IEEE 802.11ah protocol is specifically designed to provide network connectivity to a large number of energy efficient heterogeneous quality of service (QoS) Internet of things (IoT) devices. Restricted access window (RAW) mechanism of the protocol is an innovative feature that aims at reducing medium access contention by slotting the beacon interval and allowing limited number of nodes to contend in a specific slot. In this paper, we evaluate important medium access control (MAC) layer performance metrics of differentiated QoS IoT nodes in the IEEE 802.11ah RAW mechanism. Our analysis evaluates the feasibility of coexistence of priority and nonpriority traffic in IoT devices without degrading network performance.