Constrained devices will play a crucial role in the Internet of Things. These devices use communication technologies which often support the formation of wireless multihop topologies. Therefore, end-to-end data transfer involves the collaboration of multiple protocol layers. However, the settings and mechanisms used in a specific layer affect performance of the others. In this paper, we assess a set of crucial network design criteria for potential MAC layer, network layer and transport layer protocols for networks of constrained devices. We evaluate the default and alternative settings and mechanisms for these protocols on a 60-node testbed. The experiments show how performance can be improved significantly by using different settings and mechanisms from the default ones.