WO2014092138A1

WO2014092138A1 - Network system and control method therefor

Info

Publication number: WO2014092138A1
Application number: PCT/JP2013/083267
Authority: WO
Inventors: 篤熊谷; 昌之三浦; 邦雄尾高
Original assignee: 古河電気工業株式会社
Priority date: 2012-12-12
Filing date: 2013-12-11
Publication date: 2014-06-19
Also published as: JP5778357B2; BR112015013547A2; JPWO2014092138A1

Abstract

[Problem] To rapidly optimize a path even if the status of a network link, etc., has changed. [Solution] A network system that sends a notification signal having information indicating that a first prescribed node and a second prescribed node have been connected, as a result of a new link, so as to be capable of communicating, and information indicating the metric to the first or second node, to a node other than the first and second nodes, by using a transmission means (a packet relay processing unit (11)), if the first node and the second node have been connected by a new link so as to be capable of communicating. The other node that received the notification signal adds the metric up to same from the immediately preceding node that sent the signal, to the information indicating the metric for the notification signal, transfers same to another node by using a transfer means (the packet relay processing unit (11)), and, if a notification signal is received, refreshes path information stored in a routing table by using a refresh means (control unit (12)).

Description

Network system and control method thereof

The present invention relates to a network system and a control method thereof.

Patent Document 1 discloses a technique related to a distribution line remote monitoring control communication system to which IP is applied. This technology uses a ring network and performs redundancy using a SW-HUB (switching hub). In such a network configuration, IEEE (Institute of Electrical and Electronics)
By using the STP (spanning tree protocol) function shown in Non-Patent Document 1 which is a standard of Engineers), it is possible to duplex communication paths without looping data and circulating permanently.

In such a slave station that is branched from the ring network, there is a problem that if a failure occurs in the branched communication path, the slave station becomes isolated and communication becomes impossible.

Therefore, connect communication lines branched from two different points on the same ring network, or connect to other ring networks to build a mesh network, and establish a communication path to each slave station. By multiplexing, it is possible to perform communication even when a failure occurs in one of the communication paths connected to the branched slave station.

JP 2005-210818 A

By the way, in the technique disclosed in Patent Document 1, when STP is used, there is a problem that a relatively long incommunicable time occurs when the state of a link or the like changes. This time when communication is disabled is not a problem in a general network, but is particularly problematic in a network for the purpose of remote monitoring and control of distribution lines because real-time correspondence is important.

In addition, when there is an unstarted node in the network and another node executes a route search, the unstarted node does not respond, so this route search ends in failure. In order to prevent the search from being repeated until it succeeds when the route search is unsuccessful, the other nodes are set in a block state in which another route request cannot be transmitted for a certain period of time (see, for example, AODV 6.5). However, when other nodes are in such a block state, there is a problem in that the incommunicable state continues for a certain period of time even if a node that has not been activated is activated.

Therefore, an object of the present invention is to provide a network system capable of quickly optimizing a route even when the state of a network link or the like changes, and a control method therefor.

In order to solve the above-described problem, the present invention provides a network system in which a plurality of nodes are communicably connected by a link, and a predetermined first node and a predetermined second node constituting the network system are newly linked. When the first and second nodes are communicably connected to each other, the first and second nodes send notification signals having information indicating metrics up to the first or second node to other nodes other than the first and second nodes. On the other hand, the other node that has transmitted the notification signal and received the notification signal adds another metric from the node immediately before transmitting the signal to itself to the information indicating the metric of the notification signal. Transfer to the other node by the transfer means, and when the notification signal is received, it is stored in the routing table. And updates by the update means the routing information that is.
According to such a configuration, it is possible to quickly optimize the route even when the state of the network link or the like changes.

Further, according to one aspect of the present invention, the updating unit compares the metric of each entry stored in the routing table with the metric stored in the notification signal, and stores the metric in the notification signal. An entry having a metric larger than the metric by a predetermined value is deleted.
According to such a configuration, the route can be optimized efficiently by deleting the entry based on the metric.

Further, according to an aspect of the present invention, the notification signal stores a metric of the new link, and the update unit is stored in the notification signal in a metric stored in the notification signal. An entry having a metric larger than the value obtained by adding the metrics of the new link is deleted.
According to such a configuration, even if the metric of the new link is an arbitrary value, the route can be optimized efficiently.

Further, according to one aspect of the present invention, the metric is the number of hops, and the updating unit adds the number of hops of the new link stored in the notification signal to the number of hops stored in the notification signal. An entry having a hop number larger than the value obtained by addition is erased.
According to such a configuration, the route can be optimized efficiently with a simple calculation based on the number of hops.

Moreover, one aspect of the present invention is characterized in that the update unit deletes all entries stored in the routing table when the notification signal is received.
According to such a configuration, the determination process can be simplified by erasing all the data regardless of the metric.

Also, one aspect of the present invention is characterized in that the transmission means transmits the notification signal with information for identifying its own node.
According to such a configuration, it is possible to determine whether or not the notification signal has already been received.

