In a stop-and-wait Automatic Repeat reQuest (ARQ) system, how does the transmitting terminal operate after sending a data block?

Difficulty: Easy

Correct Answer: It waits for positive or negative acknowledgement from the receiving terminal

Explanation:


Introduction / Context:
Stop-and-Wait ARQ is one of the simplest error-control protocols in data communication. It ensures reliable delivery of data frames by requiring acknowledgements before sending new blocks.


Given Data / Assumptions:

  • Sender transmits one block at a time.
  • Receiver responds with ACK (positive) or NAK (negative).
  • Timeout is set if no response is received within a fixed duration.


Concept / Approach:
The sender must wait for confirmation before transmitting further data. This prevents data loss and ensures order but reduces throughput compared to more advanced ARQ protocols.


Step-by-Step Solution:

Step 1: Sender transmits one block of data.Step 2: Receiver checks and responds with ACK (if correct) or NAK (if error).Step 3: Sender either proceeds (ACK) or retransmits same block (NAK).Step 4: If no response within timeout, retransmission occurs.


Verification / Alternative check:

Networking textbooks confirm Stop-and-Wait ARQ as a fundamental example of reliable transmission.


Why Other Options Are Wrong:

Immediate sending without waiting breaks reliability.Only ACK and NAK responses govern transmission control.Continuous transmission is Go-Back-N or Sliding Window, not Stop-and-Wait.


Common Pitfalls:

Confusing Stop-and-Wait ARQ with Go-Back-N ARQ or Selective Repeat ARQ.


Final Answer:

It waits for positive or negative acknowledgement from the receiving terminal

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