The present invention aims to provide a communication system capable of optimizing network processing. The communication system according to the present invention includes an application server (10) configured to detect a behavior of a communication terminal (50) and a service common apparatus (20) configured to receive an identifier of the communication terminal (50) and behavior information on the communication terminal (50) transmitted from the application server (10) via a first interface defined between the service common apparatus (20) and the application server (10) and to transmit the identifier of the communication terminal (50) and the behavior information on the communication terminal (50) to a mobile network node (40) via a second interface defined between the service common apparatus (20) and the mobile network node (40) to optimize a parameter regarding the communication terminal (50).