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DATA COMMUNICATION Lecture-39
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Recap of Lecture 38 Flow Control Stop-and-Wait Sliding Window
Error Control Stop-and-Wait ARQ
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Overview of Lecture 39 Error Control Stop-and-Wait ARQ
Sliding Window ARQ Go-back-n Selective Reject Data Link Protocols
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Error Control
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Stop-and-Wait ARQ: Damaged Frame
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Stop-and-Wait ARQ: Lost Frame
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Stop-and-Wait ARQ: Lost ACK
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Go-Back-n ARQ: Damaged Frame
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Go-Back-n ARQ: Lost Frame
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Go-Back-n ARQ: Lost ACK
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Selective-Reject ARQ: Damaged Frame
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Data Link Protocols Data link protocol is a set of specifications used to implement the data link layer It contains rules for line discipline, flow control, and error handling
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Data Link Protocols
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Asynchronous Protocols
Start and stop bits, variable-length gaps between characters Inherent slowness Not complex and inexpensive Used primarily in modems Being replaced by higher-speed synchronous mechanisms
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Asynchronous Protocols
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XMODEM File transfer protocol between PCs using telephone line
Half-duplex stop-and-wait ARQ protocol Control frames from the receiver ACK: Acknowledgement NAK: Error or start of transmission CAN: Aborts the transmission
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XMODEM
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Summary Error Control Stop-and-Wait ARQ Sliding Window ARQ Go-back-n
Selective Reject Data Link Protocols
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Suggested Reading Section 10.3, 11.1,
“Data Communications and Networking” 2nd Edition by Behrouz A. Forouzan
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