1. In a network, the ratio (1– x/y,) where: y is the number of cells that arrive in an interval at the ingress of the network; and x is the number of these y cells that leave at the egress of the network. 2. In a network element, the ratio (1– x/y,) where y is the umber of cells that arrive in an interval at the ingress of the network element; and x is the number of these y cells that leave at the egress of the network element.