Tainaor...what you have mentioned here are all part of the 3rd-4th layer of the OSI. ANSAP is on the 1st Layer. Which means that for the VPN/MIP/VOIP to work they have to get thru the 1st Layer (Physical Layer)which in case of the Wi-Fi/Cellular Network the Physical Layer is the Radio Signal. Layer 2 corresponds to the Network Layer (which also includes the equipment that processes these Radio signal). Layer 3 (Data Layer) is also the IP Layer (this has the IP Addresses to identify to source and destination of the Data/Traffic). 4th Layer is the (Transport Layer) TCP/UDP layer. These two layer's of the OSI is where the MobileIP/VPN/VOIP operates. If you are going to look closely you can clearly tell the dependencies of each OSI layer to another in order to have a successfull processing of information from one end to the other.
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