 follows the 3GPP specifications). The UE learns the PGW link-local address from the received Router Advertisement, and since there are no link-layer addresses in the 3GPP link, the UE does not need to perform address resolution for the PGW link-local address. 4.5 Bearer Establishment and Fallback Scenarios This section discusses the initial PDN Connection activation and handover cases and how different PDN Types behave in various UE and network configurations. 4.5.1 Initial Connection Establishment The PDN Type that the PDN Connection eventually gets after the completion of the connection activation depends on various parameters. Since we are only concerned with the IP support on the user plane (the IP addressing delivered and seen by the end user), not every packet core network element has to understand the differences in IP addressing. Still, multiple networking elements within the 3GPP system have to support the requested PDN Type in order for the PDN Connection creation to succeed: The UE requested PDN Type (and the UE IP and radio modem capabilities); APN-specific allowed PDN Types stored in the subscription profile in the HLR/HSS; The SGSN release, capabilities, and settings; The GGSN/PGW release, capabilities, and settings; The DAF setting in the SGSN/MME; The external PDN settings and capabilities, for example in case the IP address man- agement is delegated to an external AAA server; and Vendor specific means to override standard PDN Type handling logic (obviously we cannot say much about these). The radio modem and its firmware has to support the corresponding PDN Type for the PDN Connection creation. The PDN Connection creation can be initiated by the UE or the network. In some cases the host operating system and the IP stack within the UE may not have the full knowledge of the radio modem support for different PDN Types e.g., when the end host (TE) and the modem (MT) are separate. A 3GPP Release-8 (for EPS) or a Release-9 (for GPRS) compliant UE should adhere the follow- ing rules: If the UE is an IP