?
Option 1: RTP Translator Procedure
Option 2: ECN Endpoint Procedure
Option 3: Media Flow Adaptation Procedure
Option 4: IP Header Modification Procedure
Explanation: According to Explicit Congestion Notification support guidelines for IMS-ALG and IMS-AGW, if an entity supports both ECN Transparent (i.e., transparent forwarding of ECN bits in the IP header) as well as transcoding, it is mandated to also support the ECN Endpoint procedure. This ensures seamless end-to-end rate adaptation capabilities when interacting with ECN-capable peers, whether through direct forwarding or after applying media transcoding.