KR100541949B1 - Method for performing ??? using information maintained by access router to achieve fast handoff in ???6 environment - Google Patents

Abstract

In the wireless communication environment according to the present invention, a method for performing a DAD of a mobile node connecting to a network including a router managing a node cache list including IP addresses of nodes includes a new CoA of the mobile node from the mobile node to the router. Transmitting a neighbor node request message; determining whether the same IP address exists as the CoA of the mobile node by searching the node cache list; and if the same IP address does not exist, the router notifies that the CoA can be used. Transmitting a neighbor node advertisement message to the mobile node; and performing a communication in the network by the mobile node using the CoA. Therefore, the DAD execution time can be shortened, so that a quick handoff can be performed and thus packet loss can be prevented.

Mobile Node, IPv6, Access Router, IP Address, DAD

Description

Method for performing DAD using information maintained by access router to achieve fast handoff in IP6 environment

1 is a view for explaining a method in which a mobile node performs a DAD in an IPv6 environment according to an embodiment of the present invention;

2 is a view illustrating a signal flow between a mobile node and a router according to a DAD method according to a preferred embodiment of the present invention in comparison with the prior art;

3 is a block diagram illustrating an apparatus for managing a node cache list for an access router;

4 is a flowchart illustrating a method of performing DAD according to the present invention.

* Description of the symbols for the main parts of the drawings *

110: mobile node 120: access router

130: access point 140: node

The present invention relates to a method of performing DAD (Duplicate Address Detection) using information managed by an access router for fast handoff in an IPv6 environment, and more particularly, to an NCE (managed by an access router for fast handoff in an IPv6 environment). The present invention relates to a method for reducing the time required for DAD required when a care-of address (CoA) allocation of a mobile node is performed using address information of neighbor nodes stored in a neighbor cache entry.

Recently, wireless Internet users are increasing due to the rapid spread of the Internet, the development of wireless communication technology, and the improvement of the performance of mobile terminals such as portable computers and personal digital assistants (PDAs). Under the wireless Internet environment, the mobile terminal frequently changes its location to change its network connection location. Such a mobile terminal is called a mobile node.

According to the Mobile IPv6 technology, a mobile node uses its home address (HA) through a home agent, which is a router that has its own registration information even when it moves to a foreign network. Communicates with a communication target node (CN). When a mobile node is linked to an external network, the mobile node receives a CoA (Care of Address), which is a temporary address, from the external network and registers a home agent with a home address, that is, a binding update.

In order to be assigned a CoA, the mobile node receives a Router Advertisement (RA) message from any router in the network after a link layer connection is established with an external network. To this end, the mobile node can multicast the Router Solicitation message throughout the network.

The Router Advertisement message provides the network's prefix information. Therefore, the mobile node generates a new CoA using the prefix information of the network and its link-layer address (LLA). The mobile node sets the generated CoA as a temporary address.

The mobile node subscribes to the solicited-node multicast address in the linked external network, multicasts the neighbor solicitation message to the newly linked network, and then duplicates the address detection. Start called "DAD".

If a neighbor advertisement is not received from a node using the same address as the generated CoA within a predetermined time limit, the CoA is recognized as the only CoA, and the mobile node uses this to communicate. Done. The predetermined time limit is 1000 ms by default.

Accordingly, the mobile node randomly regenerates an ID for the corresponding interface, regenerates a new CoA, and performs DAD again on the generated CoA. If after 5 consecutive DADs, the only CoA cannot be determined, the mobile node abandons communication in the corresponding external network and waits until the link is changed.

As described above, according to the conventional mobile IPv6 protocol, even if the DAD succeeds, the mobile node must wait without communicating with the communication target node for at least RetransTimer, and in case of failure, several times that number. It takes time. Therefore, during this time, the mobile node cannot use the CoA set as a temporary address, cannot update the binding, and cannot transmit and receive packets, resulting in considerable packet loss.

The proposed method to solve this problem is ODAD (Optimistic DAD). ODAD is based on the assumption that DAD is likely to succeed rather than fail. Therefore, the mobile node communicates using the generated NCoA as a temporary address immediately without waiting for DAD success.

