Study Message Syntax In Megaco/H.248 Communication Protocol And Program From Softswitch Controll Layer

Softswitch is controller function entity of the next generation network.It provide call control and connect control function for the operation which needs to be real time in the next generation network(NGN).Softswitch equipment is located on control layer.It provides function such as connect control,router,network resource management,count the charge,authentication and so on.Softswitch equipment communicates with all kinds of media gateway,terminator,application server and other softswitch equipment by standard protocol.It’s easy to say,softswitch is entity to realize the function which is named “call control” of the traditional program control switch.There are three parts in the softswitch architecture: signal gateway(SG),media gateway(MG)and media gateway control(MGC).This architecture realizes separating call control form carrying control.There are some protocol between these two separate units and two of them are abroad supported.One is MGCP(Media Gateway Control Protocol).It’s a RFC documentation(RFC 2705)which includes a normative content of a protocol yet.MGCP belongs to application layer control protocol which makes MGC control MG to realize the connection among MG in network and manage the alternation between MG and MGC.Later on,IETF MEGACO work group and ITU-T 16 study group brought forward Megaco and H.248 protocol based on MGCP separately to expand MGCP.Although MGCP has some characteristics such as easy to realize and so on,its ability to get through each other and support operation is limited.Megaco/H.248 is taken importance of due to its flexible function,strong ability to support operation.And constantly,its ability is supplemented by new accessory to make it the artery protocol between media gateway and softswitch.This tutorial discusses the detailed process of studying message syntax in Megaco/H.248 communication protocol based on text encoding and program from softswitch controll layer including: analyzing each message,parsing their syntax and realize MGC software.This project follows the 8 instruction set items(Command Application Programming Interface: Add,Modify,Subtract,Move,AuditValue,AuditCapabilities,Notify,ServiceChange)to be developed.At last,functions based on MG controlled by MGC such as voice call,call transfer and so on are realized.It provides a stable foundation for further communication software development.