Partial Fragments

elof2 at sentor.se elof2 at sentor.se
Fri Oct 24 06:31:59 EDT 2014


Hi Carter!

                                                                                            spkts     dpkts      sbytes       dbytes         state      ltime
...
...
02:56:56.508553  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.508553
02:56:56.509244  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.509244
02:56:56.509580  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.509580
02:56:56.516669  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.516669
02:56:56.516748  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.516748
02:56:56.531167  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.531167
02:56:56.531575  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.531575
02:56:56.531704  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.531704
02:56:56.535491  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.535491
02:56:56.536158  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.536158
02:56:56.537324  M    F      udp      10.20.20.20.59297  <->        10.10.10.10.443        8725    44994      1273843     45412854           CON    02:57:01.718200
02:56:56.540186  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.540186
02:56:56.541504  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.541504
02:56:56.543402  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.543402
02:56:56.546622  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.546622
02:56:56.550524  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.550524
02:56:56.552348  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.552348
02:56:56.560982  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.560982
02:56:56.566569  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.566569
02:56:56.568299  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.568299
02:56:56.570430  e    f      udp        10.10.10.10         ->      10.20.20.20               1        0          135            0           INT    02:56:56.570430
...
...and so on for tens of thousands of lines...



So, 10.20.20.20:59297 is talking to 10.10.10.10:443 via UDP.
44994 of the responses over the next minute was matched and hence 
connected to the above udp flow.
Within this traffic (and/or in the 8725 packets from the client), there 
were fragments, so this flow is flagged with a "F".

However, over this minute (and before), there seem to also have been tens 
of thousands of "partial fragments" (flagged "f").
Each such UDP packet gets logged as a new flow.
Result: the argus logfile grows exponentially in size.

(I noted this because the traffic logged above ran constantly for two 
hours, filling my harddrive)

Questions:

Q1: When is argus flagging something as a "Partial Fragment" ("f") and 
not a Fragment ("F")?

Q2: Why don't these packets also get matched to the udp flow, and 
increase the 44994 counter by the tens of thousands instead?

/Elof



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