  Decentralized, distributed storage offers a way to reduce the impact of data
silos as often fostered by centralized cloud storage. While the intentions of
this trend are not new, the topic gained traction due to technological
advancements, most notably blockchain networks. As a consequence, we observe
that a new generation of peer-to-peer data networks emerges. In this survey
paper, we therefore provide a technical overview of the next generation data
networks. We use select data networks to introduce general concepts and to
emphasize new developments. Specifically, we provide a deeper outline of the
Interplanetary File System and a general overview of Swarm, the Hypercore
Protocol, SAFE, Storj, and Arweave. We identify common building blocks and
provide a qualitative comparison. From the overview, we derive future
challenges and research goals concerning data networks.
