Question: What happens when an IMS-ALG (IMS Application Level Gateway) that does not support OMR (Optimized Media Routing) and does not allocate a TrGW (Traversal Gateway), transparently forwards an SDP (Session Description Protocol) offer with unrecognized OMR-related attributes?
Option 1: The SDP offer is blocked by the next hop due to unrecognized attributes.
Option 2: Other OMR-compliant IMS-ALGs can still perform user plane optimizations downstream.
Option 3: The call flow defaults to a non-IMS media path, bypassing further IMS processing.
Option 4: The SDP answer will automatically include OMR support, enabling optimization.
Explanation: When an IMS-ALG that doesn't support OMR transparently forwards the SDP offer (including unrecognized OMR attributes), it allows downstream OMR-compliant IMS-ALGs to potentially optimize the user plane. This is because the critical OMR information, though unrecognized by the first ALG, remains intact for subsequent processing by capable nodes, thus enabling possible optimizations further along the media path.