In data communications, which summation operation over the bits is commonly used to verify an error-detecting code (i.e., to detect whether data was corrupted during transmission)?

Introduction / Context:
In digital data communications, error detection ensures that the bits received are the same as the bits sent. Common schemes add a small check value to each frame so the receiver can test for corruption without re-sending the whole payload.

Given Data / Assumptions:

• We are concerned with error detection, not error correction.
• The question asks which summation operation over bits is used to verify an error-detecting code.
• Typical link-layer mechanisms include parity, checksum, and cyclic redundancy check (CRC).

Concept / Approach:
A checksum is computed by performing arithmetic over a block of data (often ones-complement addition of words, or another defined sum) and appending the result as a short field. At the receiver, the same computation is performed and compared to the attached value. A mismatch signals an error.

Step-by-Step Solution:
1) Partition the data stream into fixed-size words (implementation dependent).2) Sum all words using the scheme's defined arithmetic (e.g., ones-complement addition).3) Fold/carry as required by the checksum definition to keep the result in a fixed width.4) Transmit the data plus the checksum.5) Receiver repeats the same sum; if computed value matches the received checksum, the frame is assumed intact; otherwise it is flagged as corrupted.

Verification / Alternative check:
If any bit flips, re-summing at the receiver changes the total. While some error patterns can evade simple checksums, they still detect a large fraction of random errors and are lightweight to compute.

Why Other Options Are Wrong:
Codec: A general term for encoder/decoder components, not a specific summation-based error check.
Coder–decoder: Same idea as codec; not an error check method.
Attenuation: Physical-layer signal loss, not a logical integrity test.
Parity totaling: Parity counts ones but is not the general summation operation referred to here; parity is weaker than checksums.

Common Pitfalls:
Confusing error detection (checksum/CRC) with error correction (Hamming, Reed–Solomon). Also assuming checksum guarantees correctness; it only reduces undetected error probability.

Final Answer:
Checksum