JP6413674B2 - COMMUNICATION CONTROL PROGRAM, COMMUNICATION CONTROL METHOD, AND COMMUNICATION CONTROL DEVICE - Google Patents

Description

  The present invention relates to a communication control program and the like.

  Each node included in the ad hoc network transmits and receives hello packets between adjacent nodes, and constructs a plurality of routes to a final destination. Information on a plurality of routes to the destination is registered in the routing table. Even after constructing a route, each node periodically transmits / receives a hello packet to calculate the communication quality of each route, maintains the route, learns the optimum route, and updates the routing table as needed. When there are a plurality of routes to the same destination, each node sets a priority for each route, selects a route with a higher priority, and transmits data. In addition, each node generates a link table in which radio wave intensity with an adjacent node, the number of hops to a destination, and the like are associated by using transmission / reception of a hello packet.

  FIG. 22 is a diagram illustrating an example of a conventional ad hoc network. As shown in FIG. 22, this ad hoc network includes nodes 10a, 10b, 10c, 10d, 10e, 10f, 10g, 10h, 10s, and 10x.

  FIG. 23 is a diagram illustrating an example of a conventional routing and link table. FIG. 23 shows an example of the routing table 1d and the link table 2d of the node 10d as an example. As shown in FIG. 23, the routing table 1d associates GD (Global Destination) with LD (Local Destination). GD indicates a destination of the packet, and LD indicates an adjacent node that is a transfer destination when the packet is transmitted to the destination. The upper LD indicates a higher priority. The priority order of the LD is determined based on the evaluation value of the link table.

  The link table 2d associates the node identification information, the number of hops, the radio wave intensity, and the evaluation value. Node identification information is information that uniquely identifies an adjacent node. The number of hops is the number of nodes through which a packet passes to reach a predetermined destination + 1. The radio field intensity is the radio field intensity between the adjacent node and the own device. The evaluation value is a value calculated from the radio wave intensity or the like.

  In the example of the routing table 1d illustrated in FIG. 23, when a packet is transmitted to the node 10x, it is indicated that any one of the nodes 10a, 10b, and 10c is a transfer destination. In addition, the magnitude relationship of the priority order is node 10a> node 10b> node 10c. For this reason, when the node 10d transmits a packet to the node 10x, the packet is transmitted to the node 10a based on the routing table 1d. When the packet transfer fails, the node 10d transmits the packet again to another node, for example, the node 10b.

JP 2008-301444 A

  However, the above-described conventional technique has a problem that a packet cannot be transmitted to a communication destination due to a temporary communication failure.

  FIG. 24 is a diagram for explaining the problems of the prior art. For example, as shown in FIG. 24, an obstacle 20 occurs between the node 10x and the nodes 10a, 10b, and 10c, and wireless communication is disconnected between the node 10x and the nodes 10a, 10b, and 10c. To do. Even when the obstacle 20 is temporary, the process of changing the route in the routing table using the hello packet is not in time. Then, for example, even if the node 10d transfers the packet addressed to the node 10x to any of the nodes 10a, 10b, and 10c based on the routing table 1d, the packet cannot reach the node 10x.

  An object of one aspect is to provide a communication control program, a communication control method, and a communication control apparatus that can transmit a packet to a communication destination.

  In the first plan, the computer executes the following processing. When communication via a communication path set in advance with a communication destination via at least one relay device becomes impossible, the computer can communicate with the communication destination and the number of communication devices included in the communication path. Reference is made to a storage unit that stores information associated with Based on the reference result, the computer switches to communication with a communication destination using a communication path having a larger number of relay devices than the communication path in which communication is disabled.

  According to one embodiment of the present invention, there is an effect that a packet can be transmitted to a communication destination.

FIG. 1 is a diagram illustrating an example of an ad hoc network according to the present embodiment. FIG. 2 is a diagram illustrating an ad hoc network for explaining the pattern 1. FIG. 3 is a diagram illustrating an example of a routing table of each node for explaining the pattern 1. FIG. 4 is a diagram illustrating an example of a node link table for explaining the pattern 1. FIG. 5 is a diagram illustrating an example of an ad hoc network for explaining the pattern 2. FIG. 6 is a diagram illustrating an example of a routing table of each node for explaining the pattern 2. FIG. 7 is a diagram illustrating an example of a link table of nodes for explaining the pattern 2. FIG. 8 is a diagram illustrating an example of an ad hoc network for explaining the pattern 3. FIG. 9 is a diagram illustrating an example of a routing table of each node for explaining the pattern 3. FIG. 10 is a diagram illustrating an example of a link table of each node for explaining the pattern 3. FIG. 11 is a diagram (1) illustrating an example of a data structure of a packet. FIG. 12 is a diagram illustrating an example of an ad hoc network for explaining the pattern 4. FIG. 13 is a diagram illustrating an example of a routing table of each node for explaining the pattern 4. FIG. 14 is a diagram illustrating an example of a link table of each node for explaining the pattern 4. FIG. 15 is a diagram (2) illustrating an example of a data structure of a packet. FIG. 16 is a diagram illustrating an example of an ad hoc network for explaining the pattern 5. FIG. 17 is a diagram illustrating an example of a routing table of each node for explaining the pattern 5. FIG. 18 is a diagram illustrating an example of a link table of each node for explaining the pattern 5. FIG. 19 is a functional block diagram illustrating the configuration of the node according to the present embodiment. FIG. 20 is a diagram illustrating an example of a processing procedure of the node according to the present embodiment. FIG. 21 is a diagram illustrating an example of a computer that executes a communication control program. FIG. 22 is a diagram illustrating an example of a conventional ad hoc network. FIG. 23 is a diagram illustrating an example of a conventional routing and link table. FIG. 24 is a diagram for explaining the problems of the prior art.

  Hereinafter, embodiments of a communication control program, a communication control method, and a communication control device disclosed in the present application will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 is a diagram illustrating an example of an ad hoc network according to the present embodiment. As shown in FIG. 1, this ad hoc network includes nodes 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h, 100s, and 100x. In the following description, the nodes 100a to 100x are collectively expressed as a node 100 as appropriate. The node 100 is an example of a communication control device.

  The node 100 transmits and receives hello packets between adjacent nodes, and constructs a plurality of communication paths that reach the final destination. The node 100 registers information on a plurality of communication paths reaching the destination in the routing table. In addition, the node 100 generates a link table by using transmission / reception of a hello packet. The node 100 may generate the routing table and the link table using any conventional technique.

