How does Facetime work?

http://manuals.info.apple.com/enUS/iPhone_iOS4_UserGuide.pdf

Page 65.

I assume you want the operational and not the technical info:
First, both of you need iphone4's and wifi.
1) Call the party you want to speak to via regular cell.
2) When a call is established, press the facetime button on the iphones. It is bottom row, center when call is in progress.
3) The facetime call is then established over wifi, provided you both have good wifi without a blocking firewall.

Cheez...

The voice call ends as soon as the FaceTime call connects, the FaceTime call is then done over Wi-Fi. So, in theory it should work anywhere, as long as both parties have an iphone 4 and are connected to Wi-Fi.

Well, if you read the manual you'd understand how it works. I'm done here. Good luck.

Ah, so the manual mentions that there is a STUN server somewhere out there that aids with NAT traversal. Would it be against forum policy for someone to scan and link pictures of the manual relating to how Facetime works?

Don't try to understand it, the technical understanding is quite complex.

You should look up Bonjour. It's actually a pretty cool technology. 🙂

But I do want to understand it. That's why I own a PC and not a Mac. 😉

1. Initiating iPhone contacts receiving iPhone using standard telephone protocol (using AT&T).
2. iPhones communicate to determine if both support FaceTime and both are on WiFi.(Done in Background)
3. iPhones then create a direct peer to peer connection over the internet. The iPhones deal with all IP addresses, firewalls, NAT issues automatically.(Again, Done in Background)
4. Participants can now do a video call over WiFi without use of the cellular network.

Again, in theory it "should" work overseas, but the initiating call(if the other party is overseas) MUST be done on the AT&T network. I can't however guarantee that it will in fact work if the other party is out of AT&T"s network, only saying that in theory, it should work.

Apple integrated the software with AT&T's system to make this possible.

ROF,L! I love it.

Sorry but I think what you posted may be misinformed rubbish. Steve stated himself that STUN is in use when using Facetime. This means that there is a server out there that handles part of the call setup, even if it is only NAT translation part.

I suggest you read up on how VoIP and NAT work before saying that the phones do it all themselves.

Sorry, that seemed overly harsh. To clarify, if you and the other caller are sitting behind NAT routers, and you both have private IPs, how do the phones communicate? They can't because, assuming that you are sane, you aren't port forwarding any ports and even if you were, how could you know which ports you need to forward?

This is where the STUN server comes in. It works out what your public IP is and what ports the given application is using. Without this you just have two applications that are able to shout out to the Internet but have no way of answering back because your firewall will block them.

At least that is my understanding of it. There are many articles out there that describe how it works and since Apple want to make Facetime an open standard, and they are already using existing open standards to facilitate its use, then I'm sure more detailed documentation is available, if not now then shortly, so that developers can get to grips with it.

This cant Be correct We have facetime in Germany As well but no at&t