JP2012095234A - Route control method and communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a route control method capable of suppressing the amount of control messages required for reconstruction of a network in case of fault occurence.SOLUTION: A route control method for a communication system constituting a tree type network having a gateway terminal as a root, includes such steps as: holding a route information between the other radio communication terminal and the gateway terminal via an own terminal by a radio communication terminal constituting a tree type network ; notifying by a radio communication terminal 2-3 the gateway terminal of the route information held by the own terminal as a trouble route information when the radio communication terminal 2-3 detects a trouble on the route heading for the gateway terminal when transferring packets to the gateway terminal (S5, S6); and searching the route to the radio communication terminal 2-3 as a virtual tunnel route and updating the route by changing the route included in the trouble route information into the route passing through the virtual tunnel route by the gateway terminal (S9).

Description

  The present invention relates to a route control method in a communication system in which a multihop network is built in a tree shape rooted at a gateway terminal.

  Ad hoc that enables communication between communication terminals without using existing network infrastructure, compared to conventional infrastructure-type communication forms, as wireless communication technology progresses in recent years and electronic devices become smaller and more sophisticated. -Interest in networks is increasing. This ad hoc network is different from the conventional fixed infrastructure type network. (1) Communication between objects and devices, (2) Autonomous network construction with huge objects and devices, (3) Existing (4) Constructing a network that is easy and temporarily used. Ad hoc networks can also autonomously respond to topology changes.

  Currently, many routing protocols (ad hoc routing protocols) for forming an ad hoc network have been proposed in order to realize the above features. For example, DSR (Dynamic Source Routing) (RFC (Request for Comments) 4728, see Non-Patent Document 1 below), AODV (Ad Hoc On Demand Distance Vector Routing) (RFC3561, see Non-Patent Document 2 below), OLSR (Optimized Link) State Routing) (RFC 3626, see Non-Patent Document 3 below).

  DSR and AODV are on-demand type routing protocols, and perform communication by obtaining a route from a transmission source to a transmission destination when a communication request occurs. OLSR, on the other hand, is a proactive routing protocol that manages topology information by exchanging route information at all times, and communicates based on the stored route information when a communication request occurs. Can start.

  In recent years, a sensor network or data collection / control network in which a large number of wireless terminals are installed over a wide area and information is collected from each wireless terminal or control is performed on an arbitrary wireless terminal. There is also growing interest. This sensor network or data collection / control network is also a kind of ad hoc network (or multi-hop network or mesh network).

  In data collection and control networks, etc., the communication pattern is mainly communication between a specific node (gateway terminal) and each wireless terminal, and a tree-structured network (tree type network) with the gateway terminal as the root (root) Has been built. Various methods have been proposed for building a tree-type network. For example, when an on-demand type mesh routing protocol is applied, a bidirectional route is constructed between the gateway terminal and the terminal by the gateway terminal implementing a route search method for each terminal. In the On-demand mesh routing protocol, each terminal holds the next terminal for the destination terminal as route information.

  In the above tree-type network, when a packet from a gateway terminal to a wireless terminal is in error during transfer, a route error notification is notified to the source gateway terminal and the route is re-searched by the gateway terminal. It becomes. On the other hand, when an error occurs during the transfer of a packet from the wireless terminal to the gateway terminal, a route failure is notified to the transmitting wireless terminal, and the route is reconstructed from the terminal. Alternatively, using the characteristics of a tree-type network in which all terminals hold a route toward the gateway terminal, the terminal that detected the failure locally queries the adjacent terminal for the route toward the gateway terminal. It is also conceivable to restore the route toward the gateway terminal (local route restoration).

