This latter statement means that a handful of customers can have consistently crappy service, but the carrier can still meet 99.99 percent if most customers have good service. Finally, the length of an outage is measured from when it s reported, not when it actually occurs. Just try to tell your subs that you meet 53 minutes maximum downtime per year when you don t count the headend, drop, program source, loss of both commercial and backup power and so on. Yes, ma am, someone did load our headend in a U-Haul and drive away with it, but that s not an outage. Availability calculations Seriously, availability is defined as the ratio of time that a service is available to total time.
Reliability is the probability that something won t fail during some defined period of time.
I ll spare you and CT s editors. If you re interested in learning more, I suggest you peruse Chapter 17 in Modern Cable Television Technology. The authors provide an excellent overview of the subject. Let s see. It depends on how you define an outage and do the math.