  Here, the node 100 is a node other than the node set in the routing table based on the link table when communication by the communication path set in the routing table becomes impossible due to a temporary obstacle. Perform processing to switch to the communication path that passes through. Hereinafter, the processing of the node 100 will be described in more detail.

  In the following, processing executed by the node 100 of the ad hoc network according to the present embodiment will be described for each of a plurality of patterns. First, a description will be given of Pattern 1 in which communication is disabled when a temporary obstacle occurs in a state where a normal network is constructed, and a packet is routed to a destination by performing route detouring.

  FIG. 2 is a diagram illustrating an ad hoc network for explaining the pattern 1. FIG. 3 is a diagram illustrating an example of a routing table of each node for explaining the pattern 1. In FIG. 3, the routing tables of the nodes 100a, 100b, 100c, 100d, 100h, and 100g are shown as an example. The routing table of the node 100a is assumed to be a routing table 150a. The routing table of the node 100b is a routing table 150b. The routing table of the node 100c is a routing table 150c. The routing table of the node 100d is assumed to be a routing table 150d. The routing table of the node 100h is a routing table 150h. The routing table of the node 100g is defined as a routing table 150g. The routing tables of the nodes 100f and 100e are not shown. In the following description, the routing tables 150a, 150b, 150c, 150d, 150h, and 150g are collectively referred to as a routing table 150 as appropriate.

  As shown in FIG. 3, the routing table 150 associates GD (Global Destination), LD (Local Destination), and a use prohibition flag. GD indicates the final destination of the packet. The LD indicates an adjacent node that is a transfer destination when a packet is transmitted to the GD. The use prohibition flag is a flag indicating whether or not the node is allowed to transmit a packet. If the node is allowed to transmit a packet, the use prohibition flag is “OFF”. If the node is not allowed to transmit a packet to the transfer destination, the use prohibition flag is “ON”. Become.

  FIG. 4 is a diagram illustrating an example of a node link table for explaining the pattern 1. FIG. 4 shows a link table 160d of the node 100d as an example. As shown in FIG. 4, the link table 160d associates node identification information, the number of hops, radio wave intensity, an evaluation value, and a bypass prohibition flag. Node identification information is information that uniquely identifies an adjacent node. The number of hops is the number of nodes through which a packet passes before reaching the GD + 1. In this embodiment, as an example, the number of hops when the GD is the node 100x is shown.

  The radio wave intensity indicates the radio wave intensity between the adjacent node and the node 100d. The evaluation value is a value calculated based on the radio wave intensity between nodes from the transfer destination to the GD. In this embodiment, it is assumed that the lower the evaluation value, the higher the priority of the node when transmitting a packet. As will be described later, the bypass prohibition flag is a flag indicating whether or not the node is a node that permits transmission of a packet when determining a packet transfer destination based on the link table 160d. The bypass prohibition flag is set to “OFF” when the node is allowed to transmit the packet, and the bypass prohibition flag is set to “ON” when the node is not allowed to transmit the packet to the transfer destination. Become.

  Returning to the description of FIG. Step S10 in FIG. 2 shows an example of a normal ad hoc network. The node 100 transmits the packet to the destination based on the routing table. For example, when transmitting a packet to the node 100x, the node 100d transmits the packet to the adjacent node based on the routing table 150d.

  Step S11 in FIG. 2 shows an example of an ad hoc network when the obstacle 20a occurs. The obstacle 20a disconnects the wireless communication between the node 100x and the nodes 100a, 100b, and 100c. Hereinafter, a case will be described in which packet transmission is attempted from the node 100d to the node 100x.

  (1) When performing data communication with the node 100x, the node 100d transmits a packet to the node 100a that is the first candidate based on the routing table 150d.

(2) The node 100a transmits a packet to the first candidate node 100x based on the routing table 150a, but does not respond, so the use prohibition flag corresponding to the node 100x in the routing table 150a is set to “ON”. . Thus, node 100a, the routing table 150a, and updates the routing table 150a _1.

(3) nodes 100a, based on the routing table 150a _1, and transmits the packet to the node 100b is a second candidate.

(4) Based on the routing table 150b, the node 100b transmits a packet to the first candidate node 100x but does not respond, so the use prohibition flag corresponding to the node 100x in the routing table 150b is set to “ON”. . Thus, the node 100b is a routing table 150b, and updates the routing table 150b _1.

(5) node 100b based on the routing table 150b _1, and transmits the packet to the node 100c is a third candidate. Here, since the node 100b receives the packet from the second candidate node 100a in (3), the node 100b does not transmit the packet to the node 100a.

(6) Based on the routing table 150c, the node 100c transmits a packet to the first candidate node 100x but does not respond, so the use prohibition flag corresponding to the node 100x in the routing table 150c is set to “ON”. . Thus, the node 100c is the routing table 150c, and updates the routing table 150c _1.

(7) Node 100c, based on the routing table 150c _1, transmits the packet to the node 100d is a third candidate. Here, since the node 100c receives the packet from the second candidate node 100b in (5), the node 100c does not transmit the packet to the node 100b.

(8) In order to receive the packet transmitted to the node 100a from the node 100c, the node 100d sets the use prohibition flag corresponding to the nodes 100a and 100c to “ON” in the routing table 150d. Thus, the node 100d is a routing table 150d, and updates the routing table 150d _1.

Step S12 in FIG. 2 will be described. (9) node 100d, based on the routing table 150d _1, transmits the packet to the node 100b to disable flag is not "ON".

  (10) Since the node 100b has received the packet transmitted to the node 100c in (5) again from the node 100d, the node 100b determines that the packet cannot be transmitted for all routes in the routing table 150b. As a result, the node 100b returns the packet to the node 100d.

(11) node 100d because sent back data from the node 100b, the routing table 150d _1, the disable flag corresponding to the node 100b to "ON". Thus, the node 100d is a routing table 150d _1, updates the routing table 150d _2.

(12) node 100d is the routing table 150d _2, since all the disabling flag is set to "ON", based on the link table 160, to detect a possible node reaches the node 100x. For example, the node 100d detects a node that satisfies the following condition 1, condition 2, and condition 3.

Condition 1: A node having a hop count (3) obtained by adding 1 to the hop count (2) of the local apparatus (node 100d).
Condition 2: A node for which the bypass prohibition flag in the link table (link table 160d) is “OFF”. However, the node whose use prohibition flag is “ON” in the routing table (routing table 150d ₂ ) is excluded.
Condition 3: Of the nodes corresponding to condition 2, the node having the smallest evaluation value.

