Definition

network availability

Contributor(s): Alex Gillis

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 service being provided is consistently kept running for end-users.

Network availability is typically recorded by real-time performance monitoring tools in a proactive manner. This allows networking professionals to catch pauses in availability as they happen. Additionally, most networks also provide users with reactive availability tools that allow them to submit a support ticket 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 network availability can help organizations with disaster planning, recognizing when issues arise and providing users with a standard quality of service.

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 will typically include a specified level of network availability in a service level agreement (SLA).

Formula for network availability
Formula for measuring network availability

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 for maintenance, unplanned failures or for the time it takes for a system to recover.

100% availability is considered to be when a network system is fully operational and available for its entire runtime. Typically, high availability will strive from around 99-99.999% (or the 5 9’s).

Network availability vs. reliability

Network reliability is similar to availability; however, instead of measuring the amount of uptime in a system, reliability is the measured likelihood of a failure occurring in a system. Reliability will track how long a network’s infrastructure is functional without interruption. Network reliability is also measured in percentages, where a fully reliable system has 100% availability. Reliability can be calculated through either dividing the total time in service by the number of failures (known as mean time between failures- MTBF) or by dividing the number of failures by total time in service (known as failure rate).

This was last updated in April 2019

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