The Design And Implementation Of Service Switch In Softswitch

NGN, short for Next Generation Network, is derived from the combination of traditional PSTN and IP based packet network. NGN is able to provide various services, such as voice, video and data. Softswitch is the control function entity in NGN, which provides NGN with real-time service\call control and connection control.The call control function and the service control function assembled in one switching system of the public switched telephone network.One of the most important features of Softswitch is that the service control function departs from the call control function.Softswitch is only responsible for the basic call control,and the service control function was moved into the Application Server.Because of the departing,softswtich needs to establish the relationship between application layer and network layer,the service switch model of Softswitch takes charge of this mission.The service switch function,which is the base of service,is a must of softswitch.This paper focuses on the design and implementation of service switch model in Softswitch.Softswitch provides two main functions for application layer through service switch model:1. Providing a mechanism of service triggering and detection, Application Server can distribute its triggering criteria and interested events into Softswitch.when the interested event has happened or the triggering criteria has been triggered,softswitch can detect it and send a notification to Application Server;2. Mapping the service control of application layer into the basic call control of network layer. The paper mainly describes two aspect of the service switch model.One is service view model which is responsible for mapping the multi-party control mode into the basic call control mode;The other is service triggering and detection model which takes charge of detecting the triggering criteria and interested events.The service switch model of Softswitch is solving these two problems:1. Mapping the multi-party control mode of the standard service interface (such as Parlay APIs) into the single-party control mode of Softswitch, strongly enhancing the capability in supporting multimedia services for Softswitch;2. Working out the detection point management solution for multi-agent environment, strongly improving the throughput of Softswitch.Softswitch provides its network capability for Application Server through the service switch subsystem, gives strong support for developing multimedia services.