[Snort-devel] Average delay per packet observation

Navdeep Uniyal Navdeep.Uniyal at neclab.eu
Fri Jul 7 04:52:16 EDT 2017

Thank you for your reply.

In my case I am using a set of 5 rules repeated over(with different sid). So approximately each set should take the same amount of time relatively.
Example: 80 rules have (16*5) rules
                    40 rules have (8*5) rules
                    20 rules have (4*5) rules
                    10 rules have (2*5) rules

By this way, I assume the delay should get halved in each case from 80 to 40. But this is not happening as we can see from the results. Could you please help me in getting the explanation.

Best Regards,

From: Steven Sturges [mailto:ststurge at cisco.com]
Sent: Mittwoch, 5. Juli 2017 13:43
To: Navdeep Uniyal; snort-devel at lists.snort.org
Subject: Re: [Snort-devel] Average delay per packet observation

Rules are not processed sequentially.  Your expectations should depend on the nature of the

individual rules themselves.
On 7/4/17 10:16 AM, Navdeep Uniyal wrote:
Hello everyone,

I got some interesting results running snort (inline) for experiment with 80, 40, 20, 10 number of rules:
All rules are matching all the incoming UDP packets. Below are the average delay per packet I found in the 4 experiments:

80 rules:              Average delay:  0.000680666813409 seconds
40 rules:              Average delay:  2.06440535385e-08 seconds
20 rules:              Average delay:  1.6644513569e-08   seconds
10 rules:              Average delay:  1.43723338507e-08 seconds

These results are quite confusing as I expect, on decreasing from 80 to 40 rules the average delay should be approximately halved. But I can't see such behavior here.

What could be the possible reason, if someone could explain.

Best Regards,


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