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New Member

DFM Bandwidth Utilization Calculation

If I have a 100Mb full duplex link and it is transmitting at full capacity but receiving a negligible amount of traffic will DFM show this as being 50% utilised or 100%?

You can see my quandary, what do I set my threshold to? If I leave it at 40% I could get alarms when the link is transmitting at half capacity and receiving at half capacity i.e. 50% utilization. If I set it at 60% the link could be transmitting at full capacity and receiving negligible traffic, the utilization would be 50+% and not alarmed!

The first of these two situations is ok but I get an alarm, the second is not ok but significantly I do not get an alarm.

Can someone please advise on how DFM calculates utilization and what I should set my threshold to.

Thanks,

Paul

3 REPLIES
Cisco Employee

Re: DFM Bandwidth Utilization Calculation

Here is the formula ,it is explained here in a general mathematical language ,this calculation shows how current utilization is calculated .

if NetworkAdapterOperational && UtilizationThreshold < 100 &&

MaxSpeed > 0 && DuplexMode != ICIM_NetworkAdapter::UNSPECIFIED

Check

TrafficRate >= 0 && CurrentUtilization > UtilizationThreshold;

CurrentUtilization = ((TrafficRate * 8) / MaxSpeed * 100;

TrafficRate =

= ifInOctetsRate + ifOutOctetsRate; if DuplexMode is HALFDUPLEX

= max(ifInOctetsRate, ifOutOctetsRate); if DuplexMode is FULLDUPLEX

ifInOctetsRate = rate(ifInOctets, PollingInterval);

ifOutOctetsRate = rate(ifOutOctets, PollingInterval);

UtilizationThreshold = 40

New Member

Re: DFM Bandwidth Utilization Calculation

I take it that the line 'max(ifInOctetsRate, ifOutOctetsRate)' in english is use the maximum of ifInOctetsRate OR ifOutOctetsRate?

If so this is exactly how I would like it to work i.e. calculate the utilisation for either the transmit or recieve, whichever is the greater. This means if sending at 75% and receiving at 30% and the threshold is 60% I will get an alarm for the 75%.

Excellent stuff, where did you get the information from?

Cisco Employee

Re: DFM Bandwidth Utilization Calculation

I believe that is the case, I would need to doublecheck.

I got this information from one of the developers I worked a DFM case with a while back.

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