back to TS 24.228
- When the resource reservation is completed, UE1 sends the UPDATE request to the terminating endpoint, via the signalling path established by the INVITE request.
- Request-URI: Takes the value of the Contact header of the received 183 Session Progress response.
- Via: Takes the value of either the IP address or FQDN of the originating UE.
- CSeq: Takes a higher value than that in the previous request.
- Security-Verify: Contains the security agreement as represented by the received Security-Server header.