KR101213159B1 - Mobile terminal and method for assigning ip address in wireless network - Google Patents

Abstract

The present invention discloses a portable terminal and method for assigning an IP address in a wireless network. In a wireless network applied to a system including an access router and a mobile terminal that store and manage IP addresses used on a connected link according to the present invention in an address cache and perform DAD (Duplicate Address Detection) based on the IP addresses. A method for assigning an Internet Protocol (IP) address includes checking whether a notification message sent from the access router is received, and if the notification message is received, automatically configuring an IP address and automatically configuring the IP address. Requesting the access router to perform DAD on an IP address.

Wireless Network, IPv6, Access Router, Router Advertisement (RA) Message, Duplicate Address Detection (DAD), Neighbor Solicitation (NS) Message, Neighbor Advertisement (NA) Message, Address Cache

Description

MOBILE TERMINAL AND METHOD FOR ASSIGNING IP ADDRESS IN WIRELESS NETWORK

1 is a configuration diagram schematically showing an IPv6-based wireless network according to an embodiment of the present invention.

2 is a flowchart illustrating a method for allocating an IP address to a mobile terminal in a wireless network according to an embodiment of the present invention.

3 is an exemplary diagram for describing a format of a notification message according to an embodiment of the present invention.

4 is an exemplary diagram for describing a format of a request message according to an embodiment of the present invention.

5 is an exemplary diagram for describing a format of a response message according to an embodiment of the present invention.

6 is a block diagram illustrating a portable terminal for allocating an IP address in a wireless network according to an embodiment of the present invention.

7 is a diagram illustrating an access router for allocating an IP address in a wireless network according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: wireless network

110, 700: access router

120: base station

130, 600: mobile terminal

610, 710: control unit

611: component

612, 712: generator

613: allocation unit

614: confirmation unit

711: detection unit

620, 720: transceiver

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless network, and more particularly to assigning an IP address in a wireless network that can prevent collisions between IPv6 (Internet Protocol version 6) addresses automatically configured in a mobile terminal. It relates to a portable terminal and a method.

In general, IPv4-based networks have been used for data communication between mobile terminals and communication nodes in wired and wireless communication networks. Because IPv4 is a 32-bit address system, IPv4-based networks are running out of addresses that can be assigned as Internet usage increases. To this end, the Internet Engineering Task Force (IETF) has standardized on IPv6 using a 128-bit addressing scheme.

As this increase in IP addressing scheme makes it difficult for users to manually set IP addresses, efforts must be made to automatically assign IP addresses through interaction between mobile terminals and communication nodes in IPv6-based networks. do.

IPv6 addresses are largely assigned to mobile terminals by the following three methods. That is, 1) a static configuration method of manually setting network information in each host, and 2) a dynamic configuration of providing network information to a host using a network protocol such as DHCP (Dynamic Host Configuration) upon request. Dynamic Configuration) method, and 3) Automatic Configuration methods for setting network information according to a policy set according to an appointment among all hosts on a network.

The dynamic configuration method is also called statefull auto-configuration method, which uses a server such as DHCP to obtain an address. When the host side requests an address from a DHCP server, one of the server-assignable addresses is assigned to the host side. To assign. Therefore, the server must have a large database and strict management is required.

The autoconfiguration method is also called a stateless auto-configuration method in which the host generates its own address. The host generates its own address, that is, its interface ID information and the prefix information obtained from the router. The address is created using known prefix information. Thus, the host is responsible for creating and assigning its own address.

However, because the access router must manage all IP addresses used by the mobile terminal on the network, even if the mobile terminal automatically sets the IP address itself, problems may occur in network operation if the access router does not know the automatically set IP address. have.

The present invention has been made to solve the above problems, and in order to prevent conflicts between IPv6 (Internet Protocol version 6) addresses that are automatically configured in a mobile terminal, the access router is itself a managed access router. Sending a message indicating that the mobile terminal automatically configures an IPv6 address and assigns an IP address in a wireless network such that the automatically configured IPv6 address can be duly used after performing a DAD through an access router; It is an object to provide a method.

In order to achieve the above object, an access router and a portable device for storing and managing IP addresses used on a connected link according to an embodiment of the present invention in an address cache and performing DAD (Duplicate Address Detection) based on the IP addresses. The method for allocating an IP (Internet Protocol) address in a wireless network applied to a system including a terminal may include checking whether a notification message sent from the access router is received, and if the notification message is received, And automatically configuring an IP address and requesting the access router to perform DAD on the automatically configured IP address.

