This paper focusses on one of the methods for bandwidth allocation in an ATM network: the convolution approach. The convolution approach permits an accurate study of the system load in statistical terms by accumulated calculations, since probabilistic results of the bandwidth allocation can be obtained. Nevertheless, the convolution approach has a high cost in terms of calculation and storage requirements. This aspect makes real-time calculations difficult, so many authors do not consider this approach. With the aim of reducing the cost we propose to use the multinomial distribution function: the Enhanced Convolution Approach (ECA). This permits direct computation of the associated probabilities of the instantaneous bandwidth requirements and makes a simple deconvolution process possible. The ECA is used in Connection Acceptance Control, and some results are presented.Our study focusses on the stationary model. In this case the effect of statistical multiplexing is the dominant factor, and it considers that all the excess cells are lost when the instantaneous rate is greater than the bandwidth provided by the link.Several limitations have been found in the previous studies: a) only sources of two-state, ON-OFF sources are presented; b) accurate evaluations have been simplified in order to reduce the complexity of calculations and the memory, and in [7] the convolution approach is applied only as binomial distribution over homogeneous sources; c) no distinctions have been made applying different QOS to the individual connections; and d) all models studied describe the behavior of the sources without considering the interactions in the network. The impact of the sources is studied in an individual manner (fluid-flow model), or a statistical evaluation is applied to a set of sources (stationary model).Our study has been carried out under the following premises:The basic objective of a bandwidth management and traffic control strategy in ATh4 network is to allow for high utilization of network resources, whle sustaining an acceptable QOS for all connections. In ATM, all the existing connections on a link are statistically multiplexed. Note that statistical multiplexing is efficient and allows more calls to enter the network than in the case of peak rate allocation, since it exploits the small probability that a larger number of calls will be active simultaneously [9] and [17].It is possible to assign an equivalent bandwidth (effective bandwidth for some authors) to each source which reflects its characteristics. Several network traffic control functions such as congestion control and routing depend on the characterization of the equivalent bandwidth of individual connections and the resulting load on networks links. A major challenge is to provide traffk control hctions in real-time. This normally involves a reduction in the complexity, and of course the accuracy, of the evaluation models.The analytical approaches to the blocked probabilities are due to [lo]. Other graphcal results for source load are presen...
In this paper, we cansider the ATM networks in which the Virtual Path concept is implemented. The question of how to multiplex two or more diverse traflic classes while providing different Quality of Service requirements is a very complicated, open problem. Two distint options are available: integration and segregation. In an integration approach all the W c from Merent c o~e c t i~~l s are multiplexed onto one VP. This implies that the most restrictive QOS requirements must be applied to all services. Therefore, link utilization will be decreased because unnecessarily stringent QOS is provided to all C O M~O I I S . With the segregation approach the problem can be much simplified if different types of traflic are separated by assigning a VP with dedicated resources (bUgers and links). Therefore, resources may not be aciently utilized because no sharing of bandwidth can take place across the VP. The probability that the bandwidth required by the accepted co~ections exceeds the capacity of the link is evaluated with the Probability of Congestion (PC). Since the PC can be expressed as the CLP, we shall simply cany out bandwidth allocation using the PC. We first focus on the influence of some parameters (CLP, bit rate and burstiness) on the capacity required by a VP supporting a single traffic class using the New Convolution Approach. Numerical resuits are presented both to compare the required capacity and to observe which conditions under each approach are preferred.
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