KR20060000497A - Method for supporting mobility for mobile ip service - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a mobility support method for a mobile IP service.

2. The technical problem to be solved by the invention

The present invention eliminates the load concentrated on the home agent when performing the handoff by adjusting the anchor node height indicating the hierarchical value of the anchor node, which is one of the plurality of agents, and setting the packet path through the handoff in the wireless. Its purpose is to provide a mobility support method for mobile IP services.

3. Summary of Solution to Invention

The present invention provides a mobility support method for a mobile IP service applied to a network system including a plurality of agents, mobile nodes, and counterpart nodes having a hierarchical structure, wherein a first agent of the plurality of agents is selected from a lower layer side. A binding update receiving step of receiving a binding update packet; An information comparing step of the first agent comparing binding information in a packet with binding information stored in an internal cache; As the first agent matches the binding information in the packet and the stored binding information, the first agent maintains an anchor node height indicating a hierarchy value of an anchor node which is one of the plurality of agents, and the first agent maintains the anchor node height. Anchor node height adjustment that transmits information and binding update packet to the upper layer side, and updates binding information stored in the internal cache and increases anchor node height by one step as the binding information in the packet and the stored binding information are inconsistent. step; And a binding response transmitting step of transmitting the anchor node height information and the binding response to a lower layer.

4. Important uses of the invention

The present invention is used for mobile IP service.

Mobile IP, Mobile Node, Anchor Node, Partner Node, Agent

Description

Mobility Support Method for Mobile IP Service {METHOD FOR SUPPORTING MOBILITY FOR MOBILE IP SERVICE}             

1 is a flowchart illustrating a general method of discovering another agent in an external agent;

2 is a flowchart illustrating a process of processing a registration request in a general registration method of an external agent;

3 is a flowchart illustrating a registration response processing method among general registration methods in an external agent;

4 is a flowchart illustrating a registration request processing method among general registration methods in a home agent;

5 is a flowchart illustrating a general method of managing agent information in a mobile node;

6 is a flowchart illustrating a general agent discovery method in a mobile node;

7 is a flowchart illustrating an operation in a mobile node of a mobility support method for a mobile IP service according to the present invention;

8 is a flowchart illustrating an operation of an agent in a mobility support method for a mobile IP service according to the present invention;

9 is a diagram illustrating a network system to which a mobility support method for a mobile IP service of the present invention is applied.

Explanation of symbols on the main parts of the drawings

901: Mobile Nodes 911-914, 921, 931: External Agent

951: Relative Node

The present invention relates to a mobility support method for a mobile IP service of a portable terminal, and more particularly, to a mobility support method for a mobile IP service of a portable terminal based on a public key cryptographic algorithm.

Various information devices such as PDAs, smart phones, Internet terminals, Internet TVs, etc. are being converged with wireless communication technologies such as Bluetooth and 802.11b to change the existing computing paradigm of fixed desktop PCs to mobile. This paradigm allows users to access information anytime and anywhere. In particular, with the recent growth in the use of the Internet and wireless networks, not only wired users but also wireless users want to freely access various services regardless of place. In the age of knowledge informatization, computer and internet technologies are emerging that enable anytime, anywhere and anyone access to the knowledge and information they want. Among them, Mobile-IP technology provides a way to freely and easily obtain various knowledge and information services provided from outside or inside by interconnecting information appliances. Home refrigerators and information appliances have already been connected to networks such as internet refrigerators and electronic ovens. As a result, the digital life era and the ubiquitous era are approaching the domestic high-speed network and cyber apartments. In order to provide such mobility, certain IP protocols have been proposed, and these IP protocols provide continuous service even when a wireless user temporarily moves to another subnet.

In a wireless Internet environment, since the terminal moves and its location always changes, the mobility of the terminal must be supported and at the same time, the Internet service as in the existing wired network must be provided. Representative technologies for supporting the mobility of these terminals include mobile IP, W-TCP, and Mobile Ad-hoc NETwork (MANET). Here, mobile IP is a technology for providing an IP service regardless of where a mobile node is in the current network, and Wireless-TCP is a technology for improving existing TCP to a form suitable for a wireless network. Finally, MANET is a technology for supporting the situation where all nodes move without a fixed infrastructure such as a base station.

