In dynamic CAC, bandwidth allocation to a connection assumes a dynamic adjustment every fixed time period. The scheme estimates the distribution of the number of arriving cells with a renewal mechanism called exponential forecasting. This distribution is estimated from the measured number of cells arriving at the output buffer during the fixed interval and traffic parameters specified by users. Call acceptance (connection admission) is decided on the basis of on-line evaluation of the upper bound of cell loss probability, derived from the estimated distribution of the number of cells arriving. QoS standards can be guaranteed using this control when there is no estimation error. This control can achieve higher utilization than a control that uses only traffic parameters, and can cope with excessive flow from an individual source.