  Delay/Disruption-Tolerant Network (DTN) protocols typically address sparse
intermittently connected networks whereas Mobile Ad-hoc Network (MANET)
protocols address the fairly stable and fully connected ones. But many
intermediate situations may occur on mobility dynamics or radio link
instability. In such cases, where the network frequently splits into evolving
connected groups, none of the conventional routing paradigms (DTN or MANET) are
fully satisfactory. In this paper we propose HYMAD, a Hybrid DTN-MANET routing
protocol which uses DTN between disjoint groups of nodes while using MANET
routing within these groups. HYMAD is fully decentralized and only makes use of
topological information exchanges between the nodes. The strength of HYMAD lies
in its ability to adapt to the changing connectivity patterns of the network.
We evaluate the scheme in simulation by replaying synthetic and real life
mobility traces which exhibit a broad range of connectivity dynamics. The
results show that HYMAD introduces limited overhead and outperforms the
multi-copy Spray-and-Wait DTN routing protocol it extends, both in terms of
delivery ratio and delay. This hybrid DTN-MANET approach offers a promising
venue for the delivery of elastic data in mobile ad-hoc networks as it retains
the resilience of a \textit{pure} DTN protocol while significantly improving
performance.