  Note that, when the node 100d detects a node satisfying the conditions 1 to 3, the node 100d excludes the node set in the LD of the routing table 150d from the detection target. For example, the node 100d is excluded from detection targets because the nodes 100a to 100c have already been adopted as the route of the routing table 150d.

  When the node 100d searches for a node satisfying the conditions 1 to 3 based on the link table 160d, the node 100h satisfies the conditions 1 to 3. For this reason, the node 100d detects the node 100h as a new transfer destination of the packet. If it demonstrates using FIG. 4, the node which satisfy | fills the conditions 1 and 2 will be the node 100h. The node 100h also satisfies the condition 3. For this reason, the node 100d detects the node 100h.

  Here, the basis of Condition 1 will be described. When the node 100 selects a node larger than the number of hops obtained by adding 1 to the number of hops of the own device, there is a high possibility that the packet returns again after transmitting the packet to the node. For example, referring to FIG. 1 and FIG. 4, nodes 100e and 100f have a number of hops larger than that of node 100d. When the node 100d transmits a packet having the GD as the node 100x to the nodes 100e and 100f, the node 100d is likely to receive the packet from the nodes 100e and 100f again, and a loop occurs.

  Step S13 in FIG. 2 will be described. (13) The node 100d transmits a packet to the node 100h detected in (12). (14) The node 100h transmits a packet to the node 100g that is the first candidate based on the routing table 150h.

  (15) The node 100g transmits a packet to the node 100x that is the first candidate based on the routing table 150g.

  As described above, when the node 100 executes the processes (1) to (15), the packet can be transmitted to the GD even when packet transmission fails for all the routes in the routing table 150.

  Next, pattern 2 in which the node 100d transmits the packet again after the packet is detoured and transmitted in pattern 1 until the optimum route is restored will be described. FIG. 5 is a diagram illustrating an example of an ad hoc network for explaining the pattern 2. FIG. 6 is a diagram illustrating an example of a routing table of each node for explaining the pattern 2.

FIG. 6 shows a routing table of the nodes 100d, 100h, 100g, 100j, and 100k as an example. The routing table of node 100d, and routing table 150d _2. The routing table of the node 100h is a routing table 150h. The routing table of the node 100g is defined as a routing table 150g. The routing table of the node 100j is a routing table 150j. The routing table of the node 100k is assumed to be a routing table 150k.

  FIG. 7 is a diagram illustrating an example of a link table of nodes for explaining the pattern 2. FIG. 7 shows a link table 160d of the node 100d as an example.

Step S20 in FIG. 5 will be described. (21) node 100d, when sending a packet set the GD to node 100x, referring to the routing table 150d _2. Node 100d, for the routing table 150d _2, all use prohibition flag for which is "ON", based on the link table 160d, to detect a possible node reaches the node 100x. For example, the node 100d detects the node 100h that satisfies the above condition 1, condition 2, and condition 3. The node 100d transmits a packet to the node 100h.

  (22) The node 100h transmits a packet to the first candidate node 100g based on the routing table 150h. (23) The node 100g transmits a packet to the node 100x that is the first candidate based on the routing table 150g.

  Step S21 in FIG. 5 will be described. Step S21 shows an example in which an obstacle 20b is generated in addition to the obstacle 20a. The obstacle 20b disconnects the wireless communication between the node 100g and the node 100x. It is assumed that the node 100d transmits packets to the node 100x via the nodes 100h and 100g until the obstacle 20b occurs.

(24) Since the node 100g transmits a packet to the node 100x but does not respond, the node 100g sets the use prohibition flag corresponding to the node 100x in the routing table 150g to “ON”. Thus, the node 100g is a routing table 150 g, updates the routing table 150 g _1.

(25) node 100g for all routes to GD of the routing table 150 g _1, determines that the undeliverable packet, returns the packet to the node 100h. Since the node 100h has received the packet again from the node 100g, the use prohibition flag corresponding to the node 100g in the routing table 150h is set to “ON”. Thus, the node 100h is a routing table 150h, updates the routing table 150h _1.

(26) node 100h for all routes to GD routing table 150h _1, determines that it is not possible to transmit a packet, returns the packet to the node 100d. Since the node 100d has received the packet again from the node 100h, the bypass prohibition flag corresponding to the node 100h in the link table 160d is set to “ON”. Thus, the node 100d is a link table 160d, and updates the link table 160d _1.

(27) node 100d is the routing table 150d _2, all use prohibition flag is "ON", and, since the bypass prohibition flag of the node 100h that was used in the alternate route is turned "ON" again, A node satisfying conditions 1 to 3 is detected. Node 100d is a node satisfying the condition 1-3, searching based on link table 160d _1, node 100j satisfies the conditions 1-3. For this reason, the node 100d detects the node 100j as a new detour destination of the packet.

  (28) The node 100d transmits a packet to the node 100j detected in (27). (29) The node 100j transmits a packet to the node 100k that is the first candidate based on the routing table 150j. (30) The node 100k transmits the packet to the first candidate node 100x based on the routing table 150k.

  As described above, when the node 100 executes the processes (24) to (30), even when communication is cut off by the detour path, another detour path is detected and the packet is transmitted to the GD. Can do. Note that the node 100 adds 1 to the number of bypass transfers stored in the packet when the packet is transferred using the bypass route. The node 100 transmits a packet to the detour destination node 100 only when the detour transfer count is smaller than the detour transfer count threshold held by itself. Note that when the number of bypass transfers is equal to or greater than the threshold of the bypass transfer number held by the node 100, the node 100 returns the packet to the node 100d that is the packet transmission source. A description of specific processing relating to the number of bypass transfers will be described later.

  Next, pattern 3 in which a bypass route is further used when a node of the bypass route transmits a packet will be described. FIG. 8 is a diagram illustrating an example of an ad hoc network for explaining the pattern 3. FIG. 9 is a diagram illustrating an example of a routing table of each node for explaining the pattern 3.

FIG. 9 shows a routing table of the nodes 100d, 100h, 100p, and 100q as an example. The routing table of node 100d, and routing table 150d _2. The routing table of the node 100h is a routing table 150h. The routing table of the node 100p is assumed to be a routing table 150p. The routing table of the node 100q is a routing table 150q.

  FIG. 10 is a diagram illustrating an example of a link table of each node for explaining the pattern 3. FIG. 10 shows a link table of the nodes 100d, 100h, and 100p as an example. The link table of the node 100d is assumed to be a link table 160d. The link table of the node 100h is assumed to be a link table 160h. The link table of the node 100p is assumed to be a link table 160p.

