JP3725146B2 - Communication network management apparatus and communication network communication confirmation test method - Google Patents

Description

  An object of the present invention is to identify a fault location and search for a detour path when a communication network failure occurs in a communication network that performs communication by forming an IP-VPN (Virtual Private Network) on an IP (Internet Protocol) network. The present invention relates to a communication network management apparatus that performs a communication network communication confirmation test and a communication network communication confirmation test method.

2. Description of the Related Art A VPN is a network for establishing and communicating with a virtual communication path that can be recognized only by a specific user in a global communication network such as the Internet or a public network (hereinafter also simply referred to as a network). By using this VPN, it is possible to realize security like a network constructed with a dedicated line at a low cost. In particular, an IP-VPN that uses a dedicated network provided by a telecommunications carrier has attracted widespread attention as a network for companies and telecommunications carriers because of its high closedness. As a method for realizing IP-VPN, there is MPLS (Multi Protocol Label Switching).

  In a network in which IP-VPN is used, it is common to achieve high reliability of VPN connection using a redundancy technique or a rerouting (routing relearning) technique. For this reason, even if a failure occurs in a device on the VPN route, the normal user packet is routed to a different route. However, even with various redundancy techniques and rerouting techniques, an appropriate path change is not performed due to a certain type of failure or a setting error, and an event occurs in which the VPN is disconnected.

  Examples of failures that do not change the route include when a failure occurs in the switching process, and a hardware failure called “mass failure”. “Mass failure” is a type of failure such as SNMP (Simple Network Management Protocol) -trap that cannot be notified, and it cannot recognize its own failure, so switching to a detour is not performed. It is.

In addition, as a setting information error, an appropriate route cannot be changed at the time of failure due to a design error or a setting error of a cost value when operating a routing protocol such as OSPF (Open Shortest Path First) or IGRP (Interior Gateway Routing Protocol). Such an event can be considered.
As a conventional method for investigating and grasping the network state when such a failure occurs, there is a method using a ping command or a traceroute command. This command investigates communication in a specified section on the network and identifies the fault location from the result.

  More specifically, the ping command is the most basic command used for checking whether an IP packet has reached a communication destination and whether it can be reached by IP in a TCP / IP network. If a ping command is executed and a response is returned, it is found that the partner node exists and the network software (at least at the IP layer level) is active.

  The traceroute command is a command for tracing / inspecting the route of the IP network. If the IP address or host name is given to the traceroute argument and the IP router is started, the IP router address until the node is reached and the elapsed time are three. Displayed in minutes. As a result, the number of hops that are the number of routers that have passed through the network up to the partner node, route information, delay time in each part, and the like can be known.

Moreover, there exists a thing of patent document 1 as this kind of conventional communication confirmation test methods, for example.
The content of Patent Document 1 is that a pair of measuring devices are connected to a network, a digital communication line is formed between the measuring devices via the network, and a predetermined pattern is established between the measuring devices via the communication line. It is possible to identify normality or failure of the communication line by transmitting and receiving signals and comparing them.
JP-A-8-191302

However, the conventional communication network communication confirmation test method has the following problems.
In a complex network consisting of many IP devices such as routers and switches, determine the appropriate test location (which section should be checked for communication) and analyze the test results to identify the faulty device Therefore, it was not easy to identify by analysis, and it was largely based on the experience and skills of the workers. In addition, since much time is required for investigation and analysis, it is difficult to grasp the failure status of the entire network in real time. As a result, even if there is an alternative route that can be bypassed, it is not possible to grasp it immediately, and this causes the failure time to be prolonged.

In the above-mentioned Patent Document 1, since a test must be performed by connecting measuring devices to both ends of the transmission line to be measured in the network, when performing a test of the entire network, selection of an appropriate test location and analysis of the test results are not possible. It was not easy, and it was difficult to grasp the failure status of the entire network in real time.
The present invention has been made in view of such a problem. In a communication network in which an IP-VPN is formed, when a failure such as a VPN being disconnected due to a device failure or a setting information error occurs, An object of the present invention is to provide a communication network management device and a communication network communication confirmation test method capable of quickly detecting a failure of the entire communication network and determining a detour route that can bypass this failure and reach a target end point. It is said.

