Packet Data Network

• Since it is a network identifier, the Internet APN identifies an Internet protocol (IP) Packet Data Network (PDN). Internet information travels between the mobile carrier and the computer in packets, which are small amounts of bundled data. To locate where the information is going, the APN identifies each computer using its IP address. By using the IP address, the APN is able to name the type of network a particular computer uses when connecting to a mobile phone system.
  
  

Network Services

• In addition to identifying a PDN, the APN can also define that network's services. These types of services vary from wireless Internet connections to text messaging. Without the APN identifying and defining PDNs, you would not be able to connect to the Internet using your mobile phone. The APN allows the communication between a mobile device and its carrier to occur.
  
  

Two Identifiers

• The APN, being a protocol identifier, is actually composed of two different types of identifiers. The network identifier is mandatory, while the operator identifier is optional. The network identifier, also known as the network ID, is the part of an IP address used to identify the network connection. The operator identifier indicates the exact location of the PDN and contains the network country code and the network code.
  
  

GSM Carriers

• The GSM is called a cellular network because mobile phones connect to it by searching for cells, which are the geographic areas encompassing cellular transmitters. Internet APNs directly identify and define PDNs used by GSM carriers. The GSM is actually a set of standards for 80 percent of today's global mobile networks. It was originally created for second generation (2G) cellular networks, but is used for third generation (3G) networks as of August 2011.