  The ABR service is designed to fairly allocate the bandwidth unused by higher
priority services. The network indicates to the ABR sources the rates at which
they should transmit to minimize their cell loss. Switches must constantly
measure the demand and available capacity, and divide the capacity fairly among
the contending connections. In order to compute the fair and efficient
allocation for each connection, a switch needs to determine the effective
number of active connections. In this paper, we propose a method for
determining the number of active connections and the fair bandwidth share for
each. We prove the efficiency and fairness of the proposed method analytically,
and simulate it by incorporating it into the ERICA switch algorithm.
