nt network environments. Diameter is a newer IETF technology aimed to supersede RADIUS and which tries to address some of its shortcomings. Alternatively, DHCP can be used for external address management. Section 4.4 describes the usage of the AAA, and the DHCP technologies for address management. Deploying IPv6 in 3GPP Networks 2.8 End-to-end View from the User Equipment to the Internet We have now learned the different building blocks that make up the 3GPP system. It is time to put this together, and to give an overview of how your packets actually get to the Internet and back. We will look at GPRS and EPS separately as the process of getting online is slightly different. 2.8.1 GPRS We will first look at how the UE gets connected to the Internet. Then we will show how the packets are transmitted over the network. Finally, we describe how the connection is torn down, and the communication is ended. Getting Connected When we turn on a UE such as a mobile phone, the first thing the UE must do is to attach to the network. During the network attachment, the UE authenticates itself to the mobile network, and the mobile network authorizes the network attachment as described in Section 2.3.1. However, at this point the UE does not have an IP address, and it is not connected to the Internet, or to any other IP network for that matter. Therefore, it has open a PDP Context before it can send or receive packets. The PDP Context activation procedure is shown in Figure 2.13. The UE can indicate either the APN it wishes to connect to, or leave the APN field empty in the Activate PDP Context message. If the APN is not provided, the network will use a default APN. The APN settings are usually operator dependent. As we want Internet access, the APN network identifier could be for instance Internet. The network would then find, based on the APN, where the GGSN is that provides Internet access, and send the Create PDP Context to it. The GGSN would allocate the IP address (IPv4, IPv6, or both, depending on the PDP Type that the UE 