JP6585133B2 - Communication path control system - Google Patents

Description

  The present invention relates to a communication path control system in a communication network system configured by connecting a plurality of autonomous systems (ASs) to each other.

  In general, a network is configured by mutually connecting AS, which is a collection of communication devices that operate under a common policy and the same environment. An identification number (AS number) is assigned to each AS connected to each other. Further, BGP (Border Gateway Protocol) is used as a route control protocol used between a plurality of ASs.

  A communication device that communicates with BGP establishes a one-to-one connection using TCP when communication is started. A transmission source communication device transmits a SYN packet, receives a SYN / ACK packet from a transmission destination communication device, and then transmits an ACK packet to establish a TCP connection.

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

  As a method corresponding to the occurrence of a communication failure in a network, a method of forming an alternative route and transmitting traffic has been proposed. Patent Document 1 discloses a method in which an autonomous system dedicated to a backup route is added as an additional network for redundancy, and packets of the existing network are transmitted using the additional network.

JP 2009-147735 A

  In the method corresponding to the occurrence of a communication failure described in Patent Document 1, the number of communication devices increases because an autonomous system dedicated to a backup route is added as an additional network. Further, if the communication function of the communication device is completely stopped, it can be switched 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 when the communication function of the communication device is not completely stopped, packets are continuously 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.

  Accordingly, an object of the present invention is to provide a communication path control system that can switch to a detour path when a communication performance failure or deterioration in communication performance 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, and a second communication device. And a path control unit that changes the communication path of the first communication device from the second communication device to the third communication device when the deterioration of the communication performance is detected.

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

  In the communication path control system, 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, the communication performance evaluation unit may further include a determination unit that determines whether the rate of change exceeds a predetermined threshold.

  The communication path control system may include a path attribute changing unit that changes a path attribute of the third communication device.

  In the 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 communication performance deterioration is permanent or temporary.

  In the above communication path control system, after changing the communication path of the first communication device from the second communication device to the third communication device, the communication performance evaluation unit determines that the deterioration of the communication performance has been recovered. Changing the communication path of one communication device from the third communication device to the second communication device may be included.

  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 to a second communication device of a first communication device, and a change in the ratio of SYN packets. And a path control unit that changes the communication path of the first communication device from the second communication device to the third communication device when the first communication device is detected.

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

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

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

  In the communication path control system, even if the communication path of the first communication device is changed from the second communication device to the third communication device, the SYN packet ratio of the first communication device to the second communication device is observed. Good.

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

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

It is a figure which shows the structural example of the network which concerns on 1st Embodiment. 1 is a configuration diagram illustrating a communication path control system according to a first embodiment. FIG. It is a graph showing the fluctuation | variation of the number of SYN packets in each time. It is a flowchart which shows the process of the communication path control system which concerns on 1st Embodiment. It is a block diagram which shows the communication path control system which concerns on 2nd Embodiment. It is a figure which shows the structural example of the network which concerns on 3rd Embodiment. It is a flowchart which shows the process of the communication path control system which concerns on 3rd Embodiment. It is a block diagram of the communication path control system which concerns on 3rd Embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. However, the present invention can be implemented in many different modes and should not be construed as being limited to the description of the embodiments exemplified below. The drawings may be schematically shown for clarity of explanation, but are merely examples and do not limit the interpretation of the present invention. Furthermore, the letters “first” and “second” attached to each element are convenient signs used to distinguish each element, and have more meaning unless otherwise specified. Absent. Note that in the drawings referred to in this embodiment, the same portions or portions having similar functions are denoted by the same reference symbols or similar symbols, and repeated description thereof may be omitted. In addition, part of the configuration may be omitted from the drawing. In addition, if it can be recognized by a person who has ordinary knowledge in the field to which the present invention belongs, no special explanation will be given.

(First embodiment)
A communication path control system according to the present embodiment will be described with reference to FIGS.

