In this blog I am going to talk about how NetFlow Analyzer reports speed and utilization and what is the use of bandwidth command used on the router.

ManageEngine NetFlow Analyzer is the first NetFlow solution to offer one minute granularity for speed, volume and utilization reports. Additionally, the product even lets you drill down from any minute and find the conversations causing this traffic giving you sub minute visibility.

We will now see how speed and utilization is calculated for a particular minute using the NetFlow exports.

Consider any report from NetFlow Analyzer with a reporting granularity of 1 minute. Here the speed value of any particular minute is calculated by adding the transmission volume of all the conversations happening on that particular minute from the interface and the value is divided by 60 seconds to derive speed.

Lets take an example scenario for better understanding.

Speed Calculation:

Let say at 10:10 - total IN traffic is 50 MB (Volume is always represented in Bytes).

Now the speed is 50 MB * 8 / 60 (The multiplication by 8 is to convert the volume to bits and division by 60 (seconds) to get the speed.)

So, from the above calculation data rate at 10:10 is 6.67 Mbps (Speed is always represented in bits per second)

Utilization calculation:

Now that the link usage at 10:10 is 6.67 Mbps, utilization can be defined as how much of the actual link capability was used for transmission of traffic.

Utilization = (Usage rate /Actual link speed) * 100. So for an 8Mbps link, the utilization is:   (6.67 Mbps /8 Mbps) * 100 = 83 %

This is how the utilization is calculated in NetFlow Analyzer every minute

What is bandwidth command in router?

Often users complain about not getting the speed set at the interface in the product or about incorrect utilization reports. User data rate depends on the operating link speed/bandwidth and not the bandwidth configured in the interface using the IOS bandwidth command. The bandwidth configured on the interface is to help routing protocols choose the best route to transmit the packets. We recommend our users to set the link speed as the bandwidth in the interface for efficient routing.

NetFlow Analyzer reports the actual data rate on the link and is not based on the bandwidth set on the interface. However, since NetFlow Analyzer fetches the link speed via SNMP from the router based on the bandwidth speed set, the utilization calculation will be effected.

So it is important to set the right speed using the bandwidth command to get better routing efficiency and correct reports in NetFlow Analyzer. And it is not possible to get the faster throughput from any interface by configuring a faster speed using bandwidth command.

With this information users should be in a better position to see the right utilization reports in NetFlow Analyzer for real time traffic and also get the efficient routing for network traffic.

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Regards,
Don Thomas Jacob