Research On The Overload Control For Media Gateway In Soft-Switch

NGN is a kind of whole network solution, belonging to the services driving network, which uses open network structure, in which service and call control, as well as call and carrying, can be separated. The goal of the separation is to make service quite independent of network and to support service flexibly and etTectively. Soft-Switch, as the core technology, is getting more and more points. Media gateway (MOW) is an important device in Soft-Switch system. Under the system structure of Soft-Switch that call control to separate with carrying, the MOW is located in the access layer and transfers kinds of media stream of users and networks into core network. Therefore when there are abrupt and a great deal of service requests which can't be anticipated in the network, the overload control of MGW is the key technique to keep the quality of the service in Soft-Switch, it plays important role in insuring the stability of the network and then providing efficiently and high-quality service in Soft-Switch. The Soft-Switch system is the new network mode, so the mechanism of overload control is the core technique in overload control of MGW in Soft-Switch.According to the standard concept of NGN, the MGW does not do any call control and just works according to the instruction of the media gateway controller (MGC) which is the control layer equipment in Soft-Switch. So the overload control of MGW in Soft-Switch researched in this paper is a kind of feedback model for service traffic control mechanism which is composed by MGW and MGC together.At first, this paper introduces the research of overload control of MGW in Soft-Switch, and also introduces the research result of overload control technique in existing and various networks. And then the structure of the Soft-Switch system is introduced, the H.248 protocol is detailed introduced. Based on this, according to the characteristic of Soft-Switch that call and carrying can be separated, we studies the related problems of overload control of MGW, including the principle of the overload control, the detection method of MGW, the overload control algorithm adopted byMGC, combining the priority of context to the overload control mechanism, and the evaluation standards of overload control etc...Then this paper put forward the strategy of overload control of MGW, set up the overload control model that based on message feedback, elaborate the work principle of the close-loop control model according to the H.248 protocol. Simple OPNET simulation of overload control of MGW was described. The result of the simulation indicated that the application of this control model can availably control the overload of MGW in a great deal of calls, and ensured higher call success ratio and better network capability at the same time.