US Patent 7764680 Communication system and call control server

When congestion occurs in a RAN in a cell phone VoIP service, calls using the congested device are detected to permit generation of a restriction in call by call units. The congested device notifies call connection data passing through it to a PDSN, the PDSN finds the IP address of the terminal using the target connection, and notifies a CSCF as a restriction target terminal. The CSCF, in call connection processing, determines whether the calling/called sending/receiving user is the restriction target, and if so, determines whether or not the call should be connected with priority from subscriber data.