Flow Control and Retransmission in Computer Networks
Flow control and retransmission are two crucial mechanisms employed in computer networks, especially in connection-oriented protocols like TCP, to ensure reliable and efficient data transfer.
1. Flow Control
Flow control regulates the amount of data a sender can transmit before receiving an acknowledgment from the receiver. It prevents overwhelming the receiver with data faster than it can process, avoiding buffer overflows and data loss.
Flow control mechanisms involve sliding windows and buffer management. TCP uses a sliding window approach, where the receiver advertises a receive window size, indicating the amount of data it can accept.
a. Stop-and-Wait
In this method, the sender transmits a single data unit and waits for an acknowledgment before sending the next one. It's simple but inefficient, especially for high-latency connections.
b. Sliding Window
This technique allows the sender to transmit multiple data units before receiving an acknowledgment, up to a specified window size. It enables continuous data transmission and efficient network resource utilization.
2. Retransmission
Retransmission recovers from packet losses or corruption during data transmission. TCP employs retransmission to ensure reliable data transfer.
The process involves sequence numbering, acknowledgments, retransmission timers, and cumulative acknowledgments. If an acknowledgment is not received within a specified time, the sender retransmits the data unit.
Retransmission mechanisms ensure reliable data transfer by recovering from packet losses or corruption due to various factors like network congestion or link failures.
Flow control and retransmission work together to maintain an efficient and reliable data transfer process, crucial for applications requiring data integrity and completeness.