This OID defines the maximum acceptable bit error ratio (how many corrupted bits per billion bits) for downstream data before alerting you to quality problems. Network engineers use this to enforce acceptable quality standards—a home connection might tolerate 1 error per 100,000 bits, while a business line tolerates only 1 per 10 million bits. A value of 'eminus5' (10^-5) means you want at least 99.999% of downloaded bits to arrive correctly before triggering an alarm.