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Re: The Myth of Five 9's Reliability (fwd)

  • From: Art Houle
  • Date: Wed Apr 24 16:54:30 2002

How to calculate uptime and get 5 9s

-do not include any outage less than 20 minutes.
-only include down lines that are actually reported by customers.
-when possible fix the line and report 'no trouble found'.
-remember that your company is penalized by the FCC for bad ratings, so
don't report any problems that you do not have to.

On Wed, 24 Apr 2002, Pete Kruckenberg wrote:

> >From the Canarie news mailing list.
> I don't think I've ever experienced five 9's on any telco
> service, I have always assumed I must be the one customer
> experiencing down-time, and the aggregate was somehow five
> 9's. How is network reliability calculated to end up with 
> five 9's?
> Pete.
> ---------- Forwarded message ----------
> Date: Wed, 24 Apr 2002 10:08:18 -0400 (EDT)
> From: [email protected]
> Subject: [news] The Myth of Five 9's Reliability
> For more information on this item please visit the CANARIE CA*net 3 Optical
> Internet program web site at
> -------------------------------------------
> [A good article on the truth about five 9's reliability. Some excerpts -
> BSA]
> Deep Six Five-Nines?
> For much of the 20th century, the U.S. enjoyed the best
> network money could buy; hands-down, it was the most modern,
> most ubiquitous and most reliable in the world. And one
> term--five-nines--came to symbolize the network's
> robustness, its high availability, its virtual
> indestructibility. When the goal of five-nines was set, the
> network was planned, designed and operated by a monopoly,
> which was guaranteed a return on whatever it invested. It
> was in the monopoly's interest to make the network as
> platinum-plated as possible.
> One of the key points is that "five-nines" has long been
> somewhat overrated. Five-nines is NOT an inherent capability
> of circuit-switched, TDM networks. It's a manmade concept,
> derived from a mathematical equation, which includes some
> things and leaves out others.
> It's critical to remember that when you run the performance
> numbers on ALL the items in a network--those that are
> included in the five-nines equation and those that
> aren't--you're probably going to wind up with a number less
> than 99.999 percent. A well-run network actually delivers
> something around 99.45 percent.
> The gap between the rhetoric of five-nines and actual
> network performance leads to the conclusion that five-nines
> may not be a realistic or even necessary goal.

Art Houle     				e-mail:  [email protected]
Academic Computing & Network Services 	 Voice:  850-644-2591
Florida State University		   FAX:  850-644-8722