[OpenSIPS-Users] How to overcome SIP ALG on Wi-Fi routers

[Bogdan-Andrei Iancu]

So far, yes. But to be 100% you need to check via a pcap the 
fragmentation flags in the IP packet(s) for the SIP INVITE. This will 
tell you (1) if the packet is fragmented and (2) if all the IP packets 
(UDP fragments) are present.

Regards,

Bogdan-Andrei Iancu
OpenSIPS Founder and Developer
http://www.opensips-solutions.com

On 17.05.2016 20:07, Nabeel wrote:
>
> In that case, the answer to your question seems to be that the UDP 
> packets did not reach the OpenSIPS server, because nothing was added 
> to the OpenSIPS logs using debug level 4. All of this seems to point 
> to the cause being UDP packet fragmentation. Is this correct?
>
> On 17 May 2016 4:24 pm, "Bogdan-Andrei Iancu" <bogdan at opensips.org 
> <mailto:bogdan at opensips.org>> wrote:
>
>     The TCP/IP stack of your server may decide to drop an UDP packet
>     if it cannot re-assemble it correctly (like not all the IP
>     fragments were received).
>     In such a case, you see the IP packets (carrying the fragments) on
>     network level, but they are never delivered at application level.
>
>     Regards,
>
>     Bogdan-Andrei Iancu
>     OpenSIPS Founder and Developer
>     http://www.opensips-solutions.com
>
>     On 17.05.2016 16:05, Nabeel wrote:
>>
>>         The next question - is this INVITE reaching your opensips
>>         script ? to be sure that the OS delivers the UDP packet to
>>         the opensips application.
>>
>>
>>     I don't have any firewall on my server. Why would the UDP packet
>>     get blocked between entering the server and reaching opensips
>>     script? The opensips server is running without errors. Other
>>     calls work fine.
>

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