This counter counts received cells that failed the ATM Header Error Control checksum on this physical line. Since HEC errors indicate corrupted cell headers, typically from a noisy or faulty physical link, a rising count is a strong signal of line-level physical layer trouble rather than a higher-layer protocol issue. An admin seeing atmLineRcvHecErrorCells climb steadily on one line, while atmLineTotalRcvCells stays roughly flat, would suspect a degraded cable or connector on that specific line.