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11.17 HDLC frame
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11.18 HDLC frame types
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11.19 I-frame
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11.21 U-frame control field in HDLC
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Table 11.1 U-frame control command and response
Control Variables and Timers
Acknowledgment Resending Frames Operation
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11.6 Sender top-and-Wait ARQ system, the bandwidth of the line is 1 Mbps, and 1 bit takes 20 ms to make a round trip. What is the bandwidth-delay product? If the system data frames are 1000 bits in length, what is the utilization percentage of the link?
11.1 Normal operation
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11.2 Stop-and-Wait ARQ, lost frame
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11.3 Stop-and-Wait ARQ, lost ACK frame
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Note: In Stop-and-Wait ARQ, numbering frames prevents the retaining of duplicate frames.
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11.15 NRM
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11.16 ABM
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11.4 Selective-Repeat ARQ
Sender and Receiver Windows Operation Sender Window Size Bidirectional Transmission Pipelining
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11.14 Selective Repeat ARQ, sender window size
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Example 1
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11.9 Go-Back-N ARQ, normal operation
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11.10 Go-Back-N ARQ, lost frame
Solution
The bandwidth-delay product is still 20,000. The system can send up to 15 frames or 15,000 bits during a round trip. This means the utilization is 15,000/20,000, or 75 percent. Of course, if there are damaged frames, the utilization percentage is much less because frames have to be resent.
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Note: Error control in the data link layer is based on automatic repeat request, which is the retransmission of data.
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11.20 S-frame control field in HDLC
00:Receive ready, RR 10:Receive not ready, RNR 01:Reject, REJ 11:Selective reject, SREJ
11.13 Selective Repeat ARQ, lost frame
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Note: In Selective Repeat ARQ, the size of the sender and receiver window must be at most one-half of 2m.
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11.2 Stop-and-Wait ARQ
Operation Bidirectional Transmission
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11.7 Receiver sliding window
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11.8 Control variables
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Chapter 11
Data Link Control and Protocols
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11.1 Flow and Error Control
Flow Control
Error Control
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11.4 Stop-and-Wait ARQ, delayed ACK
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Note: Numbered acknowledgments are needed if an acknowledgment is delayed and the next frame is lost.
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11.11 Go-Back-N ARQ: sender window size
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Note: In Go-Back-N ARQ, the size of the sender window must be less than 2m; the size of the receiver window is always 1.
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11.12 Selective Repeat ARQ, sender and receiver windows
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11.5 Piggybacking
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11.3 Go-Back-N ARQ
Sequence Number Sender and Receiver Sliding Window
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11.5 HDLC高级数据链路控制
Configurations and Transfer Modes Frames Frame Format Examples Data Transparency
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