Bad Network Design – Availability of a system is mainly measured with two parameters. Mean time between failure (MTBF) and Mean time to repair (MTTR)
MTBF is calculated as average time between failures of a system. MTTR is the average time required to repair a failed component (Link, node, device in networking terms)
Operator mistakes is widely seen as the source of the failure of the systems. Thus although it is not individually used to calculate availability value of a system, Mean time between mistakes (MTBM) is commonly used term among the network engineers.
Most failures are caused by human error;estimate range between 70 to 80 percent. How can so many people are so incompetent?
Actually they are not ! It’s a design problem.