remain IPv6-only from the UE and the network point of view to the point that the UE actually requests the IPv4 address using DHCPv4. At this point, the PGW would assign the IPv4 address to the UE, and use additional signaling between the SGW and the PGW to modify the PDN Connection with the newly assigned IPv4 address. Eventually, the UE learns the IPv4 address through DHCPv4. The UE could also release the IPv4 address later on, which would not lead to a deletion of the PDN Connection but only make it IPv6-only from the UE and the network point of view. 4.4.5 Static IPv6 Addressing The 3GPP architecture allows assignment of a static IPv4 address and/or an IPv6 prefix to a UE. Typical to 3GPP system architecture, there are multiple provisioning and address man- agement methods. The most straightforward method is placing the static addresses/prefixes into the per APN HLR/HSS subscription profile. In addition to the HLR/HSS based method, the Non-Transparent access to an Intranet or ISP [25] (see Section 4.2.4) may use external to PGW methods over the (S)Gi-Interface to allocate addresses/prefixes to a UEs. These methods include AAA (PGW being a RADIUS or Diameter client), DHCPv6 (PGW being a client), and various tunneling methods such as L2TP [89] (PGW being a LAC). In certain cases even the GTPv2 is able to differentiate whether the assigned IP address was statically assigned; more specifically the Indication information element [3] may contain static IP address information flags for the charging purposes [83] during the modify bearer procedure. Unfortunately, it is not clear from the specifications whether the Indication information element also applies to cases where other methods than the subscription profile were used for the static address allocation. There are certain deployment considerations that need to be understood regarding static addressing. Static IP addresses and prefixes are always anchored to a specific PGW where the IP addresses topologically belong and eventually get routed to from a PDN. The 3GP