session layer
- Initially, the session layer was used to refer to layer 5 of the OSI reference model. Later, this layer was referred to as the communication control layer.
- In the IPMultimedia Subsystem( IMS), the Call Session Control Function( CSCF) for the control functions of the connection status between IP networks and UMTS is located on the session layer. In addition, the session layer of the IMS architecture is used for terminal registration and Session Initiation Protocol( SIP) routing and provides the required quality of service. In addition, this layer houses the database of all registered users, the Home Subscriber Server( HSS). It controls the reservation of sessions in which the IMS system and the conventional telephone network cooperate.