KR100520040B1 - Method for detecting the change of the subnet in a mobile IP network through checking the IP address of the DHCP server - Google Patents

Abstract

The present invention relates to a wireless LAN AP to which a specific mobile node wirelessly connects, a specific subnet provided with a DHCP server, and a current subnet to which the specific mobile node belongs in a mobile IP network including HA differs from the previous subnet. A method of identifying and checking an IP address of a server, the method comprising: a first step of monitoring a change in a MAC address of an AP to which a specific mobile node accesses; and when there is no FA in the current subnet when the MAC address of the AP is changed Checking the IP address of the DHCP server of the current subnet, and if the IP address of the DHCP server of the current subnet and the IP address of the previous DHCP server are different, determining that the subnet has been changed, and determining that the subnet has been changed And a third step of assigning an IP address from a DHCP server of the current subnet, and a fourth step of registering the assigned IP address with the HA.

Description

Method for detecting the change of the subnet in a mobile IP network through checking the IP address of the DHCP server}

The present invention relates to a method for checking a subnet change using a Dynamic Host Configuration Protocol (DHCP) server in a mobile Internet Protocol (IP) network. In particular, a mobile node may be configured to have a DHCP node in a subnet without a FA (Foreign Agent). It's about how to check if a subnet has changed by checking the server's IP address.

As described in the Request for Comments (RFC) 2002 document provided by the Internet Engineering Task Force (IETF), a mobile IP network is based on a FA with a mobile node and a home agent (HA). The default configuration is one HA for the entire mobile IP network and one for each FA.

1 is a diagram illustrating a procedure in which a mobile node recognizes a current subnet and registers a location in a conventional mobile IP network. In the same diagram, a mobile node 1 is connected to a target node at a remote location when an initial connection or a subnet is changed. In order to communicate, the location registration procedure for registering its current location with the HA (3) must be performed.

In the conventional mobile IP network, the mobile node 1 finds out from the agent advertisement message information of the FA 2 whether the subnet has changed. The mobile node 1 sends (S11) an agent solicitation message requesting the agent propagation message to the FA 2 in order to obtain the agent propagation message, and sends the agent propagation message from the FA 2. It is provided (S12). The agent advertisement message contains the IP address of the FA (2). The mobile node 1 grasps the IP address of the FA 2 which is the current location information from the agent propagation message provided from the FA 2, and the IP address of the FA 2 and the address of the self-stored HA 3 (or If the subnet is changed, check whether the subnet has been changed by comparing the IP address of FA in the previous subnet. If the subnet is changed, the registration process is performed (S13).

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The registration procedure refers to a procedure of registering the current location address of the mobile node with the HA (3). The current location address of the mobile node 1 is one of a Care of Address (CoA) method using the IP address of the FA (2) and a Co-located CoA method using the IP address of the mobile node (1) assigned from a DHCP server. use. That is, in the CoA method, the mobile node registers the IP address of the FA (2) to the HA (3), and in the Co-CoA method, the mobile node 1 registers the IP address of the mobile node (1) assigned by the DHCP server to the HA Register in (3).

In this case, if the CoA method using the IP address of the FA 2 is used in the location registration method, the mobile node 1 carries the IP address of the FA 2 in the location registration request message and transmits the HA through the FA (2). (3) (S14, S15). The HA (3) updates the self-stored mobile node location management table with the received location information of the mobile node (1) (S16). The HA (3) updates the mobile node (1). After registering the current location address of), a response message informing that the location registration is completed is transmitted to the mobile node 1 through the FA 2 (S17, S18). Then, the mobile node 1 receives the FA ( The location registration procedure ends when the response message provided from 2) is received.

After the location registration procedure as described above, the mobile node 1 is able to transmit packets with the target node 4 located at a remote location as shown in FIG. 2. FIG. 2 illustrates data communication in a conventional mobile IP network. As shown in FIG. 1, data communication is performed after the mobile node 1 performs the process illustrated in FIG. 1 as the mobile node 1 moves from the first subnet sub1 to the second subnet sub2.