  In order to achieve the above object, a communication network management apparatus according to claim 1 of the present invention performs a communication confirmation test of a communication network in which a VPN for transmitting a packet is constructed using encryption processing. And a first designation means for designating a start point and an end point device among a number of devices constituting the communication network, and a test packet from the start point designated by the first designation means to the end point. The first confirmation means for confirming the first route from the start point to the communication end point, which is an end point where communication is possible, by receiving this, and outside the first route confirmed by the first confirmation means A second designation means for designating the number of hops in the shortest route from the devices on the first route, and on the first route confirmed by the first confirmation means; Starting from the equipment Then, the test packet is transmitted from the starting point to the device adjacent to the starting point outside the first route, and the device receiving the test packet is set as the starting point, and the testing packet is transmitted from the starting point to the device adjacent to the starting point. The second route from the starting point on the first route to the communication end point outside the first route is confirmed by repeating the process of transmitting the number of hops designated by the second designation means. And a detecting means for comparing the first and second routes confirmed by the first and second confirming means and the route of the entire communication network to detect a fault location. It is characterized by.

  According to this configuration, the start point and the end point are specified from among a large number of devices in the communication network, and if the number of hops is specified, the first route from the device on the first route from the start point to the end point with which communication is possible. The communication confirmation test by the route search from the neighboring device to other neighboring devices is repeated sequentially and comprehensively, so the failure status of the entire communication network including the periphery between the specified start point and end point Can be confirmed automatically.

According to claim 2 of the present invention, the communication network management device according to claim 1 can reach the end point from the start point specified by the first specifying unit by bypassing the failure point detected by the detecting unit. It is characterized by further comprising a determination means for determining a detour route.
According to this configuration, when a failure occurs in the route between the specified start point and end point among many devices in the communication network, the detour route that bypasses the failure and reaches the end point is automatically determined. be able to.

According to claim 3 of the present invention, the communication network management device according to claim 1 or 2 displays an image of at least one of the fault location detected by the detection means and the detour path determined by the determination means. It is characterized by further comprising display means for displaying on the communication network.
According to this configuration, the failure location in the communication network and the detour route of the failure are displayed on the communication network, so that the administrator can easily recognize the failure location and the detour route.

  A communication network communication confirmation test method according to claim 4 of the present invention is a communication network communication confirmation test method for performing a communication confirmation test of a communication network in which a VPN for transmitting a packet is constructed using encryption processing. A first step of designating a start point and an end point device from among a large number of devices constituting the communication network, and transmitting a test packet from the start point designated by the first step to the end point. And a second step of confirming a first route from the start point to a communication end point that is a communication end point, and a first step that is outside the first route confirmed in the first step. A third step of designating the number of hops indicating the number of the shortest route from the device on the first route, and the device on the first route confirmed in the first step as a starting point Then, the test packet is transmitted from the starting point to the device adjacent to the starting point outside the first route, and the device receiving the test packet is set as the starting point, and the testing packet is transmitted from the starting point to the device adjacent to the starting point. To confirm the second route from the starting point on the first route to the communication end point outside the first route by repeating the number of hops specified in the third step. The fifth step of comparing the first and second routes confirmed in the second and fourth steps with the route of the entire communication network to detect a fault location, and the fifth step A sixth step of detouring the fault location detected in the step and determining a detour route that can reach the end point from the start point specified in the first step; and the fault location detected in the fifth step; Above 6 at least one of the determined detour path in step, and characterized in that it comprises a seventh step of displaying on the image display the on communication networks.

  According to this method, when the start point and the end point are specified from among a large number of devices in the communication network, and the number of hops is specified, the first route from the device on the first route from the start point to the end point with which communication is possible. The communication confirmation test by the route search from the neighboring device to other neighboring devices is repeated sequentially and comprehensively, so the failure status of the entire communication network including the periphery between the specified start point and end point Can be confirmed automatically. Further, when a failure occurs in the route between the designated start point and end point, a detour route that bypasses the failure and reaches the end point can be automatically determined. Furthermore, since the failure location and the detour route are displayed on the communication network, the administrator can easily recognize the failure location and the detour route.

