SIPx and symmetric NAT

I'm currently running a small ITSP over Asterisk, and am looking at expansion options. Portaone seems to be the most reasonably priced, however they include many billing features I don't need, and at $40k it is still very expensive.

I found SIPx today and it seems interesting. However, nowhere in the documentation (that I have found) does it discuss the problem of symmetric NAT. Direct peer to peer media routing is great for about 40% of the users, but the remaining 60% using symmetric NAT need a proxy.

Does SIPx have a solution for this? Can anyone who has successfully implemented SIPx comment on this? Is there a way to automatically detect the symmetric NAT callers and route them via Asterisk or another far end NAT traversal proxy?

Thank you for any information. SIPx looks interesting, I'm just wondering if it is practical for a real service.

Hi there,

sipx does not sit in the media stream proxying RTP like asterisk does. As such, it's nat detection capabilities are nothing to do with dialogs, only transactions. sipx will allow a nated ua to register with it (whether sipx is nated or not), and allows itself to register (when nated) to a service provider.

To perform your NAT detection, you could either use the proxy parts of the sipfoundry applications, or a dedicated SIP proxy like OpenSER/SER. I've never performed selective routing based on NAT type's in sipx, but have with openser/ser and it works great.

Cheers,
X-C