Maybe a strange question when usually people ask why things do not work for them... but:

The N900s SIP-implementation is based on the telepathy-framework, right? And it "just works". I never made any adjustment (like port forwarding etc.) to the routers my N900 connects to. I get a call, I hear them, they hear me, all well.

Now on my desktop computer, I use basically the same setup - or so I thought. It's a GNU/Linux system with all the Telepathy-goodness we find on our N900... only the client is different, of course. Instead of Nokias phone client I use Empathy.

Guess what? Don't work. I do receive calls and if I dial out, the other phone rings, but I never hear what the other party says. These are symptoms I know from my early VoIP days and they always had to do with broken NAT traversal.

So I started wondering - why the hell is Nokia's implementation working? Is there somebody who's familiar with how they do things? Is there something they do at the "top" (=within their phone client), outside of the underlying Telepathy components, that eases NAT traversal? How is it possible, technically, if the router isn't prepared for it? What could I be missing on my desktop PC that prevents it from working like my N900 does?

(I checked the packages: Most of the relevant packages I have on my desktop are newer than the ones found on the N900. The only package not available for my desktop is telepathy-stream-engine, which they say is superseded by the other components meanwhile.)

Does Diablo SIP work under the same conditions? AFAIK the main difference in Fremantle is that is also uses UPnP discovery if STUN is unconfigured or fails for whatever reason.

ah... need to check both - upnp on my desktop and sip on diablo. i'm using gentoo, and if i remember correctly, upnp is a use flag you can set or un-set for the respective packages. maybe i don't have it. thanks a lot, at least i know what to try when i'm home