Decompression Failing for multiple UDP stream

Asked by Khaan on 2011-12-09


Incase of multiple UDP servers sending data to a Machine "A" Decompression fails and due to CRC failing. This pattern is periodic and it only happened with the fast rate UDP stream. Im unable to identify the UDP stream as I have log for 2 UDP transmission servers as follow,

Compressing Packet #1
Compressing Packet #1

decompressing #1
decompressing #2

SN seems to be not unique too, is there any possible solutions/debugs?


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I reformulate your problem to be sure to correctly understand it:
 - you send several UDP streams to machine A across a ROHC
   compressor/decompressor pair,
 - a regular interval of time the decompressor reports a CRC failure
   while decompressing a ROHC packet.

Is it correct?

To debug this kind of problem, you may:
 - Capture the uncompressed UDP streams before they go across the
   compressor/decompressor pair. You may use tcpdump for example
   (with tcpdump please use option -s0 to avoid to truncate packets).
 - Start the UDP streams that cause the problem.
 - Wait for the problem to be reproduced.
 - Stop the decompressor and the network capture.
 - Look at the decompressor traces. Search for the CRC failure. Collect
   information about the paquet in the traces (IP addresses, UDP ports...).
   You should also find a dump of the (malformed) decompressed packet.
 - Try to identify the corresponding packet in the network capture.
 - When found, compare the packet from the capture with the one dumped
   in the decompressor traces.

The differences you may find between the 2 packets often give some information
about the problem. Contact me on the mailing list if you need some help for
further analysis.


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