One aspect of the present invention is characterized in that the transmission means has identification information for identifying the notification signal in order to cope with a case where a plurality of notification signals are transmitted.
According to such a configuration, it can be determined whether or not they are the same notification signal, so that it is possible to avoid the occurrence of duplicate processing.

According to another aspect of the present invention, when the first node is a newly activated node, the first and second nodes transmit information indicating that the first node has been newly activated to other nodes. When the other node receives the information indicating that it has been newly activated, the other node releases the block for the first node.
According to such a configuration, a delay until the start of communication can be shortened.

Also, one aspect of the present invention is characterized in that the first node transmits information indicating that it has been newly activated.
According to such a configuration, the burden on the network can be reduced.

In another aspect of the present invention, when the other node receives the information indicating that it has been newly activated, the route information regarding the first node is deleted.
According to such a configuration, a delay until the start of communication can be shortened.

Also, one aspect of the present invention is characterized in that the information indicating that the device has been newly activated is added to the notification signal and transmitted.
According to such a configuration, it is possible to notify that the state of a network link or the like has changed, and to notify that a newly activated node exists.

Moreover, one side of this invention is used for distribution line remote monitoring control, It is characterized by the above-mentioned.
According to such a configuration, it is possible to quickly optimize the route even when the state of the network link for distribution line distant monitoring control changes.

Further, according to the present invention, in a control method of a network system in which a plurality of nodes are communicably connected by a link, a predetermined first node and a predetermined second node constituting the network system can communicate by a new link The first and second nodes transmit a notification signal having information indicating a metric up to the first or second node to other nodes other than the first and second nodes. Each of the nodes transmitted by each step and receiving the notification signal adds the metric from the node immediately before transmitting the signal to its own information to the information indicating the metric of the notification signal, and further to another node. In contrast, when the transfer step transfers and the notification signal is received, the process stored in the routing table is performed. Information update step and updates.
According to such a method, it is possible to quickly optimize the route even when the state of the network link or the like changes.

According to the present invention, it is possible to provide a network system and a network system control method capable of quickly optimizing a route even when the state of a network link or the like changes.

It is a figure which shows the structural example of the network system which concerns on embodiment of this invention. It is a figure which shows the detailed structural example of the node shown in FIG. It is a figure which shows an example of the routing table of the node shown in FIG. It is a figure which shows the state by which the new link was added to the network system shown in FIG. It is a figure which shows an example of the format of a notification signal. It is a figure which shows the transmission condition of a notification signal, and the value of a cost field. It is a figure which shows the state from which the routing information of the routing table was erase | eliminated by the notification signal. It is a figure which shows the state by which the routing table was reset after the routing information was erase | eliminated. It is a figure which shows the condition where the node was newly added. It is a flowchart for demonstrating an example of the process performed in the node to which the link was added. It is a flowchart for demonstrating an example of the process performed in the node which received the notification signal. It is a figure which shows an example of a routing table. It is a figure which shows embodiment which erase | eliminates all the path | route information, when a notification signal is received. It is a figure which shows an example of the other format of a notification signal. It is a figure which shows the structural example of the network system which concerns on other embodiment of this invention. It is a figure which shows the state which added the link to the network system shown in FIG. It is a figure which shows an example of the format of a notification signal. It is a figure which shows the transmission condition of a notification signal, and the value of a cost field. It is a figure which shows the state from which the routing information of the routing table was erase | eliminated by the notification signal. It is a figure which shows the state by which the routing table was reset after the routing information was erase | eliminated. It is a figure which shows generation | occurrence | production of the timeout at the time of starting. It is a figure which shows the state of the network with an unstarted node. It is a figure which shows an example of the RLINK signal containing a new starting flag. It is a flowchart for demonstrating an example of the process performed in the node to which the link was added. It is a flowchart for demonstrating an example of the process performed in the node which received the notification signal. It is a figure which shows an example of a block release signal. It is a flowchart for demonstrating an example of the process performed by the node which received the block release signal.

Next, an embodiment of the present invention will be described.

(A) Description of Configuration of Embodiment FIG. 1 is a diagram illustrating an example of a configuration of a network system according to an embodiment of the present invention. In addition, this invention is a network system used for the distribution line remote monitoring control etc. which have the function to perform monitoring, control, or measurement of a high voltage distribution system, for example. As shown in FIG. 1, the network system according to the present embodiment includes nodes 10-1 to 10-7 and links 21 to 28. FIG. 2 shows a detailed configuration example of the node. Since the nodes 10-1 to 10-7 have the same configuration, they will be described as the node 10 below. As shown in FIG. 2, the node 10 includes a packet relay processing unit 11, a control unit 12, a storage unit 13, receiving units 14-1 to 14-n, and transmitting units 15-1 to 15-n. Yes.

