Routing solutions for delay-tolerant networks (DTNs) are plentiful and can be ordered in various taxonomy designs. But when it comes to deep-space missions showing very high link delays with very precious volume limits, the usage of opportunistic or probabilistic behaviors to find an end-to-end path for the messages is, at best, sub-optimal, but in most cases not enviable.

Space networks give however precise topological information that can be leveraged. The node mobility patterns are in general predictable for long-planned deep-space missions, and by extension, the interval of connectivity between the nodes can also be predictable. This information permits the development of deterministic path-finding solutions, to permit message scheduling through a path with sufficient delivery confidence, at any time, and without the need for a convergence phase that might be required when using a probabilistic approach. The path-finding approach is also suitable for the high link constraints, as the zero-replication aspect of this method reduces the risk of congestion.

However, the delays and the intermittent nature of the links, the possible great size of the DTN messages coupled with the valuable link volumes to be managed, variable access to space cost, and a predictable increasing interest in highly connected space networks, bring new challenges to the table.

This conference intends to cover the present and future solutions available for routing in such extreme networks, as well as present open research questions in the context of routing in DTN environments.