[SR-Users] NAT problem with recvonly calls

[Richard Fuchs]

Use IPv6 😃

Cheers

On 07/12/2020 23.01, David Cunningham wrote:
> Hello,
>
> We have a problem with a SIP doorbell device which sends media one way 
> only, and NAT at the receiving device.
>
> When the doorbell button is pressed it makes a call to a configured 
> destination. Since the doorbell only sends and doesn't receive it 
> sends the INVITE with sendonly in the SDP, and the destination then 
> replies with a 200 OK with recvonly in the SDP. The problem is that 
> the destination is behind NAT, and its reply contains a private 
> network IP in the SDP.
>
> Normally Asterisk when nat=yes works around that by adjusting the 
> destination for RTP to be the address it actually receives audio from, 
> however because this device is recvonly Asterisk never receives audio 
> from it. This means Asterisk keeps trying to send the doorbell's RTP 
> to the private network IP which of course fails, and the destination 
> never gets the RTP from the doorbell.
>
> We haven't found a solution in Asterisk to this, so are now looking to 
> Kamailio which acts as a load-balancing proxy in front of Asterisk for 
> one. For example, maybe we could use fix_nated_sdp, but only on 200 
> OK's with recvonly.
>
> Has anyone else encountered this, and are there any recommended solutions?
>
> Thank you in advance!
>
> -- 
> David Cunningham, Voisonics Limited
> http://voisonics.com/ <http://voisonics.com/>
> USA: +1 213 221 1092
> New Zealand: +64 (0)28 2558 3782
>
> _______________________________________________
> Kamailio (SER) - Users Mailing List
> sr-users at lists.kamailio.org
> https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
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