Here, the packet relay processing unit 11 transmits the packets received by the receiving units 14-1 to 14-n according to the control of the control unit 12 according to the information stored in the header. Transmitted from the units 15-1 to 15-n. The control unit 12 controls the packet relay processing unit 11 according to the routing table 13a stored in the storage unit 13, relays the packet, and executes processing related to RLINK as a notification signal as described later. Note that the routing table 13a includes an ID or address of a packet transmission destination (Destination), a next hop (Nexthop) when the packet is transmitted to the transmission destination, and information indicating a metric to the transmission destination (for example, Information such as the number of hops) is associated and stored as route information. For example, the node 10-5 associates ID: 01, which is the packet transmission destination ID, ID: 04 as the next hop, and “3” as the cost, as route information having the node 10-1 as the transmission destination. Have. As a result, when the node 10-5 receives the packet having the destination ID “01”, the packet is transferred to the node 10-4 that is the next hop based on this path information.

The storage unit 13 is composed of a semiconductor memory, has a routing table 13a that is information for transferring packets, and stores programs and data for executing the processing related to the notification signal described above. The receiving units 14-1 to 14-n receive packets via the link. Further, the transmission units 15-1 to 15-n transmit packets via the link. In addition, the receiving part and the transmission part to which the same number was given after the hyphen are connected to the same link. For example, the reception unit 14-1 and the transmission unit 15-1 are connected to the same link.

Next, the operation of the embodiment of the present invention will be described. In the following, the outline of the operation will be described by taking as an example a case where communication with the node 10-1 is performed, and then executed in each node based on the flowcharts shown in FIGS. Details of the processing will be described.

FIG. 3 is a diagram illustrating an example of route information related to the node 10-1 possessed by each node when communication is performed with the node 10-1. In FIG. 3, the table shown in the vicinity of each node is route information corresponding to the node 10-1, NXT (Next) indicates the node ID of the next hop that is the next transfer destination, and Cost is The number of hops as a metric to the transfer destination is shown. For example, when the node 10-4 communicates with the node 10-1, it is necessary to go through the node 10-2. Therefore, the NXT is set to “02” because the node 10-4 passes through the node of ID: 02. Since it is 2, it is set to “2”.

In such a network system, it is assumed that the node 10-1 and the node 10-5 are newly connected by a link 29 as shown in FIG. When the link 29 is newly established in this manner, the nodes 10-1 and 10-5 located at both ends of the link 29 send “RLINK (Route Link)” signals, which are notification signals indicating that the links have been added, to other nodes. Send to node.

FIG. 5 is a diagram illustrating an example of an RLINK signal that is a notification signal. As shown in this figure, the RLINK signal has an identifier field, a node ID field, and a cost field. Here, the identifier field is a field in which a specific bit string indicating that this signal is an RLINK signal notifying the establishment of a link is stored. The node ID field is a field in which the node ID of the transmission source of this RLINK signal is stored. The cost field is a field to which the cost of the route is added every time this RLINK signal is transferred, and the initial value is “1”.

The RLINK signal shown in FIG. 5 is transmitted from the nodes 10-1 and 10-5 in which the links are newly established, but the following description will be made by paying attention to the RLINK signal transmitted from the node 10-5. As shown in FIG. 5, in the RLINK signal transmitted from the node 10-5, “05” that is the ID of the node 10-5 is stored in the node ID field, and “1” as an initial value is stored in the cost field. "Is stored. FIG. 6 shows an RLINK signal transmitted from the node 10-5 to the other nodes 10-4 and 10-7. In FIG. 6, the arrow indicates the flow of the RLINK signal transmitted from the node 10-5, and the number attached in the vicinity of the arrow indicates the value stored in the cost field of the RLINK signal. The node receiving the RLINK signal recognizes that this signal is the RLINK signal as the notification signal by referring to the identifier field, and knows that the link has been newly established. Further, the node that has received the RLINK signal adds 1 to the value stored in the cost field and transfers it to the next node, and the value stored in the cost field and the Cost value ( The values stored in the routing table 13a of the storage unit 13 are compared, and if the Cost value exceeds the value +1 stored in the cost field, the route information is deleted. When the Cost value exceeds the value +1 stored in the cost field, the route information is deleted if the destination node is the closest, it may exist at a distance of +1 from the new route. Because there is sex.

For example, in the node 10-5, since the Cost value is “3” and the value stored in the cost field is “1”, the value obtained by adding 1 to the latter is 2, and the Cost value is more Since the node 10-5 is large, the route information destined for the node 10-1 is deleted, and the RLINK signal is transferred to the nodes 10-4 and 10-7. In the node 10-4, since the Cost value is “2” and the value stored in the cost field is “1”, the value obtained by adding “1” to the latter is “2”. In 10-4, the route information having the node 10-1 as the transmission destination is not deleted, and the RLINK signal with “1” added to the cost field is transferred to the node 10-2 and the node 10-6. On the other hand, in the node 10-7, since the Cost value is “4” and the value stored in the cost field is “1”, the value obtained by adding 1 to the latter is 2, and the Cost value is more Since the node 10-7 is large, the route information with the node 10-1 as the transmission destination is deleted, and the RLINK signal with “1” added to the cost field is transferred to the node 10-6. FIG. 7 is a diagram showing a state in which route information has been erased by the above operation. In FIG. 7, the route information of the nodes 10-5 and 10-7 (route information with the node 10-1 as the transmission destination) is deleted.

