29.1633GPPInterworking between the IP Multimedia (IM) Core Network (CN) subsystem and Circuit Switched (CS) networksTS
The MGCF shall support the following H.245 indication messages: Function Not Understood Indication / Function Not Supported Indication, Jitter Indication. The MGCF may support the H.245 User Input Indication message. All these H.245 messages are conveyed between the MGCF and the CS side through the IM-MGW, as described in clause E.4.2.3.
E.188.8.131.52 Function Not Understood / Function Not Supported message
This indication message is used to return requests, responses and commands that are not understood back to the transmitter.
If the MGCF receives a Function Not Understood or Function Not Supported message from the CS side, the MGCF may choose to attempt simpler H.245 interaction than the previous H.245 interaction that caused this indication. If this is not possible, the MGCF may release the call.
If the MGCF receives a H.245 request, response or command that can not be understood, the MGCF shall send H.245 Function Not Supported indication message to the CS side.
E.184.108.40.206 User Input Indication message
The User-Input-Indication message is used e.g. to transport the in-band DTMF information in the H.324 system.
The MGCF and IM-MGW may support transporting the DTMF information both from the CS side to the IMS side, and from the IMS side to the CS side.
Upon Receipt of a H.245 User-Input-Indication message, the MGCF may apply the procedures in clause 220.127.116.11 to request the IM-MGW to send corresponding RTP telephone-event(s) towards the IMS side.
Upon receipt of RTP telephone events from the IMS, the MGCF will be notified by the IM-MGW using the procedures in clause 18.104.22.168, if the MGCF has previously configured the IM-MGW as also described in this subclause. Upon receipt of the notification, the MGCF may send a H.245 User-Input-Indication message to the CS side.