Automatic repeat request

Definition

Automatic repeat request (ARQ) is a communication protocol for error control in data transmission, where the sender automatically resends data packets if an error is detected or if an acknowledgment is not received. This mechanism enhances the reliability of data transfer by ensuring that corrupted or lost data is retransmitted, ultimately leading to a more efficient communication process.

5 Must Know Facts For Your Next Test

1. ARQ is essential for reliable communication in networks where data may be lost or corrupted during transmission.
2. There are different types of ARQ protocols, including Stop-and-Wait, Go-Back-N, and Selective Repeat, each with varying levels of efficiency and complexity.
3. The use of ARQ can introduce delays in data transmission due to the need for retransmissions, especially in high-error environments.
4. ARQ works best in environments where the likelihood of errors is moderate, as excessive errors can lead to significant performance degradation.
5. In many systems, ARQ is combined with error detection and correction techniques to enhance overall data integrity.

Review Questions

• How does the automatic repeat request protocol enhance data transmission reliability?
  • Automatic repeat request enhances data transmission reliability by ensuring that any lost or corrupted packets are automatically retransmitted by the sender. When a packet is sent, the receiver checks for errors and sends an acknowledgment back to the sender. If the acknowledgment is not received within a specified time frame or if an error is detected, the sender knows to resend the packet. This continuous cycle ensures that all data is correctly received and minimizes data loss.
• Compare and contrast different ARQ protocols such as Stop-and-Wait and Go-Back-N in terms of efficiency and application scenarios.
  • Stop-and-Wait ARQ is straightforward, sending one packet and waiting for an acknowledgment before sending the next. While easy to implement, it can be inefficient over long distances due to idle time during waits. Go-Back-N allows multiple packets to be sent before needing acknowledgment but requires retransmitting all packets following an error, which can lead to inefficiencies in high-error environments. Each protocol has its strengths and weaknesses, making them suitable for different applications based on network conditions.
• Evaluate the impact of combining ARQ with error detection methods on overall data integrity in communication systems.
  • Combining ARQ with error detection methods significantly improves data integrity in communication systems. Error detection techniques identify issues in transmitted data before it reaches its destination, enabling timely corrective actions through ARQ. This synergy not only minimizes the risk of incorrect data being processed but also optimizes retransmission strategies based on error patterns. As a result, systems become more resilient to communication challenges, ensuring that users receive accurate and reliable information even in adverse conditions.

Related terms

Error Detection: Techniques used to identify errors in transmitted data, often using checksums or cyclic redundancy checks (CRC).

Acknowledgment: A signal sent from the receiver to the sender indicating that a packet has been received successfully.

Stop-and-Wait Protocol: A simple ARQ protocol where the sender transmits one packet and waits for an acknowledgment before sending the next one.