11-5 NOISY CHANNELS有噪声信道 Although the Stop-and-Wait Protocol gives us an idea of how to add flow control to its predecessor,noiseless channels are nonexistent.We discuss three protocols in this section that use error control. 尽管停等协义增加了流量控制的概念，但无噪声信道 仅是理想的，不存在的。需要讨论三个使用差错控制 的链路协议。 Topics discussed in this section: Stop-and-Wait Automatic Repeat Request停等ARQ Go-Back-N Automatic Repeat Request 后退N帧ARQ Selective Repeat Automatic Repeat Request选择性重传ARQ 11.26
11.26 11-5 NOISY CHANNELS 有噪声信道 Although the Stop-and-Wait Protocol gives us an idea of how to add flow control to its predecessor, noiseless channels are nonexistent. We discuss three protocols in this section that use error control. 尽管停等协义增加了流量控制的概念，但无噪声信道 仅是理想的，不存在的。需要讨论三个使用差错控制 的链路协议。 Stop-and-Wait Automatic Repeat Request 停等ARQ Go-Back-N Automatic Repeat Request 后退N帧ARQ Selective Repeat Automatic Repeat Request 选择性重传ARQ Topics discussed in this section:
Note Error correction in Stop-and-Wait ARQ is done by keeping a copy of the sent frame and retransmitting of the frame when the timer expires. 停等ARQ协议中，差错控制检测由保留已发 送帧的副本并当重传定时器到时时重传这个 帧来实现。 11.27
11.27 Error correction in Stop-and-Wait ARQ is done by keeping a copy of the sent frame and retransmitting of the frame when the timer expires. 停等ARQ协议中，差错控制检测由保留已发 送帧的副本并当重传定时器到时时重传这个 帧来实现。 Note
Note In Stop-and-Wait ARQ,we use sequence numbers to number the frames. The sequence numbers are based on modulo-2 arithmetic. 停等ARQ使用序列号为每一个帧编号。序列 号基于模2运算。 11.28
11.28 In Stop-and-Wait ARQ, we use sequence numbers to number the frames. The sequence numbers are based on modulo-2 arithmetic. 停等ARQ使用序列号为每一个帧编号。序列 号基于模2运算。 Note
UNIN Note In Stop-and-Wait ARQ,the acknowledgment number always announces in modulo-2 arithmetic the sequence number of the next frame expected. 停等ARQ,确认编号是期望收到下一帧的编 号（模2域计算）。 11.29
11.29 In Stop-and-Wait ARQ, the acknowledgment number always announces in modulo-2 arithmetic the sequence number of the next frame expected. 停等ARQ，确认编号是期望收到下一帧的编 号（模2域计算）。 Note
Figure 11.10 Design of the Stop-and-Wait ARQ Protocol 停等ARQ协议设计 NI Next frame Next frame to send to receive .010i0. 010i0!. Sender Receiver Data frame ACK frame Deliver Network Get data 中 data Network seqNo ackNo Data link Data link Physical Receive Send Receive Send Physical frame frame frame frame Event: Request from network layer Repeat forever Repeat forever Algorithm for sender site Time-out Algorithm for receiver site Event: Event: Notification from Notification from physical layer Event: physical layer 11.30
11.30 Figure 11.10 Design of the Stop-and-Wait ARQ Protocol 停等ARQ协议设计