First, in the packet transmitted from the mobile node 1 to the target node 4, the home network address of the mobile node 1 (IP address belonging to the subnet where the HA 3 is located) is recorded as an IP source address, As the address of the target node 4 is recorded as the IP target address, the corresponding packet is transmitted directly from the mobile node 1 to the target node 4 via the Internet.

On the other hand, in the packet transmitted from the target node 4 to the mobile node 1, the IP address of the target node 4 is recorded as the IP source address, and the home network address of the mobile node 1 is recorded as the IP target address. As recorded, the packet arrives at the HA 3, and is then tunneled to the CoA address of the mobile node 1 recorded in the location management table of the HA 3. In this case, since the COA address is an IP address of the FA 2, the corresponding packet is tunneled to the FA 2, and then de-tunneled from the FA 2 to the mobile node 1. .

As described above, the conventional mobile IP network checks the subnet change using the IP address of the FA and performs the location registration procedure.

However, such a conventional mobile IP network has to check the subnet change from the agent advertisement message of the FA, and therefore, a FA must be installed for each subnet. On the other hand, many subnets are connected to the Internet, and DHCP servers are already installed in each subnet. On the other hand, because the mobile IP network is not widely established, the subnet where the FA is installed is very small.

Therefore, in the conventional mobile IP network method, since each FA needs to be installed in each subnet, there is a problem in that the FA is expensive and the DHCP server that is already installed cannot be efficiently used.

The present invention has been made to solve the above-mentioned problems of the prior art, in a subnet without FA, the mobile node checks the DHCP server address to confirm the subnet change, if the subnet is changed, assigns an IP address from the DHCP server An object of the present invention is to register a received IP address in the HA. The present invention provides a wireless LAN (Access Point) and a DHCP server to which a specific mobile node wirelessly connects. A method for determining whether a current subnet to which a specific mobile node belongs to is different from a previous subnet in a mobile IP network including a specific subnet and HA, wherein the specific mobile node accesses the IP address of the DHCP server. A first step of monitoring a change in an AP's MAC (Media Access Control) address, and when there is no FA in the current subnet when the AP's MAC address is changed Check the address of the DHCP server of the current subnet and compare the IP address of the DHCP server of the current subnet with the IP address of the previous DHCP server (the IP address of the DHCP server of the previously connected subnet). A second step of determining that the subnet has changed when the IP address of the IP address is different from that of the previous DHCP server, and a third step of receiving an IP address from the DHCP server of the current subnet when determining that the subnet has been changed; And a fourth step of registering the assigned IP address with the HA.

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Hereinafter, exemplary embodiments of the present invention described above will be described in detail with reference to the accompanying drawings. At this time, there is no FA in the subnet to which the present invention is applied.

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3 is a diagram illustrating a process of recognizing a current subnet by a mobile node according to an embodiment of the present invention.

In the same figure, when the user turns on the mobile node 10 (S301), the mobile node 10 requests agent solicitation message of the FA to check the information of the current subnet in which the mobile node 10 is located. A message and a DHCPDISCOVER message for searching for a DHCP server 20 are broadcasted around (S302 and S303). At this time, the mobile node 10 broadcasts the agent solicitation message to check whether there is an FA in the vicinity. If there is a FA around the mobile node 10, the FA broadcasts the agent advertisement message in response to the agent solicitation message. On the other hand, the present invention assumes that no FA exists because it is for a subnet where no FA exists. Therefore, since there is no destination of the agent solvation message broadcasted by the mobile node 10, the solicitation message disappears, and the DHCPDISCOVER message is received by the DHCP server 20. The DHCP server 20 In response to the DHCPDISCOVER message, sends a DHCPOFFER message to the mobile node 10 (S304). At this time, the DHCPOFFER message includes the IP address information of the DHCP server 20.

