Note Byte stuffing is the process of adding 1 extra byte whenever there is a flag j or escape character in the text. 字节填充是当文本中存在一个标记字符或者 转移字符时，添加一个额外字节的过程。 11.6
11.6 Byte stuffing is the process of adding 1 extra byte whenever there is a flag or escape character in the text. 字节填充是当文本中存在一个标记字符或者 转移字符时，添加一个额外字节的过程。 Note
Figure 11.3 A frame in a bit-oriented protocol面向比特位的帧 Data from upper layer Variable number of bits 01111110 Header 01111010110··11011110 Trailer 01111110 Flag Flag 11.7
11.7 Figure 11.3 A frame in a bit-oriented protocol 面向比特位的帧
Note Bit stuffing is the process of adding one extra 0 whenever five consecutive 1s follow a 0 in the data,so that the receiver does not mistake the pattern 0111110 for a flag. 比特位填充是每五连1时，插入一个比特0的 过程，以便接收方不会误认为是帧的标记。 11.8
11.8 Bit stuffing is the process of adding one extra 0 whenever five consecutive 1s follow a 0 in the data, so that the receiver does not mistake the pattern 0111110 for a flag. 比特位填充是每五连1时，插入一个比特0的 过程，以便接收方不会误认为是帧的标记。 Note
Figure11.4 Bit stt4 fing and unstuffing透明的比特位填充和移除达 Data from upper layer 0001111111001111101000 Stuffed Frame sent Flag Header 000111110110011111001000 Trailer Flag Extra 2 bits Frame received Flag Header 000111110110011111001000 Trailer Flag Unstuffed 0001111111001111101000 Data to upper layer 11.9
11.9 Figure 11.4 Bit stuffing and unstuffing 透明的比特位填充和移除过程
11-2 FLOW AND ERROR CONTROL 流量控制和差错控制 The most important responsibilities of the data link layer are flow control and error control.Collectively, these functions are known as data link control. 数据链路层最重要的职能就是流量控制和差错控制。 通常一起称为数据链路控制。 Topics discussed in this section: Flow Control 流量控制 Error Control 差错控制 11.10
11.10 11-2 FLOW AND ERROR CONTROL 流量控制和差错控制 The most important responsibilities of the data link layer are flow control and error control. Collectively, these functions are known as data link control. 数据链路层最重要的职能就是流量控制和差错控制。 通常一起称为数据链路控制。 Flow Control 流量控制 Error Control 差错控制 Topics discussed in this section: