It's pretty interesting issue about so called "fine nines" concept.
What is the hard fast requirement for Carrier-Grade? Is “five-nines” or 99.999% up
or 0.99999 available a hard, fast requirement of telecommunications or is it the
telecommunications equivalent of an Urban Myth?
..
www.pipelinepub.com/0407/pdf/Article%204_Carrier%20Grade_LTC.pdf
