Traditional telephony systems such as Lucent 5E and MetaSwitch are engineered to 5-9’s reliability standards.
5-9’s is 99.999% uptime.
If you do the math, you will see this is a bit over 5 minutes per year of downtime.
That is an extraordinary level of reliability, and it was achieved with, in the case of the Lucent 5E, 1970s discrete TTL logic chip technology. By modern standards, it was done with antiques, the kind of circuitry you’d find in a 1970’s transistor radio.
The MetaSwitch brought that up to state of the art for the 2000s, but, both solutions require the redundant components to be collocated in the same chassis.
Cloud-ready architecture is very powerful, but requires a whole different approach to application design.
Current “cloud voice” systems are based on a “load balance across multiple stateless backend” architecture. This is fine for web sites and web applications where there is no 5-9’s expectation. But communications DOES still have a 5-9’s expectation: for 911 calls, for important business-critical functions, for guaranteed delivery, etc. Today, cloud voice providers can wave off “you don’t have 5-9’s” objections by noting (correctly) that “nobody offers 5-9’s”.
Well, that only works until someone DOES.
“Cloud-ready 5-9’s” will be the competitive advantage of the future.