Performance evaluation and comparative study of main VDTN routing protocols under small- and large-scale scenarios

This paper presents a performance evaluation through simulations and a comparative study of main routing protocols dedicated to Vehicular Delay-Tolerant Networks. The assessment is conducted under small- and large-scale scenarios with realistic vehicle mobility patterns as defined in the TAPAS Cologne simulation scenario. Through the literature, several evaluations have been conducted on routing for Vehicular Networks, but with an abstraction or a simplification regarding the delay tolerant aspect. Furthermore, considered scenarios were relatively small and too idealistic compared to the real-world environment and its multiples challenges. Moreover, to the best of our knowledge, this is the first extensive study that compares, in the same realistic simulation environment, the main flag-carriers of various categories of VDTN routing protocols, namely Epidemic, Direct Delivery, Prophet and GeoSpray protocols. Simulation results reveal better performance for the geographical approach advocated by GeoSpray compared to the predictive one of Prophet, under all considered scenarios. Moreover, they highlight the possibility for a minimalist and naive protocol such as Direct Delivery to perform well, under specific network conditions, as when considering an anycast communication scheme. Finally, deeper analysis was undertaken on both GeoSpray and Prophet. The studies reveal the potentialities to increase the performances of GeoSpray to some extent and highlight the difficulties of adapting Prophet settings for optimal performance in realistic scenarios.