[Users] UA behind NAT puts public IP in Contact, Via - help

[Bogdan-Andrei Iancu]

Hi Arek,

Arek Bekiersz wrote:

> Hi Bogdan,
>
>
> Thanks for all the help.
>
> Bogdan-Andrei Iancu wrote:
>
>> Hi Arek,
>> looking on the signalling, you cannot detect the call as nated from 
>> proxy point of view, so there is not much you can do. It's a 
>> typically situation where the the phones tries to perform nat 
>> traversal on its sides but does not do a complete job, preventing 
>> also the proxy to do it :(
>
>
>
>
> So what is your final advice about how to speak with German vendor?
>
> They are not violating RFC, but clearly, ther device will NOT work 
> with SER or OpenSER in NAT-traversal scenario.
>
> They say to us everytime that they "sold approx. 2 milion of those 
> boxes and nobody, no ISP complained". I do not believe at all - this 
> is DSL router/modem, so maybe they talk about non-VoIP and VoIP boxes 
> together. But you will never know, this is marketing talk..
>
> They say that "ITU-T has given them an approval. This approval 
> described that they are fully compatible with the RFC´s for VoIP". 
> Well, yes, they do not break RFC. But one flavour of this device is an 
> ATA box, without DSL modem. Majority of my customers will buy this ATA 
> to use with existing DSL router, cable modem/router or such. They WILL 
> have unfriendly NAT there, so what is the sense of ATA box?
>

it's not about RFC compliance here, but about making it work, about the 
logic used to detect and traverse NATS , things that are not specified 
by RFC.

I guess it should be reasonable from them to accept to make this auto 
NAT detection configurable in order to disable it.

alternative solutions will be (1) to consider all these UAC as nated - 
by looking at UA hdr- or (2) to try to remember the NAT flag from the 
non-authenticated REGISTER until the auth-ed one - the first 
(challenged) register will reveal the true status of the clients (nated 
or not) as it's also used by client for nat detection....but I guess it 
will be quite complicated

regards,
bogdan