A disclosed technology can accurately measures the data frame loss between a pair of communication devices even when link aggregation is present between the communication devices. An embodiment of the apparatuses includes a roll including a first outer surface; a continuous belt including an inner surface and a second outer surface forming a nip by contact with the first outer surface, the belt being driven by rotation of the roll; and a heater disposed inside of the belt. The attachment end includes an attachment strap and is designed to attach respectively to a left or right belt positioning clip of a child safety seat.