A Lesson in Scaling 6LoWPAN – Minimal Fragment Forwarding in Lossy Networks

This paper evaluates two forwarding strategies for fragmented datagrams in the IoT: hop-wise reassembly and a minimal approach to direct forwarding of fragments. Direct fragment forwarding is challenged by the lack of forwarding information at subsequent fragments in 6LoWPAN and thus requires additional data at nodes. We compare the two approaches in extensive experiments evaluating reliability, end-to-end latency, and memory consumption. In contrast to previous work and due to our real-world testbed setup, we obtained different results and conclusions. Our findings indicate that direct fragment forwarding should be deployed with care, since higher packet transmission rates on the link layer can significantly reduce its reliability, which in turn can even further reduce end-to-end latency because of highly increased link layer retransmissions.