Abstract: An Internet communication system including a first access point, a second access point, a first caller and a first callee is provided. The first access point and the second access point are respectively located in a first LAN and a second LAN. The first caller, having a probing-based mechanism, accesses the Internet via the first access point and has voice packets with a first transmission priority. The first callee accesses the Internet via the second access point. The first caller transmits a simulation packet to the first callee for probing a transmission quality of an end-to-end transmission path of the first caller and the first callee to determine whether to invite the first callee to communicate via the Internet.