Adaptive Algorithm for Virtual Connection on Feedback-Based Flow Control in WAN-ATM Network

F. Ahmadi Djajasugita & Rendy Munadi

Adaptive flow control Algorithm can be applied into wide area ATM network to allocate lebar pita to virtual connection. Flow control uses closed loop control mechanism, i.e, a reactive control mechanism which dynamically controls permissible transmission speed for any virtual connection by using feedback information of the network. Information of the network is in the form of bit that can identify whether a queue length in buffer is above or below a given threshold. By this indication bit the source of cell sending can be controlled. The earlier investigation was limited to 24 VC connection and in 155 Mbps transmission speed with 6.5 cells buffer threshold. Considering that it was not enough, a further investigation was carried out with increasing connection up to 100 VC, 600 Mbps transmission speed, and buffer threshold in a wide range. Adaptive algorithm simulation results showed that by using stability criterion on single virtual connection we found the range of gain ratio parameter used on proper damping, hence, fairness can be made easier in multiple virtual connections. There are two parameters - each is important for every virtual connection, i.e minimum bandwith parameter and weight factor to gain bandwith share that provided by the network. Proper selection on the two parameters gives different service. Aggregate speed response showed that there is degradation of network bandwith use (<90%). This situation can be overcome by increasing the transmission speed, lengthening update time, and enlarging the buffer threshold.

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