This model represents an output queue ATM switch architecture. In this model, when a packet arrives at the switch it is immediately routed to the appropriate output channel and no blocking occurs in the switch fabrics. We have two On_Off sources that transmit packets to the Switch_2x2 object. When the event Packet_Generation triggers, a source sends a packet to the switch that with probability routes the packet to queue 1 (first output) and with probability routes it to queue 2 (second output). The On_Off_Source_1 object sends packets using the port named connection_1 and the On_Off_Source_2 object sends packets using the port named connection_2. The model is shown in Figure .