What Is an APN for an Internet Connection?

The General Packet Radio Service is a development of the widely accepted Global System for Mobile Communications, and allows users to connect to high-speed Packet Data Networks from cell phones and other mobile devices. The mobile device transmits an APN that contains a network identifier and an optional operator identifier. The GPRS network authenticates the APN before connecting the mobile device to the corresponding PDN using the Internet Protocol. External PDNs may be Internet Service Providers, corporate intranets or public networks.

APN network identifiers comprise a number of labels, separated by periods. Identifiers that contain more than one label take the form of an Internet domain. Examples of valid network identifiers are "internet", "epc.tmobile.com" and "internet2.voicestream.com." Where a network identifier consists of three or more labels, the first label may be a Reserved Service Label that identifies the individual service the PDN is to provide. Corporate intranet identifiers typically take the form "intranet.corporatedomain.com."

The inclusion of an APN operator identifier is optional. In the absence of an operator identifier, the default operator is taken from the home network of the mobile device. An operator identifier comprises three labels, the last of which is always "gprs." The first and second labels are a 2- or 3-digit Mobile Network Code and a 3-digit Mobile Country Code respectively. The MNC identifies a specific network operator, and U.S. MCCs range from 310 to 316. Examples of valid U.S. operator identifiers include "026.310.gprs" and "370.311.gprs."

Many cell phones have a preset APN, or perform an automatic APN configuration when a SIM card is first inserted. When changing the SIM card to use a different network, the APN settings may remain unchanged, causing a loss of GPRS service. Contacting the new network operator and reconfiguring the APN correctly should solve the problem. Using a phone for both business and personal applications can also cause conflicts, as the APN for corporate e-mail may not allow access to the Internet for social networking. A custom APN may be the only solution to this conflict.