Terminology » Networking Basics » Flow Control vs. Error Control in Data Communication

Flow Control vs. Error Control in Data Communication

data communication flow control error control data transfer network protocol

Flow control and error control are key mechanisms in data communication, ensuring efficient and reliable data transfer between sender and receiver. Here’s an explanation of each, along with examples and a comparison table.

Flow Control

  • Definition: Flow control is a technique used to manage the rate of data transmission between a sender and a receiver. It ensures that the sender doesn’t overwhelm the receiver with data faster than it can be processed.

  • Mechanism: It prevents buffer overflow at the receiver’s end by regulating the amount of data that can be sent before needing an acknowledgment.

  • Common Methods:

    • Stop-and-Wait Protocol: The sender sends one frame and waits for an acknowledgment before sending the next frame.

    • Sliding Window Protocol: The sender can send multiple frames before needing an acknowledgment, but only a fixed number of frames (window size) at a time.

  • Example:

    • In the Stop-and-Wait Protocol, if the sender sends a frame and waits for an acknowledgment from the receiver, the sender stops sending more data until the acknowledgment is received.

    • In the Sliding Window Protocol, if the window size is 4, the sender can send 4 frames before pausing and waiting for acknowledgments.

Error Control

  • Definition: Error control is a technique used to detect and correct errors in data transmission. This ensures the integrity and reliability of the communication.

  • Mechanism: It involves error detection (using methods like parity bits, checksums, or CRC) and error correction (using techniques like ARQ - Automatic Repeat Request).

  • Common Methods:

    • Error Detection: Uses methods such as CRC, checksums, and parity bits to identify errors in transmitted data.

    • Error Correction: Uses techniques such as ARQ (Automatic Repeat Request), where the sender retransmits the data if an error is detected.

    • Automatic Repeat Request (ARQ): Includes Stop-and-Wait ARQ, Go-Back-N ARQ, and Selective Repeat ARQ, which involve retransmission of erroneous frames.

  • Example:

    • If a frame is received with an error (detected using CRC), the receiver requests a retransmission of that specific frame (ARQ).

    • In Go-Back-N ARQ, if an error is detected in frame 3, all subsequent frames (3 and beyond) are retransmitted.

Difference between Flow Control and Error Control

FeatureFlow controlError control
PurposeManages data transmission rateEnsures accurate data transmission
Primary GoalPrevents receiver buffer overflowDetects and corrects errors in data
MechanismControls the flow using acknowledgments and window sizesUses error detection and correction techniques
Common MethodsStop-and-Wait, Sliding WindowCRC, Checksum, ARQ (Stop-and-Wait, Go-Back-N, Selective Repeat)
Impact on ThroughputOptimizes throughput by balancing data flowCan reduce throughput due to retransmissions
Handling OverheadPrevents sender from overwhelming receiverNot directly related to flow, but handles corrupted data
Type of Issue AddressedFlow issues (e.g., sender too fast)Data integrity issues (e.g., corrupted frames)
Data LossNo data loss, just flow regulationHandles data loss through retransmission
UsageCommon in transport layer protocols (e.g., TCP)Common in data link layer protocols (e.g., HDLC, TCP)
ExampleSliding Window with a size of 4 allows sending 4 frames before stoppingCRC detects error, ARQ requests retransmission

Conclusion

Flow control and error control complement each other in data communication. Flow control ensures smooth data transfer rates, while error control maintains data integrity and reliability.