Internet Engineering Task Force (IETF), “RFC 4728 The Dynamic Source Routing Protocol (DSR) for Mobile Ad Hoc Networks for IPv4”, February 2007 IETF, “RFC 3561 Ad hoc On-Demand Distance Vector (AODV) Routing”, July 2003 IETF, “RFC 3626 Optimized Link State Routing Protocol (OLSR)”, October 2003

  However, in the conventional tree-type network, when a route failure is notified to the transmission source wireless terminal (transmission source terminal), only the reconstruction of the route between the transmission source terminal and the gateway terminal is performed. For this reason, a route re-search is performed for each of the other routes that pass through the corresponding failure location, and there is a problem that the number of route re-searches increases in a large-scale network.

  In addition, when the route toward the gateway terminal is reconstructed by local route restoration, only the route toward the gateway terminal is restored. For this reason, the route from the gateway terminal to the terminal in the network via the failure point (route for communication in the opposite direction to the repaired route) is not repaired, and the message transmission from the gateway terminal has not been achieved. After the detection, the search is performed again for the route in the reverse direction. As described above, there is a problem that it is necessary to re-search a plurality of routes for one failure location.

  The present invention has been made in view of the above, and an object of the present invention is to provide a path control method and a communication system that can suppress the amount of control messages required for network reconstruction when a failure occurs.

  In order to solve the above-described problems and achieve the object, the present invention provides a path control method in a communication system that configures a tree-type network rooted in a gateway terminal, and the wireless terminal that configures the tree-type network includes: A route holding step for holding route information of a route between the other wireless terminal and the gateway terminal passing through the own terminal, and the wireless terminal heads for the gateway terminal when transferring a packet addressed to the gateway terminal. When a failure on the route is detected, a failure route notification step of notifying the gateway terminal of the route information held by the terminal as failure route information; and the wireless terminal that is the notification source of the failure route information The route to the terminal is searched as a virtual tunnel route, and the route included in the failure route information is Characterized in that it comprises a route update step of updating the path through virtual tunnel path, a.

  According to the present invention, there is an effect that it is possible to suppress the amount of control message necessary for network reconstruction when a failure occurs.

FIG. 1 is a diagram illustrating a configuration example of a communication system according to the first embodiment. FIG. 2 is a diagram illustrating an example of a path restructuring procedure when a failure occurs in a conventional tree network. FIG. 3 is a diagram illustrating an example of a route restructuring procedure when a failure occurs in a conventional tree network. FIG. 4 is a diagram illustrating an example of a path restructuring procedure when a failure occurs in a conventional tree-type network. FIG. 5 is a sequence diagram illustrating an example of a path control procedure when a failure is detected according to the first embodiment. FIG. 6 is a diagram illustrating an example of information stored in the path error notification packet according to the first embodiment. FIG. 7 is a sequence diagram illustrating an example of a route control procedure according to the second embodiment. FIG. 8 is a diagram illustrating an example of information stored in the route information notification packet.

  Embodiments of a path control method and a communication system according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration example of a first embodiment of a communication system according to the present invention. As shown in FIG. 1, the communication system of the present embodiment includes a gateway terminal 1 having a wireless communication function, wireless terminals 2-1 to 2-N (N is an integer of 1 or more) having a wireless communication function, Consists of. The gateway terminal 1 and the wireless terminals 2-1 to 2-N (N is an integer equal to or greater than 1) include a tree-type network 4 that is a multi-hop network constructed in a tree shape with the gateway terminal 1 as a root. Constitute. The gateway terminal 1 is connected to the server 3 via a network.

  The gateway terminal 1 collects information from the wireless terminals 2-1 to 2-N installed in an area over a wide area, and notifies control information and the like to the wireless terminals 2-1 to 2-N. The wireless terminals 2-1 to 2-N are, for example, smart meters, and are terminals that acquire measurement results, observation results, and the like.

  The wireless terminals 2-1 to 2-N and the gateway terminal 1 constituting the tree network 4 construct a multi-hop network by executing an on-demand ad hoc routing protocol. The gateway terminal 1 manages information such as identifiers for communication of the wireless terminals 2-1 to 2-N. The server 3 is a server that manages the entire communication system.

