Internet of Things (IoT) exposes various vulnerabilities at different levels. One such exploitable vulnerability is Denial of Service (DoS). In this work, we focus on a large-scale extensive study of various forms of DoS and how it can be exploited in different protocols of IoT. We propose an attack and defense framework called OWL which is tailored for IoT and that can perform various forms of DoS on IP, Bluetooth, and Zigbee devices. We consider various DoS vulnerabilities such as illegitimate packet injection, Bluetooth Low Energy (BLE) scanning attack, Zigbee frame counter-attack, etc., regarding IP, Bluetooth and Zigbee devices. To understand how resilient is IoT for DoS, we propose two new metrics to measure the Resilience and the Quality of Service (QoS) degradation in IoT. We have conducted large-scale experimentation with real IoT devices in our security IoT testbed. The experiments conducted are for DoS, Distributed Denial of Service (DDoS) by setting up Mirai and Permanent Denial of Service (PDoS) using BrickerBot on various IoT devices. We have also compared our framework with the existing state of the art tools.IoT environment, analyzes, monitors and mutates the packets that will be accepted by the IoT device. OWL produces legitimate and illegitimate packets to perform the DoS. Not to forget, OWL also includes techniques in performing classical resource exhaustion for DoS. However, OWL stands out in performing DoS attacks through a few mutated packets by exploiting various DoS vulnerabilities of IoT devices. We have compared and evaluated OWL with two of the state-of-the-art DoS tools, LOIC (Low Orbit Ion Cannon) [12] and hping3 [13], where LOIC and hping3 can perform DoS only on IP based IoT devices and only through resource exhaustion. Next, we introduce a DoS and DDoS defense framework for IoT. The framework is capable of analyzing the network traffic to determine if there is a DoS or a DDoS attack on a specific IoT device. Suppose there is an attack, the defense framework takes appropriate steps to mitigate the attack by changing the IP address of the IoT device and providing alerts for Bluetooth and Zigbee devices. On the other hand, if an IoT device within the network is launching a DoS attack on other devices, the defense framework will automatically disconnect the network connection of the attacking IoT device.Second, we have introduced IoT Resilience (R IoT ) metric to evaluate the resilience of an IoT device against DoS, DDoS and PDoS. IoT Resilience will be calculated based on the services running on an