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Data Link Control

ผศ . ดร. อนั�นัต์ ผลเพิ่��มAsst. Prof. Anan Phonphoem, Ph.D.

anan@cpe.ku.ac.thhttp://www.cpe.ku.ac.th/~anan

Computer Engineering DepartmentKasetsart University, Bangkok, Thailand

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Physical characteristics of interface

Stream of Bits (e.g., 001010100100)

Line config. (e.g., point-to-point)

Topology (e.g., bus, star)

Transmission mode

(e.g., half-duplex, full-duplex)

Encoding

Error detection (and correction)

TCP/IP Protocol Suite

Application5

4 Transport

3 Network

2 Data Link

1 Physical

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Line Discipline

Flow Control

Error Control

TCP/IP Protocol Suite

Application5

4 Transport

3 Network

2 Data Link

1 Physical

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Data Link Control

Line Discipline

Flow Control

Error Control

Who Should send data and When ?

How much data may be sent?

How can errors be Detected and correct?

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Data Link Control

Line Discipline

Flow Control

Error Control

ENQ / ACK

Poll / Select

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Line Discipline: ENQ/ACK

Peer-to-peer communication

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Line Discipline: ENQ/ACK

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Line Discipline:Poll/Select

Primary-secondary communicationMultipoint Discipline

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Select

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Poll

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Data Link Control

Line Discipline

Flow Control

Error Control

Stop-and-wait(one frame at a time)

Sliding window(several frames at a time)

a set of procedures used a set of procedures used to restrict the amount of to restrict the amount of data that the sender can data that the sender can sendsend

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Stop-and-wait

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Sliding window

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Sender sliding window

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Receiver sliding window

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Example of sliding window

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Control variable

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Example of sliding window

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Data Link Control

Line Discipline

Flow Control

Error Control

Stop-and-wait ARQ

Sliding window ARQ• Go-back-n• Selective-reject

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Stop-and-wait ARQ: Normal Operation

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Stop-and-wait ARQ: Damaged frame

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Stop-and-wait ARQ: Lost data frame

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Stop-and-wait ARQ: Lost ACK frame

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Stop-and-wait ARQ: Delay ACK

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Stop-and-wait ARQ: Piggybacking

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Sliding WindowGo-back-n: Normal Operation

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Sliding WindowGo-back-n: Damaged data frame

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Sliding Window Go-back-n: Lost Data Frame

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Sliding Window Go-back-n: Lost ACK

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Sliding Window Selective-reject: Damaged data frame

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Sliding window ARQ Comparison

Go-back-n Simple More practical

Selective-reject Complex (sorting, storage, extra select frame

logic) Better performance