Abstract—The Internet of Things (IoT) is a developing technology that can enhance the communication capabilities of Wireless Sensor Networks (WSN) when integrated together. The nature of IoT networks is characterized by self-organization and decentralization, leading to changes in the nodes’ position. Therefore, routing in the IoT is essential for the successful transmission of data. RPL (routing protocol for low-power and lossy networks) was evaluated for IoT objects. This paper’s aim is to examine the efficiency of IoT based on RPL as a routing protocol when bit and piece distributed denial-of-service (DDoS) cyber attack mitigate the traffic into the network. Cyber attacks had affect any IoT network by increasing the delay, jitter and reducing the throughput resulting in degradation in IoT network performance. Bit and piece DDoS is taken in this paper as an example of any cyber attack, other types could be taken like malware, phishing with the affect the IoT performance also. This simulation is done in number of NetSim verified scenarios in terms of throughput, delay, Jitter, packet delivery rate and bit error rate Quality of Service (QoS) parameters. The results show that RPL when applied to the IoT network investigated a better QoS improvement than any Ad-Hoc Routing Protocol like (AODV). The improvement had been investigated by increasing the throughput and decreasing the delay, Jitter and BER which are the QoS parameters taken in this paper.