Bandwidth

If you're a high bandwidth customer then our usual "gigabytes per month" data transfer commitment may not make sense for you. It's not the way that bandwidth is usually purchased in large quantities and it's not how BitFolk deals with its suppliers either.

Therefore, attempting to sell you a limit of a simple number of gigabytes transferred per month risks giving you a bad deal or exposing us to overage charges that we can't pass on.

95th percentile billing

The most common industry standard billing method for burstable bandwidth charges is referred to as 95th percentile billing. If you're in the market for large amounts of bandwidth then you probably know how 95th percentile works and just want to know our pricing. Here goes.

Item	Monthly cost	Quarterly cost	Yearly cost
Base VPS including 512kbit/s bandwidth 95th percentile	£8.99	£24.70	£89.90
Additional 512kbit/s bandwidth 95th percentile	£5.00	£13.75	£50.00
Additional 1Mbit/s yearly commitment, minimum 5Mbit/s	N/A	N/A	£72.00
Overage outside of commitment, per 256kbit/s or part thereof, 95th percentile	£3.50	N/A	N/A

All prices exclude VAT.

For low levels of bandwidth usage you can choose whichever billing method you like. The majority of customers do very little data transfer and will probably find it much simpler to go with the included transfer quota of the usual method, therefore that is the default and we will not ask you about it unless you start doing much more data transfer.

If you try to order much more than about 750GB/month data transfer we will most likely insist that you switch to 95th percentile billing.

How it works

If you haven't heard of 95th percentile billing before, here follows a full explanation which should enable you to work out if it could make sense for you to switch to it.

We also specify our exact method since there are a few little variations in how providers do such calculations.

Concept

95th percentile billing is designed to give a fair treatment of bursting bandwidth requirements. It recognises the fact that there will be some spikes of usage but that most of the time the requirements will be much lower, and matches costs to those requirements.

Our procedure

The procedure is as follows:

1. Rates of data transfer in and out in bits/second are measured every 5 minutes.
2. At the end of the 30-day measurement period the 5 minute readings are ordered low to high, one set for the in readings and one set for the out readings.
3. The top 5% of each (there's 8,640 5-minute readings in 30 days, so that is the top 432 readings) are discarded.
4. The highest remaining reading in each set is your 95th percentile measurement for in or out.
5. We bill you based on the higher figure of those two.

The above method will discard the top 5% of traffic spikes. That is, 95% of all individual readings will be at or below the level you are billed at. As a consequence:

• If you have a mostly constant bandwidth requirement then you will generally do quite well out of 95th percentile billing.
• If you have very spiky requirements then you will generally do less well.
• An anomalous bandwidth use event lasting less than 36 hours (432 × 5 minutes) should not feature in your billing at all.

Frequently asked questions

How do I know how much I can transfer for a given 95th percentile commitment?

An example of a Cacti 95th percentile bandwidth graph.

It totally depends on how "spiky" your traffic is.

If your traffic is very constant and remains near 512kilobits/sec at all times (less than 5% of readings above 512kbit/s) then it is a simple calculation:

512 × 1,000 bits × 60 seconds × 60 minutes × 24 hours × 30 days =	1,327,104,000,000	bits per month
1,327,104,000,000 bits ÷ 8 =	165,888,000,000	bytes per month
165,888,000,000 bytes ÷ 1,000 =	165,888,000	kilobytes per month
165,888,000 kilobytes ÷ 1,000 =	165,888	megabytes per month
165,888 megabytes ÷ 1,000 =	165.8	gigabytes per month

Very few people's traffic remains constant, however, and estimating visually can be quite difficult.

If you'd like to get a figure from past data you can ask BitFolk support to do a calculation for any time period in the last 6 months. If you'd like to get an estimate for the future then you can ask BitFolk support to enable a 95th percentile bandwidth graph for you in Cacti. It'll end up looking something like the image on the right.

The red line represents the 95th percentile reading for the displayed time span. Since BitFolk bills you by 30 day spans of time, the monthly graph would be the most appropriate to look at. Do note however that Cacti figures are approximate and are not used by BitFolk for billing. Cacti averages away the detailed readings and as a result will usually very slightly under-report. The actual 95th percentile measurement for the example graph shown here was in fact 10.82Mbit/s.

During the time period displayed, this VPS transferred 1.98TB of data.

Under BitFolk's usual pricing for data transfer this would cost you (yearly, plus VAT):

Item	Quantity	Amount	Line total
A base VPS incl. 200GB/mo data transfer	1	£89.90	£89.90
10GB additional data transfer	178	£5.00	£890.00
Total			£979.90

However that is irrelevant because BitFolk would not agree to sell you 1,980GB of data transfer per month.

Using the 95th percentile billing scheme detailed above:

Item	Quantity	Amount	Line total
A base VPS incl. 512kbit/s 95th percentile	1	£89.90	£89.90
11Mbit/s 95th percentile, yearly commit	11	£72.00	£792.00
Total			£881.90

In this case the customer ends up slightly better off.