4 Replies Latest reply on Mar 2, 2015 12:16 PM by mharvey

    how to calculate bandwith utilization

      I want to know how NPM calculate  bandwidth utilization I used this formula found in thwack

       

      Bandwidth Utlization formula:

      Utilization:  The average percentage of bandwidth utilization rates the report period.

       

      Bandwidth Utilization   | (Total Bytes In + Total Bytes Out) x 8 x 100% |

                                          |---------------------------------------------    |  / report period

                                          |  (Speed In + Speed Out)                                 |

       

       

      still I don't get the utilization that shown in the interface detail page . please tell me how to calculate this ,

       

      thank you

        • Re: how to calculate bandwith utilization
          ecklerwr1

          Cisco suggests it is calculated this way:

          Problem

          It is sometimes necessary to calculate bandwidth use with SNMP.

          Solution

          Use this solution to solve this problem.

          How you calculate use depends on how data is presented for what you     want to measure. Interface use is the primary measure used for  network use. Use     this formulas, based on whether the connection you measure is  half-duplex or     full-duplex. Shared LAN connections tend to be half-duplex, mainly  because     contention detection requires that a device listen before it  transmits. WAN     connections are full-duplex because the connection is  point-to-point; both     devices can transmit and receive at the same time because they know  there is     only one other device that shares the connection. Because MIB-II  variables are     stored as counters, you must take two poll cycles and figure the  difference     between the two (hence, the delta used in the equation).

          This explains the variables used in the formulas:    

          calculate_bandwidth_snmp.gif

          Note: ifSpeed does not accurately reflect the speed of a WAN  interface.      

          For half-duplex media, use this formula for interface use:    

          calculate_bandwidth_snmp1.gif

          It is more challenging to calculate for full-duplex media. For  example,     with a full T-1 serial connection, the line speed is 1.544 Mbps.  Therefore, a     T-1 interface can both receive and transmit 1.544 Mbps for a  combined possible     bandwidth of 3.088 Mbps!

          When you calculate the interface bandwidth for full-duplex  connections,     you can use this formula, where you take the larger of the in and  out values     and generate a use percentage:

          calculate_bandwidth_snmp2.gif

          However, this method hides the use of the direction with the lesser     value and provides less accurate results. A more accurate method is  to measure     the input use and output use separately, with this formula:    

          calculate_bandwidth_snmp3.gif

          These formulas are simplified because they do not consider overhead     associated with the protocol. For example, refer to RFC 1757     Ethernet-utilization formulas that consider packet overhead.

          All of the MIB attributes listed are also in     RFC1213     MIB.

          Details of the MIB variables used in these formulas are:

          .1.3.6.1.2.1.2.2.1.10
          ifInOctets
          OBJECT-TYPE
          -- FROM RFC1213-MIB, IF-MIB
          SYNTAX          Counter
          MAX-ACCESS      read-only
          STATUS          Mandatory
          DESCRIPTION    "The total number of octets received on the interface, including framing characters."
          ::= { iso(1) org(3) dod(6) internet(1) mgmt(2) mib-2(1) interfaces(2) ifTable(2) ifEntry(1) 10 }

          .1.3.6.1.2.1.2.2.1.16
          ifOutOctets
          OBJECT-TYPE
          -- FROM RFC1213-MIB, IF-MIB
          SYNTAX          Counter
          MAX-ACCESS      read-only
          STATUS          Mandatory
          DESCRIPTION    "The total number of octets transmitted out of the interface, including framing characters."
          ::= { ISO(1) org(3) DOD(6) Internet(1) mgmt(2) mib-2(1) interfaces(2) ifTable(2) ifEntry(1) 16 }

          .1.3.6.1.2.1.2.2.1.5
          ifSpeed
          OBJECT-TYPE
          -- FROM RFC1213-MIB, IF-MIB
          SYNTAX          Gauge
          MAX-ACCESS      read-only
          STATUS          Mandatory
          DESCRIPTION    "An estimate of the interface's current bandwidth in bits per second. 
          For interfaces which do not vary in bandwidth or for those where no accurate estimation can be made,
          this object should contain the nominal bandwidth."
          ::= { ISO(1) org(3) DOD(6) Internet(1) mgmt(2) mib-2(1) interfaces(2) ifTable(2) ifEntry(1) 5 }