M2M/IoT is rapidly growing and since its early days different “standard” protocols have emerged (e.g. OMA-DM, TR-069, MQTT, …) or are emerging (e.g. CoAP or Lightweight M2M). Understanding which protocol to use for which application can be intimidating, therefore we propose to give an overview of these protocols to help you understand their goals and characteristics. We’ll present common M2M use cases and why they usually require more than just one protocol ; we will also see whether CoAP associated with Lightweight M2M allows to forge “one protocol to rule them all”.