本文对一个多机系统中数据通信网的链路层作了一般性介绍。重点围绕局部计算机网的数据链路层所应完成的功能与任务进行了几个方面的讨论和介绍,它们包括:介质访问控制,差错控制,链路层协议等。在程序实现方面也给出了一些说明 This article gives a general introduction to the link layer of a data communications network in a multi-machine system. Focus on the local computer network data link layer functions and tasks should be completed in several aspects of the discussion and introduction, they include: media access control, error control, link layer protocol. In program implementation also gives some instructions