[Snort-users] 2.1.3rc1 Performance

Gary_Portnoy at ...11307... Gary_Portnoy at ...11307...
Tue May 18 13:21:03 EDT 2004

Yesterday I replaced my 2.1.1RC1 build with 2.1.3RC1.  Today I checked the 

perfmon stats and nearly fell off my chair.  They are reporting that snort 

is dropping on average about 15% of traffic.  With 2.1.1RC1 perfmon has 
always reported 0% pkts dropped and I believed it.  Now I am seeing that 
there are times when snort is dropping as much as 89%, and that is at 
times with only 0.9mbps throughput and using 11% of the cpu.  Some other 
times i am seeing drop rates of 12% with 5.1mbps throughput while using 
77% of the cpu.

Two questions:

1.  Is there a bug with reporing stats in 2.1.3 or was there one in 2.1.1 
where %pkts dropped simply wasn't reported?  Or is snort 2.1.3rc1 just 
that much less efficient?

2.  What is the most common bottleneck: the cpu or the nic?  In other 
words, why would i be dropping 89% of the traffic while using only 11% of 
the CPU sometimes while at other times I am dropping much less with more 
cpu used?

Gary Portnoy

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