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The mobile node 10 receives the DHCPOFFER message transmitted from the DHCP server 20, checks the IP address of the DHCP server 20 included in the received DHCPOFFER message (S305), and then requests a request for IP address allocation. The DHCP server 20 allocates an IP address to the mobile node 10 according to the IP address allocation request message transmitted from the mobile node 10 (S307).

The mobile node 10 transmits its own IP address assigned from the DHCP server 20 to the HA 30 in a location registration request message (S308, S309). The HA 30 transmits from the mobile node 10. The address management table managed by the user is updated according to the received location registration request message, and the current location address of the mobile node 10 is registered (S310).

The HA 30 transmits the current location registration fact to the mobile node 10 as a response message, so that the mobile node 10 can confirm its current location registration fact (S311).

As such, since the current location of the mobile node 10 is registered in the HA 30, the mobile node 10 may perform packet exchange with the target node in the subnet to which the mobile node 10 is connected.

4 is a diagram illustrating a process of recognizing a new subnet by a handoff mobile node according to an embodiment of the present invention.

In the figure, the mobile node 10 monitors whether or not the MAC address of the WLAN AP to which it is connected changes the AP to which it is connected (S401). If there are multiple WLAN APs in the same subnet, the subnet does not change even if the WLAN APs are connected differently. However, the subnet cannot be changed without changing the access point of the WLAN AP. Accordingly, the mobile node 10 checks whether the subnet is changed when the accessing AP is changed. The MAC address of the AP is different for each AP. In addition, the AP periodically broadcasts a signal indicating its presence, that is, a beacon signal, which includes its MAC address information.

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If the mobile node 10 determines that the MAC address of the AP has been changed by performing the step S401, the mobile node 10 performs the following procedure of checking whether the subnet has been changed. The agent solution message for finding the FA 2 and the DHCPDISCOVER message for finding the DHCP server 20 are respectively broadcasted (S402 and S403). At this time, if the FA (2) is present in the subnet where the mobile node 10 is located, the mobile node 10 receives the agent propagation message in response to the agent solution message from the FA (2), the FA exists By performing the same operation as in the conventional mobile IP network, it performs its own location registration and packet exchange with the target node. Meanwhile, the present invention is based on the premise that the FA 2 does not exist in the subnet where the mobile node 10 is located.

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That is, if the FA 2 does not exist in the subnet where the mobile node 10 is located, the mobile node 10 receives a DHCPOFFER message from the DHCP server 20 as a response signal of the DHCPDISCOVER message, and includes it in the DHCPOFFER message. Confirm the IP address of the DHCP server 20 (S404, S405).

The mobile node 10 compares the checked IP address of the DHCP server 20 with the IP address of the stored DHCP server, and determines whether the mobile node 10 enters a new subnet (S406). The IP address of the DHCP server stored in the mobile node 10 is the IP address of the DHCP server of the subnet that was previously connected. The mobile node 10 is the IP address of the DHCP server 20 confirmed through the process (S406). If and the IP address of the stored DHCP server is the same, it is determined that the same subnet, if different, it is determined that the new subnet entered (S407).

The mobile node 10 does not register the current location if its current location is in the same subnet in step S407, but if it determines that its current location has entered a new subnet, the IP address assigned from the previous DHCP server. Has become obsolete, it transmits a signal to the DHCP server 20 requesting to be allocated a new IP address from the new DHCP server 20 (S408).

The DHCP server 20 allocates an IP address to the mobile node 10 according to the IP address allocation request signal received from the mobile node 10 (S409).

When the mobile node 10 receives an IP address from the DHCP server 20, the mobile node 10 transmits the allocated IP address, that is, the co-located COA, to the HA 30 in a registration request message (S410). The HA 30 updates the mobile node location management table as the Co-located CoA included in the registration request message, so that the new current location of the mobile node 20 is updated and registered (S411). After completing the location registration process, a response message is transmitted to the mobile node 10 (S412).

