针对仅具有文件交换且没有其他信息交换手段的通信双方,提出了点对点有序可靠的数据链路层设计方法.通过对交换的文件附加控制信息,实现链路基本控制;结合使用滑动窗口和超时重发,解决链路可能存在的失序与丢失问题;对交换的文件附加MD5等校验码,结合使用数据校验技术,可及时发现可能的毁损,保证交换文件的完整一致性.实际应用表明,即使通信双方仅具有文件交换手段,只要能找到合适的滑动窗口参数,可以实现有序可靠的通信链路服务.

For the communication parties which only have file exchange and no other means of information exchange, this paper proposes a design method of a point-to-point ordered reliable data link layer. Control information is appended to the exchanged files to realize the basic link control function. Mechanisms of sliding window and timeout retransmission are also introduced to address the problem of disorder and even loss. Furthermore, MD5 or some other check codes are also appended to the exchanged files to achieve an efficient verification of possible damage, guaranteeing the integrity and consistency of the exchanged files. The practical application shows that ordered reliable communication link service can be realized as long as all appropriate sliding window parameters could be found, even though the communication parties only have the means of file exchanges.