JP7280998B2 - Communication path control system - Google Patents

Description

The present invention relates to a communication route control system in a communication network system configured by interconnecting a plurality of Autonomous Systems (AS).

A network is generally configured by interconnecting ASs, which are collections of communication devices that operate under common policies and the same environment. An identification number (AS number) is assigned to each AS connected to each other. In addition, BGP (Border Gateway Protocol) is used as a route control protocol used between a plurality of ASs.

A communication device that communicates by BGP establishes a one-to-one connection using TCP when starting communication. The source communication device transmits a SYN packet, receives a SYN/ACK packet from the destination communication device, and then transmits an ACK packet to establish a TCP connection.

When a TCP connection is established, the source communication device and the destination communication device exchange basic BGP information (OPEN message) with each other. At this point, a BGP session is established. After the BGP session is established, the source communication device and the destination communication device exchange routing tables with each other. After that, the transmission source communication device transmits a KEEPALIVE message to confirm the existence of the transmission destination communication device.

As a method for coping with the occurrence of a communication failure in a network, a method of forming an alternative route and transmitting traffic has been proposed. Patent Literature 1 discloses a method of adding an autonomous system dedicated to a backup route as an additional network for redundancy, and transmitting packets of an existing network using the additional network.

JP-A-2009-147735

In the method for coping with the occurrence of communication failures described in Patent Document 1, an autonomous system dedicated to backup routes is added as an additional network, so the number of communication devices increases. Also, if the communication function of the communication device is completely stopped, it is possible to switch to the backup route as described above. However, no measures are taken against temporary deterioration of communication performance such as when the communication function of the communication device is not completely stopped.

Even if the communication function of the communication device is not completely stopped, packets continue to be transmitted to the communication device as usual. As a result, there arises a problem that the communication device discards the packet or destroys the packet.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a communication route control system capable of switching to a detour route when communication performance failure or communication performance deterioration of a communication device is detected.

A communication path control system according to an embodiment of the present invention includes a communication performance evaluation unit that evaluates communication performance of a network based on the number of SYN packets transmitted from a first communication device to a second communication device; a route control unit that changes the communication route of the first communication device from the second communication device to the third communication device when deterioration of the communication performance is detected.

In the communication path control system described above, the communication performance evaluation unit may further include a measurement unit that measures the number of SYN packets.

In the communication path control system described above, the communication performance evaluation unit may further include a calculation unit that calculates the rate of change based on the number of SYN packets.

In the communication path control system described above, the communication performance evaluation unit may further include a determination unit that determines whether or not the rate of change exceeds a predetermined threshold.

The communication path control system may further include a path attribute changer for changing the path attribute of the third communication device.

In the above communication path control system, the path attribute may be a WEIGHT attribute.

The communication path control system may further include a performance deterioration determination unit that evaluates whether the deterioration in communication performance is permanent or temporary.

In the above communication path control system, after the communication path of the first communication device is changed from the second communication device to the third communication device, when the communication performance evaluation unit determines that the deterioration of the communication performance has recovered, It may include changing the communication path of one communication device from a third communication device to a second communication device.

A communication path control system according to an embodiment of the present invention includes a communication performance evaluation unit that evaluates communication performance of a network based on a ratio of SYN packets of a first communication device to a second communication device; and a route control unit that changes the communication route of the first communication device from the second communication device to the third communication device when the is detected.

In the above communication path control system, the ratio of SYN packets is the ratio of SYN packets transmitted from the first communication device to the second communication device and SYN/ACK packets transmitted from the second communication device to the first communication device. There may be.

In the communication path control system described above, the path control unit may have a path attribute change unit that changes the path attribute of the third communication device.

In the above communication path control system, the path attribute may be a WEIGHT attribute.

In the above communication path control system, even after the communication path of the first communication device is changed from the second communication device to the third communication device, even if the ratio of SYN packets of the first communication device to the second communication device is observed, good.

In the above communication path control system, after the communication path of the first communication device is changed from the second communication device to the third communication device, if the communication performance evaluation unit determines that the deterioration of the communication performance has recovered, The communication path of one communication device may be changed from the third communication device to the second communication device.