  As described above, according to the present invention, in the communication network in which the IP-VPN is formed, when a failure such as a VPN disconnection due to a device failure or a setting information error occurs, the entire communication network can be quickly There is an effect that it is possible to detect a failure and determine a detour route that can bypass the failure and reach the target end point.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a communication network system in which an IP-VPN is formed while using a communication network management apparatus according to an embodiment of the present invention.
A communication network system 10 shown in FIG. 1 further includes IP devices 12-1 to 12-1 in an IP network (also simply referred to as a network) configured by connecting a large number of IP devices 12-1 to 12-17 with each other by wire or wirelessly. An IP-VPN is constructed between 12-17, and a communication network management device 14 for managing all the IP devices 12-1 to 12-17 is connected to each IP device 12-1 to 12-17. Configured.

  A feature of the present embodiment is that the communication network management device 14 acquires route information from a start point specified on the network to an end point, or from the specified start point to the end point, from the start point to a communicable end point. A section by designating an adjacent route from an IP device on the route from which the information is acquired to an adjacent IP device outside the route, and further designating an adjacent route from the adjacent IP device to another adjacent IP device It is possible to confirm the failure status of the entire network including the periphery of the specified section by repeating the comprehensive communication confirmation test sequentially and exhaustively.

  As illustrated in FIG. 2, the communication network management device 14 includes a start point / end point designation unit 21, a hop number designation unit 23, a trace route communication confirmation unit 25, an adjacent route communication confirmation unit 27, and a test execution route creation unit 29. A communication network DB (database) 31, a test result management unit 33, a test history file DB 35, a fault location detection unit 34, a detour route determination unit 36, and a display unit 37.

The start point / end point designation unit 21 designates a test target section by designating an IP device as a start point and an IP device as an end point on the network. For example, as shown in FIG. 1, the IP device 12-1 is designated as the start point and the IP device 12-5 is designated as the end point.
The trace route communication confirmation unit 25 obtains route information between the start point and the end point by issuing a traceroute command from the start point to the end point, and checks the communication state between the start point and the end point from this route information. Hereinafter, this confirmation test is also referred to as a trace route test. In this trace route test, when there is no trace route between the start point and the end point, or when there is no communication between the start point and the end point, the trace route to the IP device whose communication is confirmed is confirmed.

Thereafter, when the trace route communication confirmation unit 25 issues a traceroute command from one IP device to the other IP device, the trace route communication confirmation unit 25 performs telnet connection to the one IP device and the other IP device. This means issuing a traceroute command to the device. This is the same when the adjacent route communication confirmation unit 27 described later issues a ping command.
The telnet connection is a line connection by a protocol and client software for logging in to another computer connected by TCP / IP by remote access from an external machine.

  The hop number designating unit 23 designates the hop number indicating the number of IP devices that pass through the adjacent route during the communication confirmation test. However, the larger the number of hops, the more the network status can be grasped. On the other hand, since the network and the communication network management device 14 are loaded, the processing capacity and the scale of the network and the communication network management device 14 are increased. Specify the necessary and sufficient value.

The communication network DB 31 is a database that centrally manages information on all IP network configurations related to the IP network such as connection information of the IP devices 12-1 to 12-17 and IP-VPN construction information. The communication network DB 31 is assumed to exist in the communication network management apparatus 14 in the present embodiment, but may be outside the communication network management apparatus 14. The IP network configuration information includes adjacent information indicating which IP device is adjacent in each of the IP devices 12-1 to 12-17.
However, when it is difficult to manage the communication network DB 31 such as when the network configuration is frequently changed, a well-known method of holding adjacent information in each IP device 12-1 to 12-17 itself is used. You can also

The test execution route creation unit 29 creates a test execution route according to the result of the trace route test, the IP network configuration information held in the communication network DB 31, and the number of hops designated by the hop number designation unit 23.
In this case, if there is no failure between the start point and the end point in the trace route test, the adjacent information of the IP device adjacent to the IP device on the trace route between the start point and the end point is included in the IP network configuration information according to the specified number of hops. Acquired from.

  When the number of hops is 1, for example, the first IP devices 12-6, 12- outside the trace route from the IP devices 12-1 to 12-5 on the trace route from the start point to the end point shown in FIG. The adjacent information of 7, 12-8, 12-9 is acquired and a test execution route is created. If the number of hops is 2, further test is performed by acquiring adjacent information of the second IP devices 12-10, 12-11, and 12-12 outside the trace route from the IP devices 12-1 to 12-5. Create an execution route. Thereafter, it is created in the same manner as the number of hops increases.