Step S30 in FIG. 8 will be described. (31) node 100d, when sending a packet set the GD to node 100x, referring to the routing table 150d _2. Node 100d, for the routing table 150d _2, all use prohibition flag for which is "ON", based on the link table 160d, to detect a possible node reaches the node 100x. For example, the node 100d detects the node 100h that satisfies the above condition 1, condition 2, and condition 3. The node 100d transmits a packet to the node 100h.

  FIG. 11 is a diagram (1) illustrating an example of a data structure of a packet. As illustrated in FIG. 11, for example, a packet associates LD, LS, GD, GS, the number of bypass transfers, and actual data. Here, the description regarding LD and GD is the same as the above description. LS (Local Source) indicates an adjacent node that is a packet transfer source. GS (Global Source) indicates a node that first transmits a packet. The number of detour transfers indicates the number of times that a packet was transferred through a detour path. The actual data includes user data such as sensor data measured by each node 100.

  For example, the packet transmitted from the node 100d to the node 100h in (31) is the packet 30a in FIG. The node 100d sets “node 100h” in the LD of the packet 30a, sets “node 100d” in LS, sets “node 100x” in GD, and sets “node 100d” in GS. Also, the node 100d sets an initial value “1” to the number of bypass transfers. Each time a packet is transferred, the node information stored in the LD and LS is updated. In the following description, the description regarding the data structure of the packet is omitted unless otherwise specified.

  Returning to the description of FIG. (32) The node 100h transmits a packet to the node 100g that is the first candidate based on the routing table 150h. (33) The node 100g transmits a packet to the node 100x that is the first candidate based on the routing table 150g.

  Step S31 in FIG. 8 will be described. In step S31, it is assumed that the obstacle 20a further disconnects the wireless communication between the node 100h and the nodes 100g, 100l, and 100m. Assume that the node 100d transmits packets to the node 100x via the nodes 100h and 100g until the wireless communication is disconnected between the node 100h and the node 100g.

  (34) Since the node 100h transmits a packet to the node 100g but does not respond, the node 100h sets the use prohibition flag corresponding to the node 100g in the routing table 150h to “ON”.

  (35) Since the node 100h transmits a packet to the second candidate node 100l but does not respond, the node 100h sets the use prohibition flag corresponding to the node 100l in the routing table 150h to “ON”.

(36) Since the node 100h transmits a packet to the third candidate node 100m but does not respond, the node 100h sets the use prohibition flag corresponding to the node 100m in the routing table 150h to “ON”. The above (34) - (36), the node 100h, as shown in FIG. 10, the routing table 150h, updates the routing table 150h _1.

(37) the node 100h determines, for all the paths leading to the GD of the routing table 150h _1, as a packet undeliverable. In pattern 3, a case where the node 100h detects an adjacent node serving as a detour destination based on the link table 160h will be described. When the node 100h searches for a node satisfying the conditions 1 to 3 based on the link table 160h, the node 100p satisfies the conditions 1 to 3.

  The node 100h transmits a packet to the node 100p. The data structure of the packet that the node 100h transmits to the node 100p is as shown in the packet 30b of FIG. The node 100h sets “node 100p” in the LD of the packet 30b, sets “node 100h” in LS, sets “node 100x” in GD, and sets “node 100d” in GS. Further, the node 100h sets the detour transfer count to “2” by adding 1 to the detour transfer count. The node 100h transmits a packet to the detour destination node 100p only when the number of detour transfers is smaller than the detour transfer count threshold held by the node 100h. Note that the node 100h returns the packet to the node 100d that is the transmission source of the packet when the number of detour transfers is equal to or greater than the detour transfer number threshold held by the node 100h. In the following description, a case where the number of bypass transfers is smaller than the threshold value of the bypass transfer held by itself will be described.

  (38) The node 100p transmits the packet to the node 100q that is the first candidate based on the routing table 150p. (39) The node 100q transmits the packet to the node 100x that is the first candidate based on the routing table 150q.

  As described above, the node 100 executes the processes (31) to (39), so that even when communication is further disconnected at the detour route destination, another detour route is detected and the packet is transferred to the GD. Can be sent.

  Next, a description will be given of the pattern 4 that uses the detour route when the detour route node transmits a packet. FIG. 12 is a diagram illustrating an example of an ad hoc network for explaining the pattern 4. FIG. 13 is a diagram illustrating an example of a routing table of each node for explaining the pattern 4.

FIG. 13 shows a routing table of the nodes 100d, 100h, 100p, and 100q as an example. The routing table of node 100d, and routing table 150d _2. The routing table of the node 100h is a routing table 150h. The routing table of the node 100p is assumed to be a routing table 150p. The routing table of the node 100q is a routing table 150q.

  FIG. 14 is a diagram illustrating an example of a link table of each node for explaining the pattern 4. FIG. 14 shows a link table of the nodes 100h and 100p as an example. The link table of the node 100h is assumed to be a link table 160h. The link table of the node 100p is assumed to be a link table 160p.

Returning to the description of FIG. (41) node 100d, when sending a packet set the GD to node 100x, referring to the routing table 150d _2. Node 100d, for the routing table 150d _2, all use prohibition flag for which is "ON", based on the link table 160d, to detect a possible node reaches the node 100x. For example, the node 100d detects the node 100h that satisfies the above condition 1, condition 2, and condition 3. The node 100d transmits a packet to the node 100h. The process (41) corresponds to the process (31) in FIG.

  FIG. 15 is a diagram (2) illustrating an example of a data structure of a packet. For example, the packet that the node 100d transmits to the node 100h in (41) is the packet 30a in FIG. The node 100d sets “node 100h” in the LD of the packet 30a, sets “node 100d” in LS, sets “node 100x” in GD, and sets “node 100d” in GS. Also, the node 100d sets an initial value “1” to the number of bypass transfers. Each time a packet is transferred, the node information stored in the LD and LS is updated. In the following description, the description regarding the data structure of the packet is omitted unless otherwise specified.

  Returning to the description of FIG. (42) Based on the routing table 150h, the node 100h transmits a packet to the first candidate node 100g but does not respond, so the use prohibition flag corresponding to the node 100g in the routing table 150h is set to “ON”. .

  (43) Since the node 100h transmits a packet to the second candidate node 100l but does not respond, the node 100h sets the use prohibition flag corresponding to the node 100l in the routing table 150h to “ON”.

(44) Since the node 100h transmits a packet to the third candidate node 100m but does not respond, the node 100h sets the use prohibition flag corresponding to the node 100m in the routing table 150h to “ON”. The above (42) - (44), node 100h is a routing table 150h, updates the routing table 150h _1.

