JP2006180010A - Connection management method, router apparatus, communication terminal, and connection management system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connection management method for a communication terminal, a router apparatus, a communication terminal, and a connection management system whereby when the router apparatus receives a packet addressed to a communication terminal with which the router cannot communicate, the router apparatus can immediately return an arrival error message to a sender. <P>SOLUTION: In an IP network, a communication terminal connected to a link informs the router apparatus about its own communication state, when the router apparatus receives a notice denoting that the communication terminal is in a communication disabled state, the router apparatus shifts nearby cache entries around the communication terminal to a communication disabled state, and thereafter when the router apparatus receives a packet addressed to the communication terminal, the router apparatus immediately transmits the arrival error message to a packet sender. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for managing a communication terminal connected to a communication link in an IP (Internet Protocol) network, and particularly to a connection management method, a router device, and a connection management system when a communication terminal moves and performs handover.

  Conventionally, as a connection management method for communication terminals connected to a communication link in an IP network using the IPv6 protocol, a neighbor search method using a neighbor cache defined by IETF RFC 2461 is known.

  FIG. 19 is a diagram showing a conventional system configuration.

  In FIG. 19, the communication terminals 9 and 10 and the router device 20 are connected to the same link 110, and the router device 20 is further connected to the upper network 120, and the communication device 30 and the communication terminal connected to the upper network 120 are connected. 9 and 10 are relayed. Here, when the router device 20 receives a packet addressed to the communication terminals 9 and 10 from the communication device 30, the router device 30 manages the correspondence between the IP address of each communication terminal and the link layer address (MAC address). The link layer address (MAC address) corresponding to the destination IP address of the packet is obtained. If not entered in the neighborhood cache, the router device 20 searches for the link layer address (MAC address) of the destination communication terminal in the neighborhood.

  The main procedure of the neighbor search method is as follows. Note that IEEE802.3 is used as the link 110, and the communication terminal 10 has an IP address 3ffe: a: b: c :: 1 and a MAC address 12: 34: 56: 78: 90: ab.

  In this case, when the router device 20 receives a packet addressed to the IP address 3ffe: a: b: c :: 1 from the higher-level network 120, the router device 20 connects the link 110 to which the prefix 3ffe: a: b: c :: / 64 is assigned. The neighbor search message 200 is transmitted.

  FIG. 20 is a diagram showing the format of the neighbor search message 200, and the target address 201 is the address of the search target node.

  The router device 20 describes the IP address 3ffe: a: b: c :: 1 of the communication terminal to be searched in the target address field 201, and multicasts to all the communication terminals of the link 110.

  The corresponding communication terminal, that is, the communication terminal 10 whose IP address matches here, searches for the neighbor advertisement message 210 with the target link layer address option describing the MAC address 12: 34: 56: 78: 90: ab added. The message 200 is transmitted to the router device 20 that is the transmission source of the message 200.

  FIG. 21 is a diagram showing a format of the neighbor advertisement message 210 to which the target link layer address option is added.

In FIG. 21, an option type field 212 indicates an identifier of a target link layer address option, and a link layer address field 213 indicates a link layer address corresponding to the target address field 211. In the present embodiment, the communication terminal 10 indicates that its own IP address 3ffe: a: b: c :: 1 is described in the target address field 211, and the target link layer address is described in the option type field 212. The value “2” is stored in the link layer address field 213 of its own MAC address 12: 34: 56: 78: 90: ab.

  Next, the router device 20 that has received the neighbor advertisement message 210 receives the IP address 3ffe: a: b: c :: 1 described in the target address field 211 and the MAC address 12: described in the link layer address field 213: 34: 56: 78: 90: ab is stored in the neighborhood cache. Strictly speaking, it is stored in the neighborhood cache only when the O flag of the neighborhood advertisement message 210 is “1”.

  Thereafter, the router device 20 refers to the neighbor cache and adds a MAC header destined for the MAC address 12: 34: 56: 78: 90: ab to the packet addressed to the communication terminal 10 received from the upper network 120. To link 110. Thereby, the communication terminal 10 can receive the packet addressed to itself.

  In addition, the router device 20 performs the following processing on the neighborhood cache entry of the communication terminal that has not performed communication for a certain period of time.

  FIG. 22 shows a state transition diagram of neighboring cache entries managed by the router device 20.

  In FIG. 22, when a new entry is generated, it is placed in a reachable state (REACHABLE) 221. After that, if the connection cannot be confirmed by receiving the neighbor advertisement message from the destination for the reachable time (REACHABLE_TIME) (usually 30 seconds), the state transits to the stale state (STALE) 222. Thereafter, when a packet transmission request to the corresponding communication terminal is generated, the packet is transmitted to transit to the delay state (DELAY) 223, and at the same time, a timer for the first delay detection time (DELAY_FIRST_PROBE_TIME) (normally 5 seconds) is started. If the delay state (DELAY) 223 is reached at the time of occurrence of the timeout, the state transits to the probe state 224, and the maximum number of unicast transmissions of the neighbor search message 200 for the corresponding communication terminal at intervals of the retransmission time (RETRANS_TIME) (usually 1 second). Send up to (MAX_UNICAST_SOLICIT) (usually 3 times). When there is a response to the neighbor search message 200 from the corresponding communication terminal, the state transits to a reachable state (REACHABLE) 221, and when there is no response, the state transits to the null state (NULL) 225 and the cache entry of the relevant communication terminal is set. to erase. For this reason, after that, when the router device receives a packet addressed to the corresponding communication terminal, it is necessary to perform the neighbor search method again.

