We propose a protocol verification method capable of evaluating a telematics system using the ns simulation & emulation facilities. With simulation, we experiment delay and throughput performance of TCP and UDP transport layer protocols under wireless channels. In a repeatable, detailed and realistic emulator, we investigate performance of real telematics system. We make our emulation system more realistic by using the data and parameters of commercial cellular network provider. Our simulation results show that TCP and UDP protocols need some modifications to improve performance over wireless channel with high-mobility mobile nodes. We verified by emulation that our telematics system operates well using a proper retransmission scheme in an application layer.