However, according to the ODAD, when an address is duplicated, a problem occurs in both a mobile node using a new address and a mobile node using a first address. That is, when a newly used mobile node wants to send a packet or receive a packet from a communication target node, the transmitted packet is disconnected from the mobile node and the communication target node such that the transmitted packet is transmitted to the mobile node using the corresponding address first. You lose.

An object of the present invention is a care-of address (CoA) of a mobile node using address information of neighbor nodes stored in a neighbor cache entry (NCE) managed by an access router for fast handoff in an IPv6 (Internet Protocol Version 6) environment. It is to provide a method to reduce the time required for DAD required for allocation.

In order to achieve the above object, in the wireless communication environment according to the present invention, a method for performing DAD of a mobile node accessing a network including a router for managing a node cache list including IP addresses of nodes is provided. Sending a neighbor node request message including a new CoA of the mobile node from the router to the router; retrieving the node cache list to determine whether the same IP address as the CoA of the mobile node exists; If the IP address does not exist, the router transmits a first neighbor node advertisement message indicating that the CoA is available to the mobile node, and the mobile node communicates in the network using the CoA. Characterized in that it comprises a.

The information recorded in the node cache list includes IP addresses, link layer addresses, and state information of the nodes. The method may further include recording the CoA, the link layer address, and the state information of the mobile node in the node cache list when the same IP address does not exist.

The state information includes reachability for the node and the mobile node. In the communication performing step, the mobile node preferably performs a binding update and performs packet transmission and reception.

If the same IP address exists as a result of the determination, the router transmits a second neighbor node advertisement message indicating that the CoA cannot be used to the mobile node, and the mobile node randomly generates a CoA and generates a conventional DAD. It further comprises the step of performing. In addition, the wireless communication environment is preferably IPv6.

Hereinafter, with reference to the accompanying drawings will be described the present invention.

1 is a diagram illustrating a method for a mobile node to perform a DAD in an IPv6 environment according to a preferred embodiment of the present invention. The network under the IPv6 environment to which the present invention is applied includes an access router 120, an access point 130, and a node 140.

The access router 120 interprets the protocol included in the packet transmitted from the node connected to the network and selects an optimal path, that is, path selection at the third layer, which is the network layer of the Open Systems Interconnection (OSI) basic reference model. To send the packet.

To this end, the access router 120 maintains address information of the nodes connected to the network and state information of the nodes. The table of FIG. 1 shows a Neighbor Cache List (NCE) managed by an access router.

The access router 120 records the IP address, link-layer address (LLA), and node state information of the current link of each node connected to the network in the node cache list, and a change occurs in the recorded information. Then, the list is updated to maintain the latest information, thereby relaying packet transmission and reception of nodes.

In other words, the node cache list is a list of information about each node to which a packet was recently sent. The state information of a node is information by a neighbor unreachability detection (NUD) algorithm and includes accessibility to a node and a time when a next NUD is performed.

The mobile node 110 receives a router advertisement message from the access router 120 when a link layer connection is established with the network. The Router Advertisement message contains the prefix information of the network. Therefore, the mobile node 110 generates a CoA using the prefix information of the network and its link-layer address (LLA). The generated CoA is an address that the mobile node 110 intends to use in the network, hereinafter referred to as a target address.

The mobile node 110 supplements the existing Neighbor Solicitation (NS) message to include the target address as an option, and multicasts the supplemented neighbor node request message to all request node multicast addresses (FIG. 1). (b)). The supplementary neighbor node request message performs NDP (Neighbor Discovery Protocol) function and DAD function. NDP is a protocol used by each node in IPv6 environment to check the link layer address of another node, find a router, and maintain accessibility information for each node.

The access router 120 receives the neighbor node request message multicasted by the mobile node 110, extracts the included target address, and searches for the IP address of each node in the node cache list managed by the mobile node 110. Determine if is present.