  Here, a procedure for constructing a path when a fault occurs in a conventional tree network will be described. 2 to 4 are diagrams illustrating an example of a route restructuring procedure when a failure occurs in a conventional tree-type network. In the example of FIGS. 2 to 4, the gateway terminal 10 and the wireless terminals 11 to 16 form a tree type network. Before the failure occurs, communication from the wireless terminal 14 to the gateway 10 is performed via the wireless terminal 12 and the wireless terminal 11, and then a failure occurs in the link between the wireless terminal 11 and the wireless terminal 12. Suppose that

  FIG. 2 shows an example in which a transfer failure is detected during transfer from the wireless terminal 14 to the gateway terminal 10 after the above-described failure has occurred. When the packet from the wireless terminal 14 to the gateway terminal 10 is being transferred, the wireless terminal 12 recognizes that the transfer to the wireless terminal 11 has failed when the packet transmitted from the wireless terminal 14 is transferred. Thus, the failure is detected ((1) in FIG. 2). The wireless terminal 12 notifies the transmission source terminal 14 of the path failure ((2) in FIG. 2). Then, the wireless terminal 14 performs a route search again ((3) in FIG. 2).

  FIG. 3 shows an example in which local path repair is performed after the above-described failure has occurred. In the example of FIG. 3, as in the case of FIG. 2, when the wireless terminal 12 transfers a packet transmitted from the wireless terminal 14, a failure is detected by recognizing that the transfer to the wireless terminal 11 has failed. ((1) in FIG. 3). In the example of FIG. 3, it is assumed that the wireless terminal 12 is learning a route addressed to the gateway from the adjacent terminal ((2) in FIG. 3), and the local route repair (Local repair) is performed using the learned route to the gateway terminal 10. ) Is established ((3) in FIG. 3). In this way, a detour route via the wireless terminal 13 is set in the direction from the wireless terminal 14 to the gateway terminal 10.

  On the other hand, when the gateway terminal 10 transfers a packet to the wireless terminal 15 ((4) in FIG. 3), a route passing through the link between the wireless terminal 11 and the wireless terminal 12 is used. The route from the wireless terminal 14 to the gateway terminal 10 is set as a bypass route as described above, but the route from the gateway terminal 10 to the wireless terminal 15 is not set as a bypass route. When transferring to the terminal 12, a transfer failure occurs ((5) in FIG. 3). When the wireless terminal 11 detects a transfer failure, the wireless terminal 11 reconstructs the route by restoring the local route or notifying the transmission source gateway terminal 10 of the failure.

  FIG. 4 shows that when the route is re-searched from the wireless terminal 14 by the procedure described in FIG. 2 ((1), (2), (3) in FIG. 4), the gateway terminal 10 moves to the wireless terminal 15. An example of transferring a packet is shown. The route from the wireless terminal 14 to the gateway terminal 10 is re-searched according to the procedure of FIG. 2, but the route from the gateway terminal 10 to the wireless terminal 15 is the route before the occurrence of the failure (the wireless terminal 11 and the wireless terminal 12 (Route via the link between). Therefore, when a packet is transferred from the gateway terminal 10 to the wireless terminal 15 ((4) in FIG. 4), the wireless terminal 11 detects a transfer failure ((5) in FIG. 4), and the wireless terminal 11 transmits the packet. A route error is notified to the original gateway terminal 10 ((6) in FIG. 4). Then, the gateway terminal 10 re-searches the route to the wireless terminal 15 ((7) in FIG. 4).

  In the conventional procedure described above, as described with reference to FIGS. 3 and 4, even if there is only one fault location, a re-search is required for each route, and the number of route re-searches increases in a large-scale network. There is a problem of doing.

