JPH11220487A - Simulation test device for transmission line supervisory device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simulate a network without the preparation of various transmission lines for test, various terminals for test, and various repeaters. SOLUTION: The simulation test device receives check data from a monitor 1 that monitors a transmission line 5 and sends check data to actual devices 3, 4 connecting to the transfer line 5 or a simulation device 15 that represents the actual devices 3, 4 in a simulating way. Then a destination address A addressed to an actual device, e.g. 3 in the check data is converted into an address of the simulating device 1, 5, and the destination address before address conversion is included in the check data and the data are sent to the simulating terminal, 2 and a sender address of reply data from the simulating device 15 is converted into the destination address before the conversion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simulated test apparatus for a network, and more particularly to a simulated test apparatus for a plurality of LANs.
In a large-scale network to which a WAN device or the like is connected, it is possible to use a pseudo device without preparing a device that is actually connected to a transmission path, and to verify whether or not the monitoring device can be correctly monitored. It relates to a simulated test device. Monitoring devices that monitor LAN / WAN devices are:
It is necessary to verify whether the configuration of the system is correctly grasped or whether fault information can be correctly detected when a fault occurs in an actual device. Or, create the system configuration information by absorbing the connection information from the actual device,
Alternatively, it is necessary to verify tests of various network OSs. The present invention facilitates such verification by simulating various test transmission lines, various test terminal devices, and various relay devices without physically installing or configuring them in a network. It is possible to do it.

[0002]

2. Description of the Related Art Conventionally, in a verification for evaluating whether a LAN monitoring device can be monitored correctly, an actual transmission line, a relay device, and a terminal device are prepared for verification, and verification data is stored in those actual devices. , Device information of devices connected to the network, information of devices under test such as terminal devices, fault management information for managing faults of terminal devices,
Performance management information such as the transmission speed of the modem, account management information such as the number of packet data passed or discarded through the relay device, and security management information are collected.

[0003]

Conventionally, since verification data was transmitted to an actual device to absorb information, it was necessary to actually prepare a relay device, a terminal device, and the like for verification. However, due to the large scale of the network,
Physical configuration of the network required for verification (device configuration, etc.)
It is difficult to prepare.

[0004] Bands of various transmission lines (bands such as the communication speed of a modem), data transmission delay and traffic fluctuations are also important for verification, but various devices must be prepared for such tests. Is also impossible. For example, in the test of the retransmission (retry) function for the quality fluctuation of the network transmission line, it is necessary to test on transmission lines of different qualities, but the test is performed on the transmission line with a constant loss packet occurrence rate. Even if such a device is prepared, it is difficult to perform a test in a single time.

[0005] It is an object of the present invention to provide a test apparatus that can easily perform such a test and verification of a transmission line by a LAN monitoring apparatus.

[0006]

According to the present invention, verification data is received from a monitoring device that monitors a transmission line, and the verification data is transmitted to an actual device connected to the transmission line or a pseudo device that simulates the actual device. A pseudo test device for transmitting,
The destination address A of the verification data addressed to the actual device is converted to the address of the pseudo device, the destination address before the address conversion is included in the verification data and transmitted to the pseudo terminal device, and the return data from the pseudo device is transmitted. The source address is converted to the destination address A before the conversion.

In FIG. 1, reference numeral 1 denotes a monitoring device for monitoring devices connected to a transmission line 5, such as a device A (3) and a device B (4).

[0008] Reference numeral 2 denotes a pseudo test apparatus for changing a route of verification data, setting traffic on a transfer path, and the like in order to verify the monitoring apparatus 1. Devices 3 and 4 are devices A and B, which are connected to the transmission line 5.

Reference numeral 5 denotes a transmission line. In the simulated test apparatus 2, a path conversion means 11 changes the destination address of the verification data transmitted from the monitoring apparatus 1 to the address of the simulated apparatus 15 or transmits the verification data by partially discarding the verification data. The state of the road 5 is virtually changed.

Reference numeral 12 denotes line state setting means for virtually changing the traffic by discarding part of the verification data and virtually setting the state (quality, performance, etc.) of the transmission line 5. is there.

Reference numeral 13 denotes a path conversion table, which stores information indicating whether the destination address of the verification data issued by the monitoring apparatus 1 is to be changed from the actual apparatuses A and B to the pseudo apparatus or not. To keep.

