[Asterisk-Users] "Received packet with bad UDP checksum" - whats the real problem?

Tim Karl tkarl at imminc.com
Wed Jul 27 16:23:04 MST 2005


I don't know if this will help, but the checksum is part of the UDP 
header which should be computed by the sender prior to the data being 
sent. It is computed using the data that is to be sent. UDP at the 
sender side performs the one's complement of the sum of all the 16-bit 
words in the segment. This result is put in the checksum field of the 
UDP segment. When it gets to the receiver all of the 16 bit words are 
added together with the checksum. If the result is all 1's, then there 
are no errors. Otherwise, there are errors. So, unless the hardware 
sending out the data is computing the checksum incorrectly, my guess is 
that it is network related.

--Timothy Karl

  Bryan Field-Elliot wrote:

> We have a customer trying to dial through our server, and our server 
> is throwing tons of these log messages:
>
> Jul 27 14:21:02 NOTICE[29210]: rtp.c:431 ast_rtp_read: RTP: Received 
> packet with bad UDP checksum
>
> Is it pretty certain, that these are caused by a bad or misconfigured 
> router along the path, or something else network-related? As opposed 
> to the SIP hardware itself? The SIP ATA is the same model in use by 
> many of our other customers, without any problems.
>
> Thank you,
>
> Bryan
>
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