In order to achieve the above object, a method for allocating an Internet Protocol (IP) address in a wireless network applied to a system including an access router and a portable terminal according to an embodiment of the present invention is used on a connected link. Storing and managing IP addresses in an address cache, sending a notification message to the portable terminal to indicate performing DAD (Duplicate Address Detection) based on the IP addresses, and an IP address automatically configured from the portable terminal And confirming whether a request message for performing DAD for the received message has been received.

In order to achieve the above object, an access router and a portable device for storing and managing IP addresses used on a connected link according to an embodiment of the present invention in an address cache and performing DAD (Duplicate Address Detection) based on the IP addresses. A portable terminal for allocating an IP (Internet Protocol) address in a wireless network applied to a system including a terminal receives a notification message sent from the access router and performs the DAD on an automatically configured IP address. A transceiver for transmitting a request message to the access router to the access router, and upon receiving the notification message from the transceiver, automatically constructs an IP address, generates the request message, and generates the request message. Control unit for outputting to the transceiver Characterized in that it comprises a.

In order to achieve the above object, an access router for allocating an Internet Protocol (IP) address in a wireless network applied to a system including an access router and a portable terminal according to an embodiment of the present invention is used on a connected link. All stored IP addresses are stored in an address cache, and a notification message is sent to the portable terminal to indicate that DAD (Duplicate Address Detection) is performed based on the IP addresses, and an IP address automatically configured from the portable terminal. And a transmitter / receiver for receiving a request message for requesting the DAD to be performed, and a controller for receiving the request message from the transceiver and performing the DAD according to the request message.

Hereinafter, with reference to the accompanying drawings and the contents described in the accompanying drawings will be described in detail preferred embodiments of the present invention, but the present invention is not limited or restricted by the embodiments. Like reference symbols in the drawings denote like elements.

A mobile terminal for allocating an Internet Protocol (IP) address according to the present invention includes a mobile communication terminal, a public switched telephone network (PSTN) terminal, VoIP, SIP, Megaco, personal digital assistant (PDA), cellular phone, PCS (Personal Communication Service) phones, Hand-Held PCs, CDMA-2000 (1X, 3X) phones, Wideband CDMA (WCDMA) phones, Dual Band / Dual Mode phones, GSM ( It is assumed that the present invention can be implemented as one of a Global Standard for Mobile (MBS) phone, a Mobile Broadband System (MBS) phone, and a satellite / terrestrial digital multimedia broadcasting (DMB) phone.

1 is a configuration diagram schematically showing an IPv6-based wireless network according to an embodiment of the present invention.

As shown in FIG. 1, an IPv6-based wireless network 100 according to an embodiment of the present invention includes an access router 110, a base station 120, and It may include a mobile terminal (130).

The access router 110 stores at least a notification message for notifying that it is a specific access router that stores and manages all IP addresses and corresponding link-layer addresses on the connected link in the address cache and performs a DAD on the IP address. It can transmit to one mobile terminal.

If the IP address does not exist in the address cache, the access router 110 may store the IP address in the address cache and transmit a response message to the mobile terminal 130.

The base station 120 includes a notification message including a router advertisement message (RA) message, a request message including a neighbor solicitation (NS) message, and a neighbor advertisement message (NA) between the access router 110 and the mobile terminal 130. Can send a response message.

The mobile terminal 130 automatically generates an IP address and transmits a request message to the access router 120 requesting Duplicate Address Detection (DAD) for the generated IP address. The mobile terminal 130 may legitimately use the automatically set IP address according to the result of performing the DAD.

2 is a flowchart illustrating a method for allocating an IP address to an access router in a mobile terminal in a wireless network according to an embodiment of the present invention.

As shown in FIG. 2, in the wireless network according to an embodiment of the present disclosure, the method for notifying an IP address to a mobile terminal may include receiving a notification message (S210) and automatically generating an IP address (S220). The method may include transmitting a request message (S230), performing a DAD (S240), receiving a response message (S250), and legitimately assigning an IP address (S260).

A method for allocating an IP address to a mobile terminal in a wireless network according to an embodiment of the present invention as described above is described in detail as follows.

