cing interface and no other IPv6 addresses with a different scope. Specifically, the SGW does not configure any address out of the IPv6 prefix it advertises on the link. The link has exactly one, per UE unique /64 IPv6 prefix and the UE configures its unicast IPv6 addresses based on this IPv6 prefix. The lifetime of the /64 IPv6 prefix on the link shares fate of the PDN Connection lifetime. Therefore, the /64 prefix on the link has both preferred and valid lifetimes set to infinity. The PGW (note, not the SGW) selects the IPv6 IID [21] for the UE. The IID communicated to the UE over the NAS signaling and the UE is required to configure its link-local IPv6 address using the PGW selected IID. This is to ensure that there can never be a DAD [22] failure on the link. (Several modem drivers and frameworks fail to deliver the IID from the radio modem and NAS signaling to the host side. Rather they generate their own IID, which opens a theoretical possibility for a link-local address collision on the 3GPP link.) NDP address resolution and redirection functions are not needed. There are no link- layer addresses or nodes other than the UE and the SGW on the link. However, doing for example address resolution does no harm other than generating unnecessary traffic. NDP DAD should not be needed. The DupAddrDetect Transmits [22] configura- tion variable in the host should be set to zero to turn off DAD. However, doing DAD does no harm other than generating unnecessary traffic. The situation might change the UE starts acting as an IPv6 tethering device using a Neighbor Discovery Proxy. NDP NUD is not particularly necessary but it is recommended to enable it. This could become important if UEs start doing tethering using a Neighbor Discovery Proxy. Since the first-hop router is located at the SGW, the SGW may change as a result of UE mobility and a SGW relocation. This implies that the Idle Mode mobility needs special care from the NDP point of view, since Router Advertisement sending intervals are not coordinated between SGWs.