JP6738851B2 - Network system, route switching method of network system, and communication device - Google Patents

Description

The present invention relates to a network system, a route switching method for the network system, and a communication device.

The technology defined in Non-Patent Document 1 is a reactive routing protocol and establishes a route when a request is made.

IETF RFC3561 Ad Hoc On Demand Distance Vector (AODV) Routing

By the way, in the technique disclosed in Non-Patent Document 1, when there are a plurality of routes having the same number of hops, the routes may be unnecessarily switched. In such a case, there is a problem that a packet being communicated may be lost.

Therefore, it is an object of the present invention to provide a network system, a route switching method for a network system, and a communication device capable of suppressing unnecessary route switching.

In order to solve the above problems, the present invention provides a network system having a plurality of communication devices, in which each communication device includes a monitoring unit that monitors whether or not the route is normal, and a route search packet for searching the route. When received, a switching unit that executes a process of switching the route based on the specifying unit that specifies the route information on the corresponding current route, the route search packet, and the route information specified by the specifying unit. And, when the route is determined to be normal by the monitoring unit, the sequence number included in the route search packet is newer than the sequence number of the current route identified by the identifying unit, When the number of hops included in the route search packet is equal to or larger than the number of hops of the current route specified by the specifying unit, the switching unit does not switch the route.
With such a configuration, it becomes possible to suppress unnecessary switching of routes.

Further, according to the present invention, when the route is determined to be abnormal by the monitoring unit, when the sequence number included in the route search packet is newer than the sequence number of the current route identified by the identifying unit, The switching means switches the route.
With such a configuration, when an abnormality occurs, it is possible to quickly switch the route.

Further, in the present invention, when the monitoring unit determines that the route is abnormal, the sequence number of the route search packet that arrives first is newer than the sequence number of the current route identified by the identifying unit. In the case where the route search packet that arrives after that, the sequence number included in the route search packet is newer than the sequence number of the current route specified by the specifying unit. Then, when the number of hops included in the route search packet is less than the number of hops of the current route identified by the identifying unit, the switching unit switches the route.
With such a configuration, when a valid route is found after the occurrence of an abnormality, it is possible to switch to the route.

Further, according to the present invention, in a route switching method for a network system having a plurality of communication devices, each communication device receives a monitoring step of monitoring whether or not the route is normal, and a route search packet for searching the route. In this case, a specifying step of specifying path information about the corresponding current path, the path search packet, and a switching step of executing a process of switching the path based on the path information specified by the specifying step, And the sequence number included in the route search packet is newer than the sequence number of the current route identified by the identifying step, the route is determined to be normal by the monitoring step. When the number of hops included in the search packet is equal to or more than the number of hops of the current route specified by the specifying step, the switching step does not switch the path.
According to such a method, it is possible to suppress unnecessary switching of routes.

Further, the present invention is, in a communication device which is connected to a plurality of units to form a network system, a monitoring means for monitoring whether or not a route is normal, and when a route search packet for searching a route is received, A specifying unit that specifies route information about the corresponding current route; the route search packet; and a switching unit that executes a process of switching the route based on the route information specified by the specifying unit, When the monitoring unit determines that the route is normal, the sequence number included in the route search packet is newer than the sequence number of the current route specified by the specifying unit, and the route search packet has the sequence number. When the number of hops is equal to or larger than the number of hops of the current route specified by the specifying unit, the switching unit does not switch the route.
With such a configuration, it becomes possible to suppress unnecessary switching of routes.

According to the present invention, it is possible to provide a network system, a route switching method of a network system, and a communication device capable of suppressing unnecessary route switching.

It is a figure which shows the structural example of the network system of embodiment of this invention. It is a figure which shows the detailed structural example of the communication apparatus shown in FIG. It is a figure for demonstrating the operation|movement which monitors the network in embodiment of this invention. 6 is a flowchart for explaining the operation of the embodiment of the present invention. 5 is a flowchart for explaining details of normal time processing of FIG. 4. 5 is a flowchart for explaining the details of the abnormal time process of FIG. 4. It is a figure for demonstrating the modified embodiment of this invention. FIG. 8 is a diagram for explaining the operation of the communication device shown in FIG. 7.

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

(A) Description of Configuration of Embodiment of Present Invention FIG. 1 is a diagram showing an example of a configuration of a network system according to an embodiment of the present invention. As shown in FIG. 1, the network system 1 according to the embodiment of the present invention includes communication devices 10-1 to 10-5 that function as network nodes.