INDUSTRIAL APPLICABILITY The present invention can provide a communication route control system capable of switching to a detour route when a failure or degradation of communication performance of a communication device is detected in a network.

1 is a diagram illustrating a configuration example of a network according to a first embodiment; FIG. 1 is a configuration diagram showing a communication path control system according to a first embodiment; FIG. 4 is a graph showing variations in the number of SYN packets at each time; 4 is a flow chart showing processing of the communication path control system according to the first embodiment; FIG. 10 is a configuration diagram showing a communication path control system according to a second embodiment; FIG. 11 is a diagram illustrating a configuration example of a network according to a third embodiment; FIG. 10 is a flow chart showing processing of the communication path control system according to the third embodiment; FIG. 11 is a block diagram of a communication path control system according to a third embodiment; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different aspects and should not be construed as being limited to the description of the embodiments exemplified below. Although the drawings may be represented schematically in order to make the description clearer, they are only examples and do not limit the interpretation of the present invention. In addition, the letters "first" and "second" for each element are labels for convenience used to distinguish each element, and unless otherwise specified, have more meaning. do not have. In the drawings referred to in this embodiment, the same reference numerals or similar reference numerals may be assigned to the same parts or parts having similar functions, and repeated description thereof may be omitted. Also, part of the configuration may be omitted from the drawing. In addition, no particular description will be given if it is something that can be recognized by a person who has ordinary knowledge in the field to which the present invention belongs.

(First embodiment)
A communication path control system according to this embodiment will be described with reference to FIGS. 1 to 4. FIG.

FIG. 1 shows a block diagram showing a configuration example of a network 100 according to this embodiment. A network 100 according to this embodiment is composed of autonomous systems AS1 to AS5. Autonomous systems AS1 to AS5 forming a network are interconnected by communication equipment corresponding to entrances and exits. In this embodiment, the first communication path is the path through which the communication device 111a of the autonomous system AS1 communicates with the communication device 115a of the autonomous system AS5 via the communication devices 113a and 113b of the autonomous system AS3. Also, a case will be described in which the communication device 111a of the autonomous system AS1 communicates with the communication device 115a of the autonomous system AS5 via the communication device 114a and the communication device 114b of the autonomous system AS4 as the second communication route. .

Communication devices 111a, 111b, 113a to 113d, 115a, and 115b of autonomous systems AS1 to AS5 each have a BGP communication function. In BGP, BGP used between different autonomous systems AS is called eBGP (external BGP), and BGP used within an autonomous system AS is called iBGP (internal BGP) for distinction.
For example, the communication device 111a of the autonomous system AS1 and the communication device 113a of the autonomous system AS3 use eBGP, and the communication devices 113a and 113b of the autonomous system AS3 use iBGP.

BGP establishes a one-to-one session using TCP when starting communication. For example, the source communication device 111a transmits a SYN packet, receives a SYN/ACK packet from the destination communication device 113a, and then transmits an ACK packet to establish a session.

A SYN packet used in TCP always exists in a series of data communications in a normal network state. For example, when the communication performance with the communication device 113a transmitted from the communication device 111a deteriorates, the number of SYN packets per unit time tends to increase suddenly. In this specification and the like, deterioration of communication performance includes not only communication failure but also communication speed reduction.

Therefore, in the communication path control system according to the present embodiment, the communication performance of the network is evaluated based on the number of SYN packets transmitted from the first communication device to the second communication device, and the communication performance evaluation unit evaluates the second communication device is detected, the communication path of the first communication device is changed from the second communication device to the third communication device. That is, in the communication device 111a, the priority of the second communication route passing through the communication device 114a is set higher than that of the first communication route passing through the communication device 113a. Hereinafter, the first communication device, the second communication device, and the third communication device will be described as the communication device 111a, the communication device 113a, and the communication device 114a shown in FIG.

