Discussion on HDLC Frame Format of HDLC & Transfer Mode

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Discussion on HDLC: Frame Format of HDLC & Transfer Mode(Computer Science)

Topics

  • Introduction on HDLC

  • Primary and Secondary Stations

  • HDLC Frame Format

  • Transfer Modes:

  • Asynchronous Response Mode(ARM): Normal Response Mode(NRM)

  • Asynchronous Balanced Mode(ABM)

HDLC

  • HDLC stands for High Level Data Link Control

  • It is a bit oriented transmission protocol

  • It works at a data link layer which is second layer (layer 2) of OSI seven layered architecture model for data communication

  • It embeds information in a data frame that allows devices to control data flow and correct errors

  • HDLC is proposed by IBM in 1970s from SDLC i.e. Synchronous Data Link Control Standard

  • Sessions are created for communication purpose in it.

Primary & Secondary Stations

  • Primary Station: The one who sends commands. Data Link Management and Connection/Disconnection are the basic responsibilities of primary station. Frames issued by primary station are called as commands.

  • Secondary Station: These are the stations which responses and frames issued by secondary stations are called as responses.

  • Combined Station: It acts both like primary and secondary stations. They have both commands and responses.

Frame Format of HDLC

HDLC Frame Format

HDLC Frame Format

  • I-Frame: Information Frame-0 bit in control field

  • S-Frame: Supervisory Frame-10 bit in control field

  • U-Frame: Un-numbered Frame-11 bit in control field

Transfer Mode

Transfer Modes:

  1. Normal Response Mode(NRM): Point to Point and Point to Multipoint

  2. Asynchronous Balanced Mode(ABM): Point to Point

Normal Response Mode(NRM)

Normal Response Mode(NRM)

Point to Point and Multipoint NRM

Asynchronous Balanced Mode(ABM)

  • Point to Point:

Asynchronous Balanced Mode(ABM)

Point to Point Communication

  • Workstation acts as both primary and secondary stations depending upon the requirement.

MCQ

Q1. HDLC stands for:

  1. High Data Logical Control

  2. High Level Data Link Control

  3. High Destination Logical Control

  4. High Definition Logical Control

Answer: B

Q2. HDLC is:

  1. Bit oriented

  2. Code transparent

  3. Both (a) and (b)

  4. None of these

Answer: C

#Introduction on HDLC

#Primary and Secondary Stations

#HDLC Frame Format

#Transfer Modes:

#Asynchronous Response Mode(ARM)

#Normal Response Mode(NRM)

#Asynchronous Balanced Mode(ABM)

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