the Framed-IPv6-address and the Framed-IP-address AVPs indicates that dual-stack PDN Connection was established. Some HLR and HSS subscriber databases allow prohibiting roaming in a specific (visited) network for a specified PDN Type, for example, per VPLMN granularity. The IP address management can be outsourced to an external PDN. Both RADIUS and Diameter protocols can be used to convey addressing information for the PDN Connec- tion over the (S)Gi-interface from the AAA server located in the external PDN [25]. Some vendors' products allow controlling the PDN addressing over the (S)Gi-Interface using RADIUS and Diameter protocols. This functionality can also be used to restrict IPv6 roaming to a specific VPLMN. The 3GPP-PDP-Type and the 3GPP-SGSN-MCC- MNC AVPs can be used to detect that the UE is roaming within a specific VPLMN and the requested PDN Connection is either IPv6 or dual-stack. If the AAA server then responds with IPv4-only addressing information, the PGW falls back to an IPv4-only PDN Connection. A subscription in an HLR/HSS can be associated with up to 16 difference Charging Characteristics per APN [82, 101]. Although, it is not precisely described in the 3GPP specifications, the Charging Characteristics can be used to affect the PGW selection in the SGSN or MME with some vendor products. The idea would be to associate IPv6-enabled APNs and subscribers with a Charging Characteristic that can be only IPv6 in 3GPP Networks put into effect when the UE is located in the Home PLMN (HPLMN). In all other cases, as when the UE is roaming, a PGW with IPv4-only APN gets selected. Again relying on the (S)Gi-Interface and its RADIUS or Diameter use, some vendor products allow the AAA server to override the APN during the PDN Connection estab- lishment. Similarly as earlier, specific VPLMNs would be assigned an IPv4-only APN. Finally, a rather naive solution is to dedicate specific PGWs to all inbound roamers in the HPLMN. These specific PGWs would then have IPv4-only 'mirror' APNs of the IPv6-enabled counterp