The communication devices 10-1 to 10-5 illustrated in FIG. 1 perform route construction based on an on-demand protocol by AODV (Ad hoc On-Demand Distance Vector) of MANET (Mobile Ad hoc Network), for example.

FIG. 2 is a diagram showing a configuration example of the communication devices 10-1 to 10-5 shown in FIG. Since the communication devices 10-1 to 10-5 have the same configuration, they will be described below as the communication device 10.

As illustrated in FIG. 2, the communication device 10 includes a packet relay processing unit 11, a control unit 12, a storage unit 13, receiving units 14-1 to 14-n, transmitting units 15-1 to 15-n, and The clock unit 16 is provided.

Here, the packet relay processing unit 11 sends the packet received by the receiving units 14-1 to 14-n under the control of the control unit 12 according to the information stored in the header of the packet. It is sent from the units 15-1 to 15-n. The control unit 12 rewrites the header of the received packet according to the route information 13a stored in the storage unit 13 and transmits the packet via the packet relay processing unit 11.

The storage unit 13 is configured by, for example, a semiconductor memory, stores route information 13a that is information for transferring packets, and stores programs and data for executing processing described later.

The receiving units 14-1 to 14-n receive packets from other communication devices. The transmission units 15-1 to 15-n transmit packets to other communication devices. The timer 16 measures the time and supplies it to the controller 12.

(B) Description of Operation of Embodiment of Present Invention Next, an operation of the embodiment of the present invention will be described. In the following, the problems in the operation of the conventional example will be described, and then the operation of the embodiment of the present invention will be described.

In the network system 1 shown in FIG. 1, when the communication device 10-1 communicates with the communication device 10-5, the communication device 10-1 that is the communication source transmits a route search packet to search for a route. .. Since such a route search packet is transmitted by broadcasting, the two route search packets are the communication device 10 which is the communication destination via the two first communication routes and the second communication routes shown in FIG. 1, respectively. Arriving at -5. At this time, it is assumed that the communication device 10-5 has not registered the route information with the communication device 10-1.

The route search packet has a sequence number. The sequence number is managed for each node, and its value is incremented each time it is transmitted. By referring to this sequence number, the communication devices 10-1 to 10-5 do not repeatedly process the already processed route search packet. In addition, the route search packet has a hop number whose value is incremented each time it passes through the communication device 10.

In the example of FIG. 1, since the route search packet passing through the first communication route reaches the communication device 10-5 via the communication device 10-2 and the communication device 10-4, the number of hops is 3. Further, the route search packet passing through the first communication route reaches the communication device 10-5 via the communication device 10-3 and the communication device 10-4, and thus the hop number is 3.

The communication device 10-5 at the communication destination receives such two route search packets. The communication device 10-5 refers to the hop count of the received route search packet and selects the route search packet with the smaller hop count. However, in the example of FIG. 1, both the first communication route and the second communication route have three hops. In such a case, the communication device 10-5 selects the route search packet that arrived first. For example, when the route search packet that has passed the first communication route reaches the communication device 10-5 first, the route search packet that has passed the first communication route is selected.

Next, the communication device 10-5 selects the first communication route as a route to be used, and stores information regarding this route in the storage unit 13 as route information 13a. More specifically, information (for example, address information) about the communication device 10-1 that is the communication source, a sequence number of the route search packet, the number of hops, and information about the communication device 10-4 that is the transfer destination are registered. It Information other than these may be registered.

Subsequently, the communication device 10-5 transmits a route reply packet to the communication device 10-1 via the first communication route. Such a route reply packet is transmitted to the communication device 10-1 via the communication device 10-4 and the communication device 10-2. In addition, the route information indicating the first communication route is registered in the communication device 10-4, the communication device 10-2, and the communication device 10-1 which have received the route reply packet. On the other hand, since the route search packet regarding the second communication route is discarded, the route information regarding this route is not generated.

When the first communication route is selected, it is assumed that the communication device 10-1 that is the communication source issues a new communication request to the communication device 10-5 that is the communication destination and that a route search is newly generated. In that case, as in the case described above, the communication device 10-1 transmits a route search packet to which a new sequence number is added, to the communication device 10-5. Such a route search packet arrives at the communication device 10-5, which is the communication destination, via the first communication route and the second communication route.

The communication device 10-5 receives these route search packets. Then, the sequence number of the route search packet is compared with the corresponding sequence number already stored in the route information 13a. In the present example, since the newly arrived sequence number is newer (larger in value), the newly arrived route search packet is selected. By the way, the number of hops stored in the route search packet passing through the first communication route and the second communication route is three. Therefore, the communication device 10-5 selects the route search packet that arrived first.

