"Five Nines" is Gone and Almost Nobody Actually Cares

Our user experience of applications, devices and networks is far from the “five nines” standards (99.999 percent availability) telcos used to tout. And it probably doesn't matter as much as some would suggest, as we all now have protocols for dropped calls, lost emails, momentary glitches in streaming content.

If the value of an experience or app is high enough, we simply work around availability or "reliability" issues. "Best effort" means some amount of failure for any given instance of an app session.

So, as a practical matter, today’s heterogenous, edge-powered, internet transport fabric, IP-based application environment absolutely means user experience cannot approach 99.999-percent availability for any applications. And nobody cares much, most of the time.

To be sure, some might claim "core systems" in banking, financial trading or some security-critical use cases are "five nines" in terms of availability, but that only applies to the core systems, not the end user experience of those systems. 

The problem is that no matter what any single participant in the value chain might claim for its own availability, and even if that availability is between 99 percent and 99.99 percent, the entire end-to-end value chain depends on the sum total of availability across the whole value chain, and that math is challenging. 

Consider an example where contributor availabilities are:

• Device: 99%

• Home broadband access: 99.5%

• Internet backbone: 99.99%

• App server: 99.9%

• Local power: 99.5%

The end-to-end availability requires multiplying all those discrete availabilities. So the formula is 

0.99 × 0.995 × 0.9999 × 0.999 × 0.995 ≈ 97.4 percent. That means 229 hours of downtime per year, not the 5.26 minutes per year allowed by "five nines” standard.

The only reason end users seem unaware of the change is that much of the downtime happens when they are not actively using their connections (devices not present; devices in “do not disturb” mode; user is sleeping; apps not in immediate use). 

Value Chain Component	Typical Availability (%)	Major Downtime Factors
User Devices – Mobile	95%–99%	Battery loss, OS/software issues, dropped connections
User Devices – Fixed	96%–99.5%	Power outages, device crashes, local network (Wi-Fi) issues
Access Network – Mobile	97%–99.9%	Tower outages, congestion, interference, maintenance
Access Network – Fixed	98%–99.9%	Fiber/cable cuts, power issues, last-mile failures
Global Internet Backbone	99.99%+	Rare fiber cuts, DDoS attacks, routing errors
Application Servers (Cloud)	99.5%–99.99%	Cloud region outages, software bugs, maintenance, cyberattacks
Local Power Supply	99.0%–99.9% (urban)	Grid instability, storms, infrastructure failures
End-to-End Availability	Often < 95%–98%	Cumulative failures across components

The point is that people have learned to adapt to services, networks, applications and experiences that are never "five nines" reliable. We have work-around solutions that funciton so well nobody really cares about the lack of "five nines" reliability.