How the interface traffic probe calculates the utilization of interfaces.

Document ID : KB000037271
Last Modified Date : 28/03/2018
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Introduction:
The interface_traffic probe will query the configured hosts for SNMP data on every predefined interval. Network traffic data will be collected according to a user-setup. The probe may be configured to monitor the network interface (on a PC, UNIX system, router, switch etc.) and report whenever the traffic breaches a predefined threshold.
Question:

How to interface traffic probe calculates the utilization of interface.

 

 

The below command and example for calculation of interface_traffic probe

tdiff = (double)curr.sysUptime/100 - (double)cif->previous.sysUptime/100;

Current OutOctet = 715026517864

Previous OutOctet = 712975047817

Difference = 2051470047 (delta value)

Actual delta = 2051470047/tdiff (2051470047/516) = 3975717

maxspeed=1250000

When you create a % of delta (i.e. pctOctet) = (Actual delta *100/ maxspeed)

Calculation is= 3975717*100/1250000=>318.05

As you can see, value is coming more than 100 but we restrict this value to 100% which you can see in your alarm message.

You can verify this calculation through snmpwalk for device IP 192.168.254.31 where interface id is 553 (GigabitEthernet3/1/41)

OIDifDescr= 1.3.6.1.2.1.2.2.1.2. (find GigabitEthernet3/1/41 index, as per log it should be 553)

OIDifHCInOctets= 1.3.6.1.2.1.31.1.1.1.6.553

OIDifHCOutOctets= 1.3.6.1.2.1.31.1.1.1.10.553

OIDifHighSpeed= 1.3.6.1.2.1.31.1.1.1.15.553

OIDifInOctets= 1.3.6.1.2.1.2.2.1.10.553

OIDifOutOctets= 1.3.6.1.2.1.2.2.1.16.553

OIDifSpeed= 1.3.6.1.2.1.2.2.1.5.553

 

 

Environment:
CA UIM version 8.2, 8.51
Interface traffic 5.45
 
Answer:

The below command and example for calculation of interface_traffic probe
tdiff = (double)curr.sysUptime/100 - (double)cif->previous.sysUptime/100;
Current OutOctet = 715026517864
Previous OutOctet = 712975047817
Difference = 2051470047 (delta value)
Actual delta = 2051470047/tdiff (2051470047/516) = 3975717
maxspeed=1250000
When you create a % of delta (i.e. pctOctet) = (Actual delta *100/ maxspeed)
Calculation is= 3975717*100/1250000=>318.05
As you can see, value is coming more than 100 but we restrict this value to 100% which you can see in your alarm message.
You can verify this calculation through snmpwalk for device IP 192.168.254.31 where interface id is 553 (GigabitEthernet3/1/41)
OIDifDescr= 1.3.6.1.2.1.2.2.1.2. (find GigabitEthernet3/1/41 index, as per log it should be 553)
OIDifHCInOctets= 1.3.6.1.2.1.31.1.1.1.6.553
OIDifHCOutOctets= 1.3.6.1.2.1.31.1.1.1.10.553
OIDifHighSpeed= 1.3.6.1.2.1.31.1.1.1.15.553
OIDifInOctets= 1.3.6.1.2.1.2.2.1.10.553
OIDifOutOctets= 1.3.6.1.2.1.2.2.1.16.553
OIDifSpeed= 1.3.6.1.2.1.2.2.1.5.553
Additional Information:
In addition to monitoring the interface traffic, the probe will monitor error packets, discarded packets, queue length and interface status. It will also report on "dead" lines (no traffic).