For example, when the route search packet that has passed through the second communication route arrives first, the communication device 10-5 selects the route search packet that has passed through the second communication route. Although the current route is the first communication route, the number of hops of the first communication route is 3 and is the same. In such a case, in the conventional technique, the newer sequence number (larger value) is selected, so that the route search packet via the second communication route is selected.

As a result, the communication path between the communication device 10-1 and the communication device 10-5 is changed from the first communication path to the second communication path. In this case, assuming that communication is being performed between the communication device 10-1 and the communication device 10-5, the route may be changed during the communication, so that a situation may occur in which a packet is lost during the communication. is there. In the embodiment of the present invention, the following operation is executed in order to prevent such a situation.

That is, in the embodiment of the present invention, first, whether or not the route is normal is monitored. FIG. 3 is a diagram for explaining how the route is monitored. In the example shown in FIG. 3, the communication devices 10-1 to 10-5 are connected in series in this order, and the communication device 10-1 is a communication source and the communication device 10-5 is a communication destination. There is. In such a state, for example, when a malfunction (for example, link disconnection) occurs in the communication path between the communication device 10-2 and the communication device 10-3, the communication device 10-2 detects an abnormality, The communication device 10-1 using the route is notified of the abnormality. Further, the communication device 10-3 detects an abnormality and notifies the communication device 10-5 using the route of the abnormality. Furthermore, the communication devices 10-1 to 10-5 confirm the normality by periodically transmitting a survival confirmation signal between adjacent communication devices. That is, the communication route between the adjacent communication devices is constantly monitored, and if there is an abnormality, the communication device using the route is immediately notified and the route is deleted. Therefore, if a route exists at the time of determination, it can be basically determined that the route is healthy.

Next, in the embodiment of the present invention, as a result of the route monitoring, when the route is normal, when the route search packet arrives, the number of hops is the same as the current route, or the number of hops is greater than the current route. Is large, even if the sequence number is new (large), the route search packet is ignored. For example, in the example of FIG. 1, when both the first communication path and the second communication path are healthy (when no path abnormality is notified), the sequence is performed via the first communication path and the second communication path. When a route search packet whose number is newer than the current route arrives, or when the number of hops of the route search packet is 3 or more (when it is the same as the number of hops of the current route stored in the storage unit 13) , Ignore these packets. As a result, it is possible to suppress the above-described switching of the route. It should be noted that when a route search packet having a new sequence number and a smaller number of hops than the current one arrives, there is an advantage of switching the route, and therefore the route switching process is executed.

On the other hand, when the route is abnormal, for example, when an abnormality occurs in the first communication route being used in communication, it is assumed that the route search packet arrives via the second communication route. In this case, if the sequence number is newer than the current route, for example, the process of switching from the first communication route to the second communication route can be executed regardless of the number of hops. As a result, the path is switched from the abnormal first communication path to the normal second communication path.

As described above, in the embodiment of the present invention, in the case where the route is normal, when the route search packet is received, the number of hops is the same as or greater than that of the current route even if the sequence number is new. If it is larger, the route search packet is ignored, so that unnecessary route switching can be suppressed.

Further, when a route search packet is received in the case where an abnormality has occurred in the route, the route is switched according to the route search packet regardless of the number of hops when the sequence number is new. You can switch to a normal path.

Next, the processing executed in the communication device 10 shown in FIG. 2 will be described with reference to FIGS. 4 to 6.

FIG. 4 is a diagram for explaining an example of main processing executed in the communication device 10 shown in FIG. When the process of the flowchart shown in FIG. 4 is started, the following steps are executed.

In step S10, the control unit 12 acquires a packet from the packet relay processing unit 11, determines whether or not a route search packet has been received, and determines that a route search packet has been received (step S10: Y). Proceeds to step S11, and otherwise (step S10:N), the same processing is repeated.

In step S11, the control unit 12 determines whether the route is normal. As a result, if it is determined that the route is normal (step S11:Y), the process proceeds to step S12, and if not (step S11:N), the process proceeds to step S13.

In step S12, the control unit 12 executes normal time processing, which will be described later with reference to FIG.

In step S13, the control unit 12 executes abnormal time processing, which will be described later with reference to FIG.

In step S14, the control unit 12 determines whether or not to continue the process. If it is determined that the process is to be continued (step S14: Y), the process returns to step S10 to repeat the same process as described above, Otherwise (step S14: N), the process ends.

Next, with reference to FIG. 5, details of the “normal time process” shown in step S12 of FIG. 4 will be described. When the process of the flowchart shown in FIG. 4 is started, the following steps are executed.

