imensioned according to the processing capacity. Just like Gi firewall dimensioning, real-life planning scenarios will impact on the dimensioning results. The BG is dimensioned according to the estimated inter-PLMN (Gp) roaming data traffic during the busy hour compared to the equipment processing capacity. The Gp traffic can be assumed to be around 10 % of the total data traffic but it may vary from operator to operator and also depends on the network topology. The impact of implementing IPSec VPN (Internet Protocol secured, virtual private network) functional- ity, assumed packet size and equipment tolerance are some factors that should be taken into consideration. An equipment loading factor of 90 % can also be applied for BG dimensioning. It is also recommended that the BGs should be implemented on an 'n + 1' configuration running the VRRP, for equipment redundancy and load sharing functionality. Charging Gateway Dimensioning The required number of charging gateways (CGs) is dimensioned according to the total number of CDRs generated per day. The following formula can be used to calculate the CG requirements: number of subscribers X (CDRs/busy hour) number number of CDRs/day/24 IP backbone Planning and Dimensioning A 90 % equipment load factor can be taken into consideration in the CG dimensioning. An 'n + l' node redundancy scheme is recommended. Core LAN Switch Dimensioning Each packet core site requires an LAN switch to provide interconnection between different network elements. The number of core LAN switches will depend on the number of packet core sites and the number of packet core network elements in each of the core sites. In addition, for circuit switched network elements that are co-located in the same site as the packet core nodes, the LAN port requirement for the IP interface for SIGTRAN is also taken into consideration when dimensioning is carried out. For security and traffic management purposes, different VLAN configurations should be adopted for IP backbone connections. Thus, the number of po