If the access router 120 does not exist in its node cache list for the node having the same IP address as the target address of the mobile node 110, the target router, the link layer address, and the mobile node of the mobile node 110 are not present. Record the status information in the node cache list. Also, a neighbor node advertisement message indicating that the target address can be used is created and transmitted to the mobile node 110 (FIG. 1A).

When the neighbor node advertisement message indicating that the target address is available from the access router 120, the mobile node 110 immediately updates the binding to the home agent. According to the NDP, even if the DAD succeeds, the mobile node 110 should wait for the minimum timeout period (1000 ms). Therefore, since the DAD execution of the mobile node 110 is not terminated, the target address is in the "tentative" state. In the present invention, the target address is set to the "momentary" state.

The "momentary" state is a temporary address state used by the mobile node 110 while performing the DAD. Therefore, the "momentary" state does not respond to the neighbor node request (NS) message of the neighbor node. However, if the same IP address as the target address of the mobile node 110 of the access router 120 does not exist in the node cache list as described above, the target address of the mobile node 110 is an address conflict as a unique address in the network. Since it does not cause, the mobile node 110 may receive and process the neighbor node advertisement message and the transmitted packet in the "momentary" state. In the " momentary " state, when the above-mentioned time limit (RetransTimer: 1000 ms) has elapsed according to the NDP, the target address is determined to be the unique address of the mobile node 110.

Meanwhile, the access router 120 creates a neighbor node advertisement message indicating that the target address cannot be used when a list of nodes having the same IP address as the target address of the mobile node 110 exists in its node cache list. To the mobile node 110 (Fig. 1 (a)). In this case, the access router 120 does not record address information and status information for the mobile node 110 in the node cache list.

Since another node is already using the same address on the network. The mobile node 110 performs a general auto-address generation procedure, randomly generates CoA, and performs a general DAD on the generated CoA. Such a DAD is preferably performed up to 5 times. If the DAD fails despite the 5 times, the mobile node 110 cannot normally communicate in the network.

2 is a view illustrating a signal flow between a mobile node and a router in comparison with the related art in order to explain that the handoff time is shortened according to the method of performing DAD according to the preferred embodiment of the present invention.

Referring to FIG. 2, in the prior art (a), the mobile node 220 does not receive a neighbor node advertisement (NA) message from another node using the same address as the CoA generated during the RetransTimer. Even in the case of success, the state of the mobile node 220 is set to " tentative " during the timeout period, so that no binding update can be made and no packet can be received, so all packets transmitted to the mobile node 220 are discarded.

However, according to the present invention (b), the mobile node 240 starts the DAD by generating and multicasting a supplemental neighbor node request (NS) message including the target address, and receives the target address from the access router 230. Receiving a neighbor node advertisement message indicating that it can be used, the target address can be immediately updated by binding to the home agent, and packet transmission and reception can be performed. Thus, the handoff time is shortened by at least 900 ms to 1000 ms compared to the prior art.

3 is a block diagram illustrating an apparatus for managing a node cache list for an access router. Referring to FIG. 3, the node cache list managing apparatus includes a controller 320, a recorder 330, a searcher 340, a determiner 350, and a memory 360.

The memory 360 stores a node cache list that records information about nodes connected to the network. The node cache list maintains the IP address, link layer address (LLA), and node status information of each node.

The controller 320 controls the interface unit 310 to receive a supplementary neighbor node request message, which optionally includes a multicasted target address and performs an NDP function and a DAD function, from a mobile node newly connected to the network.

The search unit 340 searches for IP addresses of nodes stored in the node cache list. This is to compare the target address of the mobile node newly connected to the network with the IP address of the other node. The determination unit 350 compares the IP addresses of the nodes searched by the searcher 340 with the target address of the newly connected mobile node and determines whether the same IP address exists.

If the list for the node having the same IP address as the target address does not exist in the node cache list, the recording unit 330 records the target address of the mobile node, the link layer address, and the status information of the mobile node in the node cache list.

Accordingly, the controller 320 transmits a neighbor node advertisement message indicating that the target address can be used to the mobile node through the interface unit 310. However, if a list for a node having the same IP address as the target address exists in the node cache list, the recording unit 330 does not record the information about the mobile node in the node cache list. In addition, the control unit 320 transmits a neighbor node advertisement message indicating that the target address cannot be used to the mobile node through the interface unit 310.

