Vehicular networks are inherently unstable networks with high mobility and intermittent connectivity. These networks can greatly benefit from Delay Tolerant Networking (DTN) solutions for opportunistic connectivity in the transmission of delay-tolerant data. In this paper, we evaluate the performance of different DTN routing protocols in real world vehicular networks with different degrees of connectivity in order to understand their feasibility in real vehicular environments. Our case-study application is the upload of delay-tolerant sensing data from vehicular nodes to a server on the Internet. We deploy DTN in 3 vehicular testbeds: a heterogeneous lab testbed with controlled mobility, a low-mobility high-connectivity network of harbor trucks, and a high-mobility low-connectivity city bus network. We compare 3 routing protocols: epidemic, static and PRoPHET, for which we measure delivery ratio, average delay, path length, as well as transmission and storage overhead. We analyze the results for experimental insight, and extract lessons for DTN routing protocol design.