  Patent Document 1 discloses a neighbor cache entry managed by a router device on a link to be connected when a mobile terminal terminates use of the Internet service for the purpose of suppressing attacks from malicious external terminals and improving security. A method of erasing is disclosed. That is, in FIG. 23, when the application running on the portable terminal 501 finishes operation, a neighbor cache entry clear message is transmitted to the router device 502 (step S521), and the router device 502 erases the corresponding neighbor cache entry. Later, a response message was transmitted to the portable terminal 501 (step S522).

  Patent Document 2 discloses a communication method for reducing traffic increase and memory resource consumption.

FIG. 24 is a diagram showing the configuration of this conventional communication network. In FIG. 24, when the communication terminal 604, the access router 603, the subdomain router 602, and the gateway router 601 form a hierarchical structure, and the communication terminal 604 moves to another subnet, the access router 603 of the subnet before the movement is “absent. Is recorded. The mobile terminal 604 is registered as a “visitor” in the access router 603 of the destination subnet, and the positioning information of the mobile terminal is transmitted to the parent node (subdomain router) 602 that is above the access router 603. As a result, the packet addressed to the communication terminal that has reached the parent node is transferred to the communication terminal 604 via the access router 603 that is the movement destination.
JP 2002-94558 A (page 8, FIG. 6) JP 2004-80733 A (pages 12-16, FIG. 1, FIG. 4)

  However, in the above-described conventional neighbor search method and the communication terminal connection management method disclosed in Patent Document 1, communication with the communication terminal that the router device 20 has entered in the neighbor cache cannot be detected for a predetermined time or has ended. In the case, the neighbor cache entry of the communication terminal has been deleted. For this reason, when a packet addressed to this communication terminal is received again, a neighbor search is performed to confirm the connection status of this communication terminal. Therefore, in order to detect that the communication terminal is not connected, it takes several seconds. It was necessary to wait for the timeout time to elapse.

  In addition, although the mobile terminal is disconnected from the link, the router device holding the neighbor cache entry explicitly performs processing for confirming that the mobile terminal is not connected to the link. In addition, packet transfer processing had to be performed.

  Furthermore, although the communication method according to Patent Document 2 is effective for movement within a domain, when moving to other than the domain, the movement destination notifies the parent node 602 of the location information of the communication terminal 604. Therefore, it is transmitted to the access router 603 before moving. The processing at this time is not disclosed, and it is difficult to appropriately process this packet.

The present invention has been made in order to solve the above-described problem, and in processing a packet addressed to a communication terminal incapable of communicating with a router device, an immediately unreachable message, for example, ICMP unreachable (ICMP
A communication terminal connection management method, a router device, a communication terminal, and a connection management system that can return an Unreachable message to a transmission source.

  In order to solve the above-described problems, the present invention is a connection management method for a router apparatus that manages connection of a communication terminal connected to a link in an IP network, and the communication terminal notifies the router apparatus of its own communication state. And when the communication state is a notification of the communication disabled state, the router device that has received the notification changes the neighboring cache entry of the communication terminal to the communication disabled state, and the router device is addressed to the communication terminal. The router device confirms the state of the neighbor cache entry when the packet is received, and if it is in a communication impossible state, immediately transmits a transfer impossible notification to the packet transmission source.

  As a result, the transmission source node can know immediately after the start of transmission that the destination communication terminal is in a communication disabled state, so that it is possible to reduce the loss of continuing to transmit unreachable packets.

The connection management method according to the present invention further includes a step in which the router device that has received the notification causes the neighboring cache entry of the communication terminal to transition to the communicable state when notifying the communicable state; When the packet addressed to the communication terminal is received, if the state of the entry in the neighborhood cache is a communicable state, the step of transferring the packet to the communication terminal is included.

  Thus, when the communication terminal changes from the communication disabled state to the communication enabled state, the packet addressed to the communication terminal can be transferred immediately.

  Further, the connection management method according to the present invention is characterized in that the communication terminal notifies the communication state by a neighbor advertisement message.

  Accordingly, it is possible to notify the communication state of the user without adding a new message by using a part of the existing message.

  In addition, the connection management method according to the present invention cancels the link connection after the communication terminal notifies the first router device of the communication disabled state, and connects to the link managed by the second router device. The communication terminal further includes a step of requesting the first router device to delete the neighbor cache entry.

  Thus, the neighbor cache entry of the source router device can be deleted in a timely manner, so that the neighbor cache area can be used more effectively.

  In addition, the connection management method according to the present invention deletes the entry of the communication terminal in the neighboring cache after a predetermined time has elapsed from the time when the router device receives the notification of the communication disabled state from the communication terminal.

  Thereby, the router device can delete the entry of the neighbor cache that is no longer used, so that the neighbor cache area can be used more effectively.

  When a router device according to the present invention receives a neighbor cache, a neighbor search processing unit that manages a communication state of a communication terminal that has entered the neighbor cache, and a packet addressed to the communication terminal, A packet transfer processing unit that transfers packets according to the communication state of the communication terminal, and the neighbor search processing unit changes the neighbor cache entry to a communication disabled state or a communication enabled state according to the communication state notification from the communication terminal. When the packet transfer processing unit changes and the neighbor cache entry is in a communication disabled state, the packet transfer processing unit transmits a transfer disabled notification to the transmission source when the packet is received.

  As a result, the transmission source node can know immediately after the start of transmission that the destination communication terminal is in a communication disabled state, so that it is possible to reduce the loss of continuing to transmit unreachable packets.

  Also, the router device according to the present invention is notified of the communication state by the neighbor advertisement message from the communication terminal entered in the neighbor cache.