4 is a flowchart illustrating a method of performing DAD according to the present invention.

When the mobile node establishes a link layer connection with the network, the mobile node generates a CoA by using the prefix information of the network included in the router advertisement message received from the access router and its link layer address. The mobile node multicasts the supplementary neighbor node request message including the generated CoA as a target address as an option (S410).

The access router receives the neighbor node request message multicasted by the mobile node, extracts the included target address, and retrieves the IP address of each node in the node cache list managed by the access node (S420). It is determined whether the same IP address as the target address exists among the IP addresses (S430).

If the access router does not exist in its node cache list for the node with the same IP address as the target node of the mobile node, the access router records the target address, link layer address and mobile node status information in the node cache list. (S435). In addition, the neighbor node advertising message indicating that the target address can be used to create and transmit to the mobile node (S440).

Upon receiving the Neighbor Advertisement message from the access router indicating that the target address is available, the mobile node immediately updates the binding to the home agent and sets the target address to the "momentary" state. Communication is performed within the network, such as by receiving and processing the data (S480).

On the other hand, if the access router lists the node having the same IP address as the target node of the mobile node in its node cache list, the access router creates a neighbor node advertisement message indicating that the target address is not available and sends it to the mobile node. (S450). In this case, the access router does not record address information and status information for the mobile node in the node cache list.

Since another node is already using the same address on the network. The mobile node performs a general automatic address generation procedure, randomly generates CoA, and performs general DAD on the generated CoA (S460). Such a DAD is preferably performed up to 5 times. If the DAD fails despite the 5 times, the mobile node cannot normally communicate in the network (S465).

Accordingly, according to the present invention, even when the DAD succeeds, the RetransTimer, which waits for confirmation of the success of the DAD, is shortened so that no other node using the same IP address as the CoA generated by the mobile node exists in the network. In this case, the generated CoA can be immediately used for communication within the network.

According to the present invention, DAD is performed by supplementing a neighbor node request message to include a CoA generated by a mobile node connected to a network as a target address, and uses a node cache list including IP addresses of each node managed by an access router. Therefore, it is possible to quickly determine whether the same IP address exists, and if the same IP address does not exist, the mobile node can immediately communicate using the target address, so that the time limit required for performing the conventional DAD (RetransTimer ), It can shorten DAD execution time.

Therefore, when the mobile node is connected to the network, the DAD execution time can be shortened, so that a quick handoff can be performed and communication delay can be prevented.

Although the above has been illustrated and described with respect to the preferred embodiment of the present invention, the present invention is not limited to the specific embodiment described above, it is usually in the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Anyone skilled in the art can make various modifications, as well as such modifications are within the scope of the claims.

Claims (7)

In a method of performing DAD (Duplicate Address Detection) of a mobile node accessing a network including a router managing a neighbor node cache list including IP addresses of nodes in a wireless communication environment, Starting a DAD by sending a neighbor node request message including a new CoA of the mobile node from the mobile node to the router; Retrieving the neighbor node cache list from the router to determine whether the same IP address as the CoA of the mobile node exists; If it is determined that the same IP address does not exist, the router transmitting a first neighbor node advertisement message indicating that the CoA is available to the mobile node; And And when the mobile node receives the first neighbor node advertisement message, immediately performs a binding update on the CoA, performs packet transmission and reception using the CoA, and performs communication in the network. How to perform a DAD for quick handoff. The method of claim 1, The information recorded in the node cache list includes an IP address of the nodes, a link layer address, and status information of the nodes. The method of claim 1, And if the same IP address does not exist, recording the CoA, link layer address, and state information of the mobile node in the node cache list. . The method according to claim 2 and 3, The state information includes the reachability (reachability) to the node and the mobile node (DAD) method for performing a quick handoff, characterized in that. delete delete The method of claim 1, The wireless communication environment is a method for performing DAD for fast handoff, characterized in that the IPv6.

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