First, the access router 110 stores all the IP addresses used on the link to which they are connected and corresponding link-layer addresses in the address cache to manage them, and to notify that the access router 110 performs a DAD for the IP address. A notification message generated by generating a message may be transmitted to at least one mobile terminal 130 (S210). Here, the announcement message includes an Internet Control Message Protocol version 6 (ICMPv6) Router Advertisement (RA) message defined in the neighbor discovery protocol for IPv6. The format of the announcement message will be described with reference to FIG.

3 is an exemplary diagram for describing a format of a notification message according to an embodiment of the present invention.

As shown in FIG. 3, a notification message according to an embodiment of the present invention includes an IP header and an ICMPv6 RA message. The ICMPv6 RA message is provided by a type field indicating a type of a message and a type of a message. Code field indicating additional code, Checksum field for performing checksum operation, Current Hop Limit field to indicate current hop limit, M field with Always Off value, and O field, O _m field to indicate that it is a specific access router, unused Reserved field, Router Lifetime field to indicate default router life time, and arrival time of NS message sent. Reachable Time field to indicate, Retrans Timer field to indicate time between NS messages being retransmitted, and options It can include an optional field for applying.

In this case, the O _m field is an expression in which the access router 110 is defined to have an omnicient access router. 1) The access router 110 stores all IP addresses used on a link to which the access router 110 itself is connected to an address cache. And 2) a newly added field to indicate that the AP is a specific access router that performs a DAD for an IP address.

To this end, the RA message may add a DAD option, which may include a field indicating the characteristics of the connected link, a field indicating the number of times a DAD is requested, a field indicating the DAD method of the connected link, and an IP address in the address cache. It may include a field indicating a time to store.

In addition, the RA message may add a prefix information option, and a prefix information option may newly add a field indicating an prefix used for a stateless address autoconfiguration method, for example, an A2 field.

Thereafter, the mobile terminal 130 checks whether a preset notification message has been received from the access router 110 (S210). That is, when receiving the notification message, the mobile terminal 130 automatically configures an IP address (S220).

The mobile terminal 130 may generate a request message including the automatically configured IP address and transmit the generated request message to the access router 110 in unicast to request the DAD (S230). Here, the request message includes an ICMPv6 Neighbor Solicitation (NS) message defined in the neighbor discovery protocol for IPv6. The format of this request message will be described with reference to FIG. 4.

4 is an exemplary diagram for describing a format of a request message according to an embodiment of the present invention.

As shown in FIG. 4, the request message according to an embodiment of the present invention includes an IP header and an ICMPv6 NS message. The ICMPv6 NS message includes a type field indicating the type of the message and an additional code provided for each type of the message. A code field indicating a, a checksum field for performing checksum calculation, an R field for requesting DAD, a reserved field not used, a target address field for a target IP address of the message, and an option field for an option. Can be.

In this case, the R field means a field newly added to the NS message in order to request DAD of the target address.

For example, the mobile terminal 130 may generate a request message including an IP header and an ICMPv6 NS message and transmit the generated request message to the access router 110. That is, the request message may have a plurality of address fields, the IP address of the access router 110 in the destination address field, the automatically set IP address in the source address field, the automatically set IP address in the target address field, and the source. It can set its own link-layer address in the link-layer address field.

Thereafter, the access router 110 checks whether a request message for requesting Duplicate Address Detection (DAD) for the automatically configured IP address is received from the mobile terminal. That is, the access router 110 may determine whether to request a DAD for the automatically configured IP address by receiving the request message and checking the R field of the NS message included in the received request message.

Since the access router 110 may store and manage IP addresses set in the plurality of mobile terminals in an address cache, the access router 110 may perform a DAD for the IP addresses included in the request message (S240). That is, when the access router 110 receives the request message, the access router 110 may check whether the IP address included in the request message exists in the address cache managed by the access router 110.

If the IP address does not exist in the address cache, the access router 110 may store the IP address in the address cache and transmit a response message to the mobile terminal 130 in unicast. Here, the response message may include an ICMPv6 NA message defined in the neighbor discovery protocol for IPv6. The format of the response message will be described with reference to FIG. 5.

5 is an exemplary diagram for describing a format of a response message according to an embodiment of the present invention.