When a communication request to the deleted transmission destination is made after the route information is deleted, for example, RREQ (Route Request) is executed, and a route search is executed. As a result, the routing information whose destination is the node 10-1 in the routing table is updated as shown in FIG. In FIG. 8, the path information of the node 10-5 is updated from NXT = 04 and Cost = 3 shown in FIG. 3 to NXT = 01 and Cost = 1. Further, the path information of the node 10-7 is updated from NXT = 06 and Cost = 4 shown in FIG. 3 to NXT = 05 and Cost = 2. As a result, the node 10-5 communicates with the node 10-1 via the link 29, and the node 10-7 communicates with the node 10-1 via the node 10-5. For nodes other than these, since the route information with the node 10-1 in the routing table 13a as the transmission destination has not been updated, communication is performed through the same route as in FIG.

As described above, in the embodiment of the present invention, when a link is newly added, nodes at both ends of the link transmit the RLINK signal, and a link is newly established at the node that has received the RLINK signal. I can know that. Further, in the node that has received this RLINK signal, the value of the cost field is compared with the value of the routing table, and the value obtained by adding “1” to the value of the cost field is greater than the cost value of the routing table. Since the route information is deleted, the route can be quickly optimized by deleting only the route information in which a new route can exist.

Note that in the case of a node for the first time after a new node is connected, only the number of branches is increased, so that no RLINK signal is transmitted. For example, as shown in FIG. 9, when the node 10-8 is added by the link 30, only the branching branch is increased and no new path is generated. Therefore, in this case, the node 10-8 has the RLINK signal. Do not send.

Next, processing executed in each node will be described with reference to FIGS. FIG. 10 is a flowchart for explaining an example of the flow of processing executed when a link is added. When the processing of this flowchart is started, the following steps are executed.

In step S1, the control unit 12 determines whether or not a link with another node has been newly established. When it is determined that a link has been newly established (step S1: Yes), the control unit 12 proceeds to step S2, and otherwise In (Step S1: No), the process ends. For example, as shown in FIG. 4, when the node 10-1 and the node 10-5 are connected by the link 29, it is determined Yes and the process proceeds to step S2.

In step S2, the control unit 12 determines whether the nodes at both ends of the newly established link have both existing links in addition to the newly established link, and determines that the nodes have existing links (step S2). In step S2: Yes, the process proceeds to step S3. In other cases (step S2: No), the process ends. For example, in the case of the node 10-5, since there are existing

links

25 and 27 in addition to the newly established link 29, the process proceeds to step S3. This step is, for example, processing for preventing the node 10-8 shown in FIG. 9 from transmitting the RLINK signal.

In step S3, the control unit 12 acquires the node ID of the own node. For example, in the case of the node 10-5, the control unit 12 acquires “05” as the node ID from the storage unit 13.

In step S4, the control unit 12 stores the node ID of the own node acquired in step S3 in the node ID field of RLINK. For example, in the case of the node 10-5, the control unit 12 stores the node ID “05” in the node ID field.

In step S5, the control unit 12 stores the initial value “1” in the cost field. For example, in the case of the node 10-5, the control unit 12 stores the initial value “1” in the cost field.

In step S6, the control unit 12 transmits an RLINK signal to other nodes via the transmission units 15-1 to 15-n. For example, in the case of the node 10-5, the control unit 12 transmits the RLINK signal from the transmission units corresponding to the link 25 and the link 27.

In step S7, the control unit 12 deletes the route information having a Cost value of “3” or more from the route information stored in the routing table 13a. For example, in the case of the node 10-5, the control unit 12 sends the node 10-1 and the node 10-3, which are route information whose cost is “3” or more, among the route information stored in the routing table 13a. The route information is deleted.

Note that the same processing is also executed in the node 10-1 in which the link 29 is newly established.

Through the above processing, when a new link is connected, an RLINK signal having an identifier indicating that the link is newly established and its own node ID and having a cost of “1” is sent to another node. Can be sent to. In addition, since it is determined whether or not an existing link exists by the processing in step S2, for example, when a new route does not occur just by adding branches as shown in FIG. May not transmit the RLINK signal.

Next, an example of processing executed in the node that has received the RLINK signal transmitted by the processing in FIG. 10 will be described with reference to FIG. When the process shown in FIG. 11 is executed, the following steps are executed.

In step S21, the control unit 12 determines whether or not the RLINK signal has been received. If it is determined that the RLINK signal has been received (step S21: Yes), the control unit 12 proceeds to step S22, and otherwise (step S21). : No), the process ends. For example, if the node 10-7 receives the RLINK signal, the determination is Yes and the process proceeds to step S22.

In step S22, the control unit 12 acquires a node ID from the node ID field of the received RLINK signal. For example, in the case of the node 10-7, “05” is acquired as the node ID from the node ID field. Note that the acquired node ID is ignored when the RLINK signal having the same ID is received immediately before to indicate that it has been transmitted twice.

