[OpenSER-Users] nat problems

[Iñaki Baz Castillo]

El Wednesday 21 May 2008 16:47:38 Pezhman Lali escribió:
> Dear
> I am testing a lot of configs, for ser, openser and
> asterisk,
> but till now, I can not find a total solution for
> solving nat,
>
> do you think ser/openser+ (defined modules) can
> support all of nat services, around the world ?

Buff... that's a terrible question...

Well, using OpenSer "nathelper" module in conjuntion with RtpProxy server 
(or "mediaproxy" module with MediaProxy server) you can solve NAT issues in 
all cases except those ones:

- You use a non-symettric SIP/RTP client (hope nowadays all are symetric).
- You are behind a router with SIP ALG enabled.

This last case is really dangerous and there is no server side solution for 
this (you need to dissable ALG in the router).
  http://www.voip-info.org/wiki/view/Routers+SIP+ALG


NAT keepalive is performed by OpenSer "nathelper" module and it works for UDP 
clients. If you use SIP TCP then you must set the REGISTER "expires" to less 
than 32 seconds. Also a recent patch for OpenSer SIP TCP stack allows OpenSer 
keeping hte TCP connection if the user sends CRLF (so OpenSer replies with 
CRLF CRLF).

The very complex draft "outbound" is not implementer in OpenSer (in fact, it's 
a draft still...). It's mechanism for keeping NAT in SIP TCP:
  http://tools.ietf.org/html/draft-ietf-sip-outbound


Regards.



-- 
Iñaki Baz Castillo
ibc at in.ilimit.es