Delay tolerant networks (DTNs) are a class of networks that experience frequent and long-duration partitions due to sparse distribution of nodes. The topological impairments experienced within a DTN pose unique challenges for designing effective DTN routing protocols. For an important class of DTNs nodes depend on their mobility to carry message to the destination. It is therefore essential to understand the impact of commonly-used mobility models on performance analysis of DTN routing schemes. This paper shows how the underlying statistical properties of a frequently used mobility model can be used to enhance our understanding of DTN simulation results. Using these results we also analyze several DTN routing techniques, including direct transmission, Spray and Wait, and a novel core-assisted routing schemes.