When the number of hops is 0, adjacency information is not acquired, and only the trace route becomes the test execution route.
On the other hand, if there is a failure between the start point and the end point, for example, as indicated by reference numeral 41 in FIGS. 4 and 5, the IP on the trace route from the start point IP device 12-1 to the reachable end point IP device 12-3. Neighbor information of an IP device adjacent to the device is acquired from the IP network configuration information according to the specified number of hops.

The adjacent route communication confirmation unit 27 starts from an IP device on the trace route, issues a ping command from this start point to an adjacent IP device outside the trace route, and starts from the IP device that is the end point of the ping command. A ping test is performed in which the process of issuing a ping command from the starting IP device to the adjacent IP device of the IP device is repeated for the number of specified hops. If the specified hop count is 0, the ping test is not performed.
If such a ping test is performed by specifying a sufficient number of hops with respect to the network size, a ping command to the outside of the trace route can reach the IP device at the final point outside the trace route.

The test result management unit 33 registers the test result information of the trace route confirmed by the trace route communication confirmation unit 25 and the test result information of the adjacent route confirmed by the adjacent route communication confirmation unit 27 in the test history file DB 35. In addition, a management process for reading out the registered test result information is performed.
The failure point detection unit 34 compares and analyzes the IP network configuration information of the communication network DB 31 and the test result information of the trace route and the adjacent route managed by the test result management unit 33, for example, FIG. As shown by the reference numeral 41 in FIG. Although the figure shows a state where the fault location 41 is detected only on the trace route, here, the fault location on the adjacent route is also detected.

The detour route determination unit 36 detours the failure point 41 detected by the failure point detection unit 34 and determines a detour route that reaches from the start point to the end point of the trace route.
The display unit 37 displays IP network configuration information, test result information, a failure location, a detour route, and the like according to an administrator's key operation command.
Next, the operation of the communication network communication confirmation test process by the communication network management apparatus 14 having such a configuration will be described with reference to the flowchart shown in FIG.

In step S1, it is assumed that the start point and end point of the trace route test and the number of hops are designated by the key operation of the administrator. The start point / end point designation unit 21 that performs processing in accordance with the designation operation designates the IP device 12-1 as the start point on the network and the IP device 12-5 as the end point shown in FIG.
After this designation, in step S2, the traceroute communication confirmation unit 25 issues a traceroute command from the starting IP device 12-1 to the ending IP device 12-5, thereby acquiring the route information between the starting point and the ending point. From this route information, the communication state of the trace route between the start point and the end point is confirmed.

  Thereafter, in step S3, the test execution route creation unit 29 determines whether or not there is a failure in the trace route between the start point and the end point as a result of the trace route test. As a result, if there is no failure, in step S4, a test execution route is created according to the IP network configuration information held in the communication network DB 31 and the hop number specified by the hop number specifying unit 23.

  For example, if the number of hops is specified as 1 in step S1 and the trace route test result is between the start IP device 12-1 and the end IP device 12-5, there is no failure. 3, the first IP devices 12-6, 12-7, 12-8, and 12 outside the trace route from the IP devices 12-1 to 12-5 on the trace route from the start point to the end point. Up to -9 is the test execution route.

On the other hand, if there is a failure between the start point and the end point, for example, as indicated by reference numeral 41 in FIG. 4, in step S5, the trace is performed from the IP devices 12-1 to 12-3 on the trace route from the start point to the end point where communication is possible. The first IP devices 12-6 to 12-8 outside the route are used as a test execution route.
In addition, when the number of hops is specified as 3 in step S1, if there is a failure between the start point and the end point, for example, as indicated by reference numeral 41 in FIG. The test execution route is from the upper IP devices 12-1 to 12-3 to the third IP devices 12-6 to 12-16 outside the trace route.
In the following description, it is assumed that the number of hops is 3, and a failure indicated by reference numeral 41 in FIG.

Next, in step S <b> 6, the adjacent route communication confirmation unit 27 executes the communication confirmation test for the test execution route created earlier. In this case, since the designated number of hops is 3, a ping command is issued from the IP devices 12-1 to 12-3 on the trace route to the third adjacent IP devices 12-13 to 12-16 outside the trace route. .
In this issue order, first, the IP devices 12-1 to 12-3 on the trace route are set as starting points, and a ping command is issued from these starting points to the adjacent IP devices 12-6 to 12-8 outside the trace route. . Next, IP devices 12-6 to 12-8 that are the end points of the ping command are set as starting points, and a ping command is sent to the IP devices 12-10 to 12-12 and 12-4 adjacent to these starting points. The IP devices 12-10 to 12-12 and 12-4 that are issued and are the end points of the ping command are set as starting points, and the IP devices 12-13 to 12-16 adjacent to these starting points are pinged. A command is issued.

