The intelligent traffic monitoring would be considered as one of the most important techniques to handle a great deal of data in Internet of Things (IoT) Networks. We consider an IoT network with three class of sensors which transmit their data to a Monitoring Center (MC). The MC with a great demand for fresh data, is equipped with one server and one buffer of capacity equal to one packet as a queueing model, representing an M/M/1/2 system. The characteristics of the group of devices, are specified with high, medium and low priorities, respectively. We consider a Rayleigh fading channel over the links between devices and the MC. We assume a non-preemptive system in the MC so that the packets with lower priority can be replaced by higher priority packets, as well. The arrival packets have different deadlines due to the diversity of information in the network. The average number of successfully served packets are obtained as the effective traffic intensity of the whole network to measure the performance of the system. The simulation results show that increasing the number of classes with priorities, does increase the traffic intensity up to service rate of the monitoring center.