As shown in FIG. 5, the response message according to an embodiment of the present invention includes an IP header and an ICMPv6 NA message. The ICMPv6 NA message includes a type field indicating a type of a message, a code field indicating a type of a message, A checksum field for checksum calculation, an R field to indicate that the sender is an access router, an S field to indicate that it is in response to an NS message, an O field to indicate that an existing cache entry should be overridden, a response to a DAD request A U field, a reserved field that is not used, a target address field for a target IP address of a message, and an option field for an option.

In this case, the U field means a field newly added to the NA message in response to the DAD request for the target address.

For example, the access router 110 may generate a response message including an IP header and an ICMPv6 NA message and transmit the generated response message to the mobile terminal 130. That is, the response message may have a plurality of address fields, the IP address of which is automatically set in the destination address field, the IP address of the access router 110 in the source address field, the IP address that is automatically set in the target address field, and the source. Link-layer address fields of the access router 110 may be set in the link-layer address fields.

At this time, since the request message received from the mobile terminal 130 can refresh the storage time for the IP address stored in the address cache, it is determined whether the link-layer address exists if the IP address exists in the address cache. You need to check.

The access router 110 acts in response to any action, e.g., responding to the request message, if the IP address is present in the address cache and another mobile terminal, i.e., a link-layer address identical to the link-layer address included in the request message. Do not do it.

The access router 110 may reset the storage time of the IP address if the IP address exists in the address cache and there is no other mobile terminal, that is, the same link-layer address as the link-layer address included in the request message.

As a result, the mobile terminal 130 may receive a response message from the access router 110 (S250), check the result of the DAD request from the received response message, and then legally assign an IP address according to the confirmed result of the DAD request. (S260). That is, the mobile terminal 130 may use the IP address legitimately when receiving the response message, and discard the IP address if it does not receive the response message.

In addition, if the mobile terminal 130 does not receive a response message for a preset time, for example, 1 second reflecting the network state, the portable terminal 130 repeats the request message a predetermined number of times, for example, 3 times reflecting the network state. After transmitting to the access router 130, if the response message is not received as a result of the transmission, the IP address may be discarded.

6 is a block diagram illustrating a mobile terminal 600 for allocating an IP address in a wireless network according to an embodiment of the present invention.

As shown in FIG. 6, the mobile terminal 600 for allocating an IP address in a wireless network according to an embodiment of the present invention may be identified by a configuration unit 611, a generation unit 612, and an allocation unit 613. The controller 610 may include a unit 614, and a transceiver 620.

When the controller 610 receives a notification message from the transceiver 620, the controller 610 may automatically configure an IP address and request a DAD (Duplicate Address Detection) for the automatically configured IP address from the access router.

For example, when the configuration unit 611 receives a notification message from the transceiver 620, the configuration unit 611 may automatically configure an IP address, and the generation unit 612 may generate a request message including the automatically configured IP address. .

When the confirmation unit 614 receives the response message from the transceiver unit 620, the confirmation unit confirms the result of performing the DAD from the input response message, and the assignment unit 613 may legitimately assign an IP address according to the confirmed result of the DAD. have.

The transceiver 620 may receive a preset notification message from the access router, transmit a request message to the access router, and receive a response message from the access router in response to the transmitted request message.

7 is a block diagram illustrating an access router 700 for allocating an IP address in a wireless network according to an embodiment of the present invention.

As shown in FIG. 7, an access router 700 for allocating an IP address in a wireless network according to an embodiment of the present invention includes a controller 710 including a detector 711 and a generator 712, and It may include a transceiver 720.

When the controller 710 receives a request message for requesting DAD (Duplicate Address Detection) for the automatically configured IP address from the transceiver 720, the controller 710 may perform the requested DAD.

For example, when the detector 711 receives a request message from the transceiver 720, the detector 711 performs a DAD for the IP address included in the received request message, and the generator 712 responds according to a result of the DAD. You can create a message.

The transceiver 720 may transmit a preset notification message to the portable terminal, receive a request message from the portable terminal, and transmit a response message to the portable terminal in response to the received request message.

In addition, when the mobile terminal 130 receives a notification message from a plurality of access routers on the same link, the portable terminal 130 automatically configures an IP address and transmits a request message including the automatically configured IP address to the plurality of access routers. Can be. That is, the mobile terminal 130 may properly assign an automatically configured IP address when all response messages are received from the plurality of access routers.

