Network Availability vs. Uptime vs. Downtime Meanings

Entuity Software

Susan George September 26, 2022

Your network and IT assets should be available around the clock. Whether we’re talking about a corporate website or server-hosted in-house resources, accessibility is a critical consideration. Of course, disruptions and network downtime do occur, and organizations need to measure outages, outage types, and overall network performance.

The real question is how to measure, rather than whether there’s a need for measuring. Do you use availability to determine reliability? What about uptime? Where does downtime fit into the equation? And what other availability metrics should you be measuring? If you’re unsure about how to measure network reliability and success, this post is for you.

What Is Availability?

Availability is one of the most critical factors for your network. It’s defined as the probability that your system will work as intended when it’s needed. In other words, when someone wants to access a particular network-hosted resource, can they do so?

IT engineer working on availability uptime and downtime in server room

How to Measure Network Availability

You might think that measuring network availability is as simple as recording the amount of time it is accessible (available). That’s not the case, though. To get the availability percentage, you’ll need to first subtract the amount of downtime from the agreed service time and then divide that by the amount of agreed service time. The result is your availability percentage.

Availability vs. Reliability

Availability and reliability are interrelated but separate measurements. Availability is a measure of the ability of a piece of networked equipment to be operated. Reliability, on the other hand, is a measure of a piece of equipment’s ability to perform its intended function for a particular amount of time without experiencing a failure.

What Is Network Uptime?

Network uptime is bandied around a lot these days. It’s used in marketing and used as a benchmark for performance. But what does uptime mean?

What Does Uptime Mean?

When you strip away all other connotations, uptime just means the percentage of time that a system is ready for operation under normal circumstances. It’s a measure of reliability and states how long a machine (or network) has been working and available, but is expressed as a percentage.

Uptime vs. Availability

Not only are these two terms not synonymous, they are two different metrics in measuring the reliability of a service. Uptime is an indicator. It is not a guarantee of a particular amount of availability, or that all services or devices connected to a system will be available while the network itself is up and operational.

network engineer using laptop to discover how to measure uptime requirements

How to Measure Uptime

Uptime calculations require simple math. In most cases, it’s expressed as an annual percentage. To determine that number, you’ll need to take the number of hours your network is up and running and then divide it by the number of hours in a year (8,760). Next, multiply that by 100. The answer is your annual uptime percentage.

Uptime Requirements

Uptime requirements refer to the total amount of time that a system is available for end-use applications. In most cases, it’s communicated as a percentage of total scheduled working hours and corresponds to downtime values.

What Is Downtime?

Speaking of downtime, what is it? It’s the opposite of uptime – time during which the network is not available for use. Downtime can be due to any number of reasons, such as a server hardware issue, or another data center challenge like the Great Google Outage, which put Gmail and other Google tools out of service for up to 20% of the company’s users for just under an hour. Cloudflare, Azure, and Amazon Web Services all experience outages that cause downtime for systems based on their architectures.

female technician using tablet to measure network uptime vs availability

How to Calculate Downtime Percentage

Calculating your downtime percentage is not much different from calculating your uptime percentage. Simply replace the number of hours of uptime with the number of hours of downtime, and then divide by the number of hours in a year and multiply by 100. Note that your result should be a very small number, something along the lines of .09 for most systems.

The Five Nines

The “Five Nines” is a common term regarding high availability of services, taken to mean 99.999% uptime. It also indicates yearly downtime durations. For example, the availability level “1 Nine” signals 90% uptime, which equates to 36.5 days of downtime per year. As availability levels increase, so does the associated uptime. When companies advertise “5 Nines”, it refers to an uptime measurement of 99.999% or approximately 5.26 minutes of downtime per year.

The Five Nines are a significant selling point, which is why suppliers market a 99.999% uptime SLA. The issue is, in many cases, each additional nine added to an availability score does not necessarily guarantee greater reliability. And with no ruling body or committee to formalize the Five Nines, each additional nine can be a waste of precious resources in pursuit of an elusive goal. As such, it’s more important for customers to focus on the supplier or service provider based on their capabilities.

Availability vs. Uptime vs. Downtime

With a better understanding of availability, uptime, and downtime, you should now be able to make an informed decision about how you measure success and reliability.

Relevant Metrics

While uptime, downtime, and availability are certainly important metrics to measure, there are others that you be aware of.

Customer Satisfaction Score

A high customer satisfaction score is a strong indicator that you are offering excellent uptime and reliability. In contrast, a low customer satisfaction score shows that you have work to do, such as unmet expectations. Delving into uptime, availability, and reliability metrics can shed light on low customer satisfaction scores.


MTTN stands for Mean Time to Notify and is an average of how long it takes before an MSP or TPM sends out an outage notification to its customers. The longer the MTTN, the lower the customer satisfaction score in most cases.


MTTR stands for Mean Time to Repair and is a measure of how long it takes an MSP or TPM to restore availability on average. The lower the MTTR score, the more satisfied your customers will be.


MTBF stands for Mean Time Between Failures. It is the average time between repairable failures of a technology product. MTBF is used to track both the availability and reliability of a product. The higher the time between failures, the more reliable the system.

Learn how you can improve MTTN, MTTR, and MTBF with the help of industry-leading enterprise network monitoring software today.

Availability or Uptime, Which Is More Important?

Ultimately, availability is the more important score. Achieving 100% uptime is an impossibility; even reaching five or six nines is a feat in itself! And although uptime is often the initial focus to drive up technical quality, service availability is a better metric for driving customer satisfaction in the longer term.

While both metrics matter, especially when crafting SLAs, it’s important to remember they are only part of the overall picture. It’s not just these metrics that are important, but more so what you do with them.

To address rising consumer expectations, IT teams must anticipate network problems and improve visibility to recover faster. Entuity Software™ from Park Place Technologies offers the industry’s most usable and comprehensive set of network reports that cater directly to the needs of your enterprise business. With Entuity™, users can choose from over 100 reports out-of-the-box for a comprehensive toolbox of analytics. A drag-and-drop custom report builder gives you the power to create your own, and a Dynamic Dashboard ensures a single pane of glass viewpoint.

Deliver the network visibility needed to ensure your organization and its clients’ networks are performing at peak efficiency and availability, and get started with Entuity Software™ today!

About the Author

Susan George,
Susan is a Senior Product Manager for Entuity Software, the industry-leading network performance monitoring software from Park Place Technologies. Susan is responsible for defining and driving the functionality available within Entuity, as well as driving the global product Roadmap.