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In HDLC (High-Level Data Link Control), the three data transfer modes are:

1.In summary, NRM is suitable for point-to-point communication, ARM provides flexibility for the secondary station to initiate communication, and ABM is ideal for peer-to-peer communication where both stations have equal roles in initiating and responding to frame transmissions.- ARM allows the secondary station to initiate transmission without waiting for a specific request from the primary station, providing more flexibility in communication initiation compared to NRM.Asynchronous Balanced Mode (ABM): ABM is a bidirectional mode where both stations can initiate frame transmission and respond to frames from the other station.Comparison:

• NRM is a unidirectional mode where the primary station initiates communication, and the secondary station responds.This mode is suitable for peer-to-peer communication between two stations.2.3.

In HDLC (High-Level Data Link Control), the three data transfer modes are:

1. 
   

   Normal Response Mode (NRM): In NRM, the primary station sends frames to the secondary station, which then responds with acknowledgments or negative acknowledgments. This mode is suitable for point-to-point communication and is the most commonly used mode in HDLC.

   
   


2. 
   

   Asynchronous Response Mode (ARM): In ARM, the secondary station can initiate the transmission of frames to the primary station without waiting for a specific request. This mode is useful for applications where both stations need to have the ability to initiate communication.

   
   


3. 
   

   Asynchronous Balanced Mode (ABM): ABM is a bidirectional mode where both stations can initiate frame transmission and respond to frames from the other station. This mode is suitable for peer-to-peer communication between two stations.

   
   

Comparison:

• 
  

  NRM is a unidirectional mode where the primary station initiates communication, and the secondary station responds. In contrast, ARM and ABM allow bidirectional communication, with both stations having the ability to initiate transmission.

  
  


• 
  

  ARM allows the secondary station to initiate transmission without waiting for a specific request from the primary station, providing more flexibility in communication initiation compared to NRM.

  
  


• 
  

  ABM is a fully bidirectional mode, allowing both stations to initiate and respond to frame transmissions. This makes it suitable for peer-to-peer communication scenarios where both stations have equal roles in the communication process.

  
  

In summary, NRM is suitable for point-to-point communication, ARM provides flexibility for the secondary station to initiate communication, and ABM is ideal for peer-to-peer communication where both stations have equal roles in initiating and responding to frame transmissions.