FIG. 2 shows a configuration diagram of a communication path control system 200 according to this embodiment. The communication path control system 200 according to this embodiment can be installed in communication equipment such as a border edge router of an autonomous system that communicates using eBGP, for example. Also, in this embodiment, an example in which the communication path control system 200 is installed in the communication device 111a shown in FIG. 1 will be described. Note that the communication path control system 200 according to the present embodiment may be any communication device that connects with other communication devices by BGP. It can also be mounted on each. The communication device 111 a also has an interface 203 in addition to the communication path control system 200 .

The communication path control system 200 has at least a communication performance evaluation section 201 and a path control section 202 . The communication path control system 200 further has a packet controller 204 , a path control message controller 205 and a routing table 206 .

Communication performance evaluation section 201 includes measurement section 211 , calculation section 212 , and determination section 213 . The route control unit 202 also includes a path attribute change unit 221 and a route calculation unit 222 .

The interface 203 establishes a connection with adjacent communication equipment and transmits and receives packets to and from the adjacent communication equipment. Also, the packet control unit 204 transmits SYN packets, receives SYN/ACK packets, and transmits ACK packets to adjacent communication devices via the interface 203 . SYN is a flag attached to the first packet requesting establishment of a TCP connection. ACK is a flag for acknowledging a response, and is a flag attached to all packets other than connection request packets. SYN/ACK means that both the SYN flag and the ACK flag are set to 1. During normal communication, a SYN/ACK packet is transmitted only when a SYN packet is received. Note that when communication performance is degraded or a failure occurs, SYN/ACK packets may not be transmitted from adjacent communication devices.

A routing control message control unit 205 transmits and receives routing control messages to and from adjacent communication devices via the interface 203 . Communication devices with BGP capabilities exchange capability information in the form of messages in order to establish peers with communication devices in different autonomous systems AS. Routing messages include, for example, OPEN messages, KEEPALIVE messages, UPDATE messages, and the like.

Here, the OPEN message is a message exchanged at the start of a BGP session. KEEPALIVE messages are messages exchanged periodically to confirm that a peer is established. The UPDATE message is a message used for exchanging BGP routing information. Sent when a route is added or deleted.

The routing table 206 holds all route information such as routes acquired by route control messages, updated routes, and routes changed by the route control unit 202 .

In the communication performance evaluation unit 201, the measurement unit 211 measures the number of SYN packets transmitted from the communication device 111a to the communication device 113a. FIG. 3 shows a graph representing changes in the number of SYN packets at each time. In FIG. 3, the time for measuring the number of SYN packets is from time T1 to time T5. The counted number of SYN packets is transmitted to the calculation unit 212 .

The calculation unit 212 calculates the rate of change in SYN packets for each time based on the number of SYN packets measured. For example, in FIG. 3, the rate of change in the number of SYN packets is calculated based on the measurement results of SYN packets at time T1 and time T2. The calculated rate of change in SYN packets is transmitted to the determination unit 213 .

The determination unit 213 determines whether or not the rate of change in SYN packets exceeds a preset threshold. When it is determined that the threshold is not exceeded, the communication is maintained as it is, assuming that the communication performance is not degraded in the communication device 113a.

If it is determined that the rate of change in SYN packets exceeds a predetermined threshold, the route control unit 202 is notified that the communication performance of the communication device 113a has deteriorated.

When the route control unit 202 detects deterioration of communication performance, it performs processing to change from the first communication route to the second communication route (detour route). In this embodiment, processing is performed to change the communication path of the communication device 111a from the communication device 113a to the communication device 114a. That is, in the communication device 111a, the priority of the second communication route passing through the communication device 114a is set higher than that of the first communication route passing through the communication device 113a.

The process of changing the communication path of the communication device 111a from the communication device 113a to the communication device 114a is performed by changing the BGP path attribute. In BGP, based on path attributes, all communication paths are compared to select the best path to be used for routing. Therefore, if multiple communication paths exist for the same destination, the path attributes of all communication paths are compared to determine the most suitable path for forwarding the traffic. In BGP, communication paths are compared in order based on the following priority.

