Studies a model of a network of links with the capacity of an integer number of bandwidth units that are shared amongst calls subdivided in K classes. A class is typified by the bandwidth requirement on each link and the average holding time of its calls. Calls arrive according to a Bernoulli-Poisson-Pascal process. The joint PDF of the number of bandwidth units in use, is found using a known recursion formula that is amenable to numerically instability. An algorithm that fixes the instability is proposed. Previous articles concentrated on time blocking probabilities. Those discussing call blocking probabilities suggest algorithms that are either approximative or time consuming. The present paper proposes a new one, that is shown to be superior in terms of accuracy and computation and storage overhead to the best exact algorithm available so far.>