| At present, Internet has already developed into the global information network, its scale and user's quantity are second only to the public telephone network (PSTN ) and cable television network. Already existing traditional telecommunication network and network of new generation will also coexist in quite a long time. So no matter technically or on the service, the integration of traditional PSTN and IP data network has already become the inexorable trend of network development. VoIP technology is exactly a result merged in PSTN and IP network. VoIP is the media of utilizing IP network to be transmitted as the pronunciation, realize a kind of brand-new communication technology of pronunciation communication, refer to in general and utilize international Internet to be a pronunciation telephone of the media. The technology that it adopts is referred to as VoIP (Voice over IP), namely convey the pronunciation in IP network. Technically, IP network telephone whether taking IP as sign network divide into groups take and taking multimedia as sign network business totalization two heavy major results that technology merge. In addition, with the maturity of the technological condition, the integration of the network is becoming the main trend of telecommunication development. The telecommunication network faces a problem now, that is how to exchange net the traditional circuit to carry out the transition to the network of dividing into groups, the soft-switch concept has offered an effective way for solving this problem, it is soft-switch main in ones that design philosophy for service /control and transmission /access not separating, join through the standard protocol between every entity and communication. Can be in case of not carrying on bigger change to the original network through soft-switch, carry on interconnection of the network of the original different protocol of use, thus meet the requirement of unification of three nets. In a situation that the original circuit exchanges (hard-switch), the software and hardware of the program-control exchanger are all controlled by the equipment supplier, the development of new service, new function is all limited by to the equipment supplier, therefore, for meet user's demands, is it develop new business and open new function seem difficulty very much at the network in PSTN to want. In addition, in original VoIP system, mostly adopt and support the single protocol like H. 323, MGCP, SIP, etc. are come to realize. Now, the fact of development requires that can be carried on interconnected by VoIP system which different producing traders develop, and require that can adopt the part not produced with the different producing trader in a new network, thus require VoIP system to possess very good opening; In addition, VoIP system can offer the unified interface, can carry on the secondary development conveniently (can be developed by the third party). Today, soft-switch system is ripe day by day; it is very meaningful how to carry on the development of VoIP system and application under soft-switch system. This paper introduces the development of VoIP, basic composition unit of VoIP system, the difference between VoIP and traditional PSTN at first; Have recommended the service of soft-switch system to offer the way; Then analyses how to set up VoIP system, including network architecture and software architecture under soft-switch system, propose adopting the thought of dividing layer to design VoIP system, isolate a core to control layer, offered the unified abstract interface to upper strata by this layer, manage the difference protocol of lower floor and various kinds of hardware, thus reached the purpose that can both carry on the secondary development realize support to many kinds of protocol conveniently; Provide under system this call transfer application to meet the need of scheme and the whole system perfect and improved work function finally. |
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