1. Routes that do not have an IGP route to the next hop are ignored.
2. A router with a WEIGHT attribute chooses the route with the largest WEIGHT attribute. (The WEIGHT attribute is a path attribute unique to Cisco)
3. Select the route with the highest value for the LOCAL_PREF attribute.
4. Choose the path with the shortest list length of the AS_PATH attribute.
5. Choose the route with the lowest type of ORIGIN attribute.
6. When routes are obtained from the same AS and multiple routes exist, the route with the lowest MULTI_EXIT_DISC attribute is given priority.
7. Prefer routes obtained by eBGP over iBGP.
8. Prefer the IGP closest route to the next hop.
9. Prefer routes learned from the peer with the lowest router ID.

Therefore, by changing path attributes such as the WEIGHT attribute, the LOCAL_PREF attribute, the AS_PATH attribute, and the ORIGIN attribute, it is possible to change the communication route from the communication device 111a to the communication device 115a. Here, a case of changing the WEIGHT attribute as the path attribute will be described.

The WEIGHT attribute is a vendor-defined (unique to Cisco) path attribute, is an attribute used only by the target communication device (communication device 111a), and is not transmitted to other communication devices. A value of "32768" is assigned by default to the communication path to which the communication device 111a is connected, and values of other routes are "0". The WEIGHT attribute favors paths with higher numbers.

Here, in the communication device 111a, the WEIGHT attribute value for the communication device 114a is set to be larger than the WEIGHT attribute value for the communication device 113a. The WEIGHT value is used only within the communication device 111a, is not added to the UPDATE message, and is not notified to the adjacent autonomous system AS.

When the path attribute changer 221 changes the BGP path attribute, the route calculator 222 calculates the optimum route. As a result of the calculation, the communication path of the communication device 111a can be changed from the communication device 113a to the communication device 114a. That is, in the communication device 111a, the priority of the second communication route passing through the communication device 114a is set higher than that of the first communication route passing through the communication device 113a. In this manner, the modified communication route is saved in routing table 206 .

Next, processing executed by the communication path control system 200 according to this embodiment will be described with reference to FIGS. 2 and 4. FIG. FIG. 4 is a flow chart of processing of the communication path control system.

First, as shown in FIG. 4, the measurement unit 211 measures the number of SYN packets that the first communication device transmits to the second communication device (step S401). Next, the calculation unit 212 calculates the rate of change in SYN packets corresponding to time based on the result of SYN packet measurement (step S402).

Next, the calculated rate of change in SYN packets is transmitted to the determination unit 213 (step S403). Next, the determination unit 213 determines whether or not the rate of change exceeds a predetermined threshold (step S404). If the rate of change does not exceed the preset threshold value (step S404; No), the process returns to step S401. If the rate of change exceeds a predetermined threshold (step S404; Yes), the path attribute of the first communication device to the third communication device is changed (step S405).

By changing the path attribute, the route calculator 222 calculates the optimum route. As a result of the calculation, in the communication device 111a, when the priority of the second communication route passing through the communication device 316a is higher than the priority of the first communication route passing through the communication device 312a, the first communication device can be changed from the second communication device to the third communication device. That is, the first communication device can change from the first communication route via the second communication device to the second communication route via the third communication device. Thus, the changed communication route is saved in the route table 206 (step S407).

According to the communication path control system according to the present embodiment, it is possible to detect deterioration of network communication performance. As a result, when deterioration of communication performance is detected in the first communication path from the communication device 111a to the communication device 115a via the communication device 113a, the second communication route (detour route) via the communication device 114a is immediately detected. can be switched to As a result, it is possible to stabilize the communication performance of the network.

(Second embodiment)
In the first embodiment, the process of immediately switching to the second communication path, which is a bypass path, when the deterioration of the communication performance is detected in the first communication path of the communication device 113a has been described. In the present embodiment, when the deterioration of the communication performance of the communication device 113a is temporary, after changing to the second communication route that is the detour route via the communication device 114a, the first communication route that is the original communication route , will be described with reference to FIGS. 1 and 5. FIG.

The communication path control system according to this embodiment includes a performance deterioration determination unit 214 in addition to a measurement unit 211 , a calculation unit 212 and a determination unit 213 in the communication performance evaluation unit 201 .

