ach is to use proprietary solutions for communicating between the modem and a driver in the operating system, but it has obvious drawbacks of requiring additional software in the operating system. Another approach includes the modem modifying the Router Advertisement it proxies from GGSN and adding the RFC 6106 [140] RDNSS options into it - this modification is not detected by hosts as Secure Neighbor Discovery (SEND) is not typically used. The third approach is to run (stateless) DHCPv6 server on the modem, and serve the RDNSS option with DHCPv6. UEs that perform tethering basically have to support some of these means for delivering RDNSS addresses downstream, as 3GPP networks are not required to provide DHCPv6 services or send RDNSS information in Router Advertisements. DHCPv6 Renew and Rebind The DHCPv6 includes Renew and Rebind features that a requesting router can use to extend the lifetime of the delegated prefix and to request the same prefix again. In 3GPP networks, the UE's PDN Connection can drop quite easily, for example due to lost network coverage. In such cases, it is desirable that the LAN should not need to be renumbered, even if the UE's PDN Connection renumbers during the connection re-establishment IPv6 in 3GPP Networks phase. By ensuring that the UE remembers the prefix that it was delegated, the IAID it has used, and having constant DUID, the UE can request for the same prefix again. Hence, the delegated prefix could, if the network would allow, remain static over UE reboots or reconnections. 4.7.6 IPv6 Application Support As long as IPv4-only applications exist for a UE, 3GPP networks cannot utilize the single- step protocol translation tools for IPv6 transition (see Section 5.4.3), but the networks have to make use of more resource consuming approaches such as dual-stack (see Section 5.4.2) or more complex setups such as double translation (see Section 5.4.4). To pave the way for providing IPv6-only connectivity at some point in the future, and to reduce the load for IPv4 Network Address Tr