MCQs on Data Link Layer, Error Detection, and Correction
1. What is the main purpose of the Data Link Layer in the OSI model?
Correct! The answer is b.
Explanation: The primary responsibility of the Data Link Layer is to ensure reliable communication between adjacent network nodes by providing mechanisms for error detection and correction.
2. Which of the following is a key issue in Data Link Layer design?
Correct! The answer is d.
Explanation: Data Link Layer design involves multiple aspects like flow control, error detection, and medium access control.
3. Which one of the following is NOT a design issue for the Data Link Layer?
Correct! The answer is c.
Explanation: Routing is a function of the network layer, not the data link layer. Error control, flow control, and medium access control are all key issues at the data link layer.
4. The sliding window protocol belongs to which category?
Correct! The answer is a.
Explanation: The sliding window protocol is a flow control protocol used at the data link layer to ensure that the sender does not overwhelm the receiver by sending too many frames at once.
5. Which of the following is responsible for error detection in the Data Link Layer?
Correct! The answer is d.
Explanation: CRC, parity check, and Hamming code are all methods used for error detection in the Data Link Layer.
6. Which of the following protocols is not a data link layer protocol?
Correct! The answer is c.
Explanation: IP is a network layer protocol, while Ethernet, Token Ring, and PPP are data link layer protocols.
6. Which of the following protocols is NOT a Data Link Layer protocol?
Correct! The answer is c.
Explanation: IP (Internet Protocol) operates at the network layer, while Ethernet, Token Ring, and PPP are protocols used in the Data Link Layer.
7. The CRC (Cyclic Redundancy Check) is based on which of the following mathematical operations?
Correct! The answer is a.
Explanation: CRC uses binary division for error detection in data transmission. The remainder of the division is appended to the data to form the codeword.
8. In Stop-and-Wait ARQ, how does the sender know that a frame has been received correctly?
Correct! The answer is b.
Explanation: In Stop-and-Wait ARQ, the sender waits for an acknowledgment (ACK) from the receiver before sending the next frame. This ensures that each frame is correctly received.
9. Which type of error is undetectable by using simple parity check?
Correct! The answer is c.
Explanation: Simple parity check can detect an odd number of bit errors, but it cannot detect even numbers of bit errors since the parity bit would not change.
10. In Go-Back-N ARQ, what happens when an error is detected in a frame?
Correct! The answer is c.
Explanation: In Go-Back-N ARQ, if an error is detected, all frames starting from the erroneous one to the most recent one are retransmitted. This ensures the receiver gets the correct sequence of frames.
11. What does ARQ stand for in Data Link Layer protocols?
Correct! The answer is b.
Explanation: ARQ stands for Automatic Repeat Request, a protocol for error control where the sender automatically retransmits frames when it doesn't receive an acknowledgment from the receiver.
12. In the Hamming code, what is the minimum Hamming distance required to detect and correct a single-bit error?
Correct! The answer is c.
Explanation: The minimum Hamming distance required to detect and correct a single-bit error is 3. It allows for one error to be corrected and another to be detected.
13. Which of the following is NOT used for error detection in the Data Link Layer?
Correct! The answer is d.
Explanation: The Spanning Tree Protocol (STP) is used in switching and operates at the data link layer, but it is not a method for error detection. CRC, parity check, and checksum are methods used to detect errors in data.
14. In Cyclic Redundancy Check (CRC), what happens if the remainder after division is zero?
Correct! The answer is c.
Explanation: In CRC, if the remainder after division is zero, it indicates that the frame is error-free and has been transmitted correctly.
15. In Parity Check, which type of error is detected by adding an extra bit to the transmitted data?
Correct! The answer is b.
Explanation: In parity checking, an extra parity bit is added to detect single-bit errors. This simple error detection method cannot detect burst or multiple-bit errors.
21. Which technique helps detect errors by summing binary values in transmitted data?
Correct! The answer is a.
Explanation: Checksum is an error-detection technique that involves adding binary values and appending the sum to the data. The receiver can recompute and compare this sum to verify data integrity.
22. What is the primary purpose of adding redundancy in error-detection schemes?
Correct! The answer is b.
Explanation: Redundant bits are added in error-detection schemes to enable the receiver to detect if any data corruption has occurred during transmission.
23. Which protocol retransmits only the erroneous frame instead of all frames after the error?
Correct! The answer is b.
Explanation: Selective Repeat ARQ retransmits only the frame with the error, rather than all subsequent frames, making it more efficient for reliable transmission.
24. In Hamming code, if the total number of parity bits required is 4, how many data bits can be checked for error detection?
Correct! The answer is c.
Explanation: In Hamming code, if there are 4 parity bits, it can check 11 data bits for errors. The formula 2m ≥ m + d + 1 is used to determine the maximum number of data bits.
25. In CRC, what is the purpose of using a generator polynomial?
Correct! The answer is b.
Explanation: The generator polynomial in CRC is used to divide data bits for error detection. The remainder of this division, appended to the data, allows error checking at the receiver end.
26. In error detection, what does the term "burst error" refer to?
Correct! The answer is b.
Explanation: A burst error refers to a series of consecutive bits in a data segment being erroneous, often due to signal issues or interference during transmission.
27. What does the Stop-and-Wait ARQ protocol do if an acknowledgment is not received within a set time?
Correct! The answer is b.