  Thereby, it is possible to know the communication state of the communication terminal by using a part of the existing message without adding a new message.

  Further, the router device according to the present invention starts a timer when the neighbor search processing unit receives a notification of a communication impossible state from the communication terminal, and when the timer counts a predetermined time, the neighbor search processing unit is in the neighbor cache. Delete the communication terminal entry.

  Thereby, the router device can delete the entry of the neighbor cache that is no longer used, so that the neighbor cache area can be used more effectively.

  In addition, the communication terminal according to the present invention is connected to the connection state detection unit that detects the connection state with the link, and when the connection state detection unit detects a change in the connection state, the communication terminal is connected to the router device on the connected link. A state transition request processing unit for notifying the state, and after notifying the router device of the first link to which the state transition request processing unit is connected to the communication disabled state, leaving the first link, When the connection is established, the router device on the second link is requested to delete the entry in the neighbor cache via the router device on the second link.

  Thus, the neighbor cache entry of the source router device can be deleted in a timely manner, so that the neighbor cache area can be used more effectively.

  The connection management system according to the present invention includes a communication terminal that notifies a router device on a link of a communicable state or a communicable state with a link, changes a neighbor cache entry of the communication terminal according to the received communication state, and communicates When the packet addressed to the terminal is received, the state of the entry in the neighborhood cache is confirmed, and if it is in a communication impossible state, it has a router device that immediately transmits a transfer impossible notification to the packet transmission source.

  As a result, the transmission source node can know immediately after the start of transmission that the destination communication terminal is in a communication disabled state, so that it is possible to reduce the loss of continuing to transmit unreachable packets.

  As described above, according to the present invention, when the router device receives a packet addressed to a communication terminal, the router device can check the communication state of the communication terminal, and when the communication with the communication terminal is impossible, An ICMP Unreachable message can be immediately returned to the sender as an unreachable notification.

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

(Embodiment 1)
FIG. 19 is a diagram showing a configuration of a communication network having a connection management system according to the present invention, which is the same as the conventional one.

  The connection management system according to the present invention includes communication devices 9 and 10 and a router device 20.

  FIG. 1 is a configuration diagram of communication terminals 9 and 10 according to the present invention. A lower layer processing unit 11 that performs physical layer processing and data link layer processing, an IP processing unit 12 that performs network layer processing, and a response to a neighbor search. Neighbor search processing unit 13 to be implemented, neighbor cache 14 in which address information of other nodes on the link 110 to be connected is recorded, and a state transition request for notifying the router device of the transition of the communication state when disconnecting or reconnecting to the link 110 A processing unit 15 is provided.

  The basic operation of the communication terminals 9 and 10 configured as described above will be described with reference to the flowcharts shown in FIGS. The neighborhood search response process performed by the neighborhood search processing unit 13 is the same as the conventional one.

  FIG. 7A is a flowchart showing processing when the communication terminal 10 leaves the link 110.

First, when the lower layer processing unit 11 determines to disconnect the link, the lower layer processing unit 11 notifies the state transition request processing unit 15 (step S71).

  Next, the state transition request processing unit 15 instructs the neighbor search processing unit 13 to notify that the communication state is shifted to the communication disabled state. The neighbor search processing unit 13 generates a neighbor advertisement message 230 that notifies the communication disabled state, and the IP processing unit 12 performs multicast transmission to all nodes on the router device 20 or the link 110 via the lower layer processing unit 11. (Step S72).

  FIG. 5 is a diagram showing a format of the neighborhood advertisement message 230 in the present embodiment, which is different from the neighborhood advertisement message 210 shown in FIG. 21 in that it has an N flag 214. This N flag 214 indicates whether or not the communication terminal is incapable of communication. When it is on, it indicates that the communication terminal is in a communication impossible state, and when it is off, it indicates that the communication terminal is in a communicable state. Yes. Here, since the link connection is disconnected and the communication is disabled, transmission is performed with the N flag 214 turned on.

  FIG. 7B is a flowchart showing processing when the communication terminal 10 reconnects (or newly connects) to the link 110.

  First, when detecting that the lower layer processing unit 11 is connected to the link 110, the state transition request processing unit 15 is notified (step S73).

  Next, the state transition request processing unit 15 instructs the neighbor search processing unit 13 to notify that the communication disabled state has been canceled. The neighborhood search processing unit 13 generates a neighborhood advertisement message 230 with the N flag 214 set to OFF. The IP processing unit 12 multicasts this neighbor advertisement message 230 to the router device 20 or all nodes on the link (step S74).

  The detection of the link connection may be performed by the lower layer processing unit 11 based on the presence or absence of a beacon, or may be performed by an upper application not shown.

  As described above, the communication terminal 10 according to the present invention explicitly notifies the node on the link 110 whether or not communication is possible according to the connection state of the link.

  FIG. 2 is a configuration diagram of the router device 20 according to the present invention, in which a lower layer processing unit 21 that performs physical layer processing and data link layer processing, an IP processing unit 22 that performs network layer processing, and a neighborhood that performs neighborhood search processing. The search processing unit 23 includes a neighbor cache 24 in which the address information and communication state of other nodes on the link 110 to be connected are recorded, and an entry valid timer 25 that measures the elapsed time of the communication terminal incapable of communication. Note that the lower layer processing unit 21 can be connected to a plurality of network links. In this embodiment, the case of connecting to two network links, that is, the upper network 120 and the link 110 is described. However, the present invention does not limit the number of connections.

