l has any real-life issues is another question. 3GPP has not defined how such a setup is supposed to work. Deploying IPv6 in 3GPP Networks Use of AAA over the (S)Gi Interface The (S)Gi-interface [25] defines both RADIUS [60-63, 91, 92] and Diameter [29, 93] profiles for GPRS and EPS use. A PGW assumes the role of an AAA client and the server is then located either within the operator PDN or in an external PDN (such as in a corporate or wireless ISP network). Independent of the user plane IP addressing, the AAA transport can be either IPv4 or IPv6. The use of the AAA interface is tightly coupled with the lifetime of a PDN Connection and invoked on any event where the PDN Connection (or rather the EPS Bearer) state changes or gets modified. The (S)Gi AAA interface is frequently used for: Authenticating/authorizing a subscriber (and a UE) during the activation of the PDN Connection. Management of IP addresses for the UE; this may involve re-authorization of the subscriber. Informing the service infrastructure in the PDN about the IP address and subscriber/UE identity and accessed service mapping. Informing the service infrastructure in the PDN about the UE location, accessed PLMN information, etc. Accounting purposes, including periodic updates to the service infrastructure and accounting servers. Informing the service infrastructure about changes in the bearer (e.g. during the creation of a Secondary PDP Context or a dedicated bearer). Terminating the PDN Connection from the network side. The AAA interface is available for both transparent and non-transparent access to the PDN. Our main interest is on the IP address management and specifically on the IPv6 part of it. Section 4.4 discusses IP address management and also links the use of the (S)Gi AAA interface to it. Figure 4.9 shows possible AAA interactions over the (S)Gi-interface, triggered by the management of the PDN Connection. Use of DHCP over the (S)Gi Interface The (S)Gi-interface [25] defines both DHCPv4 [10, 11, 94, 95] and DHCPv6 [26, 27, 54, 55, 96, 97