  FIG. 1 is a block diagram illustrating a configuration example of a network 100 according to the present embodiment. The network 100 according to the present embodiment is configured by autonomous systems AS1 to AS5. The autonomous systems AS1 to AS5 constituting the network are connected to each other by communication equipment corresponding to the entrance / exit. In the present embodiment, a 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 device 113a and the communication device 113b of the autonomous system AS3 is defined as a first communication route. Further, a case will be described in which the communication path 111a of the autonomous system AS1 uses the path for communicating with the communication apparatus 115a of the autonomous system AS5 via the communication apparatus 114a and the communication apparatus 114b of the autonomous system AS4 as the second communication path. .

  Each of the communication devices 111a, 111b, 113a to 113d, 115a, and 115b included in each of the autonomous systems AS1 to AS5 has a BGP communication function. In BGP, BGP used between different autonomous systems AS is called eBGP (external BGP), and BGP used in the autonomous system AS is called iBGP (internal BGP) to distinguish them. For example, eBGP is used for the communication device 111a of the autonomous system AS1 and the communication device 113a of the autonomous system AS3, and iBGP is used for the communication device 113a and the communication device 113b of the autonomous system AS3.

  In BGP, a one-to-one session using TCP is established when communication is started. For example, the communication device 111a as a transmission source transmits a SYN packet, receives a SYN / ACK packet from the communication device 113a as a transmission destination, and then transmits an ACK packet to establish a session.

  The SYN packet used for TCP always exists in a series of data communication in the normal state of the network. 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 at a stretch. In this specification and the like, the deterioration in communication performance includes not only a communication failure but also a decrease in communication speed.

  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 second communication device is evaluated by the communication performance evaluation unit. When the deterioration of the communication performance is detected, a process of changing the communication path of the first communication device from the second communication device to the third communication device is performed. That is, the communication device 111a performs a process for making the priority of the second communication path via the communication device 114a higher than that of the first communication path via 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 illustrated in FIG.

  FIG. 2 shows a configuration diagram of a communication path control system 200 according to the present embodiment. The communication path control system 200 according to the present embodiment can be mounted on a communication device such as a border edge router of an autonomous system that communicates using eBGP, for example. In the present embodiment, an example in which the communication path control system 200 is mounted on the communication device 111a illustrated in FIG. 1 will be described. Note that the communication path control system 200 according to the present embodiment only needs to be a communication device connected to another communication device by BGP. Therefore, the communication device 111b, 111b, 113a to 113d, 115a, 115b shown in FIG. It can also be installed in each. In addition to the communication path control system 200, the communication device 111a has an interface 203.

  The communication path control system 200 includes at least a communication performance evaluation unit 201 and a path control unit 202. The communication route control system 200 further includes a packet control unit 204, a route control message control unit 205, and a route table 206.

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

  The interface 203 establishes a connection with an adjacent communication device, and transmits and receives packets with the adjacent communication device. Also, the packet control unit 204 transmits a SYN packet, receives a SYN / ACK packet, and transmits an ACK packet to an adjacent communication device via the interface 203. SYN is a flag given to the first packet requesting establishment of a TCP connection. The ACK is a flag for confirming a response, and is a flag given to all packets other than the connection request. SYN / ACK is one in which 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. When the communication performance is deteriorated or troubled, a SYN / ACK packet may not be transmitted from an adjacent communication device.

  The route control message control unit 205 transmits and receives route control messages to and from adjacent communication devices via the interface 203. A communication device having a BGP function exchanges function information in a format called a message in order to establish a peer with a communication device in a different autonomous system AS. Examples of the route control message include an OPEN message, a KEEPALIVE message, and an UPDATE message.

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

  The route table 206 holds all route information such as the route acquired by the route control message or the updated route, and the route 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 is a graph showing the change 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 measured number of SYN packets is transmitted to the calculation unit 212.

  The calculation unit 212 calculates the rate of change of SYN packets for each time based on the measured number of SYN packets. 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 change rate of the SYN packet is transmitted to the determination unit 213.

  The determination unit 213 determines whether the change rate of the SYN packet exceeds a predetermined threshold value set in advance. If it is determined that the threshold value is not exceeded, the communication device 113a maintains communication as it is, assuming that the communication performance has not deteriorated.

  When it is determined that the rate of change of the SYN packet exceeds a predetermined threshold value set in advance, the path control unit 202 is notified that the communication performance of the communication device 113a has deteriorated.