  FIG. 6 is a diagram showing the data structure of the neighborhood cache 24. The IP address 61 and the MAC address 62 are registered in association with each other, and the current communication state of the registered node is recorded by the status 63. . This communication state is performed based on the state transition shown in FIG. The state transition of the communication terminal shown in FIG. 10 is obtained by adding an incommunicable state 226 to the conventional state transition described with reference to FIG. 22, a reachable state 221 to a probe state 224, and a null in which no entry exists. The difference is that the state 225 transits to the communication disabled state 226.

  The basic operation of the router device 20 configured as described above will be described below with reference to the flowcharts shown in FIGS.

  FIG. 8A is a flowchart showing an operation when a neighborhood advertisement message is received.

  First, when receiving the neighbor advertisement message 230 via the lower layer processor 21, the IP processor 22 notifies the neighbor search processor 23 (step S81).

  Next, the neighbor search processing unit 23 searches whether there is a corresponding entry in the neighbor cache 24 (step S82). If there is no corresponding entry, a new entry is generated (step S83).

  Next, the neighborhood search processing unit 23 checks the N flag 214 of the neighborhood advertisement message 230 (step S84). If the N flag 214 is on, the entry state is changed to the communication disabled (Not PROBE) state 226, and the entry valid timer 25 is started (step S84). On the other hand, if the N flag 214 is off, the entry state is returned to the reachable state (REACHABLE) 221 and the entry valid timer is reset (step S86).

  Thereafter, other processing of the neighborhood advertisement message is performed (step S87).

  FIG. 8B is a flowchart showing processing performed in parallel by the neighbor search processing unit 23 when the entry valid timer 25 is activated.

  The neighbor search processing unit 23 monitors whether or not the entry valid timer 25 has elapsed (step S88), and when the predetermined entry valid time has elapsed, the state of the corresponding entry is changed to the null state 225 to enter the entry. Is deleted (step S89).

  The predetermined time can be, for example, 1 minute, which is a sufficient time for completing the IEEE 802.1x authentication in the wireless LAN system.

  Next, the operation when the router device 20 receives an IP packet addressed to a communication terminal will be described with reference to FIG.

  When receiving the packet addressed to the communication terminal via the lower layer processing unit 21 (step S901), the IP processing unit 22 refers to the neighborhood cache 24 and checks whether the destination communication terminal is entered (step S902). ). If there is an entry in the neighborhood cache 24, the communication state of the corresponding entry is confirmed (step S903). If it is not the communication disabled state 226, the IP processing unit 22 refers to the MAC address associated with the IP address and notifies the lower layer processing unit 21 of the MAC address. In response to this, the lower layer processing unit 21 sets the MAC address and transmits the packet (step S904).

  On the other hand, when it is in the communication disabled state 226, the IP processing unit 22 creates an ICMP Unreachable message (step S905) and transmits it to the packet transmission source via the lower layer processing unit 21 (step S906). .

  In step S902, if the destination communication terminal is not entered in the neighborhood cache 24, an entry is generated (step S907), and neighborhood search processing is performed (step S908). As a result, if a destination communication terminal is detected, the process proceeds to step S904, and if not detected, the process proceeds to step S905. The neighborhood search process is the same as the conventional process.

  Next, the operation of the connection management system constituted by the communication terminal and the router device according to the present invention as described above will be described.

  Initially, the communication terminal 10 is entered in the neighborhood cache of the router device 20, and this operation is the same as the conventional one.

  Next, the communication terminal 10 leaves the link 110. The operation at this time will be described with reference to FIG.

  In FIG. 3, first, when the communication terminal 10 determines to leave the link 110, the communication terminal 10 transmits a neighbor advertisement message 230 that notifies the router device of the transition to the communication disabled state (step S31). The own address is described in the target address field 211 of the neighborhood advertisement message 230, and the N flag 214 in the message is set to ON.

  Next, when receiving the neighbor advertisement message 230 in which the N flag 214 is ON, the router device 20 searches for the entry of the corresponding IP address from the neighbor cache 24, and sets the state of the corresponding entry to communication disabled (Not PROBE). A transition is made to state 226 (step S32).

  Thereafter, when the router device 20 receives a packet addressed to the communication terminal 10 from the communication device 30 or the other communication terminal 9 on the higher level network 120 (step S33), the state of the neighboring cache entry of the corresponding communication terminal 10 is in communication. As long as it is in the not possible (Not PROBE) state 226, the forwarding process is not performed, and an ICMP Unreachable message indicating that the packet could not be delivered to the communication device 30 that is the transmission source of the packet is transmitted (step S34). . Note that if the communication disabled state continues for a predetermined time (entry valid time), the router device 20 deletes the entry of the corresponding communication terminal 10.

  Next, a processing procedure when the communication terminal 10 performs reconnection to the link 110 will be described with reference to FIG.

  4, when the communication terminal 10 reconnects to the link 110, the communication terminal 10 transmits a neighbor advertisement message 230 with the N flag 214 turned off to the router device 20 as a state transition request to a communicable state (step S41). .

  In response to this, the router device 20 changes the state of the corresponding entry in the neighbor cache to the reachable (REACHABLE) state 221 (step S42). Thereafter, when receiving a packet addressed to the communication terminal 10 (step S43), the router device 20 performs a transfer process according to the neighborhood cache 24 (step S44). If the corresponding neighbor cache entry does not exist, a new entry is created.

  Note that the communication terminal 10 may transmit the neighborhood advertisement message 230 that turns off the N flag 214 without being aware of whether the connection to the link 110 is a new connection or a reconnection.

