Selective Repeat is a reliable data transfer protocol that allows a sender to retransmit only the specific packets that were lost or corrupted, instead of all packets following a lost packet. This approach improves network efficiency by reducing unnecessary retransmissions and waiting times, allowing for more effective use of bandwidth and better overall performance in data communication.
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Selective Repeat requires both sender and receiver to maintain buffers to store packets, enabling the receiver to keep track of which packets have been received successfully.
This protocol uses a sliding window technique to control the flow of packets, allowing for multiple packets to be in transit before requiring an acknowledgment.
Selective Repeat can significantly enhance throughput in networks with high error rates compared to simpler protocols like Stop-and-Wait.
Retransmission in Selective Repeat is only triggered for packets that were not acknowledged within a specified timeout period, optimizing retransmission efforts.
In Selective Repeat, both the sender and receiver must handle out-of-order packets since packets may arrive at the receiver in a different order than they were sent.
Review Questions
How does Selective Repeat differ from other data transfer protocols like Go-Back-N in terms of retransmission strategy?
Selective Repeat differs from Go-Back-N by only retransmitting the specific lost or corrupted packets, while Go-Back-N requires the sender to retransmit all packets starting from the lost one. This targeted retransmission in Selective Repeat leads to better bandwidth utilization and efficiency, especially in scenarios where packet loss is common. As a result, Selective Repeat can achieve higher throughput compared to Go-Back-N, making it more suitable for networks with higher error rates.
Explain how the sliding window technique operates in Selective Repeat and its impact on data flow control.
The sliding window technique in Selective Repeat allows multiple packets to be sent before waiting for an acknowledgment, which enhances data flow control. The sender maintains a window of packets that can be sent without acknowledgment, while the receiver keeps track of which packets have been received correctly. This setup enables efficient use of network resources by minimizing idle time during transmission and allowing for concurrent transmissions, thereby improving overall throughput and responsiveness in data communication.
Evaluate the advantages and disadvantages of using Selective Repeat in a high-latency network environment.
Using Selective Repeat in a high-latency network environment offers significant advantages such as improved bandwidth efficiency and reduced wait times due to its ability to retransmit only specific lost packets. This approach minimizes unnecessary data transfer and enhances throughput compared to simpler protocols. However, it also introduces complexity since both sender and receiver must manage packet buffers and out-of-order delivery. If not implemented correctly, this complexity can lead to increased processing overhead and potential delays in packet delivery, highlighting the need for careful design and optimization in such network scenarios.
Related terms
Acknowledgment (ACK): A signal sent from the receiver to the sender to indicate that a packet has been successfully received.
Window Size: The maximum number of packets that can be sent before needing an acknowledgment, which influences the flow control in data transmission.
Go-Back-N: A data link layer protocol where the sender retransmits all packets from the lost or corrupted packet onward, regardless of whether subsequent packets were successfully received.