In step S23, the control unit 12 acquires a cost value from the cost field of the received RLINK signal. For example, in the case of the node 10-7, “1” is acquired as the cost value from the cost field.

In step S24, the control unit 12 adds “1” to the value of the cost field acquired in step S23. For example, in the case of the node 10-7, since “1” is added to the value of the cost field, “2” is obtained.

In step S25, the control unit 12 returns the value of the cost field added with “1” in step S24 to the cost field of the RLINK signal and transmits it to other nodes. For example, in the case of the node 10-7, the RLINK signal in which “2” is stored in the cost field is transferred to the node 10-6.

In step S26, the control unit 12 compares the value of the cost field added with “1” in step S24 with the cost value of each piece of route information stored in the routing table, and the current cost value is greater. If small route information exists (step S26: Yes), the process proceeds to step S27, and otherwise (step S26: No), the process ends. For example, the node 10-7 has the routing table 13a shown in FIG. In FIG. 12, when the destination Destination is the node 10-1 whose ID is 01, the transfer destination Next hop is the node 10-6 whose ID is 06 and the metric Count is “4”. It is. In step S26, the value of the cost field added with “1” in step S24 is “2”, and the count value stored in the routing table 13a includes route information of “3” or more. Therefore, it determines with Yes and progresses to step S27.

In step S27, the control unit 12 deletes the route information whose Count value is “3” or more from the routing table. For example, in the case of the node 10-7, as shown in FIG. 12B, the route information whose destinations are Destination “01” and “03” is deleted.

Note that if a communication request is made to the transmission destination included in the deleted route information after the route information is deleted, the route is reconfigured by RREQ. As a result, for example, the routing table 13a as shown in FIG. In FIG. 12 (C), route information (route information with hatching) having the nodes 10-1 and 10-3 as transmission destinations is reconfigured.

According to the above processing, when an RLINK signal is received, “1” is added to the value of the cost field and transferred to another node, and the value of the cost field to which “1” is added and the routing The current cost value stored in the table is compared, and if the current cost value is smaller, the route information is deleted. As a result, when a new link is added, only a route where a new route can exist can be erased, so that the route can be optimized quickly.

(C) Description of Modified Embodiment It goes without saying that the above embodiment is merely an example, and the present invention is not limited to the case described above. For example, in the above embodiment, the value stored in the cost field of the RLINK signal is compared with the cost value of the routing table, and the route information is deleted based on the comparison result. For example, FIG. As shown, the node that receives the RLINK signal may delete all path information regardless of the cost value. According to such a configuration, the processing can be simplified by erasing uniformly.

In the above embodiment, a signal having the format shown in FIG. 5 is used as the RLINK signal. However, for example, a signal having the format shown in FIG. 14 may be used. In the example of FIG. 14, RLINK ID is added as compared to the case of FIG. Other configurations are the same as those in FIG. Here, the RLINK ID is a unique identifier (in this example, “ab”) given to each RLINK signal, and is used for the purpose of distinguishing when a plurality of RLINK signals are transmitted. If such a RLINK signal is used, for example, when a signal having the same node ID and the same RLINK ID is received in duplicate, it is ignored as the same signal, thereby preventing duplicate processing. it can.

In the above embodiment, a node ID is assigned to each node, and the node is identified based on this node ID. However, instead of the ID, for example, an address is assigned to each node, and this address is assigned to this node. You may make it identify based.

In the above embodiment, the hop count is used as the metric. However, other indexes may be used as the metric. For example, information such as bandwidth and reliability may be combined and used as a metric such as IGRP (Interior Gateway Routing Protocol).

In the above embodiment, the links 21 to 29 have been described by taking as an example a case where all the metrics are 1. However, for example, the link metrics may be other than 1, as shown in FIG. . In FIG. 15, the metrics of the

links

24, 25, and 26 are “2”, and the other metrics are “1”. In FIG. 15, the table shown in the vicinity of each node is route information corresponding to the node 10-1. For example, “NXT to 1: 4” shown in the table near the node 10-5 indicates the next hop “4” which is the next transfer destination when the packet is transferred to the node 10-1 having the ID “1”. Show. “Cost to ID 1: 5” indicates that the metric up to the node 10-1 whose ID is “1” is “5”. “Cost to NXT: 2” indicates that the metric to the next hop node 10-4 as the next transfer destination is “2”. In FIG. 15, “-” of “NXT to 1:-” in the table in the vicinity of the node 10-1 indicates a blank, and “Cost to ID 1: 0” indicates the node 10-1 that is itself. The metric indicates “0”, and the “-” in “Cost to NXT:-” indicates a blank as described above.

Suppose that a link 29 having a metric “2” is connected between the node 10-1 and the node 10-5 as shown in FIG. 16 in the network shown in FIG. In this case, the RLINK signal as shown in FIG. 17 is transmitted from the node 10-1 and the node 10-5. In FIG. 17, a “new link cost field” is added to the RLINK signal shown in FIG. Other configurations are the same as those in FIG. Here, the new link cost field is a field in which the cost (metric) of a newly added link (new link) is stored. For example, in the example of FIG. 16, “2” that is the cost of the link 29 is stored.

