  This paper evaluates two forwarding strategies for fragmented datagrams in
the IoT: hop-wise reassembly and a minimal approach to directly forward
fragments. Minimal fragment forwarding is challenged by the lack of forwarding
information at subsequent fragments in 6LoWPAN and thus requires additional
data at nodes. We compared the two approaches in extensive experiments
evaluating reliability, end-to-end latency, and memory consumption. In contrast
to previous work and due to our alternate setup, we obtained different results
and conclusions. Our findings indicate that direct fragment forwarding should
be deployed only 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.
