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ATM, an ultimate solution of broadband-integrated service digital network (B-ISDN) to provide integrated multimedia services including voice, video, and data, has entered into the limelight with increased demand for such services. Hence, ATM is to be capable of supporting a variety of service classes and providing appropriate QoS according to classes. This may force us to sacrifice low priority traffic classes for high priority traffic classes to satisfy QoS requirements for the high priority traffic classes in case of congestion. There have been many possibilities suggested for traffic control in terms of QoS and 'Cell Loss Priority (CLP) control', which was originally introduced in ATM networks for the purpose of congestion control, must be one of them. The capability of CLP control can apply to Doubly Finite Queue buffer priority scheme. This scheme based only priority queuing disciplines that are used to secure the Cell Loss Ratio (CLR) of higher priority cells at the cost of loss of low priority cells by examining the CLP bit of each incoming cell set to '0' or '1'. The cell CLP value equal to '0' assign high priority cell and CLP value equal to '1' assign low priority cell. Priority queuing is especially appropriate in cases where WAN (Wide Area Network) links are congested from time to time. Doubly finite queues (DFQ) and multi-source virtual dynamic routing algorithm (MSVDR) use an adaptive and iterative path search approach and taken advantage of the PNNI hierarchical structure. It consists of the following six major components.