d Internet access. These will be discussed in more detail later in Section 4.8.1, Basic MPC Concepts. Figure 4.41 shows the essential network elements in a GPRS core network. Packet core remains the same for the EDGE network. An EDGE user is just another high speed user for a packet core. Hence throughput dimensioning should take care of EDGE subscribers and their Core Network Planning and Optimisation required data rate. PS core planning deals with designing, planning, dimensioning and optimising of the packet core domain of the GPRS network and other IP based solutions in a mobile phone network. It involves planning of interconnectivity, dimensioning of GPRS packet core network elements like SGSN, GGSN, DNS, DHCP (Dynamic Host Control Protocol), border gateway, legal interception gateway, etc., throughput and bandwidth calculations at various interfaces. Various techniques of IP planning like VLAN (Virtual LAN), VRRP (Virtual Router Redundancy Protocol), subnetting, etc., are used to design most bandwidth efficient, cost-effective, robust and future-proof solutions. Latest technologies like ATM, SDH, PDH, SIGTRAN and MPLS (multiprotocol label switching) are judiciously and gainfully deployed. 4.8.1 Basic MPC Concepts The packet domain allows for efficient transfer of high speed and low speed data. The network subsys- tem and the radio subsystem are kept totally separate SO that the network subsystem can be efficiently re-used by other radio access technologies. 2G and 3G networks use a common packet core network for transfer of data packets. The quality of service (QoS) is maintained for both real-time and non-real-time services. Packet core network functionality is logically implemented on two network nodes, the serving GPRS support node (SGSN) and the gateway GPRS support node (GGSN). The SGSN takes care of session and mobility management. It keeps track of the location of an individual mobile station and performs security functions and access control. The SGSN generates call data records (S-CDRs) for each se