95th Percentile Billing

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How It Works

The 95th percentile is a widely used mathematical calculation to evaluate the regular and sustained use of a network connection. The 95th percentile method more closely reflects the needed capacity of the link in question than tracking by other methods such as mean or maximum rate. The bytes that make up the packets themselves do not actually cost money, but the link and the infrastructure on either end of the link cost money to set up and support. This method of billing is commonly used in peering arrangements between corporate networks, it is not often used by ISPs because Internet Service Providers need Committed Information Rates (CIRs) for planning purposes.

Since most networks are oversubscribed, there is often some room for some bursting without advanced planning (hence burstable billing). Ignoring the top 5% of the samples is a reasonable compromise in most cases (hence 95th percentile).

The 95th percentile allows a customer to have a short (less than 36 hours, given a monthly billing period) burst in traffic without overage charges. The 95th percentile says that 95% of the time, the usage is at or below this amount. Conversely, 5% of the samples may be bursting above this rate.

The sampling interval, or how often samples (or data points) are taken, is an important factor in percentile calculation. A percentile is calculated on some set of data points. Every data point represents the average bandwidth used during the sampling interval (e.g., five minutes) and is calculated as the number of bits transferred throughout the interval divided by the duration of the interval (e.g., 300 seconds). The resulting value represents the average use rate for a single sampling interval and is expressed as bits per second (see data transfer rate).

Benifits

By using 95th percentile billing this will enable you to do those big downloads when needed without the wait. You won't need to commit to a higher speed then needed if you don't often use such a high amount.