[Serusers] RTPProxy h/w and s/w

[Nithin Rajagopal]

Valentin -
>> I am newbie to this field. We are trying to use a separate card for 
>> handling the rtp voice traffic but use the RTPProxy (IPtel) software to 
>> handle the  NAT issues. We have been fairly successful in doing that.
>> The problem now is to handle asymmetric NATs. I hear one way audio.
>>     
>
> What do you mean as "asymmmetric NAT"?
> Cone NAT or asymmetric RTP client behind NAT?
>   
The NAT uses one port to transmit to the outside world and receiveds on 
an other port during the call. This NAT (Linux router/gateway for the 
end point like an ATA or softphone) is at customer location. I gather 
from the customer that the the end point (client behind NAT) is 
symmetric w.r.t its RTP port (same port for tx and rx of the RTP stream).
>> We are not sure how to handle this when there is one machine running 
>> rtpproxy software and another card with a different IP handling the SDP 
>> (In nathelper.c of Openser new_ip= card IP). In the symmetric NAT 
>> scenario this works fine. I would appreciate and pointers to modify 
>> rtpproxy for this configuration.
>>     
> So I suppose you mean asymmetric client behind NAT, don't you?
> It's more hard case. But if only signaling IP and IP for RTP
> differs, it's good. 
The signaling IP and RTP IP are not the same.

> Problems (almost unavoidable) appear if
> client's source RTP address differs from destination RTP address
> (specified in SDP), "address" here means both host and port.
>   
The destination IP of the RTP channel opened in the card which works in 
conjunction with rtpproxy is the IP of the NAT router/gateway and source 
IP of the RTP stream coming into this card handling RTP stream is also 
that of the same router/gateway. But the ports are different. Do you 
think this is the problem?

Please note-
We use rtpproxy 0.3, Opneser 1.1.0.

 -the card only handles RTP data and has its
  own GbE port

 - made changes to nathelper.c nathelper.cfg
  source code to account for separate IP addrs

- made changes to  RTPProxy to open channels for RTPtraffic flow on the 
card.

-Openser,RTPProxy and the card , all 3 different Public IPs

Thank you for the response.

Regards
Nithin