  When the path control unit 202 detects a deterioration in communication performance, the path control unit 202 performs a process of changing from the first communication path to the second communication path (detour path). In the present embodiment, processing for changing the communication path of the communication device 111a from the communication device 113a to the communication device 114a is performed. That is, the communication device 111a performs a process for making the priority of the second communication path via the communication device 114a higher than that of the first communication path via 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, all communication routes are compared based on a path attribute, and an optimum route used for routing is selected. Therefore, when there are a plurality of communication paths for the same destination, the path attributes of all the communication paths are compared to determine the most suitable path for transferring traffic. In BGP, communication paths are compared in order based on the following priorities.

1. Routes that do not have an IGP route to the next hop are ignored.
2. A router having the WEIGHT attribute selects a route having the maximum WEIGHT attribute. (WEIGHT attribute is a path attribute unique to Cisco)
3. Select the route with the highest LOCAL_PREF attribute value.
4). Select the route with the shortest list length in the AS_PATH attribute.
5. Select the route with the lowest ORIGIN attribute type.
6). When there are multiple routes acquired from the same AS, priority is given to the route with the low MULTI_EXIT_DISC attribute.
7. Give priority to routes acquired by eBGP over iBGP.
8). Prefer the route closest to the next hop by IGP.
9. Priority is given to the route learned from the peer with the lowest router ID.

  Therefore, by changing path attributes such as the WEIGHT attribute, LOCAL_PREF attribute, AS_PATH attribute, and ORIGIN attribute, the communication path from the communication device 111a to the communication device 115a can be changed. Here, a case where the WEIGHT attribute is changed as the path attribute will be described.

  The WEIGHT attribute is a vendor-defined (Cisco original) path attribute that is 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 the values of other routes are “0”. For the WEIGHT attribute, a path with a large number is given priority.

  Here, in the communication device 111a, the value of the WEIGHT attribute for the communication device 114a is set to be larger than the value of the WEIGHT attribute for the communication device 113a. The WEIGHT value is used only in 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 changing unit 221 changes the BGP path attribute, the route calculating unit 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, the communication device 111a performs a process for making the priority of the second communication path via the communication device 114a higher than that of the first communication path via the communication device 113a. Thus, the changed communication path is stored in the path table 206.

  Next, processing executed by the communication path control system 200 according to the present embodiment will be described with reference to FIGS. FIG. 4 is a flowchart for processing of the communication path control system.

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

  Next, the calculated change rate of the SYN packet is transmitted to the determination unit 213 (step S403). Next, the determination unit 213 determines whether or not the rate of change has exceeded a predetermined threshold set in advance (step S404). When the rate of change does not exceed a predetermined threshold value set in advance (step S404; No), the process returns to step S401. If the rate of change exceeds a predetermined threshold set in advance (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 calculation unit 222 calculates the optimum route. As a result of the calculation, in the communication device 111a, when the priority of the second communication path via the communication device 316a is higher than the priority of the first communication path via the communication device 312a, the first communication device The communication path can be changed from the second communication device to the third communication device. That is, in the first communication device, the first communication path that passes through the second communication device can be changed to the second communication path that passes through the third communication device. The changed communication path is stored in the path table 206 (step S407).

  According to the communication path control system according to the present embodiment, it is possible to detect deterioration in the communication performance of the network. Thereby, when the deterioration of the 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) immediately passes through the communication device 114a. You can switch to As a result, the communication performance of the network can be stabilized.

(Second Embodiment)
In the first embodiment, the process of immediately switching to the second communication path, which is a detour path, is described when communication performance degradation is detected in the first communication path of the communication device 113a. In the present embodiment, when the communication performance of the communication device 113a is temporarily degraded, the first communication route that is the original communication route is changed to the second communication route that is a bypass route that passes through the communication device 114a. The case of returning to will be described with reference to FIGS.

