The "five nines" of availability (99.999%) are the telco gold standard. But what do they mean in practice? And more importantly — how are they actually delivered in a real network?
The math of the "nines"
A year has 525,600 minutes. An uptime percentage sets the maximum admissible downtime:
- 99% (two 9s) — 3 d 15 h 36 min/year. Unacceptable for business.
- 99.9% (three 9s) — 8 h 45 min/year. A decent residential operator.
- 99.99% (four 9s) — 52 min 34 s/year. Standard business SLA.
- 99.999% (five 9s) — 5 min 16 s/year. What Olivet Telecom commits to.
- 99.9999% (six 9s) — 32 s/year. Network cores and defence only.
What counts as downtime (and what doesn't)
An honest SLA must define what counts as downtime:
- Unplanned outages — always count.
- Planned outages with minimum notice (e.g. 5 business days) in a nightly window — usually excluded but must be defined.
- Outages caused by the customer (cutting the cable, locking the rack) — excluded.
- Force majeure (earthquake, court order) — often excluded.
Olivet Telecom's SLA counts everything except planned outages with 5-day notice (max 1 per quarter, duration < 30 min, 02:00-06:00 CET).
How it's achieved in the real world
99.999% isn't achieved simply with "better gear". It requires redundancy at every single point of failure:
- Dual power supply on the router (two PSUs on separate circuits)
- Dual fibre path physically separate (not the same duct)
- Automatic failover < 50 ms (BFD, VRRP, ERPS, MC-LAG)
- Two active-active datacenters for the Cloud Router
- 24/7 monitoring with proactive detection (alerts before the customer notices anything)
- Spare-parts stock in each covered city for fast intervention
Compensation: honest SLA vs decoration
An SLA is only worth something if it comes with financial compensation when broken. Many operators write "99.9% uptime" in the contract but compensate with derisory credits (€3 per day of outage). That's not an SLA — it's decoration.
Olivet Telecom's SLA, in contrast, compensates proportionally: if we exceed the permitted downtime, we discount from the monthly invoice pro-rata (and if we fail three months in a row, the customer can terminate without penalty). It's a real commitment.
Conclusion
Is 5 min 16 s of downtime per year what your business can absorb? If the answer is "no, not a minute", you're a critical business: you need real HA. If the answer is "more or less", you need at least 99.99%. Either way, what you really need is a contract with real compensation.
Frequently asked questions
How is uptime actually calculated?
By continuous monitoring (ping + SNMP) from the NOC. Any loss of response > 60 s is logged as an incident. At month-end the percentage is computed.
What happens if an excavator cuts the fibre?
That's an unplanned outage and it counts towards the SLA. Thanks to dual fibre on separated paths, the probability of a full outage is low. When it happens, the NOC dispatches the spare-parts team and compensation appears on the next invoice.
Want this quality at your business?
1 Gbps symmetric fibre certified to Y.1564. €149/month. No lock-in.
More articles
What is Y.1564 and why it changes business fibre
Y.1564 is the ITU-T standard that certifies speed, latency, jitter and loss of your fibre. We cover the 5 KPIs and why yours should ship with one.
Bufferbloat: the invisible problem that slows your work down
Bufferbloat is the queue "noise" that makes your Internet feel slow even on 1 Gbps. How Olivet FlowEngine fixes it, with measurable results.
ORO and QoS 802.1p: how a business gets priority over the neighbour
The ORO profile on Telefónica's NEBA network gives businesses QoS p-bit 3 priority over residential Best Effort. How it works, technically.