Among these, Mobile IP was developed to overcome the limitations of the host's movement between subnets in network IP address based routing. Other existing algorithms did not support mobility between subnets. In order for a host moved to another network to continue to connect to the Internet, a valid IP address must be assigned from the moved network system, and the host's configuration must be changed accordingly. This causes a lot of inconvenience in managing IP addresses. do. To solve this problem, a protocol called Mobile IP (RFC 2002) has been proposed by the Internet Engineering Task Force (IETF). Mobile IP provides mobility, and mobile IP, a wired core network protocol, is essential to support wireless Internet. Currently, 3GPP2 networks accept mobile IP, and UMTS sets it as standard in GPRS.

Mobile IP adopts a two-tier addressing scheme as an address translation scheme in the IP layer. That is, the first address is a care of address (COA) used for route allocation and delivery method, and the other address is a home address (HA), which is a static IP address unique to the mobile host used for identifying a mobile host and connecting a session. That is, the mobile host has a home address (HA), which is a unique Internet address corresponding to the host name, as in the existing fixed host, and a COA, which is a change address of the mobile host as it moves through the network. .

Here, the mobile node (MN) is a terminal capable of communication, such as a notebook, a computer, a wireless terminal. In addition, a mobile agent (MA) is a router for each network link at home or outside. On the other hand, a home agent (HA) is a router on a node's home network link. A foreign agent (FA) is also a router on the node's external network link. The care-of-address (COA), on the other hand, is the address of the external agent that the mobile node holds to communicate with the home agent.

Referring to the operation in the mobile IP as follows.

First, an agent discovery process is performed.

The agent discovery process is a process of determining whether the current location of the mobile host is a home network (HN) or a foreign network (FN), or whether the mobile host moves from one network to another. Every HA or FA broadcasts the COA within its link coverage periodically to advertise its current service availability. The mobile host may also send an Agent Solicitation message to obtain a COA. Agent Advertisement performs the following functions.

• Make it possible to find HA or FA.

List the COAs that the mobile host can obtain.

Inform the mobile host about the special features provided by the FA.

Allows the mobile host to distinguish whether the network it is currently connected to is a home network or an external network.

Thereafter, a registration process is performed.

The registration process is a process of conveying network information to which the mobile host currently belongs to their HA. Through the registration process, a mobility binding having a home address, a COA, and a registration valid time of a mobile host is newly created or updated in a home agent (HA). There are two main scenarios for registration: the FA sends the registration request message of the mobile host to the HA, and the mobile host sends the registration request message directly to the HA without an external agent such as the FA. .

Thereafter, a tunneling process is performed.

In the tunneling process, after a mobile host is registered with the FA and the HA, a datagram sent to the HN of the mobile host is intercepted in the HA and transmitted to the registered FA according to the COA information of the mobile host. If the mobile host exists in the HA, it is delivered directly to the mobile host without any additional tunneling process. If the mobile host is moved to the FN, the datagram is encapsulated from the HA to the COA and transmitted to the FA.

1 is a flowchart illustrating a general method of discovering another agent in an external agent, which will be described below.

First, it is determined whether the foreign agent FA has received a solicitation from the mobile node (S110). If the request is received from the mobile node, it transmits a 1: 1 advertisement toward the corresponding mobile node (Unicast) (S120). On the other hand, if the request is not received from the mobile node, the internal timer determines whether the predetermined time has elapsed, and if the predetermined time has not elapsed, the process of determining whether the predetermined time has elapsed is repeatedly performed ( S130). If a predetermined time has elapsed, a 1: N advertisement is transmitted to all possible mobile nodes (N) (Broadcast) (S140).

2 is a flowchart illustrating a process of processing a registration request in a general registration method of an external agent.

First, the external agent FA receives a registration request from the mobile node (S210). Thereafter, it is determined whether the registration request of the mobile node is within the life time of the advertisement transmitted by the external agent FA through the method of FIG. 1 (S220). If the registration request of the mobile node is received beyond the life time of the advertisement transmitted by the external agent FA, the registration request is ignored (S230). On the other hand, if the registration request of the mobile node is received within the life time of the advertisement transmitted by the external agent (FA), whether the current foreign agent (FA) is unable to perform the registration process (busy) It is determined (S240). If the current external agent (FA) is unable to perform the registration process, the mobile node information is added to a visit list (Visit list) (S250). Thereafter, the registration request of the mobile node is forwarded to the home agent (S260). On the other hand, if the current external agent (FA) can perform the registration process, the storage process is performed by storing the registration ID generated through the MD5 authentication method (S270).