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

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

  Here, the determination of the deterioration of the communication performance of the communication device 113a in the performance deterioration determination unit 214 is performed, for example, after the number of times the change rate of the SYN packet exceeds a predetermined threshold in the calculation unit 212 for a predetermined number of times. When the value falls below a predetermined threshold, it is determined that the communication performance is temporarily deteriorated. Alternatively, in the calculation unit 212, when the number of changes of the SYN packet exceeds the predetermined threshold and continues more than the predetermined number, the calculation unit 212 determines that the communication performance is permanently deteriorated. Alternatively, when the rate of change of the SYN packet increases explosively in the calculation unit 212, it is determined not as a temporary communication deterioration but as a permanent communication performance deterioration due to, for example, a Dos attack.

  The route control unit 202 changes the method of changing the communication route according to the result of the determination of the deterioration of the communication performance of the communication device 113a. When the rate of change of the SYN packet 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. Thereafter, the route calculation unit 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 first communication path via the communication device 113a can be changed to the second communication route via the communication device 114a. In this way, the changed communication path is stored in the path table 206.

  Thereafter, when the rate of change of the SYN packet falls below the predetermined threshold after the predetermined number of times that the predetermined threshold is exceeded, the performance deterioration determining unit 214 determines that the communication performance is temporarily deteriorated. The determination result is transmitted to the route control unit 202. In the path 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 value of the WEIGHT attribute for the communication device 113a of the communication device 111a and the value of the WEIGHT attribute for the communication device 114a are returned to the values before the detour route change. Thereby, it is possible to return from the detour route via the communication device 114a to the communication route via the communication device 113a. Also, when the communication path is restored, it is stored in the path table 206. 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 the present embodiment, it is determined whether the deterioration in communication performance is temporary or permanent. If the communication performance is temporarily deteriorated, the detour path can be used, and after the deterioration of the communication performance is recovered, the communication path can be returned to the original communication path. As a result, the communication performance of the network can be stabilized.

(Third embodiment)
In this embodiment, a communication path control system different from the previous embodiment will be described with reference to FIGS. In the present embodiment, a method of immediately changing to a second communication path that is a detour path when a communication performance degradation or a fault has occurred on the first communication path but the location where the fault has occurred cannot be identified will be described. In addition, a method for 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 illustrating a configuration example of the network 300 according to the present embodiment. FIG. 7 is a flowchart of the communication path control system according to the present embodiment. FIG. 8 is a block diagram of the communication path control system according to the present embodiment.

  As illustrated in FIG. 6, the network 300 according to the present embodiment includes an autonomous system AS11 to an autonomous system AS18. In FIG. 6, a communication path control system 200 according to the present invention is mounted on a communication device 311 of the autonomous system AS11.

  In the present embodiment, it is assumed that there are two communication paths from the autonomous system AS11 to the target autonomous system AS15. Of the two communication paths, the path from the autonomous system AS11 to the target autonomous system AS15 via the autonomous system AS12, autonomous system AS13, and autonomous system AS14 is defined as a first communication path. Further, a route from the autonomous system AS11 to the target autonomous system AS15 via the 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 in the first communication path, the new path is updated by the UPDATE message. Therefore, there is no deterioration or failure in communication performance. However, when there is a communication device that is in a half-broken state in the first communication path, the KEEPALIVE message and the UPDATE message can be exchanged, but the communication performance is deteriorated or failed. This is because even if a packet is transmitted to a half-broken communication device, it is discarded or broken, and communication cannot be performed normally.

  Since the communication device in a half-broken state exchanges communication control messages such as KEEPALIVE message and UPDATE message, it is difficult to identify the location where the failure has occurred. Also, when specifying the location where a failure has occurred, the location where the failure has occurred can be specified by issuing a ping command to the communication device. However, some communication devices are configured not to respond to ping. In some cases. In such a case, since the location where the failure has occurred cannot be identified, it may take time to resolve the failure. Therefore, it becomes impossible to provide stable communication.

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

  Processing executed by the communication path control system 200 according to the present embodiment will be described with reference to a 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 the present embodiment, the ratio of SYN packets in 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. Measuring the number of SYN packets and the number of SYN / ACK packets and calculating the SYN packet ratio is called observation of the SYN packet ratio. In the first communication path, there is no deterioration or failure in communication performance, and in a normal case, the ratio of SYN packets to SYN / ACK packets is 1.