  Here, the router device 20 stores the state before the corresponding entry in the neighbor cache is changed to the communication impossible (Not PROBE) state 226, and restores the state stored when the communication device 10 is reconnected. May be.

In the above description, the neighbor advertisement message 230 with the N flag 214 added is transmitted only to the router device 20, but it may be multicast to all the nodes on the link 110. As a result, when there are a plurality of router devices 20 on the link 110, it is not necessary to individually transmit messages, and the communication band can be used effectively.

  Further, in the above description, the router device 20 is described so as to manage the neighborhood cache related to the communication terminal 10, but not only the router device 20 but also each of the communication terminals 9, 10 operates the entry of its own neighborhood cache. The above processing with reference to the N flag 214 may be performed. Thereby, for example, when an application of the communication terminal 9 transmits data to the communication terminal 10, it is possible to detect that the communication terminal 10 is in an incommunicable state before transmitting the packet, so that a packet that cannot reach the destination is transmitted. Can reduce loss. In particular, in a packet billing communication system, cost merit for the user can be achieved.

  In this embodiment, the entry of the corresponding node is deleted from the neighboring cache when the entry valid time elapses in the communication disabled state. However, this is not limited to this, and the area usable as the neighboring cache is insufficient. The entries may be deleted sequentially from the entry with a short valid entry time. Thereby, the utilization efficiency of the neighborhood cache area can be improved. In particular, when the communication terminal 10 leaves the link 110 due to handover, it does not necessarily return to the separated link 110. Therefore, deleting the entry with an entry valid time is considered in resource management of the router device 20. It is valid.

  As described above, when the communication terminal 10 is entered in the neighbor cache 24, the router device 20 according to the present invention explicitly receives a communication failure notification from the communication terminal and leaves the entry until a predetermined time elapses. Management continues as a communication impossible state. Thereby, when the router device 20 receives the packet addressed to the communication terminal 10, the entry of the destination communication terminal 10 remains, so there is no need to perform a neighbor search of the corresponding communication terminal 10, and the ICMP reach is immediately impossible ( ICMP Unreachable) message can be sent to the packet source. As a result, the transmission source can immediately stop transmission of a packet that becomes unreachable, and packet loss can be reduced.

(Embodiment 2)
FIG. 11 is a diagram showing a network configuration of the connection management system according to the present invention. In FIG. 11, the communication terminal 10 leaves the connection with the router device 20 on the same link 110 and newly connects to the link 130, and communicates with the communication device 30 on the upper network 120 via the router device 40.

  First, the operation of the communication terminal 10 according to the present invention will be described with reference to the drawings.

  The configuration of the communication terminal 10 is the same as that shown in the first embodiment, except that a function described below is added to the neighborhood search processing performed by the neighborhood search processing unit 13.

  FIG. 12 is a flowchart showing processing when the communication terminal 10 connects to the links 110 and 130.

  First, when detecting that the lower layer processing unit 11 is connected to a link, the state transition request processing unit 15 is notified (step S1201). Then, the state transition request processing unit 15 checks whether or not the connected link is a new link (step S1202). If the link is the same as that before the movement, the state transition request processing unit multicast-transmits the neighbor advertisement message 230 with the N flag 214 set to OFF to all the nodes on the router device 20 or the link 110 (step) S1203).

  On the other hand, when the connected link is a new link, the state transition request processing unit 15 turns off the N flag 214, sets the current IP address in the target address 211, and further sets “2” in the type field. Is generated, and a neighbor advertisement message 230 in which the link layer address (MAC address) used for connection with the source router apparatus 20 is described in the link layer address (Link-Layer Address) field 213 is generated. The IP processing unit 22 is instructed to transmit to the device 20. The IP processing unit 22 sets the IP address of the source router device 20 in the destination IP address field of the IP header, sets its own IP address in the transmission source IP address field, and sends it through the lower layer processing unit 11 (S1204).

  The above is the difference from the operation of the communication terminal in Embodiment 1, and the other operations are the same.

  Next, the operation of the router device 20 according to the present invention will be described with reference to the drawings.

  The configuration of the router device 20 according to the present invention is the same as that of the first embodiment, except that a function described below is added to the neighbor search processing performed by the neighbor search processing unit 23.

  FIG. 13 is a flowchart showing the processing when the router device 20 receives the neighborhood advertisement message.

  In FIG. 13, first, when the IP processing unit 22 receives the neighborhood advertisement message 230 via the lower layer processing unit 21, it notifies the neighborhood search processing unit 13 (S1301). Then, the neighbor search processing unit 13 determines whether the request is for deleting a neighbor cache entry (S1302). This determination is made based on whether or not the source IP address acquired from the IP processing unit 22 is the same as the IP address 02 recorded in the neighborhood cache corresponding to the link layer address (MAC address) 213. When the transmission source IP addresses are different, the neighbor search processing unit 23 recognizes that the neighbor advertisement message 230 is transmitted from a link different from the link to which the neighbor search processor belongs. Further, when it is confirmed that the N flag 214 of the neighbor advertisement message 230 is off, it is determined that the request is a deletion request of its own neighbor cache entry.

  If it is determined in step S1302 that the request is for deleting a neighbor cache entry, the neighbor search processing unit 23 deletes the neighbor cache entry of the corresponding communication terminal 10 (step S1303). On the other hand, if it is determined that the request is not a deletion request, the normal neighborhood advertisement message reception process (steps S82 to S87) shown in FIG. 8A of the first embodiment is performed.

