95th Percentile Billing Explained

Understanding 95th Percentile Billing

The 95th percentile is a mathematical calculation widely used to determine billings for Internet connections that are provided as "burstable" (variable rate) bandwidth.

Essentially, when you subscribe to a service that includes a network bandwidth allowance you are permitted to consume as much bandwidth as you wish up to a specified limit. As long as your monthly consumption is at or below this allowance level there are no additional fees. If, however, you exceed your allowance then you are invoiced for the additional bandwidth you consume. EntirelyDigital does not throttle your connection and as such you have up to your server's physical connection speed at your disposal.

This article explains how your actual bandwidth consumption is calculated and how this information is used to determine any additional service charges that may apply to your EntirelyDigital hosted service. It is important when choosing a subscription for a bandwidth allowance that you choose a bandwidth allowance suitable to your needs.

Metering Your Consumption

Bandwidth consumption is a calculated value. It works like this:

  • Every 30 seconds EntirelyDigital takes readings off of the network switch that services your account. These reading return the amount of network traffic that has passed through the port that services your equipment, returning the number of bytes of information that has entered and left your service.

  • These values are added together to provide five minute totals. These totals are then translated into kilobits and divided by the number of seconds that have passed in order to establish the total amount of bandwidth that entered and left your service, expressed in kilobits per second (Kbps). Bandwidth is calculated separately for both inbound and outbound traffic and your bandwidth consumption is the sum of these two values.

At the end of each month these readings are sorted and the top 5% of these readings are removed. The next highest reading (called "the 95th percentile") determines if any excessive use of network traffic has occurred and determines the amount of excess service fees that would apply.

Here is a simple example that illustrates what we mean:

Over a period of 500 minutes, 100 readings of both incoming and outgoing traffic have been recorded. Assuming the billing period is also 500 minute, then the top 5% of these 100 readings (the top 5, in this case) are ignored, and you are billed at the value of the 95th reading.

If the top 10 readings of this set of 100 were:

Top 10 Entry Reading Comment
100 2,090 Kbps Ignored (top 5%)
99 1,790 Kbps Ignored (top 5%)
98 1,200 Kbps Ignored (top 5%)
97 960 Kbps Ignored (top 5%)
96 840 Kbps Ignored (top 5%)
95 825 Kbps ** "95th Percentile"
94 814 Kbps  
93 793 Kbps  
92 712 Kbps  
91 710 Kbps  

In this case, even though you sometimes sustained traffic at speeds as high as 2,090 Kbps, your actual 95th percentile consumption was 825 Kbps. If your subscription included 1,000 Kbps of network traffic then your usage is well below your subscription allowance.

While this is a simplification of the 95th percentile model, it does illustrate the general concept. For a more detailed explanation of percentile calculations please refer to statistical mathematics sources or alternatively a good explanation resides in Wikipedia.

What happens if you exceed your Allowance?

If you exceed your allowance you will be invoiced for the additional bandwidth that your service consumed. These additional fees are invoiced at a fixed rate, as defined by your signed Sales Order.

Can I increase my Bandwidth Allowance?

Yes. For information on increasing your Bandwidth Allowance please speak to your EntirelyDigital sales representative.

Is there a way for me to view how much traffic my service is using?

Yes. You will be emailed a detailed bandwidth report on the 1st of each month (if requested) which shows the previous month's traffic calculations.

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