  In the present embodiment, in order to solve the above-described problem, route control is performed according to the following procedure. FIG. 5 is a sequence diagram illustrating an example of a path control procedure when a failure is detected according to the present embodiment. In the communication system shown in FIG. 1, the wireless terminal 2-5 transmits a packet to the gateway terminal 1 via the wireless terminal 2-4, the wireless terminal 2-3, the wireless terminal 2-2, and the wireless terminal 2-1. (Step S1). The wireless terminal 2-5, the wireless terminal 2-4, the wireless terminal 2-3, the wireless terminal 2-2, and the wireless terminal 2-1 use the On-Demand type routing protocol to transmit packets whose destination is the gateway terminal 1. It is assumed that round-trip route information (next terminal information) of the transfer route is held.

  Assume that a link failure occurs between the wireless terminal 2-3 and the wireless terminal 2-2 in this state. In that case, the wireless terminal 2-5 transmits the packet in the same manner as in step S1, and the wireless terminal 2-4 and the wireless terminal 2-3 transfer the packet to the next terminal (step S2). However, the packet transfer from the wireless terminal 2-3 to the wireless terminal 2-2 fails due to the link failure (step S3), and the wireless terminal 2-3 detects the link failure due to this transfer failure (step S4). The wireless terminal 2-3 may use any method for detecting the transfer failure. For example, a method of detecting that the transfer has failed when a response to the transferred packet does not arrive for a predetermined time or more. There is.

  Next, the wireless terminal 2-3 sends a route error notification packet for notifying that a failure has occurred on the route to the wireless terminal 2-5 that is the transmission source of the packet that has failed to be transferred in accordance with the detection of the link failure. It transmits to (step S5). The route error notification packet includes route information (wireless terminal 2-5 and gateway) to the gateway terminal 1 via its own terminal held by the transmission source terminal (here, the wireless terminal 2-3) of the route error notification packet. Stores not only the route information between the terminals 1 but also the transmission source terminal stored in the route information destined for the gateway device 1 held by the own terminal. That is, the route error notification packet stores information of a transmission source terminal of a route having the terminal that detected the link failure as the next terminal. Here, for example, wireless terminals 2-6, 2-7, 2-8, 2-9 and the like that transmit packets to the gateway terminal 1 via the wireless terminal 2-3 are stored as route information (source terminal). The

  FIG. 6 is a diagram illustrating an example of information stored in the route error notification packet according to the present embodiment. As shown in FIG. 6, the route error notification packet of this embodiment includes a message type (a value indicating that it is a route error notification packet), an information flag (a value indicating the state of the packet indicated by the message type), and , The information element length (value indicating the size of the packet indicated by the message type), the communication identifier of the source terminal (source terminal of the path error notification packet), the error factor, other information, and the path error Route information (hereinafter referred to as failure route information) held by the notification source terminal. Note that the configuration example in FIG. 6 is an example, and it is not limited to the configuration example in FIG. 6 as long as the route information held by the route error notification transmission source terminal and the information necessary for communication are stored.

  The wireless terminal 2-5 that has received the route error notification packet performs a route re-search for the gateway terminal 1 (step S6). That is, the wireless terminal 2-5 floods the route search request packet. In this embodiment, in this route search request packet, in addition to the information that the conventional route search request packet has, the route error notification source terminal (route error detected by the route error notification packet) is detected. And the failure path information are stored.

  When the gateway terminal 1 receives the route search request packet transmitted from the wireless terminal 2-5 by the route search request packet in step S6, the route search of the route to the wireless terminal 2-3 that detected the route error is performed. (Step S7). In the example of FIG. 5, the route from the gateway terminal 1 to the wireless terminal 2-5 does not pass through the wireless terminal 2-2, but passes through the wireless terminal 2-1, the wireless terminal 2-3, and the wireless terminal 2-4. A route is searched.

  After performing the route search, a route search response packet is returned to the wireless terminal 2-5 via the wireless terminal (in this case, the wireless terminal 2-3) that has detected the route error (step S8). Note that when a route search response packet is returned, communication is performed in a form in which some relay terminals are designated so that the route is via a specific wireless terminal (wireless terminal that has detected a route error). That is, a virtual tunnel is constructed so that a packet from the gateway terminal 1 to the wireless terminal 2-5 is transferred via a specific wireless terminal (a wireless terminal that detects a path error, here, the wireless terminal 2-3). Is done.