(45) the node 100h determines, for all the paths leading to the GD of the routing table 150h _1, as a packet undeliverable. In Pattern 4, a case will be described in which the node 100h detects an adjacent node serving as a detour destination based on the link table 160h. When the node 100h searches for a node satisfying the conditions 1 to 3 based on the routing table 160h, the node 100p satisfies the conditions 1 to 3.

  The node 100h transmits a packet to the node 100p. The data structure of the packet that the node 100h transmits to the node 100p is as shown in the packet 30b of FIG. The node 100h sets “node 100p” in the LD of the packet 30b, sets “node 100h” in LS, sets “node 100x” in GD, and sets “node 100d” in GS. In addition, the node 100d sets the number of bypass transfers to “2” by adding 1 to the number of bypass transfers. The node 100h transmits a packet to the detour destination node 100p only when the number of detour transfers is smaller than the detour transfer count threshold held by the node 100h. Note that the node 100h returns the packet to the node 100d that is the transmission source of the packet when the number of detour transfers is equal to or greater than the detour transfer number threshold held by the node 100h. In the following description, a case where the number of bypass transfers is smaller than the threshold value of the bypass transfer held by itself will be described.

  (46) Based on the routing table 150p, the node 100p transmits a packet to the first candidate node 100q but does not respond, so the use prohibition flag corresponding to the node 100q in the routing table 150p is set to “ON”.

  (47) The node 100p transmits a packet to the second candidate node 100r based on the routing table 150p, but does not respond, so the use prohibition flag corresponding to the node 100r in the routing table 150p is set to “ON”.

(48) Based on the routing table 150p, the node 100p transmits a packet to the third candidate node 100t but does not respond, and therefore sets the use prohibition flag corresponding to the node 100t in the routing table 150p to “ON”. The above (46) to (48), the node 100p is a routing table 150p, updates the routing table 150p _1.

(49) node 100p determines, for all the paths leading to the GD of the routing table 150p _1, and a packet undeliverable. In Pattern 4, a case where the node 100p detects an adjacent node serving as a detour destination based on the link table 160p will be described. When the node 100p searches for a node satisfying the conditions 1 to 3 based on the routing table 160p, for example, the node 100v satisfies the conditions 1 to 3.

  Here, the data structure of the packet scheduled to be transmitted from the node 100p to the node 100v is as shown in the packet 30c of FIG. The node 100p sets “node 100v” to the LD of the packet 30c, sets “node 100p” to LS, sets “node 100x” to GD, and sets “node 100d” to GS. Further, the node 100p sets the detour transfer count to “3” by adding 1 to the detour transfer count. The node 100p transmits a packet to the detour destination node 100v only when the number of detour transfers is smaller than the detour transfer count threshold held by the node 100p. In the following description, a case will be described in which the number of bypass transfers is equal to or greater than the threshold value of the bypass transfer held by itself. For this reason, the node 100p stops transmitting the packet to the node 100v.

  (50) The node 100p returns the packet to the node 100h because the number of bypass transfers has reached the upper limit. (51) If there is another detour path based on the link table 160h, the node 100h transmits a packet to the corresponding node. The node 100h transmits the packet to the node 100d when there is no other detour path.

  As described above, when the node 100 executes the processes (41) to (51), it tries to send a packet to the GD using the detour path, and the number of detour transfers reaches the upper limit. In such a case, transmission of the packet is suppressed. Thereby, it is possible to prevent an increase in the traffic amount of the ad hoc network.

  Next, pattern 5 for restoring from a detour route using a link table to a route using a routing table will be described. FIG. 16 is a diagram illustrating an example of an ad hoc network for explaining the pattern 5. FIG. 17 is a diagram illustrating an example of a routing table of each node for explaining the pattern 5.

  FIG. 17 shows the routing tables of the nodes 100a, 100b, 100c, 100d, 100h, and 100g as an example. The routing table of the node 100a is assumed to be a routing table 150a. The routing table of the node 100b is a routing table 150b. The routing table of the node 100c is referred to as a routing table 150c. The routing table of the node 100d is assumed to be a routing table 150d. The routing table of the node 100h is a routing table 150h. The routing table of the node 100g is defined as a routing table 150g.

  FIG. 18 is a diagram illustrating an example of a link table of each node for explaining the pattern 5. FIG. 18 shows a link table of the nodes 100a and 100d as an example. The link table of the node 100a is assumed to be a link table 160a. The link table of the node 100d is assumed to be a link table 160d.

  Step S50 in FIG. 16 will be described. (61) When the obstacle disappears, the hello packet transmitted from the node 100x reaches the nodes 100a, 100b, 100c, 100s, and 100g. (62) Upon receiving the hello packet from the node 100x, the node 100a updates the link table 160a. For example, the node 100a updates the radio wave intensity corresponding to the node identification information “node 100x” to “good” and the evaluation value “1”. The nodes 100b, 100c, 100s, and 100g also update the link table in the same manner as the node 100a.

  (63) The node 100a reviews the routing table 150a. Since the node 100a receives the hello packet from the node 100x, the node 100a sets the use prohibition flag corresponding to the LD “100x” in the routing table 150a to “OFF”. Similarly, the nodes 100b, 100c, and 100s also set the use prohibition flag corresponding to the LD “100x” in the routing table 150 to “OFF”.

  Step S51 in FIG. 16 will be described. (64) The node 100a transmits a hello packet to the nodes 100b and 100d. (65) When receiving the hello packet, the node 100d updates the link table 160d. For example, the node 100d updates the number of hops corresponding to the node identification information “node 100a” in the link table 160d to “2”, and updates the evaluation value to “2”. Similarly, the node 100b updates the link table 160b. Illustration of the link table of the node 100b is omitted.

(66) The node 100d reviews the routing table 150d. Since the node 100d receives the hello packet from the node 100a, the node 100d sets the use prohibition flag corresponding to the LD “100a” in the routing table 150d to “OFF”. Further, the node 100d sets the node 100a as the first candidate LD and the node 100h as the second candidate LD in accordance with the update of the link table 160d. Thus, the node 100d updates the routing table 150d in the routing table 150d _1. Node 100b are similarly routing table 150b, and updates the routing table 150b _1.

  Step S52 in FIG. 16 will be described. (67) The node 100b transmits the hello packet to the nodes 100a, 100c, and 100d, and the nodes 100a, 100c, and 100d receive the hello packet.