3 is a flowchart illustrating a registration response processing method among general registration methods in an external agent.

First, the external agent FA receives a registration response from the home agent forwarding the registration request by the method of FIG. 2, and checks whether the registration response ID matches the ID sent by the external agent (S310). Then, if the registration response ID matches the ID sent by the external agent, whether the registration request of the mobile node is within the life time of the registration request forwarded by the external agent FA through the method of FIG. It is determined (S320). If the registration response from the home agent is received beyond the life time of the registration request forwarded by the external agent FA, the registration response is ignored (S330). On the other hand, when the registration response from the home agent is received within the life time of the registration request forwarded by the external agent FA, the registration response is forwarded to the mobile node that requested the registration (S340).

4 is a flowchart illustrating a registration request processing method among general registration methods in a home agent.

First, the home agent receives a registration request from a mobile node through an external agent FA (S410). Thereafter, it is determined whether the registration request of the mobile node is within the life time of the advertisement transmitted by the home agent (S420). If the registration request of the mobile node is received beyond the life time of the advertisement transmitted by the home agent), the registration request is ignored (S430). On the other hand, when the registration request of the mobile node is received within the life time of the advertisement transmitted by the home agent, it is determined whether the home agent is currently in a state in which it cannot perform a registration process (S440). If the current home agent cannot perform a registration process, the mobile node information and related external agent information are stored in a binding list (S450). Thereafter, the registration response that registration is impossible is transmitted to the mobile node through the external agent (S460). On the other hand, if the current home agent can perform the registration process, the storage process is performed by storing the registration ID generated through the MD5 authentication method (S470).

FIG. 5 is a flowchart illustrating a general method for managing agent information in a mobile node.

First, it is determined whether the mobile node has received an advertisement from an external agent FA or a home agent (S510). If the mobile node receives an advertisement from an external agent (FA) or a home agent, the mobile node stores information of the corresponding external agent (FA) or home agent in a cache memory mounted therein (S520). On the other hand, if the mobile node does not receive an advertisement from an external agent (FA) or a home agent, it is determined whether a predetermined time has elapsed by an internal timer, and if the predetermined time has not elapsed, whether the predetermined time has elapsed. The determination process is repeatedly performed (S530). If the predetermined time has elapsed, the mobile node transmits a solicitation toward the external agent FA or the home agent (S540). Then, after receiving the advertisement message from the external agent (FA) or the home agent that received the solicitation (S550), the information of the corresponding external agent (FA) or the home agent is stored in the cache memory mounted therein (S520). .

6 is a flowchart illustrating a general agent discovery method in a mobile node, which will be described below.

First, it is determined whether the mobile node has moved to a new network (S610). If the mobile node does not move to the new network, external agent information is read from the cache memory (S620). Thereafter, a registration request is made to the corresponding external agent according to the obtained external agent information (S630). Meanwhile, when the mobile node moves to a new network, new external agent information is acquired, new external agent information is read into the cache memory (S640), and then registered with the corresponding external agent according to the obtained external agent information. Request (S630).

In addition, the mobile node and the agent may support reverse tunneling, indicating that the 'T' bit is set in the advertisement message extension format of the external agent to support reverse tunneling. The mobile node sets the 'T' bit in the registration request form to inform the mobile IP service through reverse tunneling, and the home agent starts the mobile IP service through reverse tunneling. Comparing the large flow of reverse tunneling with normal tunneling, the mobile node transmits to the related node, except that it is served via the 'T' bit until the mobile node receives a packet from the connected Correspondent node. In doing so, there is a difference in where to forward the packet.

When a mobile node moves to another network in a mobile IP service, the mobile node's first connected connection is not sustained and is disconnected. This is called handoff. As shown in Figure 6, when the mobile node moves to a new network and a handoff occurs, this fact is recognized by the home agent by the mobile node's registration request. The mobile node will be disconnected from the old agent and will be connected to the new external network agent. While the handoff occurs, the foreign agent of the previous mobile node sends a packet to the home agent, but the home agent does not receive it.

In order to solve the transmission problem caused by the new connection establishment, it is necessary to retransmit lost packets to the mobile node through the connected new agent after the handoff is completed. Accordingly, the Correspondent node (meaning a counterpart node communicating with the mobile node through the agent) waits for a predetermined timeout before retransmitting the lost packet, and the home agent retransmits it. After that, the agent that the mobile node will move to has this packet through buffering and sends the packet to the mobile node when a handoff occurs.