FIG. 18 is a diagram for explaining the flow of the RLINK signal. The arrows shown in FIG. 18 indicate the flow of the RLINK signal transmitted from the node 10-5, and the numbers attached in the vicinity of the arrows indicate the values stored in the cost field of the RLINK signal. The node receiving the RLINK signal recognizes that this signal is the RLINK signal as the notification signal by referring to the identifier field, and knows that the link has been newly established. In addition, the node that has received the RLINK signal adds the cost from the immediately preceding node to the node to the value stored in the cost field, transfers the value to the next node, and also stores the value stored in the cost field. And the numerical value following Cost to ID1: in FIG. 18 is compared, and the numerical value following to ID1: exceeds the value obtained by adding the value of the new link cost field to the value stored in the cost field. In that case, the route information is deleted.

For example, in node 10-5, the value following Cost to ID1: is “5”, and the value stored in the cost field is “1”, so the value 2 of the new link cost field is added to the latter. Since the value of “3” is larger and “5” is larger, the route information destined for the node 10-1 is deleted in the node 10-5, and the RLINK signal is transferred to the nodes 10-4 and 10-4. 10-7. In node 10-4, the value following Cost to ID1: is “3” and the value stored in the cost field is “3”, so the value obtained by adding “2” to the latter is “5”. For this reason, the node 10-4 does not delete the route information with the node 10-1 as the transmission destination, and the RLINK signal with “2” added to the cost field is transferred to the nodes 10-2 and 10-6. The On the other hand, in the node 10-7, since the Cost value is “6” and the value stored in the cost field is “1”, the value obtained by adding the new link cost field value “2” to the latter is Since the cost value is “3” and the Cost value is larger, the route information with the node 10-1 as the transmission destination is deleted at the node 10-7, and the RLINK signal with “1” added to the cost field is displayed. Transferred to node 10-6. Further, in the node 10-2, the Cost value is “1”, and the value stored in the cost field is “5” obtained by adding “2” which is the metric of the link 24. The value obtained by adding the value “2” of the cost field of the new link is “7”, and the cost value is smaller. Therefore, the route information with the node 10-1 as the transmission destination is not deleted in the node 10-2. Then, the RLINK signal obtained by adding “2” of the link 24 to the cost field is transferred to the node 10-6. FIG. 19 is a diagram showing a state in which route information has been erased by the above operation. In FIG. 19, the route information of the nodes 10-5 and 10-7 (route information with the node 10-1 as the transmission destination) is deleted.

When a communication request is made to the deleted transmission destination after the route information is deleted, for example, RREQ is executed, and a route search is executed. As a result, the routing information whose destination is the node 10-1 in the routing table is updated as shown in FIG. In FIG. 20, the route information of the node 10-5 is updated to NXT to 1: 1, Cost to ID 1: 2, and Cost to NXT: 2. Further, the route information of the node 10-7 has been updated to NXT to 1: 5, Cost to ID 1: 3, and Cost to NXT: 1. As a result, the node 10-5 communicates with the node 10-1 via the link 29, and the node 10-7 communicates with the node 10-1 via the node 10-5. For nodes other than these, since the route information with the node 10-1 in the routing table 13a as the transmission destination has not been updated, communication is performed through the same route as in FIG.

In the RLINK signal shown in FIG. 17, a new link cost field is provided. For example, the new link cost field is not provided, and the new link cost field value is set as an initial value in the cost field. You may make it store. According to such a configuration, the data amount of the RLINK signal can be reduced.

Further, the routing table 13a shown in FIG. 12 is an example, and information other than this may be included. For example, you may make it have the information etc. which show the effective period of the route information.

Further, in the flowchart shown in FIG. 10, after transmitting the RLINK signal in step S6, the route information of the own node is deleted in step S7. However, after deleting the route information of the own node, the RLINK signal is transmitted. It may be.

In the embodiment shown in FIG. 1, seven nodes 10-1 to 10-7 and eight links 21 to 28 are provided. However, other numbers of nodes and links may be provided. . Further, the connection mode between the node and the link is not limited to the example of FIG.

Further, as shown in FIG. 5, the initial value of the cost field of the RLINK signal is set to “1” for transmission, but of course, other values (for example, “0”) are set. May be.

Further, as shown in FIG. 5, the node ID field is provided in the RLINK signal, but this node ID field may not be provided. This is because the identifier field recognizes the RLINK signal, and the necessity of erasure can be determined by the cost field.

