GPRS architecture had introduced two new network elements GPRS support nodes (GSN) (are just like routers), serving GPRS support node (SGSN).The following section describes the GPRS architecture:
- Figure8.14 shows the GPRS architecture reference model.
- Gateway GPRS support node (GGSN) is the interworking unit between the GPRS network and external packet data networks (PDN).
- The GGSN is connected to external networks (e.g., IP or X.25) via the Gi interface and transfers packets to the SGSN via an IP-based GPRS backbone network (Gn interface).
- This node contains all the routing information for GPRS users, and performs address conversion, and tunnels data to a user via encapsulation.
- Serving GPRS support node (SGSN) supports the MS via the Gb interface.
- SGSN requests user addresses from the GPRS register (GR), keeps track of the individual MSs’ location, is responsible for collecting billing information (e.g., counting bytes), and performs several security functions such as access control.
- The GR, which is typically a part of the HLR, stores all GPRS-relevant data.
Figure 8.14 GPRS architecture
Functions of SGSN:
- Packet routing and transfer
- Mobility management
- Logical link management
- Charging data
Functions of GGSN:
- organizes the interworking between the GPRS network and external packet switched networks
- It hides the internal network to the outside.
- It checks if the user is active, then forwards the data.