The rapid growth of IoT applications usage enables the Internet connectivity of a massive number of devices using different technologies. Most of these technologies, such as Low Power Wide Area Networks (LPWANs), are non-IP due to the difficulties of using IP on constrained devices. These nodes are characterized by more constraints with respect to other IoT technologies. According to [1], IPv6 offers many benefits for IoT, which motivated the IETF to form a Working Group (WG) to study and propose new solutions to run IPv6 on the new technologies of IoT [2], [3]. The key to solving this issue is the header compression mechanisms. In this paper, we analyze the two IETF standardized solutions, SCHC and 6LoWPAN, to compress IPv6 over constrained nodes within LPWAN. Based on [3], we implement the SCHC mechanism [4] in the network simulator NS3 [5]. We also show that SCHC protocol solution as an adaptation layer between the network layer and the link layer is better in term of header compression by providing a smaller header size compared to 6LoWPAN.