In the above embodiment, the processing when a new link is added has been mainly described. However, as described above, the present invention is a remote distribution line monitoring function having a function of monitoring a high-voltage distribution system and the like. Since it is assumed to be used for control and the like, when a power failure occurs, it is required to be able to communicate immediately after the power failure is resolved. By the way, in the current routing method, a timeout called “route search timeout” occurs, and this timeout is a dominant factor that determines the activation time. This will be described with reference to FIG. In the example of this figure, nodes 10-1 to 10-3 are connected, and the vertical direction in the figure indicates the passage of time. In the upper example of FIG. 21, the nodes 10-1 and 10-3 are in the activated state, and the node 10-2 is not activated. In such a case, for example, when a route search is executed from the node 10-1 to the node 10-2 that has not been started, the route search ends in failure. If the route search is unsuccessful, the search is repeated until it succeeds if there are no restrictions. For this reason, in order to prevent the route search from being overwhelmed, if the route search fails, for example, if a time more than twice the time-out time of the first route search has not elapsed, a block state in which another route request cannot be transmitted is set. (For example, see AODV 6.5). Since such a block state (hereinafter referred to as “first block state”) continues for a certain period of time, communication is not possible even if the node 10-2 is in an activated state during that period as shown in the middle part of FIG. Since the state continues, the communication start timing is delayed. When this state ends, the timeout is completed as shown in the lower part of FIG. 21, and when the route search is successful, the node 10-2 can communicate.

In addition, when a node repeatedly stops and returns, there is a possibility that route information at the previous operation remains in each node. In order to prevent malfunctions caused by such remaining old information, each node performs a process of blocking a route update request until the old information disappears (for example, AODV RFC3561 6.13 P27). ). Such a block state (hereinafter referred to as a “second block state”) is also a factor in delaying the communication start timing after the node is activated.

In this embodiment, in order to prevent a delay in the start of communication due to the two types of blocks described above, a newly activated node transmits a signal for canceling the block state to the entire network by broadcasting. FIG. 22 shows an example of a network that performs such an operation. In FIG. 22, nodes 10-3 to 10-6 that are hatched with crossing lines indicate active nodes, and nodes 10-2, 10-7, and 10-8 that are hatched with diagonal lines are in a blocked state. The node 10-1 without hatching indicates a newly activated node. In such a state, the newly activated node 10-1 transmits an RLINK signal as shown in FIG. 23 to other nodes by broadcast. Note that the RLINK signal shown in FIG. 23 is added with a new activation node flag as compared with the RLINK signal shown in FIG. Here, when the value is “1”, the newly activated node flag is a flag indicating that the node is a newly activated node. The peripheral nodes that have received such an RLNK signal recognize that there is a newly activated node (node 10-1 in FIG. 22) because the newly activated node flag is “1”, and the node ID If this node is blocked with reference to the field information, the first block state for this node is released. In addition, referring to the route information, if the route information related to this node exists, the old route information related to this node is deleted to eliminate the cause of the second block state. Thereby, even if there is a newly activated node, it is possible to prevent the start of communication from being delayed. When a node adjacent to the newly activated node transmits RLINK or when the new link does not have a new activation node (in the case of adding only a line), the new activation node flag shown in FIG. By transmitting in the “off” state, it can be distinguished from the case described above. In the above, information indicating that the node has been newly activated is transmitted from the newly activated node. However, according to such a method, the information is transmitted to the network as compared with the case where the adjacent node transmits. This burden can be reduced. That is, when transmitting from an adjacent node, a large amount of information is transmitted in an unactivated state, and this information places a burden on the network. On the other hand, when transmitting from a newly activated node, it is necessary to wait until the activation is completed. However, since information is not transmitted unnecessarily, the burden on the network can be reduced.

Next, details of the above-described operation will be described with reference to FIGS. First, FIG. 24 is a flowchart for explaining an example of processing executed in a node to which a link is added. In this figure, portions corresponding to those in FIG. 10 are denoted by the same reference numerals and description thereof is omitted. FIG. 24 is the same as FIG. 10 except that the processes of steps S8 and S9 are added compared to FIG. In step S8, it is determined whether or not it is a new startup node. If it is determined that it is a new startup node (step S8: Yes), the process proceeds to step S9, and otherwise (step S8: No) terminates the process. In step S9, the new activation node flag shown in FIG. 23 is set to the on (= “1”) state, and the process proceeds to step S3, where the same processing as described above is executed. According to the above processing, when the node itself is a new activation node, the RLINK signal with the new activation node turned on is transmitted.

Next, an example of processing executed in the node that has received the RLINK signal will be described with reference to FIG. In this figure, parts corresponding to those in FIG. FIG. 25 is the same as FIG. 11 except that steps S28 to S31 are added in comparison with FIG. In step S28, it is determined whether or not the new activation flag (see FIG. 23) of the RLINK signal received in step S21 is in an on state. If it is determined in an on state (step S28: Yes), The process proceeds to step S29, and in other cases (step S28: No), the process ends. In step S29, it is determined whether or not the corresponding node is in a block. If it is determined that the corresponding node is in a block (step S29: Yes), the process proceeds to step S30. Otherwise (step S29: No), the process proceeds to step S31. move on. In step S30, the block for the corresponding node is released. For example, in the example of FIG. 22, the block for the node 10-1 is released. As a result, the first block is released. In step S31, the route information related to the corresponding node is deleted. For example, in the example of FIG. 22, the route information for the node 10-1 is deleted. This eliminates the cause of the second block. According to the above processing, the first block described above can be canceled and the occurrence of the second block can be suppressed, so that it is possible to prevent a delay from occurring in the communication start.

