Figure 12.1 Data link layer divided into two functionality-oriented sub 数据链路层分为两个功能子层： 数据链路控制子层和多路访问控制子层 Data link layer Data link control Multiple-access resolution 12.2 12.2 Figure 12.1 Data link layer divided into two functionality-oriented sublayers 数据链路层分为两个功能子层: 数据链路控制子层和多路访问控制子层