ers outside the company. The reference point between the GGSN and external networks is called a Gi interface, where the access is provided to external networks via logical interfaces called access points. A single GGSN interface can provide several access points from the same physical interface. The pa- rameters that are required to configure the access points include static and dynamic IP address ranges for subscribers, server addresses, router information, IP address allocation method, etc. When planning for the Gi interface, aspects such as required bandwidth, security, reliability, scalability, network address translations, etc., should be taken into account. Connectivity to the external networks can be done through leased lines, frame relay/ATM network, etc. The process having access to external networks is initiated by the UE. The PDP context activation request along with the APN and PDP address is sent to the SGSN by the UE. After checking the resources, security, etc., the SGSN contacts the RNC for an RAB assignment and subsequently sends the PDP context creation request to the GGSN. If everything is all right, the GGSN returns its response message, which includes the assigned PDP (IP) address. This is passed to the UE by the SGSN. Once the IP address is received by the UE, data sessions are started with the server that it wants to connect on the external network. However, every UE that needs to access the external network needs to be assigned an IP address. These addresses can be statically assigned by using the HLR or dynamically assigned by using the GGSN, DHCP, etc. The address can be public or private. Since public addresses are limited, private addresses are normally used and the firewalls/edge routers are used for network address translation (from private to public IP addresses). In cases where there is a need to connect two networks together across another network, tunnelling is used. This is done by encapsulating one protocol into another protocol. The protocols used are either the IP, GRE (gener