RE: 2.1.3rc1 Performance

["Kreimendahl, Chad J" <Chad.Kreimendahl () umb com>]

If you run snort on that interface... You can kill -USR1 <pid> and it
will dump stats to syslog.  I'd also make sure to run a few different
tests.

You can tell tcpreplay to replay the packets at a certain rate, or even
at a certain multiplication of the original timing.   I'd recommend
doing it normal, doing it at twice the speed, and then doing it as fast
as possible for each of the two pcaps.    

-----Original Message-----
From: Gary_Portnoy () itginc com [mailto:Gary_Portnoy () itginc com] 
Sent: Thursday, May 20, 2004 11:10 AM
To: Kreimendahl, Chad J
Cc: snort-users () lists sourceforge net; Darren Webb
Subject: RE: [Snort-users] 2.1.3rc1 Performance

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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