IT Glossary · IT Operations

SLA (Service Level Agreement) — Uptime Percentages Explained

An SLA is a contractual commitment from an IT service provider guaranteeing minimum service quality — specifically uptime percentage and how fast they will fix problems. 99.9% uptime sounds good but allows 8.7 hours of downtime per year.

A Service Level Agreement (SLA) is a formal contract between a service provider (ISP, cloud vendor, software company) and a customer that defines the expected level of service. For internet and cloud services, the most important SLA metric is uptime percentage — the proportion of time the service is available. SLAs also define Mean Time to Repair (MTTR) — how quickly the provider must restore service after an outage — and may include financial penalties or credits if SLAs are not met. Understanding SLAs is essential for Indian businesses evaluating ISPs, cloud providers, and managed service providers.

Why it matters for Indian businesses

Indian businesses evaluating internet providers, cloud services, and SaaS tools often focus only on price. However, the difference between 99.5% and 99.9% uptime is significant: 99.5% allows 44 hours of downtime per year (nearly 2 full days), while 99.9% allows only 8.7 hours. For a business where every hour of downtime costs ₹1 lakh, the cost difference between ISP tiers is trivial compared to the cost of lost uptime. SLAs also determine how quickly providers must respond — a 4-hour MTTR means your team could be without internet for 4 hours before the provider is even obligated to fix it.

Key components

Uptime Percentage: The guaranteed availability — 99.5% means 44 hours/year of allowed downtime; 99.9% means 8.7 hours/year.
MTTR (Mean Time to Repair): The maximum time the provider has to restore service after an outage — typically 4 hours or 2 hours for premium SLAs.
Service Credits: Compensation (usually account credits) given if the provider misses the SLA — does not cover your business losses, but acknowledges the breach.
Exclusions: SLAs always have exclusions — planned maintenance windows, force majeure events, and customer-caused outages are typically not counted against uptime.

Related terms: Uptime, MTTR, Internet Leased Line, Cloud Computing, Managed Services, MSP

Frequently Asked Questions

What does 99.9% uptime mean in hours per year?

99.9% uptime = 0.1% downtime. In a year (8,760 hours), 0.1% = 8.76 hours of allowed downtime. Monthly: 0.73 hours (44 minutes). This is why "three nines" is the enterprise standard — it limits annual downtime to less than 9 hours.

Do I get money back if my ISP misses their SLA in India?

SLA credits (usually proportional to downtime as a % of monthly billing) are available if you document and report the outage. However, these credits rarely cover actual business losses. For critical operations, redundant connections (dual ISP or 4G backup) are more valuable than SLA credits.

Choose the right SLA for your business — we help Indian businesses evaluate ISP and cloud SLAs properly.