Explanation: In Stop-and-Wait ARQ, if no acknowledgment is received within a set time, the sender resends the last frame, ensuring data reliability.
28. Which of these error detection methods involves performing a polynomial division on data?
Correct! The answer is b.
Explanation: CRC uses polynomial division to detect errors. The remainder from this division is used as a check value to verify data integrity at the receiver end.
29. Which protocol can be used for error correction in addition to error detection?
Correct! The answer is c.
Explanation: Hamming Code is capable of detecting and correcting single-bit errors, making it suitable for both error detection and correction.
30. In a Go-Back-N ARQ system with a window size of 4, what happens if frame 3 is lost during transmission?
Correct! The answer is b.
Explanation: In Go-Back-N ARQ, if a frame is lost, the sender resends that frame and all subsequent frames, ensuring the receiver gets the complete sequence correctly.
31. What is the purpose of "parity bit" in error detection methods?
Correct! The answer is b.
Explanation: A parity bit is added to binary data to make the number of 1s either even or odd, helping to detect single-bit errors.
32. In Hamming code, if an error occurs, what does the syndrome value indicate?
Correct! The answer is b.
Explanation: In Hamming code, the syndrome value pinpoints the exact bit position of the error, allowing for correction.
33. Which ARQ protocol allows the sender to continue sending frames without waiting for an acknowledgment?
Correct! The answer is c.
Explanation: Go-Back-N ARQ allows the sender to transmit multiple frames up to a set window size before needing an acknowledgment for the first frame in the sequence.
34. Which method is commonly used to detect burst errors?
Correct! The answer is b.
Explanation: CRC is effective at detecting burst errors by using polynomial division, where the remainder helps identify such errors in data transmission.
35. In Selective Repeat ARQ, what does the receiver do if a frame is received out of order?
Correct! The answer is b.
Explanation: In Selective Repeat ARQ, the receiver buffers out-of-order frames and waits for missing frames to arrive, ensuring the data is complete and correctly ordered.
36. Which technique adds redundant bits to detect and correct errors in data transmission?
Correct! The answer is b.
Explanation: Hamming Code is an error-correcting code that adds redundant bits, which allows detection and correction of single-bit errors.
37. In CRC, what role does the divisor polynomial play in error detection?
Correct! The answer is b.
Explanation: In CRC, the divisor polynomial is used for error detection by dividing the data, allowing for detection of burst errors when the remainder is checked.
38. What is the function of a "window" in the sliding window protocol?
Correct! The answer is b.
Explanation: The "window" in the sliding window protocol limits the number of unacknowledged frames, helping manage flow control between sender and receiver.
39. In error correction, what is the minimum Hamming distance required to correct a single-bit error?
Correct! The answer is c.
Explanation: A minimum Hamming distance of 3 is required to detect and correct single-bit errors, providing a buffer that allows the system to detect an error and find the correct data.
40. How does the checksum method verify data integrity?
Correct! The answer is b.
Explanation: The checksum method verifies data by summing the data segments and comparing the total against the checksum value. If they match, the data is likely intact.
41. Which error detection method is known for its simplicity but is not effective for detecting burst errors?
Correct! The answer is c.
Explanation: The parity check method is simple but only effective for detecting single-bit errors, not burst errors where multiple bits are affected.
42. What does Go-Back-N ARQ do if an error is detected in a transmitted frame?
Correct! The answer is b.
Explanation: Go-Back-N ARQ retransmits all frames from the detected error onward to ensure correct data delivery and sequencing.
43. Which of these protocols does not use acknowledgment for each individual frame?
Correct! The answer is b.
Explanation: Go-Back-N ARQ does not acknowledge each frame individually; it allows several frames to be sent before requiring acknowledgment for the sequence.
44. Which protocol offers the highest efficiency in a noisy communication channel?
Correct! The answer is b.
Explanation: Selective Repeat ARQ is more efficient in noisy environments as it retransmits only erroneous frames, reducing the amount of redundant retransmissions.
45. Which of the following is true about Hamming Code in error correction?
Correct! The answer is b.
Explanation: Hamming Code is designed to detect and correct single-bit errors, making it a self-correcting code suitable for applications requiring reliability.
46. In a CRC implementation, which of the following represents a valid polynomial divisor for detecting errors?
Correct! The answer is a.
Explanation: In CRC, polynomials such as 101 (binary for x2 + 1) are used as divisors to generate checksums for error detection.
47. What is the primary function of the sequence number in a sliding window protocol?
Correct! The answer is b.
Explanation: In sliding window protocols, sequence numbers uniquely identify each frame to ensure that frames are processed in the correct order.
48. Which of the following is true for cyclic redundancy check (CRC) as an error detection mechanism?
Correct! The answer is b.
Explanation: CRC detects errors by performing polynomial division on data and comparing the remainder with the checksum value.
49. In the Stop-and-Wait protocol, what happens if an acknowledgment is lost?
Correct! The answer is a.
Explanation: In the Stop-and-Wait protocol, if an acknowledgment is lost, the sender will retransmit the frame after a timeout, ensuring reliable communication.
50. Which of these checks are effective in detecting burst errors?
Correct! The answer is c.
Explanation: CRC is highly effective in detecting burst errors due to its use of polynomial division, which ensures multiple bits are checked simultaneously.