  In addition, the gateway terminal 1 transmits a route search request message transmission source terminal (in this example, a wireless terminal) out of the route information held by itself based on the failure route information included in the route search request packet received from the wireless terminal 2-5. The route information of the route to the terminal 2-5) is updated, and the wireless terminals (in the example of FIG. 5, for example, wireless terminals 2-6, 2-7, 2-8, 2-9) included in the failure route information are updated. Etc.) is also performed together with the update of the route information of the route to (step S9). Thereafter, the packet addressed to the wireless terminal 2-5 transmitted from the gateway terminal 1 is constructed and transferred so as to pass through the wireless terminal 2-3 (step S10). Similarly, the packet addressed to the wireless terminal 2-6 transmitted from the gateway terminal 1 is transferred via a virtual tunnel to the wireless terminal 2-3 (step S11). Packets for other wireless terminals included in the failure path information such as the wirelesss 2-7, 2-8, 2-9, etc. are similarly transferred via the virtual tunnel to the wireless terminal 2-3.

  The gateway terminal 1 preferentially searches for a route for the entire network with respect to the wireless terminal included in the virtual tunnel established between the gateway terminal 1 and the wireless terminal that detected the route error.

  As described above, in the present embodiment, in a tree-type network rooted at the gateway terminal 1, a terminal that detects a path failure during upstream packet transfer notifies the packet source terminal of the path failure. In order to do this, a route error notification packet storing route information held by the own terminal (the wireless terminal that is the transmission source of the packet having the own terminal as the next terminal) is transmitted. Then, the transmission source wireless terminal that has received the route error notification packet adds the route information stored in the route error notification to the route search request message for route re-search when performing route re-search. Further, the gateway terminal 1 that has received the route search request message constructs a virtual tunnel to the wireless terminal that has notified the route failure, and is included in the route information stored in the message and the wireless terminal that is the source of the route search request message. It was made to transmit via a virtual tunnel that built a route with the wireless terminal as the destination. For this reason, it is possible to realize route reconstruction for the downstream route via the failure location by detecting the route failure in the upstream direction, and to suppress the amount of control messages required for network reconstruction. it can.

  Furthermore, an optimum route can be constructed by pre-researching the route for the entire network with respect to the wireless terminal included in the virtual tunnel constructed between the gateway terminal 1 and the wireless terminal that detected the route error. The effect is obtained.

Embodiment 2. FIG.
FIG. 7 is a sequence diagram showing an example of a route control method according to the second embodiment of the communication system according to the present invention. The configuration of the communication system of the present embodiment is the same as that of the first embodiment. Hereinafter, the description which overlaps with Embodiment 1 is abbreviate | omitted, and a different part from Embodiment 1 is demonstrated.

  In the first embodiment, a path failure is detected in the middle of a route in packet transfer to the gateway terminal 1, but the terminal notifies the transmission source of a route error notification packet, and the route is re-searched from the transmission source. In the present embodiment, a wireless terminal that has detected a path failure in the middle of a path in a packet transfer toward the gateway terminal 1 inquires of the adjacent terminal about the path addressed to the gateway terminal 1. As a result, the wireless terminal that has detected the path failure obtains an alternative route to the gateway terminal 1 (local route repair), and notifies the gateway terminal 1 of the route information held by itself using the alternative route. Based on the received route information, the gateway terminal 1 constructs a virtual tunnel between the gateway terminal 1 and the terminal that is the source of the route information, thereby realizing the reconstruction of the route in the downlink direction.

  As illustrated in FIG. 7, as in the first embodiment, before the occurrence of a failure, the wireless terminal 2-5 is the wireless terminal 2-4, the wireless terminal 2-3, the wireless terminal 2-2, and the wireless terminal 2-1. The packet is transmitted to the gateway terminal 1 via (step S21). Steps S21 to S24 are the same as steps S1 to S4 in the first embodiment.

