Previous 1 2 3 Next 41 Replies Latest reply: Apr 3, 2013 4:45 PM by diesel vdub
marcbyron Level 1 (25 points)
I just tried out Facetime with a co-worker who is not on my contact list. In order to do Facetime, she called me and then we pressed the facetime button. How does Facetime know who I am and where I am, since we are initally only connected via the AT&T network?

How does this work internationally? Will I be able to call a friend on an iPhone 4 overseas and do facetime with him?

MacBook Pro Core Duo 2.16, Mac OS X (10.4.8)
  • wjosten Level 10 (94,210 points)
  • marcbyron Level 1 (25 points)
    Thanks for the manual, it's going to be my nighttime read tonight, but it still doesn't explain how Facetime WORKS!!

  • red555 Level 4 (2,550 points)
    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.
  • marcbyron Level 1 (25 points)
    I know the operational info, but I am curious about the technical info:

    How does Facetime know where I am if someone just calls me? If we are in the same network (AT&T), maybe AT&T looks up if I am on an iPhone and then flags the call as "facetime capable", and does the same thing with the recipient.

    But how would this work between an iPhone 4 user in the USA and overseas? Is this even possible? Has anyone tried that out?
  • wjosten Level 10 (94,210 points)

    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.
  • marcbyron Level 1 (25 points)
    This still doesn't answer my question of how Facetime KNOWS where I am by a phone call. How does it know how to connect to me?
  • wjosten Level 10 (94,210 points)
    Well, if you read the manual you'd understand how it works. I'm done here. Good luck.
  • Faethor Level 1 (100 points)
    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?
  • EBSkater Level 2 (490 points)
    Don't try to understand it, the technical understanding is quite complex.

    You should look up Bonjour. It's actually a pretty cool technology.
  • marcbyron Level 1 (25 points)
    The manual doesn't say anything about how Facetime works technology wise. It shows me how to operate it, but not how it's done.

    I guess I'll have to wait until someone has figured this out, I am just curious.
  • Faethor Level 1 (100 points)
    But I do want to understand it. That's why I own a PC and not a Mac. <ducks>
  • wjosten Level 10 (94,210 points)
    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.
  • Lawrence Finch Level 7 (34,986 points)
    ROF,L! I love it.
  • Faethor Level 1 (100 points)
    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.
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