The performance deterioration determination unit 214 determines whether the deterioration of the communication performance of the communication device 113a determined by the determination unit 213 is temporary or permanent. The performance deterioration determination unit 214 transmits the determined deterioration of communication performance to the route control unit 202 .

Here, the determination of the deterioration of the communication performance of the communication device 113a by the performance deterioration determination unit 214 is performed, for example, by the calculation unit 212 after the rate of change in the SYN packet exceeds a predetermined threshold for a predetermined number of times consecutively. , is below a predetermined threshold, it is determined that the communication performance is temporarily degraded. Alternatively, in the calculation unit 212, when the number of times the SYN packet change ratio exceeds a predetermined threshold continues exceeding a predetermined number of times, it is determined as permanent deterioration of communication performance. Alternatively, when the rate of SYN packet change increases explosively in the calculation unit 212, it is determined that the communication performance is permanently degraded due to, for example, a DoS attack rather than temporary communication degradation.

The route control unit 202 changes the method of changing the communication route depending on the result of the determination of the deterioration of the communication performance of the communication device 113a. When the rate of change in SYN packets exceeds a predetermined threshold, the communication device 111a changes the path attribute for the communication device 113a and the path attribute for the communication device 114a. For example, the WEIGHT value described in the first embodiment is set higher for the communication device 114a than for the communication device 113a. After that, the route calculator 222 calculates the optimum route. As a result of the calculation, the communication path of the communication device 111a can be changed from the communication device 113a to the communication device 114a. That is, in the communication device 111a, it is possible to change from the first communication route via the communication device 113a to the second communication route via the communication device 114a. In this way, the changed communication route is saved in the route table 206. FIG.

Thereafter, when the rate of change in the SYN packet exceeds the predetermined threshold for a predetermined number of times consecutively and then falls below the predetermined threshold, the performance deterioration determination unit 214 determines that the communication performance is temporarily degraded. , the determination result is sent to the route control unit 202 . In the route control unit 202, the path attribute for the communication device 113a and the path attribute for the communication device 114a are changed again. For example, the values of the WEIGHT attribute of the communication device 111a for the communication device 113a and the WEIGHT attribute of the communication device 114a are returned to the values before the detour route change. As a result, the detour route passing through the communication device 114a can be returned to the communication route passing through the communication device 113a. Also, when the communication route is restored, it is also saved in the route table 206 . Note that the path attribute to be changed is not limited to the WEIGHT attribute, and other path attributes may be changed.

In the communication path control system shown in this embodiment, it is determined whether deterioration in communication performance is temporary or permanent. If the deterioration of communication performance is temporary, a detour route can be used, and after the deterioration of communication performance is recovered, the original communication route can be restored. As a result, it is possible to stabilize the communication performance of the network.

(Third Embodiment)
In this embodiment, a communication path control system different from the previous embodiment will be described with reference to FIGS. 6 to 8. FIG. In the present embodiment, a method of immediately changing to a second communication route, which is a detour route, when communication performance deterioration or a failure occurs on the first communication route but the location of the failure cannot be specified will be described. Also, a method of returning from the second communication path to the original first communication path when the deterioration of the communication performance in the first communication path is resolved will be described.

FIG. 6 is a diagram showing a configuration example of the network 300 according to this embodiment. FIG. 7 is a flow chart of the communication path control system according to this embodiment. FIG. 8 is a block diagram of a communication path control system according to this embodiment.

As shown in FIG. 6, a network 300 according to the present embodiment is composed of autonomous systems AS11 to AS18. In FIG. 6, a communication path control system 200 according to the present invention is installed in a communication device 311 of an autonomous system AS11.

In this embodiment, it is assumed that there are two communication routes from the autonomous system AS11 to the target autonomous system AS15. Among the two communication routes, the route from autonomous system AS11 to target autonomous system AS15 via autonomous system AS12, autonomous system AS13, and autonomous system AS14 is defined as the first communication route. Also, a route from autonomous system AS11 to target autonomous system AS15 via autonomous system AS16, autonomous system AS13, and autonomous system AS14 is defined as a second communication route.

