How does Facetime actually work? (network nuts n' bolts)

To ask my question in more detail...

I have a more than basic understand of computer networking, IP protocol and what not, but I'm by no means an expert and there's a lot I don't know.

My question is, how can one phone know the IP address of another phone in order to Facetime it?

The iPhone is a mobile device (obviously) by nature, so your IP address is going to change depending on where you are, and what WiFi hotspot you happen to be in. And chances are, even if you frequent the same spots, you're going to be assigned a different IP address each time you visit and connect.

Do the Facetime servers query your phone over the 3G network to find out your current IP address, then keep it stored in some kind of table/database on the server? Then when another person wants to Facetime you, it initially looks you up by phone number on the server, then finds your IP address, and then connects?

I'd love to know the internal workings of this, and someone must know, as it can't be "magical" or anything like that. Thanks.

Moved

schweb said:

Moved

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Thanks.

basically facetime is the video share feature ATT and other carriers have had for many years, however, facetime does not use the 3G network or any part of the Mobile carrier's network. Its strictly WiFi.

Facetime as I understand is a stand alone app that uses the facetime servers via WiFi.

its locked to iPhone 4's only and is done so by the IMEI of the phone which is like its serial # on the mobile network plus the actual serial # of the individual phone its self.

Pretty much the same way Skype and various IM protocols work - it connects through an intermediary server that routes the traffic. There's really nothing remarkable about it, and you can bet that it will only be a matter of time before every smartphone on the planet has a similar app.

cwa107 said:

Pretty much the same way Skype and various IM protocols work - it connects through an intermediary server that routes the traffic. There's really nothing remarkable about it, and you can bet that it will only be a matter of time before every smartphone on the planet has a similar app.

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To be able to use Facetime, do I have do dial the other iPhone's mobile number? If so, then do I get charged for the call?

The wiki answers all those questions for you.

FaceTime - Wikipedia, the free encyclopedia

The one thing it's not all that clear on... Once you open a contact, there will be a FaceTime button there without making a call first.

bobtomay said:

The wiki answers all those questions for you.

FaceTime - Wikipedia, the free encyclopedia

The one thing it's not all that clear on... Once you open a contact, there will be a FaceTime button there without making a call first.

Click to expand...

Thanks Bobtomay.