Given a firewall with an MTBF of 10,000 hours and an MTTR of 2 hours, what is the expected availability percentage?

To determine the expected availability percentage of a system, the formula to use is:

[ \text{Availability} = \frac{\text{MTBF}}{\text{MTBF} + \text{MTTR}} ]

Where MTBF (Mean Time Between Failures) indicates the average operational time before a failure occurs, and MTTR (Mean Time To Repair) indicates the average time taken to repair the system after a failure.

In this case, the MTBF is 10,000 hours and the MTTR is 2 hours. By plugging these values into the formula:

[ \text{Availability} = \frac{10000}{10000 + 2} ] [ \text{Availability} = \frac{10000}{10002} ] [ \text{Availability} \approx 0.999800 ]

To convert this decimal to a percentage, multiply by 100:

[ \text{Availability} \approx 99.98% ]

This indicates that the firewall is available and operational 99.98% of the time, which confirms the choice as the correct answer. This high level of availability reflects well on the reliability of the firewall, characterized by a long MTBF and relatively