In the above embodiment, the new activation node flag is added to the RLINK signal to notify the other nodes of the occurrence of new activation. However, such information may be sent separately from the RLINK signal. Good. FIG. 26 is a diagram illustrating a configuration example of a block release signal for requesting a new activation node to release a block to another node. In the example of FIG. 26, an identifier field and a node ID field are provided. Here, the identifier field stores information indicating that this packet is a deblocking signal. The node ID field stores the ID of the node that is to be unblocked. Note that the transmission timing of this block release signal may be either before or after transmission of the RLINK signal. By transmitting such a deblocking signal, the neighboring nodes recognize that the node having the ID stored in the node ID field is the target of deblocking, as described above, By deleting the related information, the first block described above can be canceled and the occurrence of the second block can be suppressed.

FIG. 27 is a flowchart for explaining the operation when the block release signal shown in FIG. 26 is received. When the process shown in FIG. 27 is executed, the following steps are executed. That is, in step S51, it is determined whether or not a deblocking signal has been received. If it is determined that it has been received (step S51: Yes), the process proceeds to step S52, and otherwise (step S51: No). The process ends. In step S52, the node ID is obtained from the node ID field. In step S54, it is determined whether or not the corresponding node is in a block. If it is determined that the node is in a block (step S54: Yes), the process proceeds to step S55. Otherwise (step S54: No), the process proceeds to step S56. move on. In step S55, the block for the corresponding node is released. In step S56, the route information related to the corresponding node is deleted, and the process ends. According to the above processing, when the block release signal is received, the block can be released and the related route information can be erased, so that the first block described above is released and the second block is generated. Since it can suppress, it can prevent that a delay arises in communication start.

10-1 to 10-8 Node 11 Packet relay processing unit (transmission means, transfer means)
12 Control unit (update means)
13 storage unit 13a routing table 14-1 to 14-n receiving unit 15-1 to 15-n transmitting unit 21 to 29, 30 link

Claims

In a network system in which a plurality of nodes are communicably connected by a link,
When the predetermined first node and the predetermined second node constituting the network system are communicably connected by a new link, the first and second nodes are communicably connected by the new link. A notification signal having information indicating that and information indicating a metric up to the first or second node are transmitted to other nodes other than the first and second nodes by transmission means, respectively.
The other node that has received the notification signal adds the metric from the node immediately before transmitting the signal to its own information to the information indicating the metric of the notification signal, and further forwards it to another node by the transfer means. And updating the route information stored in the routing table when the notification signal is received by the updating means,
A network system characterized by this.
The updating means compares the metric of each entry stored in the routing table with the metric stored in the notification signal, and determines a metric that is larger by a predetermined value than the metric stored in the notification signal. The network system according to claim 1, wherein an entry having the information is deleted.
The notification signal stores a metric of the new link;
The update unit deletes an entry having a metric larger than a value obtained by adding the metric of the new link stored in the notification signal to the metric stored in the notification signal.
The network system according to claim 2.
The metric is the number of hops;
The updating means deletes an entry having a hop number larger than a value obtained by adding the hop number stored in the notification signal to the hop number stored in the notification signal. The network system according to claim 2 or 3, wherein
The network system according to claim 1, wherein the update unit deletes all entries stored in the routing table when the notification signal is received.
The network system according to any one of claims 1 to 5, wherein the transmission unit transmits the notification signal by adding information for identifying the own node.
The said transmission means has the identification information for identifying the said notification signal in order to respond | correspond to the case where two or more of the said notification signals are transmitted, The any one of Claim 1 thru | or 6 characterized by the above-mentioned. The network system described in 1.
When the first node is a newly activated node, the first and second nodes transmit information indicating that the first node has been newly activated to other nodes;
When the other node receives the information indicating that it has been newly activated, it releases the block for the first node.
The network system according to claim 1, wherein:
9. The network system according to claim 8, wherein the first node transmits information indicating that it has been newly activated.
When the other node receives the information indicating that it has been newly activated, the other node deletes the route information related to the first node.
The network system according to claim 8 or 9, wherein
10. The network system according to claim 8 or 9, wherein the information indicating that it is newly activated is added to the notification signal and transmitted.
The network system according to any one of claims 1 to 11, wherein the network system is used for distribution line remote monitoring control.
In a control method of a network system in which a plurality of nodes are communicably connected by a link,
When the predetermined first node and the predetermined second node constituting the network system are communicably connected by a new link, the first and second nodes are communicably connected by the new link. A notification signal having information indicating that and information indicating a metric up to the first or second node are transmitted to other nodes other than the first and second nodes by a transmission step, respectively.
The other node that has received the notification signal adds the metric from the node immediately before transmitting the signal to its own information to the information indicating the metric of the notification signal, and further forwards it to another node through a transfer step. And updating the route information stored in the routing table when the notification signal is received by an update step,
A control method for a network system.