[Kamailio-Users] Detecting Two Phones Behind Same NAT

[Daniel-Constantin Mierla]

Hello,

On 07/28/08 17:11, Ross Beer wrote:
> Hi Alex,
>  
> The problem I am having is that I am receiving one way audio or none 
> at all for some calls.
>  
> For example I have two pones behind the same NAT and they can call 
> each other without any problems, they can also call out through an 
> asterisk gateway. The problems occur when there are incoming calls 
> from the gateway.
>  
> I have looked at the SDP and they have local addresses, so I use the 
> fix_nated_sdp("15") option and calls from the gateways work, however 
> now calls between the two phones inside of the same NAT fail. I think 
> this is because the devices can talk to each other directly, however 
> when the SDP is changed to the NAT'ed address they can not.
>  
> If there is a way to check if they are behind the same NAT device, I 
> could then only fix_nated_sdp("15") only when needed.
the nat router box cannot bridge two local ports to close the loop. In 
case you have paralel forking for same user (many phones registered with 
same SIP id), then it is just a bit more complex as you have to play 
with branch_route.

The algorithm is:
- after lookup location and relaying is the place where you check if 
destination is behind nat
- at that point, if the destination is behind nat, the dst URI field is 
set ($du) to address of the nat router
- if the source ip is the same as the destination URI IP, then they come 
from same box, condition will be like:

if($si == $dd)
{
    # source IP and destination IP are the same
}

Cheers,
Daniel

>
>
> ------------------------------------------------------------------------
>
> > Date: Mon, 28 Jul 2008 09:50:20 -0400
> > From: abalashov at evaristesys.com
> > To: ross_beer at hotmail.com
> > CC: users at lists.openser.org
> > Subject: Re: [Kamailio-Users] Detecting Two Phones Behind Same NAT
> >
> > Ross Beer wrote:
> >
> > > Is there a way to detect two phones behind the same NAT device?
> >
> > What do you mean by "detect?"
> >
> > If they register, their Contacts will (presumably) be to different 
> NAT'd
> > signaling ports on the NAT device.
> >
> > --
> > Alex Balashov
> > Evariste Systems
> > Web : http://www.evaristesys.com/
> > Tel : (+1) (678) 954-0670
> > Direct : (+1) (678) 954-0671
> > Mobile : (+1) (706) 338-8599
>
>
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-- 
Daniel-Constantin Mierla
http://www.asipto.com