  The determination of the deletion request for the neighbor cache entry is made based on the current IP address of the communication terminal described in the target address and the IP address 02 recorded in the neighbor cache corresponding to the link layer address (MAC address) 213. It is also possible to carry out depending on whether or not they are the same. It is also possible to make the determination only by changing the IP address with the N flag turned on. Alternatively, as shown in FIG. 14, an old router / IP address field 215 of the neighbor advertisement message is further provided, and the IP address of the source router device 20 is further described in the old router / IP address field 215. It is also possible to determine that this is an entry deletion request by specifying its own IP address in this field.

Also, even if the router device receives a neighbor advertisement message not addressed to itself, it merely relays and does not perform other processing.

  Next, the operation of the connection management system including the communication terminal and the router device according to the present invention will be described. Note that the operation in the present embodiment is different from the first embodiment only in the operation when the communication terminal 10 moves and connects to a new link, and the other operations are the same.

  FIG. 15 is a sequence diagram showing an operation when the communication terminal moves.

  In FIG. 15, when the communication terminal 10 leaves the link 110, the communication terminal 10 notifies the router device 20 of the transition to the communication disabled state (step S1501).

  Upon receiving this, the router device 20 updates the communication state of the corresponding entry in the neighborhood cache to the communication disabled state (step S1502).

  Next, when the communication terminal 10 moves from the previously connected link 110 and connects to the link 130 (step S1503), the neighbor advertisement message for deleting its own neighbor cache entry to the source router device 20 230 is generated (step S1504) and transmitted to the router device 40 (step S1505). The router device 40 relays this neighbor advertisement message addressed to the router device 20 and transfers it to the destination router device 20 (step S1506).

  Next, when receiving the neighbor advertisement message, the router device 20 determines that it is a neighbor cache entry deletion request, and deletes the corresponding entry from the neighbor cache (S1507).

  As described above, according to the present embodiment, after the communication terminal 10 managed by the router device 20 leaves the link, when the communication terminal 10 is connected to a new link, the communication terminal 10 is transferred to the source router device 20. A request is made to delete the neighbor cache entry. For this reason, the source router device 20 can delete the neighbor cache entry of the communication terminal 10 in response to this request. As a result, even if the router device 20 leaves an entry of the communication terminal 10 in the communication disabled state in the neighboring cache so that the transmission failure notification when the packet addressed to the communication terminal is received can be immediately notified to the transmission source, Since the entry can be deleted in a timely manner, it is possible to effectively use the neighboring cache area in the router device.

  Further, according to the present embodiment, even when an entry is automatically deleted after the entry valid time has elapsed, unnecessary entries can be deleted without waiting for the entry valid time to elapse. Is more preferable.

(Embodiment 3)
The communication network configuration in the present embodiment is the same as that in the second embodiment shown in FIG. 11, but when the communication terminal 10 moves to the destination router device 40, the communication terminal 10 moves to the source router device 20. The message transmission method for deleting the entry is different.

  The configuration of the communication terminal 10 according to the present invention is the same as that shown in the second embodiment, but the neighbor search processing performed by the neighbor search processing unit 13 is different in terms of functions described below.

  FIG. 16 is a flowchart showing processing when the communication terminal 10 connects to the links 110 and 130.

First, when it is detected that the lower layer processing unit 11 is connected to the link, the state transition request processing unit 1
5 is notified (step S1601). Then, the state transition request processing unit 15 checks whether or not the connected link is a new link (step S1602). When the link is the same as that before the movement, the state transition request processing unit 15 multicast-transmits the neighbor advertisement message 230 with the N flag 214 set to OFF to the router device 20 or all the nodes on the link (step). S1603).

  On the other hand, if the connected link is a new link, the state transition request processing unit 15 sends the IP address of the source router device 20 and the link layer address (MAC) of the interface used for the connection with the source router device 20. Address advertisement) to the destination router device 40 is generated.

  FIG. 14 shows the format of the neighborhood advertisement message at this time. In FIG. 14, the target address field 211 indicates the IP address of the transmission source of this neighbor advertisement message, the type field indicates the type code of the option field 220, and the link layer address field 213 is at the time of connection with the source router apparatus 20. The link layer address (MAC address) used is shown, and the old router / IP address field 215 shows the IP address of the source router device 20.

  In this case, the current IP address of the communication terminal 10 itself is described in the target address field 211, the type code “3” is set in the type field, and the link layer address of the communication terminal 10 itself is set in the link layer address field 213. (MAC address) is described, and the IP address of the source router device 20 is described in the old router / IP address field 215. Note that the N flag 214 is set to OFF.

  Then, the state transition request processing unit 15 instructs the IP processing unit 22 to transmit the neighborhood advertisement message 230 to the destination router device 40. The IP processing unit 22 sets the IP address of the destination router device 40 in the destination IP address field of the IP header, sets its own IP address in the source IP address field, and sends it through the lower layer processing unit 11 (Step S1604).

  The above is the difference from the operation of the communication terminal in the second embodiment, and the other operations are the same.

  Next, operations of the router devices 20 and 40 according to the present invention will be described with reference to the drawings.

  The configurations of the router devices 20 and 40 according to the present invention are the same as those in the second embodiment, but the neighbor search processing performed by the neighbor search processing unit 23 is different in the following points.

  FIG. 17 is a flowchart showing processing when the router devices 20 and 40 receive the neighborhood advertisement message.

