© 2016 Elsevier B.V. The goal of the Internet of Things (IoT) is to create an integrated ecosystem for devices to communicate over the Internet. To achieve this goal, efficient inter-operation is needed among Device to Device (D2D) communication technologies that make up the ecosystem. Currently, these technologies operate in vertical silos with different protocols. We explore the challenges associated with the integration and interoperability of these D2D technologies by focusing on network layer functions such as addressing, routing, mobility, security and resource optimization. We identify the limitations of the current TCP/IP architecture for D2D communication in the IoT environment. We also discuss some of the limitations of the 6LoWPAN architecture and describe how it has been adopted for D2D communication. Finally, we present solutions to address the limitations we have identified for the network layer functions as applicable to D2D communication in the IoT environment.