RE: 2.1.3rc1 Performance

[Gary_Portnoy () itginc com]

I'll know for sure tonight.  I am capturing exactly 1 million packets with 
tcpdump.  Tonight I'll connect two systems with a cross-over cable and run 
snort on one side with a stripped conf file and tcpreplay (Thanks Chad!) 
on the other side to dump out the packets.  I'll run this with both 
versions and see what gets reported.  If libpcap 0.7.2 keeps reporting 0 
dropped, I'll try to increase the rate to see if there is a point when it 
actually reports anything....

-gary-
-------------------------------------------
Gary Portnoy




"Kreimendahl, Chad J" <Chad.Kreimendahl () umb com>
05/20/2004 11:24 AM

 
        To:     "Darren Webb" <spyder007 () charter net>, <Gary_Portnoy () itginc com>
        cc:     <snort-users () lists sourceforge net>
        Subject:        RE: [Snort-users] 2.1.3rc1 Performance



The problem isn't freebsd, as far as anyone can tell.  The problem appears 
to be with libpcap 0.8.3.  Using 0.7.2 resolves this reporting of dropped 
packets problem.   At this point I'm not completely sure that 0.8.3 is 
actually dropping packets, but may just be reporting drops when there are 
none. 

-----Original Message-----
From: Darren Webb [mailto:spyder007 () charter net] 
Sent: Wednesday, May 19, 2004 11:55 PM
To: Gary_Portnoy () itginc com
Cc: snort-users () lists sourceforge net
Subject: RE: [Snort-users] 2.1.3rc1 Performance

We recently switched from Redhat based sensors to FreeBSD and noticed an
alarming jump in dropped packets as well.

You can also try this in addition to perfmon.  (FreeBSD 5.2.1 Snort 2.1.2
Libpcap 0.8.3)

Ps aux | grep snort
Kill -USR1 <pid>
Tail -100 /var/log/messages

(Of course, your commands will vary somewhat on Solaris.)

The output will show stats from when the Snort session was started.  You 
can
then check the frag2 and stream4 preprocessors for possible memory faults
and discarded packets.  We were seeing 40% to 80% packet loss at times and
by giving these preprocessors extra memory and defining the TTLs better in
the snort.conf file we are now at 1% or lower.

Hope this helps some.

Darren







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