[Snort-users] high packet loss - low throughput

Michal Purzynski michal at ...16244...
Thu Jul 18 05:07:40 EDT 2013


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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