An embodiment of the present invention may include a computer readable medium including program instructions for performing various computer-implemented operations. The computer readable medium may include program instructions, local data files, local data structures, or the like, alone or in combination. The media may be those specially designed and constructed for the purposes of the present invention, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical recording media such as CD-ROMs, DVDs, magnetic-optical media such as floppy disks, and ROM, RAM, flash memory, and the like. Hardware devices specifically configured to store and execute the same program instructions are included. Examples of program instructions may include machine language code such as those generated by a compiler, as well as high-level language code that may be executed by a computer using an interpreter or the like.

Although specific embodiments of the present invention have been described so far, various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

As can be seen from the above description, the portable terminal and method for allocating an IP address in a wireless network according to an embodiment of the present invention transmits a message indicating that the access router is a management access router. Automatically configures the IPv6 address and automatically uses the automatically configured IPv6 address after performing the DAD through the access router to avoid conflicts between IPv6 addresses that are automatically configured in the mobile terminal. It has the effect of making it possible.

Claims (28)

Internet Protocol (IP) in a wireless network applied to a system including an access router and a portable terminal that store and manage IP addresses used on a connected link in an address cache and perform DAD (Duplicate Address Detection) based on the IP addresses. In the method for allocating an address, Confirming whether a notification message sent from the access router has been received; And If the announcement message is received, automatically configuring an IP address and requesting the access router to perform the DAD for the automatically configured IP address Including, The notification message, A Router Advertisement (RA) message defined in a neighbor discovery protocol for IPv6, including a DAD option, wherein the DAD option includes a field indicating a characteristic of a connected link, a field indicating a number of times the DAD is requested, And a field indicating a time for storing an IP address in the address cache. delete delete The method according to claim 1, The notification message, A prefix information option, wherein the prefix information option includes a field indicating that the prefix is used for stateless address autoconfiguration IP address allocation method, characterized in that. The method according to claim 1, The requesting step, If the notification message has been received, automatically configuring the IP address; Generating a request message that includes the automatically configured IP address; And Sending the generated request message to the access router to request the DAD to be performed. IP address allocation method, characterized in that. 6. The method of claim 5, The request message, Including a neighbor solicitation (NS) message defined in a neighbor discovery protocol for IPv6, wherein the NS message includes a field for requesting performing the DAD for a target address; IP address allocation method, characterized in that. The method according to claim 1, Receiving a response message from the access router and confirming a DAD request result; And Legally allocating the IP address according to the result of the confirmed DAD request IP address allocation method further comprising. 8. The method of claim 7, The response message is, A NA (Neighbor Advertisement) message defined in a neighbor discovery protocol for IPv6, wherein the NA message includes a field responsive to the DAD request for a target address. IP address allocation method, characterized in that. 8. The method of claim 7, The allocating step, If no other mobile terminal uses the same IP address as the IP address, assigning the IP address legitimately; And If there is another portable terminal using the same IP address as the IP address, discarding the IP address. IP address allocation method, characterized in that. The method according to claim 1, The requesting step, Upon receiving a plurality of announcement messages from a plurality of access routers, automatically configuring an IP address and requesting the plurality of access routers for a DAD for the automatically configured IP address. IP address allocation method, characterized in that. A method for allocating an Internet Protocol (IP) address in a wireless network applied to a system including an access router and a portable terminal, Storing and managing IP addresses used on a connected link in an address cache, and sending a notification message to the mobile terminal to indicate performing DAD (Duplicate Address Detection) based on the IP addresses; And Confirming whether a request message for performing DAD for an automatically configured IP address has been received from the mobile terminal; Including, The notification message, A Router Advertisement (RA) message defined in a neighbor discovery protocol for IPv6, including a DAD option, wherein the DAD option includes a field indicating a characteristic of a connected link, a field indicating a number of times the DAD is requested, And a field indicating a time for storing an IP address in the address cache. 12. The method of claim 11, Upon receiving the request message, performing a DAD for the IP address; And Transmitting a response message to the mobile terminal according to a result of performing the DAD; IP address allocation method further comprising. 