What is network availability?
Network availability is the amount of uptime in a network system over a specific time interval. Uptime refers to the amount of time a network is fully operational. Network availability is measured as a percentage and is monitored to ensure the network runs consistently for end users.
Network professionals typically record availability in a proactive manner with real-time network performance monitoring tools. This approach helps networking professionals catch pauses in availability as soon as they occur. Additionally, most networks provide users with reactive availability tools that permit them to submit support tickets when the network becomes unavailable.
The uptime and availability of a network are important KPIs for network service providers to measure, especially those that use multiple data centers. Maintaining a certain level of availability can help organizations with network disaster planning, recognize when issues arise and provide users with a standard quality of service (QoS).
How to measure network availability
Network availability is measured as the percentage of time a system stays fully operational over a period of time, usually over a year. Service providers typically include a specified level of network availability in a service-level agreement (SLA).
The formula for availability is equivalent to the uptime divided by the total time, where the total time is uptime plus downtime. Measured downtime includes all times where the network system is down, such as during maintenance, unplanned failures or the time it takes for a system to recover.
Network professionals aim to achieve 100% availability, which is when a network system is fully operational and available for its entire runtime. High availability typically strives for 99.999%, also known as five-nines availability.
Network availability vs. network reliability
Network reliability is similar to availability, but instead of measuring the amount of uptime in a system, reliability is the measured likelihood of a failure occurring in a system. Reliability tracks how long a network's infrastructure will remain functional without interruption.
Network reliability is also measured in percentages, where a fully reliable system has 100% availability. Network professionals calculate reliability by dividing the total time in service by the number of failures -- known as mean time between failures -- or by dividing the number of failures by total time in service, known as failure rate.
Editor's note: This article was republished in December 2022 to improve the reader experience.