Abstract: Opportunistic networks are one of the most interesting evolutions of MANETs. In opportunistic networks, route connecting to the mobile nodes never exits, mobile nodes communicate with each other when they got opportunity to communicate. Furthermore, nodes are not supposed to possess or acquire any knowledge about the network topology. Routes are built dynamically, while messages are route between the source and the destination, and any possible node can opportunistically be used as next hop, provided it is likely to bring the message closer to the final destination. These requirements make opportunistic networks a challenging and promising research field.