Burstable Bandwidth and the 95th Percentile - what does it mean?

Burstable Bandwidth and the 95th Percentile - what does it mean?

Every day, the provision of scalable, reliable and robust connectivity is becoming more important to the enterprise. Organisations continue to increase adoption of cloud technologies, utilise online communication tools to collaborate and often operate their own web facing applications.

Now, not only is the availability of the connection critical, but that connectivity must perform optimally in order to ensure that no bottlenecks, undue latency or jitter issues impact user experience.

So when we purchase bandwidth, we want to balance these requirements with the commercial concerns relating to enterprise class connectivity services.

Burstable Bandwidth a facility that allows clients to automatically consume greater bandwidth than the contracted amount for short periods of time at no additional cost. 95th Percentile Billing is the method of billing excess usage.

So how does it work?

You acquire a 10Mbps synchronous network (€50 per Mb for this example) with burstable bandwidth limited to 40Mbps. Now, over a period of 30 days, your ISP will take a measurement of usage every 5 minutes (that’s 8,640 measurements). At the end of the billing cycle, the ISP removes the top 5% (432 measurements) and discards them. The next highest measurement is then taken and that figure is used for billing.

So, let’s say that after removing the first 5% (which is 36 hours by the way), the highest remaining reading is 9Mbps. In this case there is no additional charge as it falls under your contracted rate of 10Mbps. Billing is as follows:

10Mb x €50 = €500 (nice and simple!)

However, if this reading was 17Mb, then the ISP will take the 7Mb excess and bill this at a premium (usually about 20%). In this case, you will be billed as follows:

(€500 normal billing) + (7Mb x €50 x 120%) = €920

When is 95th percentile billing a good idea?

Using burstable bandwidth is a good idea when you know your normal working requirements are below a certain level, but want to facilitate short term bursts of activity without paying for increased bandwidth. For example, you may have a daily routine that hogs bandwidth for half an hour or a regular month end activity that requires a 12 hour data dump. You may even want to mitigate potential DDoS impacts. Once you are confident that you won’t consistently use the excess, then it’s a great facility.

When is it not?

Put simply, if your organisation consistently uses higher bandwidth than the contracted rate for over 5% of the month, then you need to either fix the limit (remove bursting) or increase the capacity. Another potential hazard is if consumption in a given period is unduly high and not properly monitored, you may get an unwelcome surprise when you get your next bill!

Servecentric is a Dublin based provider of Cloud, Connectivity and Data Centre Colocation services. For more information, visit https://www.servecentric.com

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