Burstable billing is a procedure or a method that is used for measuring bandwidth on the basis of highest usage points. It allows exceeding of usage with reference to a predetermined threshold for smaller duration's of time, without having to pay an extra penalty for the same or without having to purchase a higher CIR or committed information rate from an ISP or an internet service provider. Majority of internet service providers use a sampling period of 5 minutes and a usage of 95% when usage is calculated.
This 95 percentile is a widely accepted and fairly accurate mathematical calculation for evaluating regular as well as sustained usage of a connection. This method is preferred because it gets the closest to the required capacity of the said link instead of tracking by means of other methods such as maximum or mean rate. Primarily, the bytes that make up the data packets do not cost money. However, the infrastructure required for setting up the link costs money for support and setup.
Commonly, the method of Burstable billing is used more often in peering arrangements set up among corporate networks. It is not used very often by internet service providers because they require committed information rates.