However, according to the conventional method described above, there is a problem that not only solves the handoff, but also increases the overhead and loses almost all packets to be transmitted during the handoff.

An example of triangular routing will be described with reference to the above problem.

First, all packets sent from the counterpart node are sent to the home network. The home agent tunnels the packets and sends them to the foreign network.

The partner node sends a packet to the mobile node in the external network through the home agent. Subsequently, when the mobile node moves to another network, transmission performed along the unoptimized path may be a factor causing delay in hand off. In order to solve this problem, an optimized path of packet transmission from a counterpart node is required. For this purpose, a binding cache is provided at each node. To this end, the home agent must store the location information of the mobile node in its binding cache and notify the other node through a binding update whenever there is a change. The home agent sends the binding update information to the counterpart node, and simultaneously sends the packet sent from the counterpart node to the external agent through tunneling.

Direct transmission to foreign agent is performed through information bound to partner node. That is, when the mobile node moves from the external network managed by the first external agent FA1 to the external network managed by the second external agent FA2, the second external agent FA2 sends a registration request to the home agent. As a result, the home agent binds the mobile node's movement information. However, the counterpart node does not know this, and thus the packet is continuously transmitted to the first foreign agent FA1, which is the previous agent.

The home agent receiving the registration request binds the information of the mobile node. However, since the partner node did not update this information, it continues to transmit to the first foreign agent FA1 and loses a packet to be transmitted. To this end, when the mobile node moves from the previous agent, the first external agent FA1, the counterpart node may request the home agent to update the binding information. First, when the first external agent FA1 sends the mobile node's movement information to the home agent as a binding warning request message, the home agent notifies the counterpart node to update the binding cache. The counterpart node can transmit the packet directly to the second external agent FA2 after updating the mobile node's movement information.

According to the smooth hand off method, when a mobile node moves to another network, the mobile node sends a registration request to the home agent through a new external agent. At this time, the new external agent requests the previous external agent to update the binding along with the registration request, which uses the reserve bit of the registration request header of the mobile node. When the mobile node moves, the second external agent FA2 sends a registration request message to the home agent, and requests the binding update from the first external agent FA1. At this time, the first external agent FA1 stores the data of the counterpart node to be transmitted to the mobile node through the first external agent FA1 through the temporary buffer, and when authentication of the home agent is completed, the second external agent FA2. Will be sent to the mobile node.

That is, the hand off mechanism for supporting the above-mentioned conventional mobility is performed in the handoff over the air because all registration requests for solving the handoff of the mobile node are made through the home agent. There is a problem in that a delay is large and a packet is likely to be lost.

The present invention has been proposed in order to solve the above problems, by adjusting the anchor node height indicating the hierarchical value of the anchor node, which is one of the plurality of agents during handoff in the wireless, by setting the packet path through the handoff, An object of the present invention is to provide a mobility support method for a mobile IP service that can eliminate a load concentrated on a home agent when executed.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

The method of the present invention for achieving the above object is a mobility support method for a mobile IP service applied to a network system including a plurality of agents having a hierarchical structure, a mobile node and a partner node, among the plurality of agents A binding update receiving step of receiving, by the first agent, a binding update packet from a lower layer side; An information comparing step of the first agent comparing binding information in a packet with binding information stored in an internal cache; As the first agent matches the binding information in the packet and the stored binding information, the first agent maintains an anchor node height indicating a hierarchy value of an anchor node which is one of the plurality of agents, and the first agent maintains the anchor node height. Anchor node height adjustment that transmits information and binding update packet to the upper layer, and updates binding information stored in the internal cache and increases the anchor node height by one step when the binding information in the packet and the stored binding information are inconsistent. step; And a binding response transmitting step of transmitting the anchor node height information and the binding response to a lower layer.

In addition, the method of the present invention for achieving the above object is a mobility support method for a mobile IP service applied to a network system including a plurality of agents, mobile nodes and partner nodes having a hierarchical structure, the plurality of A binding update receiving step of receiving, by a first agent of the agent, a binding update packet from a lower layer side; An information comparing step of the first agent comparing binding information in a packet with binding information stored in an internal cache; The first agent transmits the anchor node height information and the binding update packet to an upper layer according to whether the binding information in the packet matches the stored binding information, and the anchor is one of the plurality of agents. An anchor node height adjustment step of adjusting an anchor node height indicating a hierarchy value of the nodes; And a binding update transmission step of transmitting the anchor node height information and the binding response to a lower layer.

