Most Vehicle to Vehicle (V2V) network protocols are evaluated by simulation. However in most network simulators, the physical layer suffers from a lack of realism. Therefore, realistic V2V channel modeling has become a crucial issue in Intelligent Transportation Systems (ITS) networks. V2V channels are known to exhibit specific features which imply the design of new simulation models. In this survey paper, we first recall the main physical features of such wireless time and frequency dispersive channels. Next, three "simulation-ready" V2V channel models found in the literature are reviewed. Finally, two complete VANET simulation frameworks are presented. They illustrate the importance of a realistic channel and physical layer modeling in vehicular networking.