The Reliability Study Of Control Between Layers In NGN

Softswitch is originated from Voice over IP, whose mainly character is the structure of division, that is to say, the bearer control is divided from call control. The softswitch architecture is the future of communication network. And also, softswitch is one key technology of NGN (Next Generation Network).MEGACO (Media Gateway Control Protocol)/H.248 protocol is the media gateway control protocol of NGN. It selects Termination, Context and Stream as its connection model, defines signal and event, and provides powerful API command. Also it defines Package to realize its better extensibility. The Service Change API is used to management the control association between softswitch machine and MGW. The Service Change Procedures that are the encapsulation of Service Change parameters realize the distributed function and manage the state of the terminations in MGW, MGW and softswitch machine. Service Change API and procdures that are the base theory of the following are detailed.The distributed function is realized through the control association between softwitch machine and MGW. The control association is defined as MEGACO Control Association in the present paper. The control association state machine is put up to manage control association. Then the process scheme and state transition are detailed. At last, the realization scheme is given. MEGACO Control Association is the control association between control layer and bearer layer in the divided layers network, whose reliability is one part of network reliability. The common theory of communication network reliability is firstly summarized. Then the network configuration requirements of high reliability control between layers are discussed. Based on the configuration requirements the network architecture is put up. At last the iniation, malfunction analyses and methods are realized based on control association state machine.