  After step S24, the wireless terminal 2-3 that has detected the link failure broadcasts a route search request packet (packet that inquires about the route to the gateway terminal 1) for local route repair to the adjacent terminal (step S25). The wireless terminal 2-1 that holds the route to the gateway terminal 1 that has received the route search request packet for local route repair transmits the route search response packet that notifies the route to the gateway terminal 1 as the transmission source terminal of the route search request packet. To the wireless terminal 2-3 (step S26).

  The wireless terminal 2-3 updates the route information to the gateway terminal 1 held by itself to the route to the gateway terminal 1 notified by the route search response packet, and updates the packet that failed to be transferred in step S23. It transmits toward the gateway terminal 1 using the route obtained (step S27). Specifically, in this example, a packet is transmitted to the gateway terminal 1 via the wireless terminal 2-1 as the updated route.

  In addition, the wireless terminal 2-3 includes the transmission source terminal (in this case, for example, the wireless terminals 2-5, 2-6, 2-7, 2-7) out of the route information held by the own terminal. -8, 2-9, etc.) are transmitted to the gateway terminal 1 (step S28).

  FIG. 8 is a diagram illustrating an example of information stored in the route information notification packet. The message type, information flag, information element length, and identifier for communication of the transmission source terminal are the same as the information stored in the route error notification packet of the first embodiment. In the present embodiment, in addition to these pieces of information, among the route information held by the wireless terminal that transmits the route information notification packet, a communication identifier (hereinafter referred to as failure route information) of the transmission source terminal that uses the own terminal as the next terminal. )including. Note that FIG. 8 is an example, and it is sufficient to include failure path information, and the information stored in the path information notification packet is not limited to the example of FIG.

  The gateway terminal 1 that has received the route information notification packet performs a route search to the wireless terminal 2-3 that is the transmission source of the route information notification packet (step S29). Then, the gateway terminal 1 determines the route to the wireless terminal included in the failure route information stored in the route information notification packet as the route via the virtual tunnel to the wireless terminal 2-3 that is the transmission source of the route information notification packet. The route information is updated so as to do this (step S30).

  Thereafter, as in the first embodiment, a packet addressed to the wireless terminal 2-5 transmitted from the gateway terminal 1 is transmitted via a virtual tunnel to the wireless terminal 2-3 (step S31), and similarly the gateway. The packet addressed to the wireless terminal 2-6 transmitted from the terminal 1 is transmitted via the virtual tunnel to the wireless terminal 2-3 (step S32). The operations of the present embodiment other than those described above are the same as those of the first embodiment.

  The gateway terminal 1 preferentially searches for a route for the entire network with respect to the wireless terminal included in the virtual tunnel established between the gateway terminal 1 and the wireless terminal that detected the route error.

  In the present embodiment, the example in which the route information (failure route information) is notified from the wireless terminal 2-3 that detects the failure to the gateway terminal 1 using the route information notification packet has been described. For example, when a procedure for grouping and managing the route from the gateway terminal 1 to each wireless terminal (for example, the procedure prescribed in Japanese Patent No. 4335945) is used, the protocol concerned instead of the route information notification packet is used. It is also possible to use a message for notifying the change of the route defined in.

  In the first embodiment, the wireless terminal 2-3 that has detected the failure notifies the wireless terminal 2-5 of the failure route information by the route error notification packet, and the failure route information is transmitted from the wireless terminal 2-5 by the route search request packet. Is notified to the gateway terminal 1. That is, the failure route information is notified from the wireless terminal 2-3 to the gateway terminal 1 via the wireless terminal 2-5. In this embodiment, the wireless terminal 2-3 notifies the failure route information directly to the gateway terminal 1 using the route information notification packet. These two embodiments show an example in which the wireless terminal 2-3 notifies the gateway terminal 1 of failure route information (route information held by the wireless terminal 2-3). As long as the failure route information (route information held by the wireless terminal 2-3) can be notified to the gateway terminal 1, the method is not limited to the method described in the above two embodiments, and any method may be used.