FIG. 7 is a flowchart illustrating an operation of a mobile node in a mobility support method for a mobile IP service according to the present invention.

First, an advertisement is received from an external agent FA, which is a mobility support agent, in the mobile node (S710). In this case, the advertisement reception is an advertisement transmitted by the advertisement transmission operation of the agent according to FIG. 1, and the mobile node may perform the solicitation operation for this purpose, but as described above, the description thereof is omitted for convenience. .

Thereafter, the mobile node generates a care of address (CoA) using the information included in the advertisement (S720).

Thereafter, the mobile node transmits binding information including the home agent address and the CoA as a binding update packet (S730).

8 is a flowchart illustrating an operation of an agent in the mobility support method for the mobile IP service according to the present invention.

First, an external agent FA, which is a mobility support agent, receives a binding update (BU) packet from a lower layer (S810). In this case, the lowest layer may include a mobile node, and the highest layer may include a home agent (HA), but is not limited thereto.

Thereafter, the foreign agent FA, the mobility support agent, compares the binding information in the packet with the binding information stored in the internal cache (S820).

If the binding information in the packet matches the stored binding information, the foreign agent FA, the mobility support agent, maintains the anchor node height indicating the hierarchical value of the anchor node, which is one of the plurality of agents. S830).

On the other hand, if there is a mismatch between the binding information in the packet and the stored binding information, the external agent FA, the mobility support agent, updates the binding information stored in the internal cache and increases the anchor node height by one step (S840). ).

At this time, when the anchor node height changes, the external agent FA, which is the mobility support agent, may transmit the anchor node height information and the binding update packet to an upper layer side (S850).

Thereafter, the anchor node height information and the binding response are transmitted to the lower layer side (S835).

Here, since the range of the height of the anchor node is determined by the number of hierarchies of agents existing between the home agent and the mobile node, it is obvious that it cannot be increased indefinitely.

9 is a configuration diagram illustrating a network system to which a mobility support method for a mobile IP service of the present invention is applied. Referring to this, a mobility support method for a mobile IP service of the present invention will be described below.

Anchor nodes are dynamically determined in the network hierarchy according to the mobile node's movement characteristics. They are located in the minimum network layer including the network area in which the mobile node is active. It provides a delivery point for forwarding packets that are mobile nodes to a new location. At this time, the current position information CoA of the mobile node known to the counterpart node is the address of the anchor node. All mobility support agents in the layer between the foreign agent FA and the anchor node, which are the connection points of the mobile node, store the binding information of the mobile node in the cache. Local movement (①) that moves the position within the network area where the mobile node is active based on the anchor node is processed transparently to the counterpart node to reduce the signaling load incurred when registering the location. When the mobile node moves its location (①, ②, and ③), it sends a binding update message to notify the other node of the new location information.The binding information is updated to the first path (911, 921, or 931) that meets the previous path. At that point, the packets are rerouted between the destination 951 and the mobile node 901 to minimize delays and interruptions due to handoff.

When the mobile node moves its location, it sends a binding update message to notify the other node of the new location information. In this case, the source address is a mobile node 901, the destination address is a counterpart node (CN) 951 receiving the location information of the mobile node 901, and CoA is an external agent 911, which is a connection point of the mobile node 901, 921 or 931). However, when the mobile node is activated for the first time, the anchor node height, which is the network layer height of the anchor node, is 0 (lower limit value).

Anchor nodes 911, 921, or 931 are dynamically determined in the hierarchical structure of the network according to the mobility characteristics of the mobile node 901. If the mobile node 901 is a local move that moves its position within the active network area relative to the anchor node 911 (1), the current anchor node is maintained, but if the mobile node is anchored Moving to a new network area that is not based on the (Anchor) node (2 or 3) increases the network layer height of the anchor node and determines a new anchor node. This follows the rule of placing an anchor node in a higher layer of the network hierarchy as the mobile node 901 has a larger network area movement range. That is, the smaller the moving range of the mobile node 901 is, the anchor node exists in the lower layer of the network hierarchy. Therefore, an anchor node exists in the minimum network layer including the network area in which the mobile node 901 is active, and is dynamically determined according to the degree of movement of the mobile node 901, and thus exists in a fixed top layer. Prevents load concentration on home agents, which are mobility support agents.