In step S30, the control unit 12 acquires the sequence number Sp of the route search packet received in step S10 of FIG.

In step S31, the control unit 12 acquires the hop count Hp of the route search packet received in step S10 of FIG.

In step S32, the control unit 12 acquires the sequence number Sc regarding the current route from the route information 13a of the storage unit 13.

In step S33, the control unit 12 acquires the hop count Hc for the current route from the route information 13a in the storage unit 13.

In step S34, the control unit 12 compares the sequence number Sp of the route search packet acquired in step S30 with the sequence number Sc of the current route acquired in step S32 to determine whether Sp>Sc is satisfied (route search). It is determined whether or not the sequence number of the packet is newer than the sequence number of the current route), and if it is determined that Sp>Sc is satisfied (step S34:Y), the process proceeds to step S35, otherwise. In (Step S34:N), the process returns to the original process.

In step S35, the control unit 12 compares the hop count Hp of the route search packet acquired in step S31 with the hop count Hc of the current route acquired in step S33, and determines whether Hp<Hc is satisfied (route search). If the hop count of the packet is smaller than the hop count of the current route), and if it is determined that Hp<Hc is satisfied (step S35:Y), the process proceeds to step S36, and otherwise. The original process is returned to (step S35: N).

In step S36, the control unit 12 executes a process of switching to the route specified by the route search packet. More specifically, the control unit 12 generates a route reply packet and sends it to the new route via the packet relay processing unit 11. In addition, the information about the route search packet is stored in the storage unit 13 as the route information 13a. As a result, the path switching is executed.

Next, with reference to FIG. 6, the details of the “abnormality process” shown in step S13 of FIG. 4 will be described.

In step S50, the control unit 12 acquires the sequence number Sp of the route search packet received in step S10 of FIG.

In step S51, the control unit 12 acquires the sequence number Sc regarding the current route from the route information 13a of the storage unit 13.

In step S52, the control unit 12 compares the sequence number Sp of the route search packet acquired in step S50 with the sequence number Sc of the current route acquired in step S51 to determine whether Sp>Sc is satisfied (route search). It is determined whether the sequence number of the packet is newer than the sequence number of the current route), and if it is determined that Sp>Sc is satisfied (step S52:Y), the process proceeds to step S53, and otherwise. The original processing is returned to (step S52: N).

In step S53, the control unit 12 executes a process of switching to the route specified by the route search packet. More specifically, the control unit 12 generates a route reply packet and sends it to the new route via the packet relay processing unit 11. In addition, the information about the route search packet is stored in the storage unit 13 as the route information 13a. As a result, the path switching is executed.

According to the above processing, the above-mentioned operation can be realized.

(C) Description of Modified Embodiments Needless to say, the above embodiments are merely examples, and the present invention is not limited to the above cases. For example, in the above embodiment, as shown in FIG. 2, the communication devices 10 exchange information with each other by an electric signal, but the information may be transmitted/received by an optical signal. ..

FIG. 7 shows a network system 1 that transmits information by an optical signal. In the example of FIG. 7, the communication devices 20-1 to 20-5 are connected in a ring shape, the communication device 20-1 is the communication source, and the communication device 20-5 is the communication destination. Further, the example of FIG. 7 indicates that an abnormality has occurred in the communication device 20-4.

FIG. 8 is a diagram showing a configuration example of the communication devices 20-1 to 20-5 shown in FIG. 7. Since the communication devices 20-1 to 20-5 have the same configuration, they will be described below as the communication device 20.

As shown in FIG. 8, the communication device 20 has a communication processing unit 21 and an optical switch 22. The communication processing unit 21 converts an optical signal supplied via the optical switch 22 into an electric signal, performs routing processing and the like, converts the optical signal again into an optical signal, and outputs the optical signal via the optical switch 22.

The optical switch 22 executes an operation of bypassing an optical signal to the communication processing unit 21 in order to prevent the communication from being interrupted when the communication processing unit 21 fails or is not supplied with power.

More specifically, FIG. 8A is a diagram showing an operation of the communication device 20 at the normal time. During normal operation, the first optical port and the second optical port are connected to the communication processing unit 21 via the optical switch 22. On the other hand, FIG. 8B is a diagram showing the operation of the communication device 20 in the event of an abnormality. At the time of abnormality (for example, when the communication processing unit 21 fails or when power is not supplied), the optical switch 22 directly connects the first optical port and the second optical port and bypasses the communication processing unit 21. .. As a result, the optical signal is transmitted and received by the optical switch 22 bypassing the communication processing unit 21.

