[OpenSIPS-Users] [OpenSIPS-Devel] [RFC] NAT pinging

[Iñaki Baz Castillo]

El Lunes, 15 de Diciembre de 2008, Bogdan-Andrei Iancu escribió:
> Hi Iñaki,
>
> Iñaki Baz Castillo wrote:
> > 2008/12/11 Bogdan-Andrei Iancu <bogdan at voice-system.ro>:
> >> A) contact info versus network info
> >>
> >> When considering a REGISTER request, you have two sets of information: I
> >> - registered contact ; II - network info (source IP/port, proto, local
> >> socket where the request was received on).
> >> When comes to determine the destination for pinging, right now, the
> >> logic uses the network info (as more or less NAT at network level).
> >> But, according to RFC 3261, the REGISTER request may carry whatever
> >> contact, like a REGISTER via UDP may register a contact for TCP (or
> >> vice-versa). In case of NAT, this will not work at all (as we assume
> >> that the source of REGISTER and registered contact point to the same
> >> network location).
> >
> > Well, but it is obviously the only way. The registrar can never know
> > if the private address in the Contact is behind the same public IP as
> > the received one.
> >
> > AFAIK registering a Contact different that the address of the UA
> > sending the REGISTER is just used in IMS (some exotic stuf...).
> >
> > Is there any other case in which the REGISTER Contact could be different?
>
> Generic case of third party registration (but such a scenario in NAT
> envs. is completely broken).

Humm, but the above is not 3rd Party Registration (3rd Party Registration 
means: "From: alice at domain, To: bob at domain, Contact: alice at ip".



> > Ufortunatelly I know no UA's sending a TCP Contact via UDP. Do they
> > exist?
>
> I do not, but from SIP point of view is perfect possible - like a device
> that supports both TPC and UDP, may use UDP to register both UDP and TCP
> contacts..

I hope that any UA behind NAT who wants to register a TCP location will use 
TCP. If not it's just impossible to contact him!



Thanks.


-- 
Iñaki Baz Castillo