13. The method of claim 12, The transmitting step, Discarding the received request message if there is another portable terminal using the same IP address as the IP address; And If there is no other mobile terminal using the same IP address as the IP address, storing the IP address in the address cache and transmitting a response message in response to the request message. IP address allocation method, characterized in that. A computer-readable recording medium having recorded thereon a program for executing the method of any one of claims 1 to 13. Internet Protocol (IP) in a wireless network applied to a system including an access router and a portable terminal that store and manage IP addresses used on a connected link in an address cache and perform DAD (Duplicate Address Detection) based on the IP addresses. In a mobile terminal for allocating an address, A transmitter / receiver configured to receive a notification message transmitted from the access router and to transmit a request message for requesting the access router to perform the DAD for an automatically configured IP address; And A control unit for automatically configuring an IP address, generating the request message, and outputting the generated request message to the transmitter / receiver when the notification message is input from the transceiver; Including, The notification message, A Router Advertisement (RA) message defined in a neighbor discovery protocol for IPv6, including a DAD option, wherein the DAD option includes a field indicating a characteristic of a connected link, a field indicating a number of times the DAD is requested, And a field indicating a time for storing an IP address in the address cache. delete delete The method of claim 15, The notification message, A prefix information option, wherein the prefix information option includes a field indicating that the prefix is used for stateless address autoconfiguration The mobile terminal comprising: The method of claim 15, The control unit, A configuration unit configured to automatically configure the IP address when receiving the notification message from the transmission / reception unit; And Generating a request message including the automatically configured IP address and outputting the generated request message to the transceiver; The mobile terminal comprising: The method of claim 19, The request message, Including a neighbor solicitation (NS) message defined in a neighbor discovery protocol for IPv6, wherein the NS message includes a field for requesting performing the DAD for a target address; The mobile terminal comprising: The method of claim 15, The control unit, A confirmation unit confirming a result of performing DAD when receiving a response message from the transceiver; And An allocator for legitimately allocating the IP address according to the confirmed DAD execution result The mobile terminal further comprises. 22. The method of claim 21, The response message is, A NA (Neighbor Advertisement) message defined in a neighbor discovery protocol for IPv6, wherein the NA message includes a field responsive to the DAD request for a target address. The mobile terminal comprising: 22. The method of claim 21, The allocation unit, If there is no other portable terminal using the same IP address as the IP address, the IP address is justly assigned, If there is another portable terminal using the same IP address as the IP address, discarding the IP address. The mobile terminal comprising: The method of claim 15, The mobile terminal, Upon receiving a plurality of announcement messages from a plurality of access routers, automatically configuring an IP address and requesting the plurality of access routers for a DAD for the automatically configured IP address. The mobile terminal comprising: The method of claim 15, The mobile terminal, Mobile communication terminals, Public Switched Telephone Network (PSTN) terminals, VoIP, SIP, Megaco, Personal Digital Assistant (PDA), cellular phones, Personal Communication Service (PCS) phones, Hand-Held PCs, CDMA-2000 (1X, 3X) phones, Wideband CDMA (WCDMA) phones, Dual Band / Dual Mode phones, Global Standard for Mobile (GSM) phones, Mobile Broadband System (MBS) phones, and satellite / terrestrial DMB One of the (Digital Multimedia Broadcasting) phones The mobile terminal comprising: An access router for allocating an Internet Protocol (IP) address in a wireless network applied to a system including an access router and a portable terminal, All IP addresses used on the connected link are stored and managed in an address cache, and a notification message is sent to the mobile terminal to indicate Duplicate Address Detection (DAD) based on the IP addresses. Transmitting and receiving unit for receiving a request message for requesting to perform the DAD for the IP address consisting of; A controller which receives the request message from the transceiver and performs the DAD according to the request message Including, The notification message, A Router Advertisement (RA) message defined in a neighbor discovery protocol for IPv6, including a DAD option, wherein the DAD option includes a field indicating a characteristic of a connected link, a field indicating a number of times the DAD is requested, And a field indicating a time for storing an IP address in the address cache. The method of claim 26, The control unit, A detector for performing DAD on the IP address when receiving a request message from the transceiver; And And a generator configured to generate the response message according to a result of performing the DAD of the detector and to output the generated response message to the transceiver. An access router, characterized in that. The method of claim 27, The generation unit, If there is another portable terminal using the same IP address as the IP address, the received request message is discarded. Generating a response message in response to the request message after storing the IP address in the address cache if there is no other mobile terminal using the same IP address as the IP address; An access router, characterized in that.

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