1. Architecture and Specifications
The GPRS core network, which this book calls the GPRS Core, provides packet-switched connectivity to a mobile subscriber and is the direct predecessor of the Evolved Packet Core (EPC) architecture that Part II describes. This chapter describes the GPRS Core in Iu mode with Gn/Gp interfaces, based on the configuration that 3GPP TS 23.060 clause 5.4.0 shows in Figure 2 ("Overview of the GPRS Logical Architecture when based on Gn/Gp interfaces"), with the optional PCRF and the charging systems of the policy and charging control architecture added.
The figure above shows the path of packet-switched traffic from the UE, through the UTRAN and the two GPRS Support Nodes, to an external packet data network. The figure also shows the control-plane nodes that serve the GPRS Support Nodes: the HSS/HLR, which holds subscription data for the SGSN and the GGSN, the PCRF, which provides policy and charging control to the GGSN, and the OCS and the OFCS, which charge for the traffic that the GGSN carries. Each reference point in the figure carries the 3GPP specification and the protocol that it uses.