In-vehicle networking is a method for transferring data among distributed electronic modules via a serial data bus. The classification of In-vehicle networks was introduced in this article and communication protocols such as LIN, CAN, VAN, J1850, and J1939 etc. were compared. There was a case study on character and performances of CAN protocol which is widely used in automotive industry and automation. The simulation results showed the error handling mechanism and bus load feature of CAN network. Layered-architecture of vehicle networks and protocols was explained considering communication requirement. The future trend of vehicle network communication protocols was also discussed.