Web Commerce Security Design and Development

Reliability

Reliability is a prime requirement for websites performing e-commerce activities. The inability of Web commerce systems to meet customers' demands when required and in a prompt and efficient manner can result in significant revenue losses and damage to the supplier's reputation.

In its reliability, availability, and maintainability (RAM) publication,⁷ the United States DoD defines reliability as “the probability of an item to perform a required function under stated conditions for a specified period of time.”

The reliability of a system depends on a number of factors, including the following items:

• Proper design, implementation, and testing
• Operation within design limitations
• Conduct of proper maintenance
• Physical environment
• Length of time of operation

The RAM document also includes some of the following definitions associated with reliability:

• Failure Rate (λ): The total expected number of failures within an item population, divided by the total time by that population, during a particular measurement interval under stated conditions.
• Hazard Rate: Instantaneous failure rate. At any point in the life of an item, the incremental change in the number of failures per associated incremental change in time.
• Mean Time Between Failure (MTBF): A basic measure of reliability for repairable items. The average time during which all parts of the item perform within their specified limits during a particular measurement period under stated conditions.
• Mean Time Between Maintenance ...