Below is an overview of each of the features added into software 10.5.3 SP18
Feature F-19620 SIP reroute on RTP inactivity. The RTP Media Inactivity Detection (MID) functionality has been enhanced to add an option for reentering routing rules so an incoming call can be retried with another external gateway, using a sequential method such as Route List routing, until IMG is able to receive RTP. Refer to the links in the Related Topics section below for more information.
Feature F-19625 200 OK response only in SIP OPTIONS. The SIP OPTIONS functionality has been enhanced to add an option for 200 OK as the only valid response for determining availability. All other responses would be treated the same as a no response. Refer to the links in the Related Topics section below for more information.
SIP Options KeepAlive Configure (Busy Out)
Feature F-19720 P-Access-Network-Info header interworking. This feature consists of implementing the interworking for the P-Access-Network-Info SIP header and the Location Number ISUP parameter of the ISUP IAM message. Refer to the links in the Related Topics section below for more information.