(68) The node 100d reviews the link table 160d. For example, the node 100d updates the number of hops corresponding to the node identification information “node 100b” in the link table 160d to “2”, and updates the evaluation value to “2”. Thus, the node 100d is a link table 160d, and updates the link table 160d _1. Although not shown, the nodes 100a and 100c similarly review the link table.

(69) node 100d is to review the routing table 150d _1. Node 100d is due to receiving a hello packet from the node 100b, it sets the disable flag corresponding to the LD "100b" in the routing table 150d ₁ to "OFF". Thus, the node 100d is a routing table 150d _1, updates the routing table 150d _2.

Similarly, the nodes 100a and 100c also review the routing tables 150a and 150c. The node 100a sets the use prohibition flag corresponding to the LD “100b” in the routing table 150a to “OFF”. Thus, node 100a, the routing table 150a, and updates the routing table 150a _1. Further, the node 100c sets the use prohibition flag corresponding to the LD “100b” in the routing table 150c to “OFF”. Thus, the node 100c is the routing table 150c, and updates the routing table 150c _1.

  Step S53 in FIG. 16 will be described. (70) The node 100c transmits the hello packet to the nodes 100b and 100d, and the nodes 100b and 100d receive the hello packet.

(71) node 100d is to review the link table 160d _1. For example, the node 100d updates the number of hops corresponding to the node identification information “100c” in the link table 160d to “2”, and updates the evaluation value to “2”. Thus, the node 100d is a link table 160d _1, updates the link table 160d _2. Although illustration is omitted, the node 100b similarly reviews the link table.

(72) node 100d is to review the routing table 150d _2. Node 100d receives a hello packet from the node 100c, for updated as shown in the link table 160d _2, and updates the third candidate LD to "node 100c", sets the disable flag to "OFF". Thus, the node 100d updates the routing table 150d ₂ in the routing table 150d _3. Similarly, the node 100b is also a routing table 150b _1, and updates the routing table 150b _2.

  Step S54 in FIG. 16 will be described. (73) The node 100s transmits a hello packet to the node 100d, and the node 100d receives the hello packet.

(74) node 100d is to review the link table 160d _2. For example, the node 100d updates the number of hops corresponding to the node identification information “100s” in the link table 160d ₂ to “2”, and updates the evaluation value to “3”. Thus, the node 100d is a link table 160d _2, updates the link table 160d _3.

(75) node 100d is to review the routing table 150d _3. Here, the evaluation value of the node 100s is not already higher than the first to third candidates. Therefore, the node 100d is the information in the routing table 150d ₃ as it is.

  As described above, when the node 100 executes the processes (61) to (75), the data communication using the communication path before the obstacle 20a is generated can be restored.

  Next, an example of the configuration of the node 100 that executes the processes of the above-described patterns 1 to 5 will be described. FIG. 19 is a functional block diagram illustrating the configuration of the node according to the present embodiment. As illustrated in FIG. 19, the node 100 includes a communication unit 110, an input unit 120, a display unit 130, a storage unit 140, and a control unit 180.

  The communication unit 110 is a processing unit that performs wireless communication with other nodes using wireless communication. The communication unit 110 is an example of a communication device. The control unit 180, which will be described later, transmits and receives hello packets and other packets via the communication unit.

  The input unit 120 is an input device that inputs various types of information to the node 100. For example, the input unit 120 corresponds to a touch panel or an input button. The display unit 130 is a display device that displays various types of information output from the control unit 180. For example, the display unit 130 corresponds to a liquid crystal display, a touch panel, or the like.

  The storage unit 140 includes a routing table 150, a link table 160, and a detour transfer count threshold 170. The storage unit 140 corresponds to a storage device such as a semiconductor memory element such as a random access memory (RAM), a read only memory (ROM), and a flash memory.

  As described with reference to FIG. 3 and the like, the routing table 150 is information in which GD, LD, and use prohibition flags are associated with each other. The explanation about GD, LD, and use prohibition flag is the same as the above explanation.

  As described with reference to FIG. 4 and the like, the link table 160 is information in which the node identification information, the number of hops, the radio wave intensity, the evaluation value, and the bypass prohibition flag are associated with each other. The description regarding the node identification information, the number of hops, the radio wave intensity, the evaluation value, and the detour prohibition flag is the same as the above description.

  The bypass transfer number threshold 170 is a threshold that is compared with the bypass transfer number stored in the packet described in the pattern 3 and the like. As the detour transfer count threshold, a unique value is set for each node 100. The node 100 transmits the packet to the detour destination node only when the number of detour transfers stored in the packet is smaller than the detour transfer count threshold 170.

  The control unit 180 includes an update unit 180a and a communication control unit 180b. The control unit 180 corresponds to an integrated device such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). Moreover, the control part 180 respond | corresponds to electronic circuits, such as CPU (Central Processing Unit) and MPU (Micro Processing Unit), for example.

  The update unit 180a is a processing unit that updates the routing table 150 and the link table 160 by transmitting and receiving packets to and from adjacent nodes. When receiving the packet, the updating unit 180a transmits a response to the node 100 corresponding to the LS of the packet.

  An example of processing in which the updating unit 180a updates the routing table 150 will be described. The update unit 180a determines an LD that reaches a predetermined GD in the process of transmitting and receiving a packet, and sets the LD in the routing table 150. For example, when the update unit 180a receives a packet and “node 100x” is set in the GS of the packet and “node 100a” is set in the LS, the LD that reaches the GD “100x” is “100a”. Is determined. When there are a plurality of LDs that reach the same GD, the update unit 180a refers to the evaluation value of the link table 160, and raises the priority as the LD value is lower.

  When the update unit 180a transmits a packet to the node 100 of the LD set in the routing table 150 and does not accept a response from the transmitted node 100, the update unit 180a sets the use prohibition flag of the corresponding LD to “ON”. In addition, when receiving a packet from the node 100 of the LD whose use prohibition flag is “ON”, the update unit 180a sets the use prohibition flag to “OFF”.

  An example of processing in which the update unit 180a updates the link table 160 will be described. The updating unit 180a updates the number of hops, the radio wave intensity, and the evaluation value in the process of transmitting / receiving a packet to / from an adjacent node. For example, the update unit 180a receives a packet, and when “node 100x” is set in the GS of the packet, “node 100a” is set in the LS, and “2” is set in the hop count, The number of hops corresponding to 100a is set to “2”.

