[Users] openser setup as a telephony gateway (to PSTN) for NAT'd clients

[Taylor Carpenter]

I may be misunderstanding things (very probably so), but all the  
examples for both SER and OpenSER that I have seen either do not do  
NAT or NAT but are not the "end point" for a UAC to the PSTN.  From  
what I can tell they are just sending on the SIP request to the next  
destination as is.  The setup I am trying to accomplish is

    * SIP clients are all on a private network with connectivity to  
OpenSER directly on one interface (on the same private network)
    * OpenSER's other interface is on the external network (internet  
facing)
    * SIP clients are only sending telephone numbers  
(sip:telephone_number@*... do not know about PSTN providers)
    * OpenSER connects to the PSTN provider and send the number to  
dial that came from the SIP client
    * OpenSER "proxies" the entire call (with the help of rtpproxy or  
mediaproxy for RTP of course)
    * No incoming calls from the internet to OpenSER (no support for  
that is needed)
    * Registration not required for sip clients (they are all on same  
private network and authorized)

I have found several posts, example configs, documents that have  
pieces of what I need (from what I can tell).. and I have tried to  
put it together, but it does not quite work...

So is there some example that fits this type of usage?  If not one  
then possibly several pieces from a few documents?  I have been  
thinking that OpenSER setup as a outbound proxy configured for  
multihome, but everything I have seen on that just routes the calls  
through to where ever the SIP client was requesting as a final  
destination and I need to send to one destination (the PSTN  
provider).  Any help is greatly appreciated.

BTW, I was thinking the NAThelper or outbound proxy example from

	http://www.voip-info.org/wiki-SER+tips+and+tricks

Looked close to what is needed, but have a bunch of stuff (seemingly)  
unneeded for my scenario and have nothing about PSTN connectivity.

Thanks for taking the time to read this long post (if you made it  
this far).

Taylor