When the mobile node 10 receives the response message from the HA 30, the mobile node 10 confirms that its current location is registered, and can exchange packets with the target node. The process of communication between the mobile node 10 and the target node is the same as the mobile IP network using the conventional C0-located COA method. FIG. 5 is assigned an IP address from a DHCP server according to an embodiment of the present invention. In this figure, the packet transmitted from the mobile node 10 is transmitted directly to the target node, and the packet transmitted from the target node is transmitted to the target node. After being delivered to the HA 30, it is tunneled directly to the mobile node 10 according to the information of the mobile node location management table of the HA 30. Packets tunneled to the mobile node 10 are de-tunneled by the mobile node 10.

The embodiment of the present invention described above has described the WLAN as an example. If the embodiment of the present invention is applied to a wired LAN, the present invention monitors the active state of a wired LAN card, such as determining the handoff of the mobile node by determining that the MAC address of the AP is changed in the WLAN. To judge the handoff.

Here, in the case of the wired LAN, in order to change the subnet, the wired LAN cable must be unplugged and plugged back in. At this time, the LAN card is inactivated and then activated again.

The technical spirit of the present invention has been described above with reference to the accompanying drawings, but this is by way of example only and not intended to limit the present invention. In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

As described above, in the present invention, in a subnet without FA, the mobile node confirms the subnet change by using a DHCP server and receives an IP address from the DHCP server. Therefore, since the FA does not need to be separately installed in the subnet where the DHCP server is already installed, it is possible to easily provide the mobile IP communication service while reducing the overall installation cost of the mobile IP network.

1 is a diagram illustrating a procedure for a mobile node to recognize a current subnet and register a location in a conventional mobile IP network;

2 is a diagram illustrating data communication in a conventional mobile IP network;

3 is a diagram illustrating a process of recognizing a current subnet by a mobile node according to an embodiment of the present invention;

4 is a diagram illustrating a process of recognizing a new subnet by a handoff mobile node according to an embodiment of the present invention;

5 is a diagram illustrating receiving an IP address from a DHCP server according to an embodiment of the present invention, registering the assigned IP address with the HA, and then transmitting a data packet.

Claims (4)

In a mobile IP network including a WLAN AP to which a specific mobile node wirelessly connects, a specific subnet provided with a DHCP server, and HA, an IP address of the DHCP server whether the current subnet to which the specific mobile node belongs is different from the previous subnet. As a way to find out, A first step of monitoring a change in a MAC address of an AP to which the specific mobile node accesses; When the MAC address of the AP is changed, if there is no FA in the current subnet, check the IP address of the DHCP server of the current subnet, if the IP address of the DHCP server of the current subnet and the IP address of the previous DHCP server is different , The second step of determining that the subnet has changed, If it is determined that the subnet has been changed, a third step of assigning an IP address from a DHCP server of the current subnet; A fourth step of registering the allocated IP address with the HA How to check the subnet change using a DHCP server in a mobile IP network comprising a. The method of claim 1, The checking of the IP address of the DHCP server of the current subnet of the second step may include: broadcasting, by the specific mobile node, a DHCPDISCOVER message; Receiving, by the specific mobile node, a DHCPOFFER message which is a response message of the DHCPDISCOVER message from a DHCP server of the current subnet; Determining, by the specific mobile node, the IP address of the DHCP server of the current subnet included in the DHCPOFFER message. How to check the subnet change using a DHCP server in a mobile IP network comprising a. On your computer, In a mobile IP network including a WLAN AP to which a specific mobile node wirelessly connects, a specific subnet provided with a DHCP server, and HA, an IP address of the DHCP server whether the current subnet to which the specific mobile node belongs is different from the previous subnet. As a way to find out, A first step of monitoring a change in a MAC address of an AP to which the specific mobile node accesses; When the MAC address of the AP is changed, if there is no FA in the current subnet, check the IP address of the DHCP server of the current subnet, if the IP address of the DHCP server of the current subnet and the IP address of the previous DHCP server is different , The second step of determining that the subnet has changed, If it is determined that the subnet has been changed, a third step of assigning an IP address from a DHCP server of the current subnet; A fourth step of registering the allocated IP address with the HA A computer-readable recording medium that contains a program that can execute a program. delete