  The update unit 180a detects the radio field intensity when transmitting and receiving a packet, and sets the detected radio field intensity information in the link table 160. For example, when the radio wave intensity of a packet received from the node 100a is “good”, the radio wave intensity corresponding to the node 100a is set to “good”. In addition, the updating unit 180a collects the radio field intensity from the adjacent node to the GD node in the process of transmitting and receiving the packet, and calculates an evaluation value based on the collected radio field intensity. For example, the update unit 180a holds a table in which the radio wave intensity is associated with the evaluation value corresponding to the radio wave intensity, and calculates the evaluation value based on the table. The updating unit 180a sets the calculated evaluation value in the link table 160.

  Also, the update unit 180a receives the packet, updates the packet information, and forwards the packet to an adjacent node when the GD of the received packet is not the local node. For example, the update unit 180a updates the packet by setting the LS of the hello packet to its own node, setting the LD to an adjacent node, and adding 1 to the number of hops. In addition, the update unit 180a stores information on the radio field strength between the own node and the adjacent node in the packet.

  The communication control unit 180b is a processing unit that determines the destination node 100 based on the routing table 150 when transmitting a packet. For example, the communication control unit 180b refers to the routing table 150, determines the LD having the highest priority among the LDs whose use prohibition flag is “OFF” as a transmission destination, and sends a packet to the node of the LD. Send.

  Here, when all of the use prohibition flags in the routing table 150 are “ON”, the communication control unit 180b determines the communication destination using a bypass route different from the communication route set in the routing table 150. Switch to communication. For example, such a detour route is a route that passes through the nodes 100b, 100h, and 100g described in FIG. 2 and the like, and is a route having a larger number of relayed nodes 100 than the route set in the routing table 150.

  Specifically, the communication control unit 180b detects, from the link table 160, nodes that satisfy the above-described condition 1, condition 2, and condition 3 based on the link table 160, and transmits a packet to the detected node 100. If the packet is returned after transmitting the packet to the extracted node 100, the communication control unit 180b sets the bypass prohibition flag of the corresponding link table to “ON” and repeats the above processing.

  Note that the communication control unit 180b adds “1” to the detour transfer number of the packet when transmitting the packet. Here, the communication control unit 180b suppresses the process of transmitting a packet when the number of bypass transfer of the packet is greater than or equal to the bypass transfer number threshold 170. In this case, for example, the communication control unit 180b waits until the use prohibition flag of the routing table 150 becomes “OFF”.

  Next, an example of a processing procedure of the node according to the present embodiment will be described. FIG. 20 is a diagram illustrating an example of a processing procedure of the node according to the present embodiment. As illustrated in FIG. 20, the communication control unit 180b of the node 100 receives the packet (step S101), and determines whether or not all the use prohibition flags in the routing table 150 are “ON” (step S102).

  If the use prohibition flags are not all “ON” (No at Step S102), the communication control unit 180b selects the node 100 based on the routing table 150, transmits a packet (Step S103), and Step S106. Migrate to

  On the other hand, when all the use prohibition flags are “ON” (step S102, Yes), the communication control unit 180b selects the node 100 that satisfies the condition 1, the condition 2, and the condition 3 based on the link table 160. (Step S104). The communication control unit 180b transmits the packet to the selected node 100 (step S105), and proceeds to step S106. In step S105, the communication control unit 180b suppresses transmission of the packet and returns the packet to the GS of the packet when the number of detour transfer of the packet is greater than or equal to the detour transfer threshold 170.

  The update unit 180a of the node 100 determines whether a response has been received from the node 100 that has transmitted the packet (step S106). If the update unit 180a has not received a response from the node (No at Step S106), the update unit 180a updates the routing table 150 (Step S107), and proceeds to Step S102.

  On the other hand, when the update unit 180a receives a response from the node (step S106, Yes), the update unit 180a updates the routing table 150 and the link table 160 based on the transmission result (step S108). For example, if the update unit 180a cannot transmit a packet to an adjacent node in step S108, the update unit 180a sets the corresponding use prohibition flag in the routing table 150 to “ON”. Further, when the detour route destination node cannot transmit the packet, the update unit 180a sets the corresponding detour prohibition flag in the link table 160 to “ON”.

  If the communication control unit 180b can transmit the packet based on the transmission result (Yes in step S109), the communication control unit 180b ends the process. If the packet cannot be transmitted based on the transmission result (No at Step S109), the communication control unit 180b proceeds to Step S102.

  Next, effects of the node 100 according to the present embodiment will be described. The node 100 refers to the link table 160 when communication via a communication path preset in the routing table 150 is disabled, and the number of relay devices is larger than the communication path where communication is disabled. The communication is switched to the communication destination using the communication path. As a result, even when an obstacle occurs temporarily and the communication path of the link table 150 cannot be used, the packet can be transmitted to the communication destination.

  The node 100 refers to the link table 150, determines an adjacent node that satisfies the conditions 1, 2 and 3, and switches to communication with a communication destination using a detour route passing through the determined adjacent node. Thereby, when a packet is transmitted, the packet can be transmitted to the communication destination while preventing the packet from looping.

  When the node 100 transmits a packet by using a bypass route, when the communication with the communication destination by the bypass route that is being used becomes unavailable, the node 100 excludes the bypass route that cannot be used, Select and continue communication. For this reason, even if the detour route currently in use becomes unavailable, it is possible to communicate with the communication destination by switching to another detour route.

  The node 100 increments the number of bypass transfers when using the bypass route, and transmits a packet to the bypass route when the number of bypass transfers is less than the bypass transfer number threshold 170. For this reason, it is possible to prevent an increase in the traffic amount due to the packet using the detour route.

  Next, an example of a computer that executes a communication control program that realizes the same function as the node 100 described in the above embodiment will be described. FIG. 21 is a diagram illustrating an example of a computer that executes a communication control program.

  As illustrated in FIG. 21, the computer 300 includes a CPU 301 that executes various arithmetic processes, an input device 302 that receives input of data from a user, and a display 303. The computer 300 includes a reading device 304 that reads a program and the like from a storage medium, and a communication device 305 that exchanges data with other computers via a network. The computer 300 also includes a RAM 306 that temporarily stores various types of information and a hard disk device 307. The devices 301 to 307 are connected to the bus 308.

  The hard disk device 307 has a communication control program 307a. The CPU 301 reads out the communication control program 307 a and develops it in the RAM 306. The communication control program 307a functions as a communication control process 306a. The processing of the communication control process 306a corresponds to the processing of the communication control unit 180b.

  Note that the communication control program 307a is not necessarily stored in the hard disk device 307 from the beginning. For example, each program is stored in a “portable physical medium” such as a flexible disk (FD), a CD-ROM, a DVD disk, a magneto-optical disk, and an IC card inserted into the computer 300. Then, the computer 200 may read and execute the communication control program 307a.

