Automatic Repeat Request (ARQ) Error Management Mechanism

The automatic repeat request (ARQ) error management mechanism is responsible for handling errors that occur during data transmission in a computer network. It ensures reliable and error-free communication by detecting and retransmitting lost or corrupted data.

This mechanism is provided by the Logical Link Control (LLC) sublayer in the data link layer of the network protocol stack.

Logical Link Control (LLC) Sublayer
The LLC sublayer is responsible for managing the flow control and error control in the data link layer. It provides a reliable link between the network layer and the physical layer.

Error Detection and Correction
The ARQ mechanism implemented by the LLC sublayer includes error detection and correction techniques to ensure the integrity of data transmission. These techniques involve the use of sequence numbers, acknowledgments, and retransmissions.

1. Sequence Numbers: The sender assigns a unique sequence number to each data frame it transmits. The receiver uses these sequence numbers to detect missing or out-of-order frames.

2. Acknowledgments: The receiver acknowledges the successful receipt of data frames by sending acknowledgments (ACK) back to the sender. These acknowledgments contain the sequence numbers of the received frames.

3. Retransmissions: If the sender does not receive an acknowledgment for a transmitted frame within a certain timeout period, it assumes that the frame has been lost or corrupted. It then retransmits the frame to ensure its successful delivery.

Advantages of ARQ Mechanism
The ARQ mechanism provided by the LLC sublayer offers several advantages:

1. Error Recovery: By detecting and retransmitting erroneous or lost data, the ARQ mechanism ensures reliable data delivery.

2. Flow Control: The ARQ mechanism helps regulate the flow of data between the sender and receiver, preventing data overload and congestion.

3. Efficiency: By using selective repeat or go-back-n techniques, the ARQ mechanism minimizes the number of retransmissions and optimizes network performance.

In conclusion, the ARQ error management mechanism is provided by the Logical Link Control (LLC) sublayer in the data link layer of the network protocol stack. It ensures reliable and error-free data transmission by employing sequence numbers, acknowledgments, and retransmissions.