No, not 45, but 99.999%, a much quoted figure for the uptime of telco systems. In other words, a downtime of less than 6 minutes per year. One of the criticisms that people level of VoIP systems is that they are too complex (software layers, processing etc) to be "five nines reliable". Interestingly I was at a conference earlier this year where one of the academics said that despite a lot of searching he had been unable to find any documentation or research that showed that "five nines" is the norm. I was reminded of this recently when I experienced a broadband failure of more than five hours (more like three nines). Wikipedia has an interesting article, Myth of the nines, which talks about the difficulty of reaching such a goal.