o a vendor specific category on both the network and the UE side. IKEv2-based Methods The 3GPP specifications also support Internet Key Exchange version 2 (IKEv2)-based [115, 116] Home Network Prefix (HNP) configuration for the S2c-interface (i.e. when the UE supports DSMIPv6 [19]) and full IPv6 address configuration for the (S)wu/S2b- interfaces [18, 105] (i.e. when the UE supports untrusted non-3GPP accesses). The (S)wu/S2b-interface case is probably the only solution to configure a network side selected /128 IPv6 address to the UE. Even in this case, the network has to have a deterministic mean to combine the IPv6 prefix and the IID in the PGW, which can turn out to be challenging, as discussed earlier. Deploying IPv6 in 3GPP Networks L2TP-based Methods L2TP-based 'external router' deployments were considered in Section 4.2.4. An LNS can use any method available to assign a static /64 IPv6 prefix to a UE. There is no 3GPP specification, which would have any language for combining L2TP and the rest of the '3GPP defined' static IPv6 prefix (or address) provisioning. Manual Configuration in UE and NAS Signaling Finally, yet another possibility is to configure a static address/prefix in the UE and use the NAS signaling to convey the address/prefix from the UE to the network. The GGSN eventually learns the UE proposed addressing during the PDP Context activation signaling. The GGSN either accepts the proposal or rejects it. It should be noted that the static address configuration and requesting of a UE configured prefix during the PDP Context activation is only possible for GPRS and not for EPS. This is due the changes in NAS signaling. More specifically, the UE-initiated PDN Connectivity Request [13] NAS message for the creation of a default EPS Bearer cannot contain a specific IPv4 and/or IPv6 address(es) anymore. On the other hand the UE initiated PDP Activate Context Request [12] NAS message for the creation of a default (i.e. primary) PDP Context contains the PDP Address information element and possibly filled