Wednesday, June 30, 2010

How is measured the monthly bandwidth usage

SkyHi @ Wednesday, June 30, 2010
What is Bandwidth ?

Bandwidth is a measure of data transfer. Computer data is fundamentally measured in bits, and bytes. Understanding the units of measure is necessary before you can do anything else. A Byte is simply 8 bits. In the world of computers measurements are conveniently represented by powers of two, while in the real world powers of ten are prevalent. This caused the confusing definition of "Kilobyte" to mean 1024 bytes instead of 1000 bytes as you might expect. Compounding the confusion, a Megabyte" is 1024 Kilobytes, or 1048576 bytes. A Gigabyte is 1024 Megabytes, or 1048576 Kilobytes, or 106954752 bytes. The number of bits or bytes per unit of time is referred to as bandwidth. Thus you see numbers such as 1.5Mbps (1,500,000 bits per second) 28.8Kb/s (28.8 Thousand bits per second) or 3GB/month (Three Gigabytes per month.)

The first lesson of understanding bandwidth is not to confuse Bits and Bytes. If you do, your numbers will be off by a factor of 8, which is usually pretty significant. Many vendors quote numbers in bits, because the result is 8 times larger and makes things look more impressve. Usually a lower-case 'b' indicates bit, and an upper case 'B' indicates byte, but you can't always rely upon that.

The second lesson is to understand that 'K' technically doesn't mean 1000, but everyone usually acts like it does. Minor discrepencies in numbers can usually be accounted for by this assumption. Unless you're talking about huge amounts of data, it's unlikely to make much difference. (less than 10% for even a Terabyte)

How is measured the monthly bandwidth usage

There are different schemes for paying for bandwidth.

I Real Data transfer ( Burstable Bandwidth)

Your host will provide you a graph ( usually MRTG graph) wich shows average bandwidth incoming and outgoing traffic in real-time. On this graph you will read several data as the Monthly Average Out and the Monthly average In.

To measure the real Monthly Data transfer used you have to use use the following equation:

  • Monthly Average Out + Monthly Average In / 8 bits x 60 seconds x 60 minutes x 24 hours x 30.5 days = total bandwidth used for the month.

    Note, some host providers counts only the Monthly Average IN or OUT. With them, you can save a lot of money.

    Sample of Measure of the real Monthly data transfer

  • Mrtg Graphs shows : Monthly average IN + OUT =1024 Kbps = 1 Mbps
  • 1024 kbps/8*60*60*24*30.5= 337305600 Kilobytes /1048576= 321 GB.

    Find here some conversion:

  • 1Mbps = 320GB
  • 10Mbps= 3200GB
  • 20Mbps =6400GB
  • 50Mbps=16000GB
  • 100Mbps =32000GB

    II Capped Bandwidth ( also unlimited transfer)

    Another common system is capped bandwidth, is simply to pay for the bandwidth that's available. For example, you might get 1 Mbps of bandwidth capped, and you can use all of it or none of it and pay the same amount. The network administrator will program the router to cap your usage at that amount.

    III The 95th percentile

    95th Percentile is a method of measuring bandwidth that bases your bill on peak utilization. Your bandwidth is measured from the switch or router and recorded in a log file. At the end of the month, your usage statistics are sorted, and the top 5%, or 37 hours, of data is thrown away, and that next measurement becomes your 'utilization' for the month.

    So, if you had a great weekend promoting your site, and used 3mb/sec for two days, you would be billed for the 3mb/sec rate -- potentially much more expensive than your average bandwidth utilization or actual utilization.

    Written by Peter Lee for