In FIG. 17, first, when receiving the neighbor advertisement message 230 via the lower layer processor 21, the IP processor 22 notifies the neighbor search processor 23 (step S1701). Then, the neighbor search processing unit 23 determines whether it is a request for proxy transmission of the neighbor cache entry from the communication terminal (step S1702). This determination is made by the proximity search processing unit 23 confirming the type 212 of the option field 220 and determining whether the type code is “3”. If the neighbor search processing unit 23 determines that the request is a proxy transmission request for a neighbor cache entry, the neighbor search processing unit 23 generates the neighbor advertisement message 210 shown in FIG. Here, the current IP address of the requesting communication terminal 10 is described in the target address field 211, the type code “2” is set in the type field, and the requesting communication terminal 10 is set in the link layer address field 213. The link layer address (MAC address) is described. The N flag 214 is set to off.

  Then, the neighbor search processing unit 23 instructs the IP processing unit 22 to transmit the neighbor advertisement message 210 to the source router device 20. The IP processing unit 22 sets the IP address of the source router device 20 in the destination IP address field of the IP header, sets its own IP address in the source IP address field, and sends it through the lower layer processing unit 21. (Step S1703).

  On the other hand, if it is determined in step S1702 that the request is not a proxy transmission request for a neighbor advertisement message, it is determined whether the request is a delete request for a neighbor cache entry (step S1704). This determination is made based on whether the source IP address acquired from the IP processing unit 22 is not the address of the communication terminal 10 but the address of the router device. If it is determined that it is not the neighbor advertisement message 230 from the communication terminal 10, the neighbor search processing unit 23 recognizes that it is a proxy neighbor advertisement message 230 from a router device on another link. Further, when it is confirmed that the N flag 214 of the neighbor advertisement message 230 is off, it is determined that the request is a deletion request of its own neighbor cache entry.

  If it is determined in step S1704 that the request is for deleting a neighbor cache entry, the neighbor search processing unit 23 deletes the neighbor cache entry of the corresponding communication terminal 10 (step S1705). On the other hand, if it is determined that the request is not a deletion request, normal neighbor advertisement message reception processing (steps S82 to S87) shown in FIG. 8A of the first embodiment is performed.

  The determination of the deletion request for the neighbor cache entry is made based on the current IP address of the communication terminal 10 described in the target address 211 and the IP recorded in the neighbor cache corresponding to the link layer address (MAC address) 213. It is also possible to carry out depending on whether or not the address is the same. Alternatively, the router device 20 is registered in its own neighbor cache by further notifying the old router / IP address field 215 of the IP address of the source router device 20 using the neighbor advertisement message shown in FIG. It is also possible to determine that this is a deletion request.

  Further, the destination router device 40 notifies the source router device 20 of the MAC address in addition to its own IP address, and the source router device 20 sets the corresponding entry of the communication terminal 10 in the neighboring cache to the old IP address and destination address. The router device 40 is updated to the MAC address. Thereby, when communication at the link layer is possible between the source router device 20 and the destination router device 40, the packet addressed to the old IP address of the communication terminal 10 is transferred to the MAC address of the destination router device 40. Can do. Further, the destination router device 40 receives the transferred communication based on information such as the old IP address, the new IP address, and the MAC address used in the source router device 20 previously acquired from the communication terminal 10. Packets destined for the old IP address of the terminal 10 are further forwarded to the current MAC address of the communication terminal 10 (which can be obtained from the MAC header when information is first obtained from the communication terminal 10) to reduce packet loss. Can be planned. Furthermore, the destination router device 40 may replace the destination IP address field of the transfer packet with the new IP address of the communication terminal 10 and send it out.

  The above is the difference between the present embodiment and the operation of the router device in the second embodiment, and the other operations are the same.

  Next, the operation of the connection management system including the communication terminal and the router device according to the present invention will be described. Note that the operation in the present embodiment is different from the first embodiment only in the operation when the communication terminal 10 moves and connects to a new link, and the other operations are the same.

  FIG. 18 is a sequence diagram showing an operation when the communication terminal 10 moves.

  In FIG. 18, when the communication terminal 10 leaves the link 110, the communication terminal 10 notifies the router device 20 of the transition to the communication disabled state (step S1801).

  Upon receiving this, the router device 20 updates the communication state of the corresponding entry in the neighborhood cache to the communication disabled state (step S1802).

  Next, when the communication terminal 10 moves from the previously connected link 110 and connects to the link 130 (step S1803), the address of the source router 20 is notified to the destination router 40 (step S1804). ).

  Next, when the destination router device 40 receives this notification, in order to delete the neighborhood cache entry of the communication terminal 10 to the source router device 20, a neighborhood advertisement message 210 is generated on behalf of the destination router device 20 (step S1805). It transmits to the original router device 20 (step S1806).

  When receiving the proxy neighbor advertisement message 210, the router device 20 determines that it is a neighbor cache entry deletion request, and deletes the corresponding entry from the neighbor cache (step S1807).

  As described above, according to the present embodiment, when a communication terminal managed by a router device leaves the link and then connects to a new link, the neighboring cache entry of the communication terminal is deleted to the source router device. Send a request to Therefore, the source router device can receive this request and delete the neighbor cache entry of the corresponding communication terminal. This allows the router device to delete the entry in a timely manner even if an entry for the communication terminal that has become inaccessible remains in the neighbor cache so that the router can immediately notify the transmission source when the packet addressed to the communication terminal is received. Therefore, it is possible to effectively use the neighboring cache area in the router device.

  Further, according to the present embodiment, even when an entry is automatically deleted after the entry valid time elapses, unnecessary entries can be deleted without waiting for the entry valid time to elapse. Is more preferable. In this embodiment, the communication terminal notifies the destination router device of the address of the source router device by expanding the old router / IP address field in the neighbor advertisement message. However, the present invention is not limited to this. If the IP address of the original router device can be notified, the same effect can be obtained even if it is notified by a message in another format.

