Method for allocating an IP address to mobile communication user equipment

A method of receiving an allocated Internet protocol (IP) address by a mobile communication user equipment (UE), the method comprising:

• transmitting, by the mobile communication UE, a packet data network (PDN) connection request message, to an entity in a network, the PDN connection request message include one or more of version information indicating an IP version requested by the mobile communication UE and information regarding capability of the UE;
• receiving, from the network entity, a request message including particular indication information indicating to maintain router information, although a timer with respect to the router information has expired, as long as the UE belongs to a particular PDN gateway, and information corresponding to an interface identity (ID);
• transmitting, by the mobile communication UE, an accept message to the network entity;
• generating, by the mobile communication UE, a link local address (LLA) by using the interface ID;
• receiving a router advertisement message from a router in the network, the router advertisement message including information regarding a prefix address part of an address of IP version 6 (IPv61) the router information, and a lifetime information regarding the router information;
• setting an address of IPv6 by using the prefix address and the interface ID;
• and transmitting uplink data to the router on the basis of the particular indication information although the lifespan with respect to the router information has expired, wherein the particular indication message is composed of 1 bit,
• when a value of the particular indication message is 0, the UE is configured to be updated by receiving a router advertisement message including a router lifetime value, and when the value of the particular indication message is 1, the UE is configured to use the router information until a connection with the particular PDN gateway is released.

A control entity of a network, the control entity comprising:

• a transceiver configured to transmit and receive a signal;
• and
• a processor configured to control the transceiver,
• wherein the processor is further configured to receive a packet data network PDN connection request message including one or more of version information indicating an Internet protocol (IP) version requested from a mobile communication user equipment (UE) and information regarding a capability of the UE;
• obtain subscriber information of the UE from a subscriber information server in response to the reception of the PDN connection request message;
• check IP version information included in the PDN connection request message;
• determine whether or not the UE moves frequently or is stationary on the basis of one or more of the subscriber information of the UE, the capability information of the UE, and a tracking area update (TAU) frequency;
• and
• when the UE is stationary, transmit to the UE a request message including particular indication information indicating to maintain router information, although a timer with respect to the router information has expired, as long as the UE belongs to a particular PDN gateway, and information corresponding to an interface identity (ID) allocated for the UE,
• wherein the interface ID is used to configure the address of IP version 6 (IPv6) for the UE,
• wherein the particular indication message is composed of 1 bit,
• when a value of the particular indication message is 0, the UE is configured to be updated by receiving a router advertisement message including a router lifetime value, and
• when the value of the particular indication message is 1, the UE is configured to use the router information until a connection with the particular PDN gateway is released.