95th Percentile Bandwidth Charging

Posted October 21st, 2007 in Networking

I am currently in the process from moving my sites over from physical servers in a co-location cabinet to a VPS (Virtual Private Server) and moving from 95th Percentile Bandwidth Charging to data charging. My new provider provides "unlimited" domestic traffic and 50GB of international bandwidth on the plan I have selected.

Part of the reason I am changing from my current set up is because I currently host servers for several customers, but a swing in data from domestic to international has made it unfeasable for me to continue hosting other people's servers unless I either a) increase their monthly charges or b) take on a number of new customers. I'm not particularly interested in the stress of hosting any more which is why I am moving on.

The swing from domestic to international bandwidth I mentioned in the last paragraph, is due almost entirely to Xtra, New Zealand's largest ISP, partnering with Yahoo! and moving their email hosting to Australia. Moving their email hosting out of New Zealand to Australia doesn't make much sense anyway, but I suspect a number of people such as myself are being hit with additional charges because of their move.

The main reason my international bandwidth charging has been affected by this move is because one of the servers I host is an email marketing server, and naturally there are a lot of Xtra mail accounts being emailed from it.

This is illustrated by the bandwidth charts below. Normally the 95th percentile for international bandwidth to my cabinet would be around the 64 to 128kbps mark (I get billed in 64kpbs increments for international). At the start of the first chart (August to September) you can see it's still falling within this range. And then around the middle of August it starts to pick up. This is around the time Xtra moved their email hosting to Australia.

The large spikes that can be seen in the above charts are caused when email campaigns are being sent out, and are what help to push the 95th percentile up. Due to Xtra moving their mail servers from New Zealand to Australia, my international bandiwdth utilisation has gone from around 64 to 128kpbs per month to about 256 to 320kpbs per month, with an associated hit in the pocket to boot.

Until this happened, I have found in the past 95th percentile bandwidth billing to be really quite good. Overall the amount of data to my cabinet has increased about 3 to 4 times in the past couple of years, but with no associated increase in monthly charges. However, due to the expense of international bandwidth to New Zealand, and Xtra moving their mail servers to Australia, I've had to review this type of billing. If I were to remain with my current providers then I'd need to move to blocks of GB charging, which is how my new provider is billing me.

In case you don't quite understand how 95th percentile bandwidth billing works, here's the definition from the terms and conditions of my contract:

"Uncapped 95th Percentile Bandwidth Option: Uncapped bandwidth purchased in 64Kbps (typically international traffic) or 1Mbps (typically national traffic) components will be calculated on a '95th percentile' basis. (i.e. measurements of bandwidth utilisation calculated from the hourly average data collection of the 5 minute interval measurements throughout The Customer's monthly billing period. [ISP Name] ignores the top 5% bandwidth utilisation peaks in its utilisation of both inbound and outbound bandwidth respectively). This calculation is performed at the end of each billing period. The higher of either the inbound or outbound bandwidth utilisation determines The Customer's monthly bandwidth fee for the month. Bandwidth charges under this option are likely to vary from month to month due to high level of burstability of bandwidth available to The Customer’s server(s)."