Section: 5.3.1.2.1 IPv4 address allocation via default bearer activation and release via PDN connection release
Content: An IPv4 address may be provided to the UE as part of the default bearer activation and the IPv4 address is released when PDN connection associated with the IPv4 address is released. When the PLMN allocates an IPv4 address, it is the PDN GW responsibility to allocate and release the IPv4 address. The PDN GW may use an internal IPv4 address pool in this case. The PDN GW allocates an IPv4 address upon default bearer activation and it releases the IPv4 address upon PDN connection release associated with the IPv4 address for a given UE. NOTE: If the PDN type is IPv4v6, when the PDN Connection is released, the IPv6 address is also released. When an IPv4 address is allocated from an external PDN, it is the PDN GW responsibility to obtain the IPv4 address from the external PDN, and to allocate, renew and release the IPv4 address. The PDN GW may use DHCPv4 to obtain, renew and release the IPv4 address from the external PDN. If RADIUS or Diameter is used towards the external PDN, as described in TS 29.061[ Interworking between the Public Land Mobile Network (PLMN) supporting packet based services and Packet Data Networks (PDN) ]  [38], the IP address can be obtained, renewed and released as part of these procedures. If DHCPv4 is used, the PDN GW functions as a DHCPv4 Client. If RADIUS is used, the PDN GW functions as a RADIUS Client. If Diameter is used, the PDN GW functions as a Diameter Client. After releasing the IPv4 address, the PDN GW should not assign that IPv4 address to other user immediately.