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

  Next, when a change in the ratio between the SYN packet and the SYN / ACK packet is detected, a process of changing from the first communication path to the second communication path, which is a detour path, is performed (step S403). The change of the communication path is performed by changing the path attribute for the communication device 316a of the communication device 311 instead of designating the autonomous system through which the autonomous system AS11 reaches the target autonomous system AS15. For example, the communication device 311 performs a process of increasing the WEIGHT attribute for the communication device 316a. When the priority of the second communication path that passes through the communication device 316a is higher than the priority of the first communication path that passes through the communication device 312a by performing the process of increasing the WEIGHT attribute, the first communication path To the second communication path.

  Next, the failure location in the first communication path is specified (step S404). In the autonomous system AS12, autonomous system AS13, and autonomous system AS14 in the first route, it is specified which communication device has an abnormality. The failure location can be identified by issuing a ping command to each communication device on the first communication path where a failure has occurred in communication performance. If the echo request is transmitted to each communication device on the first communication path and the echo response is received, the ping command is successful. On the other hand, when the echo response cannot be received, it is known that the communication device has an abnormality, and therefore the failure occurrence location can be specified.

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

  In the present embodiment, when the occurrence of communication performance failure or communication performance deterioration is detected and the change is made from the first communication path to the second communication path, the change of the WEIGHT attribute for the communication apparatus 316a of the communication apparatus 311 is changed. It is carried out. The WEIGHT attribute is a value that is emphasized in the communication route determination process, but is a value that raises the priority of route selection, and is not a value for communicating by designating an autonomous system that passes through. Therefore, it is not possible to communicate by designating an autonomous system that passes through.

  Therefore, even when the process of increasing the priority of the second communication path that passes through the communication device 316a is performed, the process may pass through the same autonomous system as the first communication path. For example, as shown in FIG. 6, in the first communication path, the target AS 15 is reached from the autonomous system AS 11 via the autonomous system AS 12, the autonomous system AS 13, and the autonomous system AS 14. In the second communication path, the target AS is reached from the autonomous system AS11 via the autonomous system AS16, the autonomous system AS13, and the autonomous system AS14. Thus, the first communication path and the second communication path reach the target AS 15 via the same autonomous system AS 13 and autonomous system AS 14.

  Therefore, even after changing the route from the first communication route to the second communication route, the ratio of the SYN packet to the SYN / ACK packet in the first communication route is continuously observed (step S405).

  If the ratio between the SYN packet and the SYN / ACK packet in the first communication path is continuously observed, and the normal SYN packet and the SYN / ACK packet can be observed for a certain period, the process proceeds to step S407. Normal observation of a SYN packet is a state in which the ratio of a SYN packet to a SYN / ACK packet is 1. Note that immediately after changing from the first communication path to the second communication path, the number of SYN packets in the first communication path is significantly reduced. Therefore, the accuracy of determining whether a failure has occurred in the first communication path is reduced. Even if the second communication path is returned to the first communication path, if an abnormality is immediately detected in the first communication path, the second communication path must be changed again. Therefore, it is necessary to confirm that the ratio of the SYN packet to the SYN / ACK packet is 1 for a certain period in the first communication path. Here, the fixed time is about 1 to 2 hours.

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

  Finally, when it is confirmed that there is no report about the occurrence of peer down in the first communication path, a 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 a process of restoring the changed path attribute. For example, when the value of the WEIGHT attribute is changed, the value of the WEGHT attribute is restored.

  Thereafter, the observation of the ratio of the SYN packet to the SYN / ACK packet in the first communication path is continued (step S401).

  When the change in the ratio between the SYN packet and the SYN / ACK packet is detected again in the first communication path (step S402), the processing from step S403 to step S408 is performed.

  In step S404, when the failure location can be identified in the first communication path (step S404; YES), the recovery of the failure location is confirmed thereafter (step S409). The restoration of the fault occurrence location can be confirmed by the UPDATE message. Thereafter, a process of returning from the first communication path to the second communication path is performed (step S408).

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

  Thereafter, the ratio of the SYN packet to the SYN / ACK packet is again observed for a certain period (step S401). If the ratio of the SYN packet is within 1, communication on the first communication path is continued.

