  After a decade of research in low-power data collection, reaching arbitrary
nodes has received comparatively little attention. The leading protocol for
low-power IPv6 routing, RPL, is no exception, as it is often studied in
multipoint-to-point scenarios. As a result, downward routing (from root to
node) is still notoriously difficult, holding back the emergence of Internet of
Things applications that involve actuation. In this paper, we focus on
achieving industrial-grade reliability levels (1e-5 failure rate) in downward
routing with RPL. We make every packet count, and classify the different causes
of packet loss. We show how to mitigate each source of packet loss, by (1)
introducing a gradient metric that favors reliable links, (2) increasing
neighborhood awareness for accurate link selection, and (3) ensuring a robust
routing state maintenance and packet forwarding. We demonstrate RPL downward
routing with loss rates in the order of 1e-5 in four different testbeds up to
352 nodes, in both sparse and dense settings. We also validate our solution on
top of a low-power TSCH scheduler, and achieve sub-percent low duty cycles and
a channel utilization of 0.07% at every node, spread over 16 channels.