  The present invention is useful for connection management of nodes in a mobile IP (Internet Protocol) network, and is suitable for quickly detecting the absence of a communication partner in a handover or the like.

The figure which shows the structure of the communication terminal in Embodiment 1 of this invention. The figure which shows the structure of the router apparatus in Embodiment 1 of this invention. The figure which shows the 1st operation | movement sequence of the connection management system in Embodiment 1 of this invention. The figure which shows the 2nd operation | movement sequence of the connection management system in Embodiment 1 of this invention. The figure which shows the format of the neighborhood advertisement message in Embodiment 1 of this invention. The figure which shows the data structure of the neighborhood cache in Embodiment 1 of this invention (A), (b) The flowchart which shows operation | movement of the communication terminal in Embodiment 1 of this invention. (A), (b) The flowchart which shows operation | movement of the router apparatus in Embodiment 1 of this invention. The flowchart which shows operation | movement of the router apparatus in Embodiment 1 of this invention. The figure which shows the state transition of the neighborhood cache entry in Embodiment 1 of this invention The figure which shows the structure of the communication network which concerns on Embodiment 2 of this invention. The flowchart which shows operation | movement of the communication terminal in Embodiment 2 of this invention. The flowchart which shows operation | movement of the router apparatus in Embodiment 2 of this invention. The figure which shows the format of the neighborhood advertisement message in Embodiment 3 of this invention. The figure which shows the operation | movement sequence of the connection management system in Embodiment 2 of this invention. The flowchart which shows operation | movement of the communication terminal in Embodiment 3 of this invention. The flowchart which shows operation | movement of the router apparatus in Embodiment 3 of this invention. The figure which shows the operation | movement sequence of the connection management system in Embodiment 3 of this invention. A diagram showing the configuration of a conventional communication network The figure which shows the format of the conventional neighborhood advertisement message The figure which shows the format of the conventional neighbor search message A diagram showing state transition of a conventional neighbor cache entry The figure which shows the operation sequence of the conventional connection management system The figure which shows the constitution of the conventional connection management system

Explanation of symbols

9, 10 Communication terminal 11 Lower layer processing unit 12 IP processing unit 13 Neighbor search processing unit 14 Neighbor cache 15 State transition request processing unit 20, 40 Router device 21 Lower layer processing unit 22 IP processing unit 23 Neighbor search processing unit 24 Neighbor cache 25 Entry valid timer 30 Communication device 110, 130 Link 120 Upper network 501 Mobile terminal 502 Router device 601 Gateway router 602 Subdomain router 603 Access router 604 Communication terminal

Claims (10)

A connection management method for a router device for managing connection of a communication terminal connected to a link in an IP network,
The communication terminal notifying the router device of its own communication state;
When the communication state is a notification of a communication disabled state, the router device that has received the notification transitions the neighboring cache entry of the communication terminal to a communication disabled state;
When the router device receives the packet addressed to the communication terminal, the router device checks the state of the neighbor cache entry, and if it is in a communication impossible state, immediately sends a transfer impossible notification to the transmission source of the packet;
A connection management method. Further, when the communication state is to notify the communicable state, the router device that has received the notification transitions the neighboring cache entry of the communication terminal to the communicable state;
When the router device receives a packet addressed to a communication terminal, if the state of the neighbor cache entry is a communicable state, the step of transferring the packet to the communication terminal;
The connection management method according to claim 1, comprising: The connection management method according to claim 1, wherein the communication terminal notifies the communication state by a neighbor advertisement message. After the communication terminal notifies the first router device that the communication is impossible, the link connection is released, and when the communication terminal is connected to the link managed by the second router device, the communication terminal transmits to the first router device. The connection management method according to claim 2, further comprising a step of requesting deletion of an entry in the neighbor cache. 3. The connection management method according to claim 2, wherein the entry of the communication terminal in the neighbor cache is deleted after a predetermined time has elapsed from the time when the router device receives a notification of the communication disabled state from the communication terminal. . Neighborhood cache,
A neighbor search processing unit that manages a communication state of a communication terminal that has entered the neighbor cache;
When receiving a packet addressed to the communication terminal, a packet transfer processing unit that transfers the packet according to the communication state of the communication terminal described in the neighbor cache;
Have
In accordance with the communication status notification from the communication terminal, the neighbor search processing unit changes the neighbor cache entry to a communication disabled state or a communication enabled state,
When the packet transfer processing unit is in an incommunicable state in the neighboring cache entry, the router device transmits a transfer disable notification to the transmission source at the time of reception of the packet. The router apparatus according to claim 6, wherein the communication state is notified by a neighbor advertisement message. The neighbor search processing unit starts a timer when receiving a notification of a communication impossible state from the communication terminal,
The router device according to claim 6, wherein when the timer counts a predetermined time, the neighbor search processing unit deletes the entry of the communication terminal in the neighbor cache. A connection state detector for detecting a connection state with the link;
When the connection state detection unit detects a change in the connection state, a state transition request processing unit that notifies the connection state to the router device on the connected link;
Have
The router device on the second link when the first link is disconnected and connected to the second link after notifying the router device of the first link to which the state transition request processing unit is connected. A communication terminal that requests the router on the first link to delete the neighbor cache entry via the first link. A communication terminal for notifying the router device on the link of a communicable state or a communicable state with the link;
According to the received communication state, the neighbor cache entry of the communication terminal is changed, and when the packet addressed to the communication terminal is received, the state of the neighbor cache entry is confirmed. A router device that immediately sends a transfer impossible notification to the sender of
A connection management system.

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