Re: TCP stream processing performance

["Al Lewis (allewi)" <allewi () cisco com>]

TCP segment traffic has to be reassembled/reordered in the correct format before rules are applied. The same thing goes 
for fragmented traffic. If there are a lot of fragments Frag3 has to reassemble them.


<http://manual-snort-org.s3-website-us-east-1.amazonaws.com/node17.html#SECTION00323000000000000000><http://manual-snort-org.s3-website-us-east-1.amazonaws.com/node17.html#SECTION00323000000000000000>http://manual-snort-org.s3-website-us-east-1.amazonaws.com/node17.html#SECTION00323000000000000000



Albert Lewis
QA SNORT/Sourcefire
SOURCEfire, Inc. now part of Cisco
9780 Patuxent Woods Drive
Columbia, MD 21046
Phone: (office) 443.430.7112
Email: allewi () cisco com<mailto:allewi () cisco com>


From: Kevin Wang <kevin.wang () Istuary com<mailto:kevin.wang () Istuary com>>
Date: Monday, June 27, 2016 at 5:59 PM
To: 'snort-users' <snort-users () lists sourceforge net<mailto:snort-users () lists sourceforge net>>
Subject: [Snort-users] TCP stream processing performance

Hello,

I am looking at Snort performance and I found that in the Preprocessor profile statistics, “s5” or “s5tcp” is taking a 
lot of time. My understanding is that s5tcp is for TCP stream reassembly and the time taking is mostly due to the 
buffering and mis-ordered packets. The actually processing by the CPU is relatively short. Is my understanding correct 
or there is other intense processing going on?

Thanks,
Kevin
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