Section: 6.2.4.2 IP address allocation via NAS signalling
Content: The UE shall set the PDU session type IE in the PDU SESSION ESTABLISHMENT REQUEST message, based on its IP stack capabilities if the UE requests IP connectivity as follows: a) A UE: 1) which is IPv6 and IPv4 capable, shall set the PDU session type IE to IPv4, IPv6 or IPv4v6 according to UE configuration or received policy. 2) which is only IPv6 capable, shall set the PDU session type IE to IPv6. 3) which is only IPv4 capable, shall set the PDU session type IE to IPv4. b) When the IP version capability of the UE is unknown in the UE (as in the case when the MT and TE are separated and the capability of the TE is not known in the MT), the UE shall set the PDU session type IE to IPv4v6. If the UE wants to use DHCPv4 for IPv4 address assignment, it shall indicate that to the network within the Extended protocol configuration options IE in the PDU SESSION ESTABLISHMENT REQUEST. On receipt of the PDU SESSION ESTABLISHMENT REQUEST message sent by the UE, the network when allocating an IP address shall take into account the PDU session type IE, the operator's policies of the network, and the user's subscription data and: a) if the network sets the Selected PDU session type IE to IPv4, the network shall include an IPv4 address in the PDU address IE; b) if the network sets the Selected PDU session type IE to IPv6, the network shall include an interface identifier for the IPv6 link local address in the PDU address IE; and c) if the network sets the Selected PDU session type IE to IPv4v6, the network shall include an IPv4 address and an interface identifier for the IPv6 link local address in the PDU address IE.