95th Percentile Explained
Vault Network’s clients are billed at the 95th percentile, depending on their bandwidth needs. This means that you pay as you use the bandwidth, with the advantage of spiking large amounts of traffic without fear of being billed overage. We will usually take one reading every 5 minutes, generating an average traffic amount over a given five minute duration. At the end of the month, the numbers are sequentially listed from highest to lowest. If there are 100 readings, the top five percent will be discarded, and the 95th reading will be the measure of the level of bandwidth used and billed. Of course, there are much more than 100 samples (about 8,640 per month), so we remove the top five percent leaving the 95th percentile. The amount of samples removed per month on average usually equals 36 hours of unbilled traffic.
Short 95th Examples
Over a period of 500 minutes, 100 readings are taken of both incoming and outgoing traffic. If the billing period was also 500 minutes, the top 5% (highest traffic usage) of these readings (5 in this case) are discarded, and you are billed at the value of the 95th reading. If the top 10 readings of this set of 100 were:
Poll – 99 : 440Kbps
Poll – 98 : 170Kpbs
Poll – 97 : 69Kbps
Poll – 96 : 40Kbps
Poll – 95 : 30Kbps – Billed Usage
Poll – 94 : 28Kbps
Poll – 93 : 27Kbps
Poll – 92 : 24Kbps
Poll – 91 : 21Kbps
You would be billed using the 30Kbps as your billed amount and charged overage based on your currently committed usage level.
In another example, let us have a Colocation customer with (1) 1u server and a contract for one Meg of service. Normally, they use 1 to 2 Megs a day of bandwidth. On Fridays, they download a large file that uses 5+ Megs of bandwidth for 15 minutes. Using the 95th percentile calculation, the 15 minutes you use every Friday would be discarded because it is in the top fifth percentile. These 15 minutes of traffic each Friday create a total of a one-hour spike of traffic during each month that we would include in the 36 hours worth of traffic discarded before billing at the 95th percentile.