  As described above, in the present embodiment, in a tree-type network rooted at the gateway terminal 1, a terminal that detects a path failure at the time of packet transfer in the upstream direction (direction toward the gateway terminal 1) is locally connected to the gateway terminal 1 The destination route is re-searched, the transfer packet is retransmitted to the gateway terminal 1 using the re-searched route, and the route information held by the own node is notified to the gateway terminal 1 using the re-searched route. Then, the gateway terminal 1 searches for a route to the terminal that detects the path failure, constructs a virtual tunnel to the terminal that detects the path failure, and based on the route information notified from the wireless terminal that detected the path failure Updated the route information held by itself. For this reason, it is possible to realize route reconstruction for the downstream route via the failure location by detecting the route failure in the upstream direction, and to suppress the amount of control messages required for network reconstruction. it can.

  Furthermore, an optimum route can be constructed by pre-researching the route for the entire network with respect to the wireless terminal included in the virtual tunnel constructed between the gateway terminal 1 and the wireless terminal that detected the route error. The effect is obtained.

  As described above, the route control method and the communication system according to the present invention are useful for a communication system in which a multi-hop network is constructed in a tree shape rooted at a gateway terminal, and in particular, an on-demand type mesh Suitable for communication systems using routing protocols.

1,10 Gateway terminal 2-1 to 2-N, 11 to 16 Wireless terminal 3 Server 4 Tree-type network

Claims (6)

A route control method in a communication system constituting a tree-type network rooted at a gateway terminal,
A route holding step in which a wireless terminal constituting the tree-type network holds route information of a route between another wireless terminal and the gateway terminal that pass through the terminal;
When the wireless terminal detects a failure on the route to the gateway terminal when transferring a packet addressed to the gateway terminal, a failure route notification that notifies the gateway terminal of the route information held by the terminal as failure route information Steps,
A route in which the gateway terminal searches for a route to the wireless terminal that is a notification source of the failure route information as a virtual tunnel route, and updates a route included in the failure route information to a route that passes through the virtual tunnel route. An update step;
A path control method comprising: The failure route notification step includes:
The failure detection terminal that is the wireless terminal that is the notification source of the failure route information stores the failure route information in a route error notification that notifies the failure, and the route error notification after the storage is the transmission source that is the transmission source of the packet An error notification step to send to the device,
A search request step in which the transmission source terminal stores the failure route information in a route search request for re-searching a route to the gateway terminal, and transmits the stored route search request;
The path control method according to claim 1, comprising:   In the failure route notification step, the wireless terminal that is the notification source of the failure route information acquires a route from the adjacent wireless terminal to the gateway terminal, and uses the acquired route to transmit the failure route information to the gateway terminal. The route control method according to claim 1, wherein notification is performed.   In the failure path notification step, the failure path is notified using a message defined by a procedure for grouping and managing each route from the gateway terminal to the wireless terminal by the wireless terminal that is the notification source of the failure path information. The route control method according to claim 3, wherein information is notified to the gateway terminal.   5. The route control method according to claim 1, wherein route re-search is preferentially performed for a terminal on the virtual tunnel route. 6. A communication system comprising a gateway terminal and a wireless terminal, and constituting a tree-type network rooted in the gateway terminal,
The wireless terminal holds route information of a route between the other wireless terminal and the gateway terminal via the own terminal;
When the wireless terminal detects a failure on the route to the gateway terminal when transferring a packet addressed to the gateway terminal, the route information held by the terminal is notified to the gateway terminal as failure route information,
The gateway terminal searches for a route to the wireless terminal that is a notification source of the failure route information as a virtual tunnel route, and updates a route included in the failure route information to a route via the virtual tunnel route. A communication system characterized by the above.

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