It’s easy to confuse the concept of the reliability of a cloud communications solution with the related—but different— concept of availability. Let’s try to simplify it.
Let’s start with availability. Cloud software—despite many advances—isn’t quite perfect. Solution providers sometimes need to take solutions offline for short periods to do maintenance (sometimes known as a scheduled outage). And sometimes circumstances outside the provider’s span of control can take a system down (natural disasters, for example).
To accommodate for these things, providers give service-level agreements (SLAs) that guarantee as little downtime as possible. An SLA of 99% annually translates to 7.2 hours of downtime a month, for example. On the other hand, an SLA of 99.999% or “five nines” (often viewed as the gold standard), translates to only 26 seconds of downtime per month.