ARQ Simulation for Stop-and-Wait Protocol Implementation

ARQ (Automatic Repeat reQuest) is a fundamental network communication mechanism primarily used to ensure reliable data transmission over unreliable communication channels. The Stop-and-Wait protocol serves as a basic ARQ implementation suitable for reliability transmission simulations in simple scenarios. In code implementations, this typically involves creating sender and receiver classes with state management for packet sequencing.

In the Stop-and-Wait protocol implementation, the sender transmits a single data packet and awaits an acknowledgment (ACK) from the receiver before proceeding with the next packet. If no ACK is received within a predefined timeout period, the sender retransmits the packet. This mechanism ensures reliability but exhibits low efficiency due to its sequential nature, unable to fully utilize network bandwidth. Programmatically, this requires implementing timer functions and packet buffering mechanisms.

Key aspects of ARQ simulation typically include: Timeout Mechanism: The sender must implement reasonable timeout durations using timer objects or system clocks to prevent indefinite waiting that could stall transmission. Error Detection: Incorporates checksum algorithms or CRC validation to detect transmission errors, triggering retransmission logic when errors are identified. ACK Confirmation: The receiver returns ACK packets upon successful data reception, with the sender maintaining state transitions based on ACK receipt. Retransmission Strategy: Implements packet resending when timeouts occur, often involving sequence number tracking and duplicate packet detection.

This simulation is valuable for educational experiments and network protocol research, helping understand fundamental reliability principles. It can be extended to implement more efficient ARQ variants like Go-Back-N (using sliding window algorithms) or Selective Repeat (requiring buffer management for out-of-order packets). Code implementations typically involve finite state machines and queue management for handling multiple concurrent packets.