When the communication device 20-4 fails as shown in FIG. 7, the communication processing unit 21 is bypassed by the optical switch 22 as shown in FIG. 8B. As a result, the route search packet passing through the communication device 20-4 bypasses the communication processing unit 21, so that the number of hops does not increase. Therefore, both the first communication path and the second communication path shown in FIG. 7 have the same hop number of 2.

In such a case, for the same reason as in the embodiment shown in FIG. 1, the route is not switched, and the route is regularly monitored to monitor the status of the bypassed communication device 20-4. Since packets may be transmitted, switching of routes may occur.

By applying the present invention also to the embodiment shown in FIG. 7, it is possible to prevent unnecessary switching of routes.

As described above, according to the embodiments of the present invention, unnecessary path switching is suppressed not only when communicating using electric signals but also when communicating using optical signals. It becomes possible to do.

In addition, in the example of FIG. 1, the case where the abnormality occurs in one of the two communication paths has been described as an example, but, for example, the abnormality occurs in one of the three or more communication paths. In this case, the route with the smallest number of hops may be selected from the two or more communication routes. That is, in the flowchart shown in FIG. 6, the route is switched without referring to the hop number, but in consideration of the case described above, the route with the smaller hop number may be selected. In addition, when the route does not exist due to an abnormality, for example, when the route can be newly established as in mobile communication, the route may be newly provided. Further, when a new route cannot be established, a warning may be issued to a higher-level device or the like.

Further, the route search packet that arrives first after detecting an abnormality in the route is an essential packet for switching the route. Therefore, as shown in FIG. 6, if the sequence number is newer than the current route, the route search packet Execute the process of switching. Then, for the route search packets received thereafter, the route may be switched when the sequence number is new and the number of hops is small (Hp<Hc).

1 Network System 10, 10-1 to 10-5 Communication Device 11 Packet Relay Processing Unit 12 Control Unit 13 Storage Unit 13a Route Information 14-1 to 14-n Reception Unit 15-1 to 15-n Transmission Unit 16 Clocking Unit 20 , 20-1 to 20-5 Communication device 21 Communication processing unit 22 Optical switch

Claims (5)

In a network system having a plurality of communication devices,
Each communication device
Monitoring means for monitoring whether the route is normal,
When a route search packet for searching a route is received, specifying means for specifying route information about the corresponding current route,
A switching unit that executes a process of switching a route based on the route search packet and the route information identified by the identifying unit;
When the monitoring unit determines that the route is normal, the sequence number included in the route search packet is newer than the sequence number of the current route specified by the specifying unit, and the route search packet has the sequence number. If the number of hops is greater than or equal to the number of hops of the current route specified by the specifying unit, the switching unit does not switch the route.
A network system characterized in that When the monitoring unit determines that the route is abnormal, when the sequence number included in the route search packet is newer than the sequence number of the current route identified by the identifying unit, the switching unit determines the route. The network system according to claim 1, wherein the network system is switched. When the monitoring unit determines that the route is abnormal, when the sequence number of the route search packet that arrives first is newer than the sequence number of the current route specified by the specifying unit, the switching unit The route search packet that arrives after that, if the sequence number of the route search packet is newer than the sequence number of the current route specified by the specifying means, the route search packet The network system according to claim 1, wherein the switching unit switches the route when the number of hops owned by is less than the number of hops of the current route identified by the identifying unit. In a path switching method of a network system having a plurality of communication devices,
Each communication device
A monitoring step for monitoring whether the route is normal,
When a route search packet for searching a route is received, a specifying step of specifying route information regarding the corresponding current route,
A route search packet, and a switching step of performing a process of switching a route based on the route information identified by the identifying step,
When the route is determined to be normal by the monitoring step, the sequence number included in the route search packet is newer than the sequence number of the current route identified in the identifying step, and the route search packet has the sequence number. If the number of hops is greater than or equal to the number of hops of the current route identified by the identifying step, the switching step does not perform route switching.
A route switching method for a network system, which is characterized by the above. In a communication device in which a plurality of units are connected to form a network system,
Monitoring means for monitoring whether the route is normal,
When a route search packet for searching a route is received, specifying means for specifying route information about the corresponding current route,
A switching unit that executes a process of switching a route based on the route search packet and the route information identified by the identifying unit;
When the monitoring unit determines that the route is normal, the sequence number included in the route search packet is newer than the sequence number of the current route specified by the specifying unit, and the route search packet has the sequence number. If the number of hops is greater than or equal to the number of hops of the current route specified by the specifying unit, the switching unit does not switch the route.
A communication device characterized by the above.

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