Rackspace introduced the concept of charging customers only for the bandwidth utilized in a given period. Other
providers use what is commonly referred to as the 95th percentile method. This method takes readings of inbound
and outbound bandwidth utilization on regular intervals. The larger bandwidth utilization of the two is
recorded. At the end of the billing period, the highest 5% of the readings are discarded and the customer is
charged for a full month of utilization at the 95% mark.While this method allows some level of protections against short traffic spikes, the disadvantage occurs during hours of lower utilization. With 95th percentile billing, your lower off-hour utilization is billed at the higher 95th percentile rate. Traditionally, this period of lower bandwidth utilization is approximately 50% of the hours in the billing period, resulting in charges for bandwidth you did not use.
Rackspace instead charges based upon aggregate transfer. This method is ideal for our hosting customers as it results in lower bandwidth charges. Instead of penalizing for peak hour consumption (as in the 95th percentile method), this method only charges you for the bandwidth you use. Referring to the graph, in the 95th percentile method you would be charged for bandwidth utilization at a rate of 377 kbps sustained across the entire month. With Rackspace, you would instead be charged for the equivalent of 196 kpbs, converted a per GB transferred.
Finally, Rackspace only charges for outbound bandwidth, meaning that routine site maintenance, such as content publishing and uploads, are not counted against your bandwidth allocation.