  The following supplementary notes are further disclosed with respect to the embodiments including the above examples.

(Supplementary note 1)
When communication via a communication path set in advance with a communication destination via at least one relay apparatus is disabled, the communication path capable of communicating with the communication destination and the number of relay apparatuses included in the communication path are indicated. Switch to communication with the communication destination using a communication path having a larger number of relay devices than the communication path in which communication is disabled with reference to a storage unit that associates and stores information.
A communication control program characterized by causing the above to be executed.

(Supplementary Note 2) In the switching process, referring to the storage unit, the number of relay devices included in a communication path from an adjacent relay device to the communication destination is included in the communication path from the own computer to the communication destination. The communication control program according to appendix 1, wherein when the number is a number obtained by adding a predetermined value to the number of relay devices, the communication control program is switched to communication with the communication destination using a communication path passing through the adjacent relay device. .

(Additional remark 3) When the communication by the switched communication path | route becomes impossible, the said switching process is except for the communication path | route where communication became impossible, and communication with the said communication destination using a new communication path | route. The communication control program according to appendix 2, wherein switching is performed.

(Supplementary Note 4) The switching process includes a communication path in which the number of relay devices is larger than the communication path in which communication is disabled when the number of bypass transfers included in the packet transmitted to the communication destination is less than a threshold value. 2. The communication control program according to claim 1, wherein the communication control program is switched to communication with the communication destination using, and a predetermined number is added to the number of detour transfer of the packet, and the packet is transmitted to the communication destination.

(Supplementary Note 5) A communication control method executed by a computer,
When communication via a communication path set in advance with a communication destination via at least one relay apparatus is disabled, the communication path capable of communicating with the communication destination and the number of relay apparatuses included in the communication path are indicated. Switch to communication with the communication destination using a communication path having a larger number of relay devices than the communication path in which communication is disabled with reference to a storage unit that associates and stores information.
A communication control method for executing the above.

(Supplementary Note 6) In the switching process, referring to the storage unit, the number of relay devices included in a communication path from an adjacent relay device to the communication destination is included in the communication path from the own computer to the communication destination. 6. The communication control method according to appendix 5, wherein when the number is a number obtained by adding a predetermined value to the number of relay devices, the communication is switched to communication with the communication destination using a communication path passing through the adjacent relay device. .

(Additional remark 7) When the communication by the switched communication path | route becomes impossible, the said switching process is a communication with the said communication destination using a new communication path | route except for the communication path | route where communication became impossible. The communication control method according to appendix 6, wherein switching is performed.

(Supplementary note 8) In the switching process, when the number of detour transfers included in the packet transmitted to the communication destination is less than a threshold, the communication path has a larger number of relay devices than the communication path in which communication is disabled 6. The communication control method according to appendix 5, wherein the communication is switched to communication with the communication destination using, and a predetermined number is added to the detour transfer number of the packet, and the packet is transmitted to the communication destination.

(Supplementary Note 9) When communication via a communication path set in advance with a communication destination via at least one relay apparatus becomes impossible, the communication path capable of communicating with the communication destination and the relay apparatus included in the communication path Communication that switches to communication with the communication destination using a communication path that has a larger number of relay devices than the communication path in which communication is disabled with reference to a storage unit that associates and stores information indicating the number of nodes A communication control device comprising a control unit.

(Additional remark 10) The said communication control part refers to the said memory | storage part, and the number of the relay apparatuses contained in the communication path from an adjacent relay apparatus to the said communication destination is contained in the communication path of the said communication destination from an own computer. The communication control according to appendix 9, wherein the communication control is switched to communication with the communication destination using a communication path passing through the adjacent relay device when the predetermined value is added to the number of relay devices to be transmitted. apparatus.

(Supplementary Note 11) When communication using the switched communication path is disabled, the communication control unit communicates with the communication destination using a new communication path except for the communication path where communication is disabled. The communication control device according to appendix 10, wherein the communication control device is switched to

(Additional remark 12) The said communication control part is communication with more number of the said relay apparatuses than the said communication path in which communication became impossible, when the number of detour transfers contained in the packet transmitted to the said communication destination is less than a threshold value The communication control apparatus according to appendix 9, wherein the communication control apparatus switches to communication with the communication destination using a route, adds a predetermined number to the number of detour transfers of the packet, and transmits the packet to the communication destination.

100 nodes 150 routing table 160 link table 180a updating unit 180b communication control unit

Claims (6)

Computer,
Via at least one relay device, a first table set the communication path with the communication destination, and, second associating the number of the relay apparatus included in the available communication path and the communication path with the communication destination A storage unit for storing the table;
In the computer,
Communication in which the number of relay devices is larger than the communication path in which communication is disabled with reference to the second table when communication through all communication paths set in the first table is disabled Switch to communication with the communication destination using a route,
A communication control program for executing a process . The switching obtaining process, by referring to the storage unit, the number of the relay apparatus included in the communication path from the adjacent relay apparatus to the communication destination, the relay device included from the own computer to the communication path of the communication destination 2. The communication control program according to claim 1, wherein when the number is a number obtained by adding a predetermined value, the communication control program is switched to communication with the communication destination using a communication path passing through the adjacent relay device. The switching obtain treatment, it switched when the communication by the communication path becomes impossible, except for a communication path that the communication becomes impossible, to switch to the communication with the communication destination using a new communication path The communication control program according to claim 2, wherein: The switching obtaining process, when the reroute the number contained in the packet to be transmitted to the communication destination is less than the threshold value, using a communication path having a large number of the relay device than the communication path communication becomes impossible The communication control program according to claim 1, wherein the communication control program switches to communication with the communication destination, adds a predetermined number to the detour transfer number of the packet, and transmits the packet to the communication destination. A communication control method executed by a computer,
The computer stores a first table in which a communication path with a communication destination is set, and a second table that associates a communication path communicable with the communication destination and the number of relay devices included in the communication path. Have
The computer
Communication in which the number of relay devices is larger than the communication path in which communication is disabled with reference to the second table when communication through all communication paths set in the first table is disabled Switch to communication with the communication destination using a route,
A communication control method for executing processing . Via at least one relay device, a first table set the communication path with the communication destination, and, second associating the number of the relay apparatus included in the available communication path and the communication path with the communication destination A storage unit for storing the table;
Communication in which the number of relay devices is larger than the communication path in which communication is disabled with reference to the second table when communication through all communication paths set in the first table is disabled communication control apparatus characterized by comprising a communication control section for switching the communication with the communication destination using the route.

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