[Snort-users] high packet loss - low throughput

Michal Purzynski michal at ...16244...
Fri Jul 19 05:16:37 EDT 2013


So, anyone got some ideas how to debug and improve the situation? Or 
should I just assume that snort isn't capable of handling a per process 
30Mbit - I can see a 5% packet loss now.

On 7/18/13 11:07 AM, Michal Purzynski wrote:
> On 7/18/13 3:39 AM, waldo kitty wrote:
>> On 7/17/2013 17:25, Michal Purzynski wrote:
>>> On 7/17/13 11:01 PM, waldo kitty wrote:
>>>> On 7/17/2013 16:04, Michal Purzynski wrote:
>>>>> Hello,
>>>>>
>>>>> I can see a strange results on a local snort installation. Either I
>>>>> don't understand something or the statistics aren't precise. 
>>>>> Please help
>>>>> me understand.
>>>>>
>>>>> It's an (expanding) two hosts snort setup with 2 x E5-2620 0 @ 
>>>>> 2.00GHz /
>>>>> 64GB RAM each.
>>>>> Intel x520 card.
>>>>> Traffic is around 1Gbit to each host.
>>>>> Around 3500 VRT only rules enabled.
>>>>> 8 snort instances load balanced by the pf_ring.
>>>> what else is this machine doing besides just snorting the traffic?
>>> netsniff-ng, barnyard, snort and that's it. Part of a Security Onion,
>>> but with most things (like Bro, argus, prads, etc) disabled.
>>>>> The traffic loss is very high - up to 9% per instance (as reported by
>>>>> Sguil which in turn read the snort logs and debug files). A single
>>>>> instance gets from 90 - 150Mbits of traffic and from 10 - 20k pps. To
>>>>> make it worse, the loss is not dependent on the traffic and/or pps at
>>>>> all. Actualy, sometimes I get a 5% of loss on 50Mbits to a single 
>>>>> instance.
>>>> what happens if you increase the number of snort instances which 
>>>> would thereby
>>>> reduce the load on each of the instances?
>>> I did it increasing from 6 to 8. And it won't help, really - if snort
>>> cannot keep up with 50Mbit / instance stream...
>> i'm not sure that it is snort, specifically... there is something 
>> causing the
>> data to be flushed or lost before it has a chance to be processed... 
>> there are
>> others running snort on pipes as large or larger...
>>
>> perhaps you are using protocol aware stream flushing and it needs 
>> tweaking?
> Yes, it's enabled with the same settings. Reading about it and I don't 
> really want to disable it.
>>
>> ###############################################
>> # Configure protocol aware flushing
>> # For more information see README.stream5
>> ###############################################
>> config paf_max: 16000
>>
>>
>> it may also be related to the timeout values in the stream5 settings??
>>
>>
> No idea, that's why asking here :) Everything is default.





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