As a result, route information from the IP devices 12-1 to 12-3 on the trace route to the third adjacent IP devices 12-5, 12-9, 12-13 to 12-16 outside the trace route is acquired. The communication status of the test execution route is confirmed from this route information.
Thereafter, in step S7, the test result management unit 33 registers the test result information of the test execution route including the trace route and the adjacent route in the test history file DB 35.

In step S8, the failure location detection unit 34 compares and analyzes the IP network configuration information of the communication network DB 31 and the test result information managed by the test result management unit 33, thereby analyzing the IP network. The upper failure point 41 is detected.
In step S9, the bypass route determination unit 36 determines a bypass route that bypasses the failure point 41 and reaches from the IP device 12-1 at the start point of the trace route to the IP device 12-5 at the end point. As shown in FIG. 5, the route connecting the IP devices 12-3, 12-7 and 12-4 bypassing the failure location 41, or the IP devices 12-3, 12-8 bypassing the failure location 41, 12-4 is a path for connecting 12-4.
The detected detour route is displayed on the display unit 37 together with the fault location 41 and the like in step S10.

  As described above, according to the communication network management apparatus 14 of the present embodiment, the start point / end point designation unit 21 designates the start point and end point IP devices from among a large number of IP devices constituting the IP network. The traceroute communication confirmation unit 25 transmits a traceroute command from the designated start point to the end point, and receives this to confirm the trace route from the start point to the communication end point that can be communicated. The hop number designating unit 23 designates the hop number indicating the number of the IP device that is outside the confirmed trace route and is the shortest route from the IP device on the trace route. The adjacent route communication confirmation unit 27 uses the IP device on the trace route confirmed by the trace route communication confirmation unit 25 as a starting point, and transmits a ping command from this starting point to the IP device adjacent to the starting point outside the trace route. Starting from the IP device that has received the ping command, and repeating the process of transmitting the ping command from this starting point to the IP device adjacent to the starting point, the starting point on the trace route Check the adjacent route from to the communication end point outside the trace route.

The failure location detecting unit 34 detects the failure location by comparing the confirmed trace route and adjacent route with the route of the entire IP network.
As a result, the start point and the end point are specified from among a large number of IP devices of the IP network, and if the number of hops is specified, the IP device on the trace route from the start point to the reachable end point is adjacent to the outside of the trace route. Since the communication confirmation test by route search from the IP device and from this adjacent IP device to other adjacent IP devices is repeated comprehensively, the failure status of the entire IP network including the periphery between the specified start point and end point is automatically detected. Can be confirmed.

Further, the detour route determination unit 36 detours the failure point detected by the failure point detection unit 34 and determines a detour route that can reach from the start point specified by the start point / end point specification unit 21 to the end point.
As a result, when a failure occurs in the route between the specified start point and end point among a large number of IP devices in the IP network, a detour route that bypasses the failure and reaches the end point can be automatically determined. it can.

Further, the display unit 37 displays at least one of the fault location detected by the fault location detection unit 34 and the detour route determined by the detour route determination unit 36 on the image-displayed IP network.
As a result, the failure location in the IP network and the detour route of the failure are displayed on the IP network, so that the administrator can easily recognize the failure location and the detour route.

In addition, the test execution route creation unit 29 may be eliminated from the communication network management device 14 and the adjacent route communication confirmation unit 27 may perform the following processing.
That is, the adjacent route communication confirmation unit 27 sets the trace route between the start point and the end point if there is no failure between the start point and the end point in the trace route test in the trace route communication check unit 25, and can communicate from the start point if there is a failure. Trace route to the end point. The adjacent information of the IP device adjacent to the IP device on the trace route thus determined outside the trace route is acquired from the IP network configuration information, and the adjacent IP device specified from the acquired adjacent information The ping command is issued starting from the IP device on the trace route.

