When either an elastic infrastructure or platform is offered by a provider, service availability is defined by the conditions that must be fulfilled by the offering and the time-frame within which service availability is assured. These two factors enable the computation of hosted application availability. With node-based availability, the service provider guarantees the availability of each application component.
Available is generally defined as being reachable and capable of performing its advertised function. This availability time-frame is expressed as a percentage. As an example, an availability of 99.95% means that a component will be available 99.95% of the time. The following figure depicts this example:
![](https://static.packt-cdn.com/products/9781788472425/graphics/assets/e2fda7d5-6452-44e8-b33a-9621b2d8d01f.png)