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Abstract
Asynchronous transfer mode (ATM) is a streamlined protocol with minimal error and flow control capabilities; this reduces the overhead 01 processing ATM cells and reduces the number of overhead bits required with each cell, thus enabling ATM to operate at high data rates. Further, its use of fixed-size cells simplifies the processing required at each ATM node, again supporting the use of ATM at high data rates So. the ATM has been deemed the transfer technique of choice in an integrated environment supporting various multimedia services Multimedia connections carrying several different classes of traffic will have a wide variety of demands for quality of service (QoS) On the other hand, network utilization is a primary concern to the network provider. Thus. effectرe control mechanisms are necessary to maintain a balance between QoS and network utilization, both at the time of call setup and during the progress of the calls across the ATM network These incudes connection admission control (CAC). usage parameter control (UPC-policing), and network resource management The main objective of this thesis to address the problem of designing an effective CAC algorithm. In the thesis, a proposed CAC with increasing priority based on waiting time of each call is introduced The proposed admission controller tries to satisfy the QoS of higher priority calls and, In the same time, avoid the problem of highly-repeated rejections of lower priority ones, which is encountered In other methods. 1Jso, the proposed admission Policy tries to satisfy the GoS requirements of the admitted calls not only at the call level but also at the call level In the proponed algorithm arrived connection requests are stored in buffers, and each cat in each buffer is dynamically assigned a priority value that increases with a specific rate, based on its class type and its waiting time in the buffer. Two strategies For serving the call requests from each buffer along with five methods for assigning priority values to the calls are proposed In order lo analyze the performance of the proposed algorithm, a number of simulations are carried for each one of the two CAC strategies along with each of the proposed five priority assi9nrnent methods. For each combination, three different simulation runs are performed assuming three different combinations of the call-classes. The used traffic parameters of these Classes have been chosen so as to reflect different business levels. Various traffic parameters are considered and the performance indices (such as the queue size, utilization, , etc) are calculated to evaluate the effectiveness of This policy. The results show that, using the proposed CAC strategy. can blocking probability and average queue Size of the high priority calls are reduced At the same time, unlike the cases of assigning fixed priorities, the results show a significant chance to admit the lower priority calls. Thus, the proposed algorithm toes to overcome the problem of highly-repeated rejections of these lower priority calls, Which is encountered in other CAC algorithms,