point (AP), or any central unit [8, 9]. This characteristic incurs several serious issues listed as follows. 1) Due to lack of central unit, central management like data collection or analysis is impossible. 2) To guarantee the routing, service discovery and data dissemination, many protocols in VANETs require the knowledge of global or partial topology of the network. However, significant overheads in terms of communication and storage are incurred due to the flooding or multi-hop forwarding [10, 11]. 3) Without the network infrastructure, steady connection between nodes is difficult to be guaranteed, especially in large scale VANETs. In other words, the scalability is difficult