If there is a communication device whose function has completely stopped on the first communication path, the new path is updated by an UPDATE message. Therefore, no deterioration or failure occurs in communication performance. However, if there is a half-broken communication device on the first communication path, the KEEPALIVE message and the UPDATE message can be exchanged, but the communication performance deteriorates and failure occurs. This is because even if a packet is sent to a half-broken communication device, it will be discarded or destroyed, making normal communication impossible.

Since communication control messages such as KEEPALIVE messages and UPDATE messages are exchanged between communication devices that are partially broken, it is difficult to identify the location of the failure. Also, when specifying the location of the failure, it is possible to specify the location of the failure by issuing a ping command to the communication device, but depending on the communication device, it is set not to respond to the ping. In some cases. In such a case, it may take time to eliminate the fault because the location of the fault cannot be specified. Therefore, stable communication cannot be provided.

Therefore, in the present embodiment, a method for quickly changing to a detour route even when the location of the failure in the communication route cannot be specified will be described. Also, a process of returning to the original communication path when the failure in the communication path is resolved will be described.

Processing executed by the communication path control system 200 according to this embodiment will be described with reference to the flowchart shown in FIG. In the following description, it is assumed that the normal communication path uses the first communication path.

In the communication path control system 200 according to this embodiment, the ratio of SYN packets on the first communication path is observed (step S401). Here, the ratio of SYN packets is the ratio of SYN packets transmitted from the first communication device to the second communication device and SYN/ACK packets transmitted from the second communication device to the first communication device. Calculating the SYN packet ratio by counting the number of SYN packets and the number of SYN/ACK packets is referred to as observing the SYN packet ratio. In the first communication path, the ratio of SYN packets to SYN/ACK packets is 1 under normal conditions without degradation of communication performance or failure.

If there is a half-broken communication device on the first communication path, the ratio of SYN packets changes on the first communication path (step S402). If the ratio of SYN packets to SYN/ACK packets exceeds 1, for example, there is a half-broken communication device on the first communication path.

Next, when a change in the ratio of SYN packets and SYN/ACK packets is detected, processing is performed to change from the first communication route to the second communication route, which is a bypass route (step S403). The communication route is changed by changing the path attribute of the communication device 311 to the communication device 316a instead of specifying the autonomous system through which the autonomous system AS11 reaches the target autonomous system AS15. To change the path attribute, for example, the communication device 311 performs processing to increase the WEIGHT attribute for the communication device 316a. By performing processing to increase the WEIGHT attribute, when the priority of the second communication route via the communication device 316a becomes higher than the priority of the first communication route via the communication device 312a, the first communication route to the second communication path.

Next, the location of the failure on the first communication path is specified (step S404). In the autonomous system AS12, the autonomous system AS13, and the autonomous system AS14 on the first communication route, it is specified which communication device has an abnormality. By issuing a ping command to each communication device on the first communication path in which communication performance has failed, the location of the failure can be identified. If an echo request can be sent to each communication device on the first communication path and an echo response can be received, the ping command has succeeded. On the other hand, if the echo response cannot be received, it can be determined that there is an abnormality in the communication device, and the location of the failure can be identified.

On the other hand, if there is a communication device that does not respond to ping on the first communication path, or if there is a half-broken communication device, the location of the failure cannot be identified. In such a case (step S404; NO), the process proceeds to step S405.

Note that in this embodiment, when detecting the occurrence of communication performance failure or communication performance deterioration and changing from the first communication path to the second communication path, the WEIGHT attribute of the communication device 311 for the communication device 316a is changed. It is carried out. The WEIGHT attribute is a value that is emphasized in the process of determining a communication route, but it is a value that raises the priority of route selection, and is not a value for specifying and communicating with an autonomous system to pass through. Therefore, it is not possible to communicate by specifying the autonomous system to pass through.

