Mobile devices connected to data transmitting carriers must be configured with APNs to transmit data through them. Carriers identify these devices to determine what type of network connection should be attributed to it (IP address attribution, security methods, and how and whether they should be connected to private customer networks).
APNs identify the packet data network (PDN) that mobile data users wish to communicate with. In addition to identifying a PDN, an APN may also be used to define the type of service, (e.g. connection to Wireless Application Protocol (WAP) server, Multimedia Messaging Service (MMS)) that is provided by the PDN. APN is used in 3GPP data access networks).