Chapter 7

Data Link Control &

Data Link Protocol

By Dr.Sukchatri P.

Contents

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•Data Link Control•Line Discipline•Flow Control•Error Control•Data Link Protocols•Asynchronous Protocols•Synchronous Protocols•Character Protocol•Bit-Oriented Protocol

Data Link Control

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Data Link Control Functions

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Line discipline categories

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Line discipline concept : ENQ/ACK

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ENQ/ACK line discipline

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Poll/Select discipline

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Multipoint discipline

Select

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Poll

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Categories of flow control

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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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Categories of error control

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Stop-and-wait ARQ

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Stop-and-wait ARQ

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Go-back-n

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Go-back-n

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Go-back-n

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Data Link Protocols

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Asynchronous Protocols

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XMODEM Frames

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Synchronous Protocols

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BSC Frames

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A Simple BSC data frame

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A BSC frame with a header

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Multiblock frame

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Multiframe transmission

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BSC Control frame

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Control Frame

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Control Frame

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Control Frame

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Byte stuffing

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Bit-Oriented Protocols

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HDLS Configurations

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HDLS Configurations

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HDLS Configurations

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HDLC Modes

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HDLC Frame types

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HDLC Frame types

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HDLC Frame types

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HDLC Flag Field

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Bit Stuffing in HDLC

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HDLC Address field

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HDLC Control Fields

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I-Frame : Information field , contains the user’s dataS-Frame : Supervisory frames, acknowledgment, flow control, & error controlU-Frame : Unnumbered frames , exchange session management and control information between connected devices.

Poll/Final in HDLC

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HDLC Information Field

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FCS Field

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S-frame control field in HDLC

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Use of P/F bit in polling and selecting

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RR : Receive Ready

Use of P/F bit in polling and selecting

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RR : Receive Not Ready

Use of P/F bit in polling and selecting

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U-frame control field in HDLC

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U-frame control field in HDLC

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Example of polling using HDLC

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Example of selecting using HDLC

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Example of peer-to-peer communication

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Example of peer-to-peer communication

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Questions/Answers

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