How does Facetime work?

I'm going to be in the same boat here in about 2 weeks. I've been using FaceTime in Airplane mode and it's working fine (with wi-fi of course). I'm hoping I can stay in airplane mode and use it as is....

ewoo wrote:
Both my wife & I have AT&T in the US and have successfully called each other using FaceTime...
I arrived in Korea (where there's no AT&T coverage) yesterday and successfully called my wife using FaceTime (Airplane Mode but with Wifi ON) using a local Wifi connection.
However, since then, FaceTime quickly fails and is unable to connect anymore... I've had my wife call me too with no luck. I also check my router settings and it doesn't seem to be the problem.

Do you think it made the first FaceTime call successfully because the iPhone had cached some info in needed the firstime?

Did you end up figuring out what happened?
I am travelling to Korea next month, and would like to know how I can stay in touch with people here through facetime..

I guess we need to think outside of AT&T here. There are millions of users using iPhone 4 internationally (sorry for being mean).
Okay, for my case me and my friend purchased an international unlocked version of iPhone 4s, and we are on different networks: SmarTone Vodafone and PCCW mobile. We tried the FaceTime call and it worked flawlessly over wifi. There is something interesting though. When we first turned on the FaceTime function on the phone there was a pop up message saying that the mobile carrier may charge standard SMS message fee for initiating the FaceTime call. But during the process I couldn't see any text being sent out (I guess it was done in the background). All these just made me really think how FaceTime really works (especially on the part that somehow the FaceTime server can locate both communicating parties just by their phone numbers).

This thread explains use of Facetime with iPhone. I intend to get a new iPod Touch mainly for the HD movie feature. Since it has Facetime but is not a phone there is clearly no facility to make a voice call first. I'd like to know how the connection between iPod Touch Facetime users would be made. Also are there network costs for Facetime calls (can't believe they would be free)?

Switchblade,

to my understanding, with the ipod touch, you have to use your e-mail to activate facetime on the ipod touch, and i believe you have to use the e-mail account that you use for your itunes. the ipod touch does have the facetime app (native) as you should be able to see it, open it up put in your account info and after that you should be able to use it. So i'm sure it works from there, and no there should be no cost to use Facetime and all you need is a wi-fi connection.

I honestly don't own the ipod touch but I've been to the apple store few times just to check out the new ipod touch. I do have the iphone 4.

Thanks for the fast and informative answer Kwopau.

Hi,
FaceTime and other VoIP systems use your IP address. You phone has one and the router/modem has one. There are a chain of them all through the connection that is created between you and the person you are calling. Just as a web server knows to send data specifically to you and not everyone. Technically the info is sent to everyone but your phone is the only one listening for that specific address packet.
It's all about the addressing of data. It's digital so the chunks of info have addresses that send the contents to the proper recipient. This all just happens fast enough so that we humans think it is real time.
Hope that helps

Somehow FaceTime uses the email account to establish a connection because even the new iPod Touch can initiate a call. But you can't make a FaceTime call to another iPhone or iPod if there's no email account set up on it.
With a gmail active sync account there's no real delay in establishing a call but I don't know if a simple POP account would work.