The Telecos and RBOCS believe they have to great features – High Availability and High Line Quality. The old commercial from US Sprint “You could hear a pin drop” was reminiscent for what this is about.
In any case, “five nines” meant you had “high availability” for a service. It is still widely used in the industry, but often ignored.
On this topic, the direct translation means
- 99.999% uptime is just over 5 minutes per year of down time.
- 99% uptime means 3 days per year – down.
- 98% uptime means 7 days per year or about 30 minutes a day – down.