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

  Next, a block diagram of the communication path control system 200 according to the present embodiment will be described with reference to FIG. Note that a case where the communication path control system 200 according to the present embodiment is mounted on the communication device 311 will be described.

  The communication performance evaluation unit 201 includes a measurement unit 211, a calculation unit 212, and a determination unit 213.

  In the present 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. Further, the number of SYN / ACK packets transmitted from the communication device 312a to the communication device 311 is measured.

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

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

  When it is determined that there is a change in the SYN packet ratio, the communication performance of the communication device 311 is deteriorated, and the path control unit 202 and the communication unit 207 are notified.

  When the path control unit 202 detects deterioration in communication performance, the path control unit 202 performs processing to change from the first communication path to the second communication path that is a bypass path. In the present embodiment, processing for changing the communication path of the communication device 311 from the communication device 312a to the communication device 316a is performed.

  In addition, when the communication unit 207 detects deterioration in communication performance, the communication unit 207 identifies a location where a failure has occurred in the communication path. As a method for identifying the location where a failure has occurred, a ping command is executed for all communication devices on the communication path in which a failure has occurred in communication performance, and the existence of the communication device is confirmed. The ping command is a command that uses the ICMP protocol to make a response request to a device connected via a network and confirm a response to the request. If the echo request can be transmitted to the communication device on the communication path and the echo response can be received, it is understood that there is no abnormality in the communication device. However, when the echo response cannot be received, it is possible to identify the failure occurrence location by assuming that the communication device has an abnormality. Here, when the failure occurrence location cannot be identified, the communication performance evaluation unit 201 observes the ratio of SYN packets in the first communication path.

  The route control message control unit 205 receives a route control message related to BGP route information in the network, such as occurrence of a peer down, identification of a communication device in which a failure has occurred on the first communication route, or an Internet failure. When there is a change in BGP route information in the network, it is sent to the route table 206.

  The route table 206 stores the communication route changed by the route control unit 202 and the route information received by the route control message (UPDATE message).

  According to the communication path control system according to the present embodiment, even if there is a communication device in which the location of the failure is difficult to identify in the first communication path, it is detected as a deterioration in communication performance or a failure and is immediately a detour path. The second communication path can be changed. In addition, after the change to the second communication path, when the deterioration or failure of the communication performance in the first communication path is resolved, the original communication path can be returned from the second communication path. Thereby, stable communication can be provided.

  Based on the above-described embodiments, those in which those skilled in the art appropriately added, deleted, or changed the design of components and processes are also included in the scope of the present invention as long as they have 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 route control system, 201: Communication performance evaluation unit, 202: Route 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 degradation determination unit, 221: path attribute change unit 222: Route calculation unit

Claims (8)

A communication performance evaluation unit that evaluates the communication performance of the network based on the number of SYN packets transmitted from the first communication device to the second communication device;
A path control unit that changes a communication path of the first communication device from the second communication device to a third communication device when the communication performance evaluation unit detects a deterioration in communication performance of the second communication device; A communication path control system.   The communication path control system according to claim 1, wherein the communication performance evaluation unit further includes a measurement unit that measures the number of the SYN packets.   The communication path control system according to claim 1, wherein the communication performance evaluation unit further includes a calculation unit that calculates a rate of change based on the number of SYN packets.   The communication path control system according to claim 3, wherein the communication performance evaluation unit further includes a determination unit that determines whether the rate of change exceeds a predetermined threshold.   The communication path control system according to any one of claims 1 to 4, wherein the path control unit includes a path attribute change unit that changes a path attribute of the third communication device.   The communication path control system according to claim 5, wherein the path attribute is a WEIGHT attribute. The communication performance evaluation unit further includes a performance deterioration determination unit that evaluates whether the deterioration of the communication performance is permanent or temporary based on a change rate of the SYN packet. The communication path control system according to claim 1. After changing the communication path of the first communication device from the second communication device to the third communication device,
The communication performance evaluation unit changes the communication path of the first communication device from the third communication device to the second communication device when it is determined that the deterioration of the communication performance has been recovered. The communication path control system described in 1.

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