The 2G3G core network is logically divided into three domains: home network domain, service network domain, and transport network domain. The home network domain refers to the network where the customer opens an account. Network elements that provide services to customers or can provide services to customers are called service network domains. The transport network domain means that once a user roams, other operator networks are used to forward data packets to the home network. These networks are called transport network domains.

Core network element 1: (G) MSC mobile switching center, this equipment is used to make calls and send short messages. Preceded by G means that it can be used as an end office to make calls directly, or as a gateway office to connect with other operators, like a fixed network switch.

Core network element 2: HLR home location register. The home network needs to store some user service information and identity information, such as what services the customer has opened. These are all registered in this home location register. In addition, the verification of the user’s identity must be completed.

Core network element 3: GSN, including SGSN and GGSN, GPRS support node.

Core network element 4: SMSC short message service center. The main function is to receive short messages. Once the called party is turned on, the short message will be sent to the called party. For details, please refer to the SMSC product.

Core network element 5: SCF business control function, docking with the OCS billing center to complete smart services such as billing and recharge.

MSC

HLR

VLR

AuC (Include in HLR)

EIR (Include in HLR)