Question: In an IMS network, when an IMS-ALG performs proactive transcoding without resource reservation, what action can subsequent IMS-ALGs take upon receiving the forwarded SDP with an indication that an address is unavailable due to transcoding selection?
Option 1: Replace the transcoder and insert a new transcoding TrGW if needed, while forwarding the SDP offer.
Option 2: Only replace the transcoder when forwarding the SDP offer, without the ability to insert a transcoding TrGW if needed.
Option 3: Reject the SDP offer due to the unavailability of the address for transcoding, prompting a new offer.
Option 4: Bypass transcoding and proceed with the original media parameters.
Explanation: When an IMS-ALG performs proactive transcoding without resource reservation, it indicates in the SDP that an address is unavailable if transcoding is selected. Subsequent IMS-ALGs can only replace this transcoder (to potentially use a different one) when forwarding the SDP offer but are not permitted to insert a new transcoding TrGW on behalf of the original IMS-ALG, highlighting the limitation in handling resource allocation for transcoding in this scenario.