采用仿真的方法实现可靠数据传输协议。发送方的协议实体从上层接收用户的报文，封装为分组后由下层发送给对方主机；接收方的协议实体接收到下层交付的分组，判断是否正确、按序接收。如果是，则将数据交付给上层，否则，通过确认机制要求发送方重传分组。-Simulation method used to achieve reliable data transfer protocol. Sender protocol entity receives from the upper user packets, packaged in packets sent from the lower to the other party after the host　receiving protocol entity receives a lower packet delivery, to determine whether the correct sequence to receive. If so, the data will be delivered to the upper, or, by identifying the mechanism requires the sender retransmission packet.