[j-nsp] Juniper Netflow

[Servet]

Hi Guys

i have a problem with juniper netflow traffic values, i think there is no problem about the config and flow-analyser. If i use a cisco device, the results of snmp polls and results of the flow-analyser are similar 
But in juniper; i get 180 mbit/s traffic value with SNMP requests from my juniper MX-960 router, but netflow says me it is 120mbit. Also my sampling rate is 1.
You can see config below, do you have any idea?  why i can't get similar results from snmp and netflow
Kind regards

  

sampling {
    input {
        family inet {
            rate 1;
            run-length 1;
            max-packets-per-second 65535;
        }
    }
    output {
        cflowd x.x.x.x {
            port 9996;
            version 5;
            autonomous-system-type origin;
        }
        flow-inactive-timeout 600;
        flow-active-timeout 60;
        interface sp-4/1/0 {
            source-address y.y.y.y;
        }
    }
}