95th percentile monitoring is a collocation technical term that relates to bandwidth. This method of monitoring logs 30 days worth of traffic samples every 5 minutes. This log is then sorted in descending order, placing the largest traffic spikes at the top of the list. These top 5% traffic spikes are thrown out.
This remaining top value, within the 95th percentile, is the bandwidth usage for the month. Colocation hosting providers often use this method to bill their corporate customers. Most collocation hosting companies feel this is the most fair and effective method for conducting business with corporate clients.
This method of billing is only really seen in peering arrangements between corporate networks. Since internet service providers need consistent data rates for planning, this method is far from appealing to them. Most sites generate the bulk of their traffic on Mondays. Therefore, Monday practically determines the billable rate for the entire month.
The primary advantage is the user can accumulate up to 36 hours of peak traffic that will be ignored on that month’s bill, regardless of the height of the spikes. Unfortunately this bill method attracts a few criticisms.
- Potential to pay for unused bandwidth
- Inbound and outbound traffic calculated separately
Although the primary advantage is attractive, it works both ways. Users can potentially pay for unused bandwidth. For example, if a website only uses 2Mbps for 5% of the time and nothing more, the client would be billed as if they had utilized 2Mbps for the entire month. If this were the case, the cost could be driven down by sending data reducing the bandwidth to the 95th percentile thus knocking the 5% off.
Another criticism is the split calculation of inbound and outbound traffic. Since these are calculated separately, the highest value is used for billing and not the total sum. This is another issue that could cause for a surprising bill. Critics of this method prefer the flat rate billing system, the average amount of data transferred or billing per byte.
Web hosting providers offer many different types of billing. Some colocation providers even offer a 90% billing method to attract those with inconsistent bandwidth usage. There are so many different steps to getting a website up and running and ever-increasing options to keep it maintained. 95th percentile monitoring is a fair and effective billing method, but it’s generally more useful for individual users to find an alternative with a better fit.