Error detection (parity, CRC, checksum) in Computer Networks - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Parity Bit Purpose

What is the main purpose of adding a parity bit to a data transmission?

A To detect if a single bit error has occurred during transmission

B To encrypt the data for security

C To increase the data transmission speed

D To correct multiple bit errors automatically

💡 Hint

Parity bits are simple error detection tools, not error correction or encryption.

A parity bit is added to data to help detect if a single bit has been flipped during transmission. It does not correct errors or encrypt data.

📋 Factual

intermediate

CRC Polynomial Role

In Cyclic Redundancy Check (CRC), what role does the generator polynomial play?

A It compresses the data to reduce size

B It encrypts the data before transmission

C It defines the pattern used to divide the data bits to generate the CRC code

D It corrects errors detected in the data

💡 Hint

The generator polynomial is a key part of the CRC calculation process.

The generator polynomial is used to divide the data bits in CRC calculation, producing a remainder that forms the CRC code for error detection.

🔍 Analysis

advanced

Checksum Error Detection Limitations

Why might a simple checksum fail to detect certain errors in transmitted data?

A Because checksum increases the data size too much

B Because different errors can produce the same checksum value, causing undetected errors

C Because checksum algorithms always correct errors automatically

D Because checksum encrypts data making errors invisible

💡 Hint

Think about how checksums summarize data and what happens if errors cancel each other out.

Checksums add data values to create a summary. Different errors can offset each other, resulting in the same checksum and missed errors.

❓ Comparison

advanced

Comparing Parity and CRC

Which statement correctly compares parity bits and CRC in error detection?

A Parity detects only single bit errors, while CRC can detect burst errors

B Parity corrects errors, CRC only detects errors

C CRC is simpler and faster than parity

D Both parity and CRC encrypt data for security

💡 Hint

Consider the types of errors each method can detect.

Parity bits detect single bit errors but cannot detect multiple or burst errors well. CRC is more powerful and can detect burst errors effectively.

❓ Reasoning

expert

Error Detection Scenario Analysis

A data packet uses even parity and a CRC code for error detection. If a single bit flips during transmission, which error detection method(s) will detect it?

A Only parity will detect the error, CRC will not

B Neither parity nor CRC will detect the error

C Only CRC will detect the error, parity will not

D Both even parity and CRC will detect the single bit error

💡 Hint

Think about how parity and CRC handle single bit errors.

Both even parity and CRC are designed to detect single bit errors. Parity checks if the number of 1s is even, and CRC uses polynomial division to detect errors.