• United States
by Steve Taylor and Joanie Wexler

Measurement issues endure

May 29, 20032 mins

* Five years on: five-nines availability is still the goal

It’s time to wrap up our look back at our first newsletters and to take a quick look forward.  Our eighth newsletter looked at the issue of how you measure downtime in networks.  In particular, we looked at the issue of the timeframe over which you measure the performance.

Over the past five years, the desire for “five nines” of network availability has become in integral part of the networking vocabulary, but the term is typically used with about “nine-fives” accuracy.  Five-nines, or 99.999% availability is only meaningful when additional parameters – like the timeframe over which the measurement is made – are also specified.  Whether the measurement is made over a weekly, monthly, or yearly basis could have very significant implications.  Additionally, the reliability of multiple components and whether these components are connected serially or in parallel has a great impact.  As an indication of the long-term implications of this question, Steve recently posted a presentation at Webtorials on how to calculate the reliability of network components.

Newsletter #9 seems to be lost somewhere in the land of lost bits.  We think it had something to do with switched virtual circuits (SVC) – obviously a hot topic at the time, but we can’t prove it.  For sure, the tenth newsletter was on MCI’s SVCs.  This time we were looking at the usage-based pricing for SVCs as opposed to usage-based permanent virtual circuit (PVC) pricing.  Both turned out to be good ideas that never really caught on.  In this case, the simplicity of fixed prices on a monthly basis won out over the possibly cheaper but less predictable usage-based options.

We can’t let this discussion of MCI’s SVC service end without pointing out one aspect that has been amazingly cyclic – mergers and renaming companies.  Five years ago, MCI was MCI.  Then came the merger/acquisition with WorldCom and the company became MCI WorldCom.  Then the MCI part was dropped and we went to just WorldCom.  And now…  🙂

Five years ago, we wondered how we could sustain this newsletter.  Five hundred newsletters later, we haven’t run out of issues that need to be covered.  Next week, we’ll continue with some of these new issues.