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====== Merge multiple thin PCAP files into a single thick PCAP ======

When you install Trisul Network Analytics , you get a free command line tool called ''trisul_ixmgtool''

This tool has a unique capability to **squish** PCAP files that is very handy to create fat pcap files useful for testing. This article explains how this free tool works.

===== What is a FAT pcap file =====
 
A FAT pcap file contains more unique flows and endpoints than a THIN pcap file.   

While testing NSM((Network Security Monitoring))  platforms we look for FAT pcap files because it stresses the memory and performance of algorithms.  Given a 10GB //thin// PCAP file with just 1 flow, and a 1GB //fat//  PCAP file with 100K flows - you should prefer the FAT file for testing.

FAT PCAP files can be hard to obtain.  You might get them from large corporate border networks for private use, but in general it is quite hard to come across these. 

With the //trisul_ixmgtool// you can merge multiple thin PCAPs into a single fat PCAP file.

===== How is it different from mergecap  =====

Mergecap  is a command line [[https://www.wireshark.org/docs/man-pages/mergecap.html|utility from the wireshark]] project.  It also combines multiple thin PCAP files into a single  fat PCAP file. But it preserves the timestamps, hence works to //fatten// the output PCAP if there is significant overlap in the time windows.

trisul_ixmgtool when run with the squish option , aligns the timestamps  of the files to the lowest timestamp and then processes the merge.  The following diagram illustrates the difference between mergecap and ixmgtool

{{:pcaps:ixmgtool.png |}}


====== trisul_ixmgtool ======

To get the free ixmgtool [[https://trisul.org/download|install Trisul Probe]] , you will find the trisul_ixmgtool in ''/usr/local/bin''

**Usage**

<code>
unpl@unpl:~$ trisul_ixmgtool 
Usage : ixmgtool [-squish|-squish10]  -r home-dir f1 f2 f3 f4 f5 ..  -out outfile 
</code>

**Options**

  * ''-squish''  :  align the timestamps to the lowest found and merge
  * ''-squish10'' : fatten by 10 TIMES by taking each TCP flow and making 10 extra duplicate flows by changing the source IP address 10 different IPs in the  10.0.0.x range 

If you run without the squish options, ixmgtool is the same as mergecap.





===== Example run =====

Say you have put 10 files in a directory  and you want to create a single FAT file. 

<code>
unpl@unpl:~/wr$ ls -lh 
total 2.5G
-rw-rw-r-- 1 unpl unpl 119M Mar 15 20:14 wrccdc.regionals.2019-03-01.111129006380000.pcap
-rw-rw-r-- 1 unpl unpl 112M Mar 15 20:14 wrccdc.regionals.2019-03-01.111133006390000.pcap
-rw-rw-r-- 1 unpl unpl 124M Mar 15 20:14 wrccdc.regionals.2019-03-01.111138006400000.pcap
-rw-rw-r-- 1 unpl unpl 125M Mar 15 20:14 wrccdc.regionals.2019-03-01.111143006410000.pcap
-rw-rw-r-- 1 unpl unpl 106M Mar 15 20:14 wrccdc.regionals.2019-03-01.111147006420000.pcap
-rw-rw-r-- 1 unpl unpl 110M Mar 15 20:14 wrccdc.regionals.2019-03-01.111151006430000.pcap
-rw-rw-r-- 1 unpl unpl 107M Mar 15 20:14 wrccdc.regionals.2019-03-01.111155006440000.pcap
-rw-rw-r-- 1 unpl unpl 105M Mar 15 20:14 wrccdc.regionals.2019-03-01.111159006450000.pcap
-rw-rw-r-- 1 unpl unpl 112M Mar 15 20:14 wrccdc.regionals.2019-03-01.111203006460000.pcap
-rw-rw-r-- 1 unpl unpl 119M Mar 15 20:14 wrccdc.regionals.2019-03-01.111206006470000.pcap
-rw-rw-r-- 1 unpl unpl 113M Mar 15 20:14 wrccdc.regionals.2019-03-01.111210006480000.pcap
-rw-rw-r-- 1 unpl unpl 118M Mar 15 20:14 wrccdc.regionals.2019-03-01.111215006490000.pcap

</code>

Running the following command 

<code>

unpl@unpl:~/wr$ trisul_ixmgtool -squish -r . *.pcap -out fatone.pcap


EOF on wrccdc.regionals.2019-03-01.111203006460000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111159006450000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111147006420000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111143006410000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111210006480000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111206006470000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111151006430000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111155006440000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111129006380000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111138006400000.pcap, bye ! 
Done.

</code>

results in a fat pcap

<code>
unpl@unpl:~/wrccdc$ ls -lh fatone.pcap 
-rw------- 1 unpl unpl 1.2G Apr 13 13:29 fatone.pcap
</code>


To get a **really fat pcap** you can use the squish 10 option



<code>
unpl@unpl:~/wrccdc$ trisul_ixmgtool -squish10 -r . *.pcap -out really_fatone.pcap

5000000 Packets  15005458762 Bytes Time Fri Mar  1 19:11:31 2019-475695
EOF on wrccdc.regionals.2019-03-01.111203006460000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111159006450000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111147006420000.pcap, bye ! 
8000000 Packets  23767761206 Bytes Time Fri Mar  1 19:11:32 2019-940185
EOF on wrccdc.regionals.2019-03-01.111143006410000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111210006480000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111206006470000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111151006430000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111155006440000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111129006380000.pcap, bye ! 
EOF on wrccdc.regionals.2019-03-01.111138006400000.pcap, bye ! 

unpl@unpl:~/wrccdc$ ls -lh really_fatone.pcap 
-rw------- 1 unpl unpl 13G Apr 13 13:35 really_fatone.pcap

</code>


====== Conclusion ======


The trisul_ixmgtool part of the Trisul NSM suite can be used for free to create FAT pcaps which can be very useful for stressing NSM solutons.  We use this in Trisul NSM to help users download PCAPs of various investigations.  

Using the squish options you can create a mega thick PCAP file for testing by throwing all your PCAP testing files in single directory from varying timestamps and creating a single thick one. 

Hope this is useful for the NSM community. 


To get the tool : Install the Trisul Probe package for your platform from  the [[https://trisul.org/download|Trisul Download page]]
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