Therefore, even if processing is performed to increase the priority of the second communication route that passes through the communication device 316a, it may pass through the same autonomous system as the first communication route. For example, as shown in FIG. 6, in the first communication path, the target AS15 is reached from the autonomous system AS11 via the autonomous system AS12, the autonomous system AS13, and the autonomous system AS14. In the second communication path, the target AS is reached from autonomous system AS11 via autonomous system AS16, autonomous system AS13, and autonomous system AS14. Therefore, on the first communication route and the second communication route, the target AS15 is reached via the same autonomous system AS13 and AS14.

Therefore, even after the route is changed from the first communication route to the second communication route, the ratio of SYN packets and SYN/ACK packets on the first communication route is continued to be observed (step S405).

The ratio of SYN packets and SYN/ACK packets on the first communication path is continuously observed, and when normal SYN packets and SYN/ACK packets can be observed for a certain period of time, the process proceeds to step S407. Observation of normal SYN packets means that the ratio of SYN packets to SYN/ACK packets is one. Immediately after changing from the first communication path to the second communication path, the number of SYN packets on the first communication path is greatly reduced. Therefore, the accuracy of determining whether a failure has occurred in the first communication path is lowered. Further, even if the second communication path is returned to the first communication path, if an abnormality is detected in the first communication path immediately, the communication path must be changed to the second communication path again. Therefore, it is necessary to confirm that the ratio of SYN packets to SYN/ACK packets is 1 for a certain period of time on the first communication path. Here, the certain period of time is about 1 to 2 hours.

Next, on the first communication path, it is confirmed that there is no peer-down occurrence, communication device failure identification, and Internet failure reports from the outside (step S407). Occurrence of peer-down, identification of communication equipment failure, and external Internet failure are confirmed by a route control message (UPDATE message).

Finally, when it is confirmed that there is no report on the occurrence of peer down or the like on the first communication path, the process of returning from the second communication path to the first communication path is performed (step S408). The process of returning from the second communication path to the first communication path is the process of restoring the changed path attribute. For example, if the value of the WEIGHT attribute is changed, restore the value of the WEGHT attribute.

After that, the observation of the ratio of SYN packets and SYN/ACK packets on the first communication path is continued (step S401).

Again, when a change in the ratio of SYN packets and SYN/ACK packets is detected in the first communication path (step S402), the processing from step S403 to step S408 is performed.

In step S404, if the location of the failure has been identified in the first communication path (step S404; YES), recovery of the location of failure is confirmed (step S409). Restoration of the failure location can be confirmed by the UPDATE message. After that, the process of returning from the first communication path to the second communication path is performed (step S408).

In step S405, if the ratio of SYN packets and SYN/ACK packets cannot be observed, the process waits for a certain period of time (step S410). The fixed period is, for example, about 1 to 2 hours. After a certain period of time has elapsed, the process proceeds to step S407. After that, if there is no report of the occurrence of peer down, etc., it is determined that the problem was temporary, and the process of returning from the second communication path to the first communication path is performed (step S408).

After that, the ratio of SYN packets and SYN/ACK packets is observed again for a certain period of time (step S401), and if the ratio of SYN packets is within 1, communication on the first communication path is continued.

According to the above process, when the communication device 311 detects deterioration of communication performance in the first communication path, it is possible to immediately switch to the second communication path, which is a bypass path. In addition, when the deterioration of the communication performance is resolved in the first communication path, the second communication path, which is a detour path, can be returned to the original first communication path. By performing the above processing, stable communication can be provided.

Next, a block diagram of the communication path control system 200 according to this embodiment will be described with reference to FIG. A case where the communication path control system 200 according to the present embodiment is installed in the communication device 311 will be described.

Communication performance evaluation section 201 includes measurement section 211 , calculation section 212 , and determination section 213 .

In this embodiment, in the communication performance evaluation unit 201, the measurement unit 211 measures the number of SYN packets transmitted from the communication device 311 to the communication device 312a. Also, the number of SYN/ACK packets transmitted from the communication device 312a to the communication device 311 is counted.

The calculation unit 212 also calculates the ratio of the measured SYN packets and SYN/ACK packets. The calculated ratio of SYN packets is transmitted to the determination unit 213 .