In other words, when the mobile node 901 performs the movement in the area controlled by the current anchor node 911 (①), the binding information stored in the cache in the anchor node 911 is transferred to the mobile node 901. This will match the binding information in the binding update packet sent by. At this time, since there is no change in the path between the mobile node 901 and the counterpart node 951, the anchor node 911 does not need to increase the anchor node height (0) and at the same time no longer need to forward the binding update packet. The binding response is then sent to the mobile node 901.

In addition, when the mobile node 901 performs a move out of the area controlled by the current anchor node 911 (②), the binding information stored in the cache in the mobility support agent 912 is stored in the mobile node 901. There is a mismatch with the binding information in the sent binding update packet. In this case, the mobility support agent 912 increases the anchor node height (0-> 1), forwards the anchor node height and the binding update packet to the higher layer mobility support agent 921, and sends it to the mobile node 901. Send a binding response. In this case, as the anchor node height increases, the mobility support agent 921 becomes a new anchor node, and the binding information of the mobile node 901 is added by the binding update packet received from the mobility support agent 912.

On the other hand, when the mobile node 901 moves out of the area controlled by the current anchor node 911 (③), the binding information stored in the cache in the mobility support agent 914 is stored in the mobile node 901. There is a mismatch with the binding information in the sent binding update packet. At this time, the mobility support agent 914 increases the anchor node height (0-> 1), forwards the anchor node height and the binding update packet to the higher layer mobility support agent 922, and sends it to the mobile node 901. Send a binding response. In addition, the binding information stored in the cache in the mobility support agent 922 is also inconsistent with the binding information in the binding update packet transmitted from the mobility support agent 914. At this time, the mobility support agent 922 increases the anchor node height (1-> 2), forwards the anchor node height and the binding update packet to the higher layer mobility support agent 931, and the mobility support agent 922. Will send a binding response. At this time, as the anchor node height increases, the mobility support agent 931 becomes a new anchor node, and the binding information of the mobile node 901 is added by the binding update packet received from the mobility support agent 922.

By the above-described process, only the path through the node located below the anchor node is changed, but the path of the upper layer is maintained, and the control of the anchor node is based on the height of the anchor node, so that the load of the home agent can be reduced. do.

As described above, the method of the present invention may be implemented as a program and stored in a recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.) in a computer-readable form. Since this process can be easily carried out by those skilled in the art will not be described in more detail.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

The present invention as described above, by adjusting the anchor node height indicating the hierarchical value of the anchor node, which is one of the plurality of agents during handoff in the radio, by setting the packet path through this, focusing on the home agent when performing the handoff There is an advantage that can eliminate the load.

Claims (3)

A mobility support method for a mobile IP service applied to a network system including a plurality of agents, mobile nodes, and counterpart nodes having a hierarchical structure, A binding update receiving step of receiving, by a first agent of the plurality of agents, a binding update packet from a lower layer side; An information comparing step of the first agent comparing binding information in a packet with binding information stored in an internal cache; As the first agent matches the binding information in the packet and the stored binding information, the first agent maintains an anchor node height indicating a hierarchy value of an anchor node which is one of the plurality of agents, and the first agent maintains the anchor node height. Anchor node height adjustment that transmits information and binding update packet to the upper layer, and updates binding information stored in the internal cache and increases the anchor node height by one step when the binding information in the packet and the stored binding information are inconsistent. step; And A binding response transmitting step of transmitting the anchor node height information and the binding response to a lower layer Mobility support method for a mobile IP service comprising a. A mobility support method for a mobile IP service applied to a network system including a plurality of agents, mobile nodes, and counterpart nodes having a hierarchical structure, A binding update receiving step of receiving, by a first agent of the plurality of agents, a binding update packet from a lower layer side; An information comparing step of the first agent comparing binding information in a packet with binding information stored in an internal cache; The first agent transmits the anchor node height information and the binding update packet to an upper layer according to whether the binding information in the packet matches the stored binding information, and the anchor is one of the plurality of agents. An anchor node height adjustment step of adjusting an anchor node height indicating a hierarchy value of the nodes; And Binding update transmission step of transmitting the anchor node height information and the binding response to a lower layer Mobility support method for a mobile IP service comprising a. The method according to claim 1 or 2, The range of anchor node heights is determined by the number of tiers of agents present between the home agent and the mobile node. Mobility support method for a mobile IP service, characterized in that.

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