The IP device that is the end point of the ping command is used as a starting point, the neighboring information of the neighboring IP device that is the starting point is acquired from the IP network configuration information, the neighboring IP device is identified, and the neighboring IP device is identified from the starting point. Issue a ping command. This process is repeated for the specified number of hops.
The same effect as described above can be obtained by performing the ping test in this way.

It is a figure which shows the structure of the communication network system in which the communication network management apparatus which concerns on embodiment of this invention was used, and IP-VPN was formed. It is a block diagram which shows the structure of the communication network management apparatus which concerns on the said embodiment. It is a figure which shows the structure of the communication network system showing the example of an adjacent route in case the number of hops is 1 in the communication network management apparatus which concerns on the said embodiment. It is a figure which shows the structure of the communication network system showing the example which a failure generate | occur | produced between the start point and the end point when the number of hops is 1 in the communication network management apparatus which concerns on the said embodiment. It is a figure which shows the structure of the communication network system showing the example which a failure generate | occur | produced between the start point and the end point in case the number of hops is 3 in the communication network management apparatus which concerns on the said embodiment. It is a flowchart for demonstrating operation | movement of the communication network communication confirmation test process by the communication network management apparatus which concerns on the said embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Communication network system 12-1-12-17 IP apparatus 14 Communication network management apparatus 21 Start point end point designation | designated part 23 Hop number designation | designated part 25 Trace route communication confirmation part 27 Adjacent route communication confirmation part 29 Test execution route creation part 31 Communication network DB (Database)
33 Test result management unit 34 Fault location detection unit 35 Test history file DB
36 Detour Route Determination Unit 37 Display Unit

Claims (4)

In a communication network management apparatus that performs a communication confirmation test of a communication network in which a VPN for transmitting packets using encryption processing is constructed,
First designation means for designating a start point and an end point device from among a large number of devices constituting the communication network;
A test packet is transmitted from the start point designated by the first designation means to the end point, and by receiving this, a first route from the start point to a communication end point that is a communication end point is confirmed. Confirmation means,
Second designation means for designating the number of hops that are outside the first route confirmed by the first confirmation means and that indicate the number of devices on the shortest route from the devices on the first route; ,
A device on the first route confirmed by the first confirmation means is set as a starting point, a test packet is transmitted from the starting point to a device adjacent to the starting point outside the first route, and the test packet is received. From the starting point on the first route, by repeating the process of transmitting a test packet from this starting point to a device adjacent to the starting point, the number of hops specified by the second specifying means Second confirmation means for confirming the second route to the communication end point outside the first route;
A communication network comprising: first and second paths confirmed by the first and second confirmation means; and a detection means for detecting a failure location by comparing the entire path of the communication network. Management device. 2. The apparatus according to claim 1, further comprising: a determination unit that detours the failure point detected by the detection unit and determines a detour route that can reach the end point from the start point specified by the first specification unit. The communication network management device described. 3. A display unit for displaying at least one of a fault location detected by the detection unit and a bypass route determined by the determination unit on a communication network displaying an image. A communication network management device according to claim 1. In a communication network communication confirmation test method for performing a communication confirmation test of a communication network in which a VPN for transmitting packets using encryption processing is constructed,
A first step of designating a start point and an end point device from among a number of devices constituting the communication network;
A test packet is transmitted from the start point designated in the first step to the end point, and a first packet from the start point to the communication end point that can be communicated is confirmed by receiving the second test packet. Steps,
A third step of designating a number of hops indicating the number of devices on the shortest route from the devices on the first route outside the first route confirmed in the first step;
The device on the first route confirmed in the first step is set as a starting point, a test packet is transmitted from the starting point to a device adjacent to the starting point outside the first route, and the test packet is received. By repeating the process of transmitting a test packet from the starting point to a device adjacent to the starting point from the starting point, by repeating the number of hops specified in the third step, the starting point on the first route A fourth step of confirming the second route to the communication end point outside the route of 1;
A fifth step of detecting a failure point by comparing the first and second routes confirmed in the second and fourth steps with the route of the entire communication network;
A sixth step of detouring the failure point detected in the fifth step and determining a detour route that can reach the end point from the start point specified in the first step;
A communication system comprising: a seventh step of displaying at least one of the fault location detected in the fifth step and the detour path determined in the sixth step on the image-displayed communication network. Network communication confirmation test method.

Images