A determination unit 213 detects a change in the ratio of SYN packets. When the ratio of SYN packets is 1, it is determined that there is no degradation in communication performance. On the other hand, when the ratio of SYN packets exceeds 1, it is determined that the communication performance is degraded.

When it is determined that the ratio of SYN packets has changed, the route control unit 202 and the communication unit 207 are notified that the communication performance of the communication device 311 has deteriorated.

When the route control unit 202 detects deterioration of communication performance, it performs processing to change the first communication route to the second communication route, which is a detour route. In this embodiment, processing is performed to change the communication path of the communication device 311 from the communication device 312a to the communication device 316a.

Further, when the communication unit 207 detects deterioration of the communication performance, the communication unit 207 identifies the location of the failure in the communication path. As a method of identifying the failure location, a ping command is executed for all communication devices on the communication path where the communication performance failure has occurred, and survival of the communication devices is confirmed. A ping command is a command that uses the ICMP protocol to request a response from a device connected via a network and to confirm the response to the request. If an echo request can be sent to a communication device on the communication path and an echo response can be received, it can be determined that there is no problem with the communication device. However, if the echo response cannot be received, it is assumed that there is an abnormality in the communication device, and the location of the fault can be specified. Here, if the location of the failure cannot be identified, the communication performance evaluation unit 201 observes the ratio of SYN packets in the first communication path.

The routing control message control unit 205 receives routing control messages related to BGP routing information in the network, such as occurrence of peer down, identification of a communication device with a failure on the first communication path, and Internet failure. When there is a change in BGP routing information in the network, it is sent to the routing table 206 .

The routing table 206 stores communication routes changed by the routing control unit 202 and routing information received by routing control messages (UPDATE messages).

According to the communication path control system according to the present embodiment, even if there is a communication device whose failure location is difficult to identify in the first communication path, it is detected as deterioration of communication performance or failure, and the detour path is immediately established. It is possible to change to the second communication path. In addition, after changing to the second communication path, if the deterioration of the communication performance or the failure in the first communication path is resolved, the second communication path can be returned to the original first communication path. This makes it possible to provide stable communication.

Appropriate additions, deletions, or design changes of components and processes by those skilled in the art based on the above-described embodiments are also included in the scope of the present invention as long as they are provided with the gist of the present invention.

100: network, 111a: communication device, 113a: communication device, 113b: communication device, 114a: communication device, 115a: communication device, 200: communication path control system, 201: communication performance evaluation unit, 202: path control unit, 203 : interface 204: packet control unit 205: route control message control unit 206: route table 211: measurement unit 212: calculation unit 213: determination unit 214: performance deterioration determination unit 221: path attribute change unit , 222: path calculation unit

Claims (4)

A rate of change in the number of SYN packets transmitted from the first communication device to the second communication device is measured every predetermined time, and the number of SYN packets at the predetermined time transmitted from the first communication device to the second communication device is measured. a communication performance evaluation unit that detects deterioration of the communication performance of the second communication device when the rate of change in the number exceeds a first threshold ;
a route control unit that changes a communication route of the first communication device from the second communication device to a third communication device when the communication performance evaluation unit detects deterioration of the communication performance of the second communication device; , has
The communication performance evaluation unit determines that the communication performance is temporarily degraded when the rate of change exceeds the first threshold for a predetermined number of times consecutively and then falls below the first threshold, The path control unit changes the communication path of the first communication device from the third communication device to the second communication device,
The communication performance evaluation unit determines that the number of times the rate of change exceeds the first threshold continues exceeding a predetermined number of times, or the rate of change exceeds a second threshold greater than the first threshold A communication path control system that determines permanent deterioration of communication performance when any of the following is satisfied . 3. When the communication performance evaluation unit determines that the communication performance is permanently degraded, the route control unit continues the communication route of the first communication device as the third communication device. 1. The communication path control system according to 1. 2. The communication route control system according to claim 1 , wherein said route control unit has a path attribute change unit that changes path attributes of said third communication device. 4. The communication routing system according to claim 3 , wherein said path attribute is a WEIGHT attribute.

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