A 99.99% uptime SLA allows about 4.4 minutes of downtime a month, or roughly 53 minutes a year, before the carrier owes you anything. The same document usually also commits the carrier to latency, packet delivery and repair-time targets, and pays service credits when it misses them. What it does not do is guarantee your business stays online, and the credits rarely come close to covering the cost of a bad outage.
"99.99% uptime" appears on nearly every enterprise quote, and most buyers nod at it and move on. It is worth a few minutes of attention, because it is one of the few numbers in a telecom contract that is actually enforceable, and because the fine print decides how much it is worth.
The arithmetic
Availability percentages are easier to judge as minutes. Using an average month of about 30.4 days:
| Availability | Allowed downtime per month | Allowed downtime per year |
|---|---|---|
| 99% | about 7.3 hours | about 3.65 days |
| 99.5% | about 3.65 hours | about 43.8 hours |
| 99.9% | about 43.8 minutes | about 8.8 hours |
| 99.95% | about 21.9 minutes | about 4.4 hours |
| 99.99% | about 4.4 minutes | about 53 minutes |
| 99.999% | about 26 seconds | about 5.3 minutes |
Contracts usually measure availability per calendar month, so the exact allowance moves slightly with the length of the month. A few quote an annual figure instead, which lets a single long outage sit inside the target. Check which one yours uses, because 53 minutes in one afternoon feels very different from four minutes a month.
The jump from 99.9% to 99.99% looks like one decimal place. It is a tenfold difference in allowed downtime, and it is the difference between a blip nobody reports and an outage that reaches your leadership team.
What else is in the document
Uptime is the headline. A good DIA SLA usually commits the carrier to more:
- Latency. A maximum average round-trip time across the carrier's own network, often stated per region.
- Packet delivery (or packet loss). For example, a stated percentage of packets delivered each month. This is what decides whether voice and video hold up.
- Jitter. Variation in delay, sometimes included for circuits carrying voice.
- Time to repair. A defined window for restoring a hard outage, sometimes called MTTR or time to restore.
- Service credits. Money back, usually as a percentage of the monthly charge, when targets are missed.
- Chronic outage terms. The right to leave without an early termination fee if the circuit fails repeatedly. Not every carrier offers this, and it is worth asking for.
Note where the promises apply. Latency and packet delivery are usually measured across the carrier's backbone, not end to end to the cloud service you actually use. Once traffic leaves their network, the SLA stops.
How service credits actually work
Credits are not automatic in most contracts. The usual pattern:
- The outage clock starts when you open a trouble ticket, not when the circuit went down. Report quickly.
- The clock stops when the carrier restores service, and time the carrier spent waiting on you (for access to the building, for example) is often excluded.
- You must request the credit in writing within a set window, commonly around 30 days after the month in question.
- Credits are capped, frequently at a portion of or all of one month's charge for that circuit.
A worked example
Hypothetical numbers for illustration only. Every carrier's credit schedule is different.
Suppose a circuit costs $1,000 a month, and the SLA pays a 10% credit for an outage between one and four hours. The circuit goes down for three hours on a Tuesday. Your credit is $100. If your business loses $2,000 an hour when offline, the outage cost you $6,000. The credit covers under 2% of it.
That is not a reason to ignore credits. Their real function is to give the carrier a financial reason to care and to give you a documented basis for escalation. They are not insurance, and should not be planned as such.
What an SLA does not cover
Read the exclusions before you read the credits. The common ones:
- Scheduled maintenance, usually announced in advance and scheduled overnight. It still takes you offline.
- Anything on your side of the demarcation point: your router, firewall, switches, internal cabling and Wi-Fi.
- Building issues such as power failures in the telecom room or a damaged riser the carrier does not own.
- Events outside the carrier's control, typically defined in a force majeure clause.
- Outages you caused, including configuration changes you requested.
An SLA on the circuit does not protect you from a failure in your own equipment room. If your firewall dies, the circuit is technically up.
Circuit uptime is not business uptime
This is the point most buyers miss. A 99.99% SLA describes one circuit on one path. A backhoe that cuts the conduit into your building takes the circuit down, and the SLA simply means you get a credit afterwards.
Real resilience comes from a second, physically diverse path. As an illustration of the principle: if two circuits were each available 99.9% of the time and failed completely independently of each other, the chance of both being down at the same moment would be tiny, far better than any single-circuit SLA. The catch is the word "independently." Two circuits that share a conduit, a building entrance or a power source fail together. We cover the design in Does your business need backup internet?, and SD-WAN is how most businesses switch between the two automatically.
Reading the fine print, clause by clause
What counts as "down"
Many SLAs count only a complete loss of service as downtime. A circuit that is up but dropping a large share of packets may not count toward the availability figure at all, even though your calls are unusable. That is what the packet delivery and latency targets are for, so check that they exist and that they carry their own credits.
Where performance is measured
Latency and packet delivery targets are usually measured between points on the carrier's own backbone, averaged over a month. A monthly average can hide a terrible hour. Ask how the figures are measured and whether you can see the data for your circuit.
Per circuit, not per business
The SLA applies to each circuit separately. If you have two circuits from the same carrier and both fail at once, you may get two small credits rather than any recognition that your site was completely offline.
Using the SLA when something goes wrong
An SLA only helps if you use it. When a circuit fails:
- Open a ticket immediately and write down the ticket number and the time. In most contracts, this starts the clock.
- Ask for the escalation contacts if the repair window is passing. Carriers publish escalation levels for business customers; ask for them before you need them.
- Keep a simple log of when service dropped, when you reported it, when it came back and what the carrier said.
- Request a reason for outage (RFO) afterwards. A written explanation tells you whether the cause is likely to repeat.
- Claim the credit in writing within the contract's window, citing the ticket.
Repeated claims also build the record you need to invoke a chronic outage clause, or to negotiate hard at renewal. That process is covered in the renewal trap. A single point of contact who does this for you is one of the practical benefits of working with an agent rather than a carrier's general support line.
Why best-effort broadband has none of this
Shared broadband carries no such obligations regardless of the speed on the box. That is the actual distinction between "business internet" tiers: not megabits, but whether anyone has contractually promised you anything. Our comparison of DIA, shared fiber and coax covers the rest of the difference.
Questions to ask your carrier
- Can I see the full SLA document, including exclusions, before I sign?
- How is availability measured: per circuit, per month, from ticket open or from detected failure?
- What is the committed time to repair for a hard outage, and does it differ nights and weekends?
- What is the credit schedule and cap, and how do I claim?
- How much scheduled maintenance should I expect a year, and how much notice do I get?
- Is there a chronic outage clause that lets me terminate without penalty?
- Where exactly is the demarcation point, and who owns the cabling from there to my suite?
If the SLA document takes more than a day to produce, that tells you something about how the relationship will go.
Getting SLA terms compared for your address
SLA terms differ between carriers more than the headline number suggests. When several carriers bid on your building, we put their terms side by side along with the price, so you are comparing the whole contract, not one percentage. The quote is free with no obligation, and you usually hear back the same day. Start on the Dedicated Internet Access page, or send us your address, call 478-758-8091 or text (347) 870-0965.
