The invention relates to method and devices of enabling determination of overall Quality of Service (QoS) of at least one Internet of Things (IoT) device. In an aspect of the invention, a method of a network node (10a) is provided of enabling determining of an overall QoS of at least one IoT device. The method comprises transmitting (S101), to a device connectivity middleware (DCM) node (14), an identifier of said at least one IoT device (11a) for which a QoS measure is to be acquired, receiving (S102), from the DCM node (14), a network profile of the IoT device (11a) associated with said identifier, transmitting (S103), to a Service Capability Exposure Function (SCEF, 15), a request for the QoS measure of the IoT device (11a) for the received network profile, the SCEF (15) acquiring the QoS measure from a Policy and Charging Control (PCC) function (16), receiving (S106), from the SCEF, the requested QoS measure of the IoT device (11a), transmitting (S107), to a Lightweight Machine-to-Machine (LWM2M) device (13), a request for availability information for said at least one IoT device (10a), and receiving (S108), from the LWM2M device (13), the requested availability information, wherein the received QoS measure and the availability information is taken into account for determining the overall QoS of said at least one IoT device (11a).