Re: [j-nsp] unexpected results of traffic sampling

From: Anthony Pardini (tony@pardini.org)
Date: Fri Feb 01 2002 - 15:45:43 EST


Rate 100 is 100%.

try a: help reference forwrding-options rate

  [edit forwarding-options sampling input]

      Description

   Set the ratio of the number of packets to mark as candidates to be
   sampled. For example, if you specify a rate of 10, every tenth packet
   (1 packet out of 10) is marked as a candidate to be sampled.

On 31 Jan 2002, Przemyslaw Karwasiecki wrote:

> All,
>
> I am trying to setup cflowd collecting flows info from
> sampled traffic on one of our M20.
>
> Everything is working fine, but I don't understand how it is
> possible that despite of sampling only every 100th packets
> I see a lot of records about complete flows with more then
> a single packet.
>
> For me, it would imply that Juniper is actually sampling all
> packets in selected flows, which seems to be in a contradiction to
> "rate 100" parameter.
>
> Is there any mechanism implemented in Internet Processor II
> which is identifying all packets in the flow and sending them
> to Route Engine?
>
> How otherwise it is possible for /usr/sbin/sampled to see all
> packets from a single flow?
>
> I would appreciate any explanation of this,
>
> Thank you
>
> Przemek
>
>
> PS.
> This is my configuration
>
> interfaces {
> so-2/0/0 {
> unit 500 {
> description "OC3 PoS to UUNET";
> family inet {
> filter {
> input sample;
> }
> address xxx.xxx.xxx.xxx/30;
> }
> }
> }
> }
>
> forwarding-options {
> sampling {
> input {
> family inet {
> rate 100;
> run-length 0;
> }
> }
> output {
> cflowd xxx.xxx.xxx.xxx {
> port 2055;
> version 5;
> }
> }
> }
> }
>
> firewall {
> filter sample {
> term all {
> then {
> sample;
> accept;
> }
> }
> }
> }
>
>
>



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