v6 Flow Label Specification 3.2.1 [155] Improved RDNSS Selection for MIF Nodes 3.10.2 [156] Table 4.12 Informational RFCs for 3GPP hosts and routers RFC Title Book Section Reference IPv6 for Some Second and Third Generation Cellular Hosts [157] Basic Socket Interface Extensions for IPv6 3.9.1 [158] Advanced Sockets API for IPv6 3.9.1 [159] Socket Interface Extensions for Multicast Source Filters 3.9.1 [160] IPv6 Socket API for Source Address Selection 3.9.1 [161] Basic Requirements for IPv6 Customer Edge Routers [162] Operational Neighbor Discovery Problems 3.4.4 [163] 4.7.4 Provisioning The 3GPP specifications prior to 3GPP Release-8 leave the decision whether to request IPv4 or IPv6 PDN Connection to the UE. The UEs then contain databases of operators and their settings, including address family parameters, and/or utilize provisioning system from Open Mobile Alliance (OMA) which has standardized for Device Management and Client Provisioning [164]. The OMA's specification defines parameters for Network Access Point IPv6 in 3GPP Networks Definitions (NAPDEFs) (see Section 4.6.5 of [164]). Unfortunately, the NAPDEF does not support definition of the IP address type, even if it allows provisioning of IPv4 and IPv6 addresses for a UE. The lack of address family setting has led to vendor-specific extensions for defining the PDN Connection type. For example, Nokia has documented a proprietary solution, which modifies the eXtended Markup Language (XML) file used for provisioning by introducing a new setting value for NAPDEF called IFNETWORKS (see Section 2.3.4 of [165]. If the IFNETWORKS is set only to IPV4 or to IPV6, then a single address family PDN Connection will be created. In Release-8, the 23.060 standard says that a UE, which is IPv4 and IPv6 capable, will always ask for an IPv4v6 type of PDN Connection [8]. The standard then gives a possibility for the network to downgrade, or narrow down, the UE's request and provide IPv4-only or IPv6-only PDN Connection, if that is what network operators prefers to use. Howe