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

[Iñaki Baz Castillo]

El Jueves, 11 de Diciembre de 2008, Bogdan-Andrei Iancu escribió:
> 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).
>
> So, the question is:  if NAT detected and such a protocol mismatch is
> detected, should a registrar refuse the registration (as it will be
> anyhow unusable) ?

I've asked in SIP-implementors about *real* usage of registration with a 
Contact different than the UA sending the REGISTER.

I've received some responses and my conclusion is clear: There is NO real 
usage of if, this is: it makes no sense *at all* that a UAC sends a REGISTER 
with a Contact differing of his own location. The responses I've received 
talk about exotic (and 100% useless and unreal) cases.

Case:

- alice sends a REGISTER with "Contact: sip:bob at domain.org".
This is a kind of forwarding and will work even if alice is behind NAT since 
when the proxy receives a call for alice it will loop over him and end 
locating bob AoR.

-- 
Iñaki Baz Castillo