Dear OpenSIPS-users,
First of all, happy new year.
I'm still reading about NATs, SIP proxies and SIP, to understand how to solve a question in my project. I'm not expert in TCP, IP, routers, NATs and networks. That is why I would like to get some help here. I guess I'm almost getting the point to solve it.
In my current network topology case I have:
Mobile Phone 1 on Internet
/ \ |
| |
| SIP |
| \/ Real IP (Internet)
NAT ------------------------------------------------
/\ | 'Nated' IP (Wan)
| |
| SIP |
| |
| |
| \/
ROUTER ------------------------------------------------
/\ | (Lan)
| SIP |
| |
SIP Proxy OPENSIPS
| |
| SIP |
| |
Mobile Phone 2 on local network
When Phone 2 calls Phone 1, everything is ok. Phone 1 is registered on OpenSIPS with 'Nated' IP, by someway. So, Phone 2 sends INVITE to such IP. When Phone 1 answers with SIP OK, the Contact header filed has the same 'Nated' IP. Then, Phone 2 can send the ACK to the correct path.
However, when Phone 1 calls Phone 2 and Phone 2 answer with SIP OK, Phone 1 can't send the ACK, because the Contact header field from SIP OK has the local IP for Phone 2.
It is true because when Phone 2 registers itself on OpenSIPS, the local IP is recorded in the local database table.
So I have the following questions:
1 - Can this problem be solved without using the Nat Traversal Module?
2 - Can NATHELPER module fix the Contact header field (as a I saw this module has functions related with it), when Phone 2 sends SIP OK to Phone 1? If yes, how can such module determine a 'good' IP to put in this header field?
3 - If Phone 2 uses a stun server, will such phone be registered on OpenSIP with a real IP, won't be? Could it be a solution too?
Any hint will be very helpful!
Thanks a lot!
RODRIGO PIMENTA CARVALHO
Inatel Competence Center
Software
Ph: +55 35 3471 9200 RAMAL 979
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