Reference numeral 15 denotes a pseudo device, which virtually represents actual devices (devices A and B) connected to the transmission line 5. The operation of the basic configuration of the present invention shown in FIG. 1 will be described.

In the monitoring device 1, the transmission line 5, the device A,
Verification data is issued for the device B, and the address of the device to which the verification data is to be transmitted (destination address) is given to the verification data. In the simulated test apparatus 2, the path conversion means 11 refers to the path conversion table 13, and if there is an instruction to change the path of the destination address, changes the destination address of the corresponding apparatus to the address of the simulated apparatus 15 and simulates the verification data. Transmit to the device 15. If there is no instruction to change the route in the route conversion table 13, the verification data is transmitted to the device of the destination address without changing the destination address.

The line state setting means 12 simulates the traffic on the transmission line, the fluctuation of the traffic, and the transmission band (for example, the data communication speed per unit time of the modem used). For example, the verification data transmitted from the monitoring device 1 is discarded. As a result, since there is no response to the verification data, the monitoring device issues the verification data again and retries. By repeating such processing a predetermined number of times and transmitting the verification data to the pseudo terminal device, device A or device B, traffic on the transmission path 5 can be set. Further, by changing such traffic with time, traffic on the transmission line and fluctuation of traffic can be provided. Further, it is possible to artificially set a change in the transmission path band (for example, halving the passing verification data is equivalent to halving the pass band).

The actual device (3, 4) connected to the transmission line that has received the verification data creates data (information) corresponding to the content specified in the verification data, and uses its own device address as the source address. And sends it to the route conversion means 11. Similarly, the simulated device 15 that has received the verification data whose path has been changed creates data (information) to respond to based on the content specified in the verification data, and sets the simulated device as a source address. The address is attached and transmitted to the route conversion means 11. And the path conversion means 1
1 converts the transmission address of the simulated device 15 into the address of the original actual device (device A or device B) and transmits it to the monitoring device 1. Monitors the return data without changing the source address returned from device A or device B.
Send to

According to the present invention, it is possible to easily verify a device connected to a transmission line without physically preparing an actual device for a test. In addition, since fluctuations in traffic and the like on the transmission line can be set and tested in a simulated manner, the test can be performed on a transmission line in a state close to actual conditions. for that reason,
A highly reliable verification result can be obtained.

[0017]

FIG. 2 is an example of an embodiment of a system configuration according to the present invention. In FIG. 2, reference numeral 2 denotes a dummy test apparatus.

Reference numeral 21 denotes a LAN monitoring device that monitors a relay device, a terminal device, and the like connected to the LAN transmission line B (26). Reference numeral 22 denotes a monitoring unit.
It monitors relay devices and terminal devices connected to the AN transmission line B (26).

Reference numeral 23 denotes a retransmission unit, which is a pseudo test device 2
When the verification data is discarded, the verification data is transmitted again. 25 is a LAN transmission line A,
Monitoring device 21, pseudo test device 2, and pseudo terminal device 51
Is to connect.

Reference numeral 26 denotes a LAN transmission line B for connecting test-related devices such as a relay device and a terminal device.
In the pseudo test apparatus 2, reference numeral 31 denotes a path conversion unit.
This is to change the path of the verification data issued from the LAN monitoring device 21 (corresponding to the path conversion unit in FIG. 1).

Reference numeral 32 denotes a line status setting unit for setting traffic fluctuation, band and the like of the LAN transmission line B (26) (corresponding to the line status setting means in FIG. 1). 3
3 is a path conversion table.

Reference numeral 41 denotes a boat A, which is a LAN transmission path A
This is a port connected to (25). Reference numeral 43 denotes a port B, which is a boat connected to the LAN transmission path B (26). Reference numeral 51 denotes a pseudo terminal device, which is a LAN transmission path B (2
Test-related devices connected to 6) (relay devices, terminal devices, etc.)
And the connection relationship thereof.

A console 52 has an input device and a display device. 61 is a relay device,
LAN transmission path B (26) and high-speed digital transmission path 62
Is to connect.

Reference numeral 63 denotes a relay device, which is a high-speed transmission line 62.
And the terminal device 64. A relay device 71 connects the LAN transmission line B (26) and the ISDN transmission line 72.

A relay device 73 connects the ISDN transmission line 72 to the terminal device 74. A relay device 81 connects the LAN transmission line B (26) and the FDDI transmission line (optical transmission line) 82.

A relay device 83 connects the FDDI transmission line 82 to the terminal device 84. The operation of the configuration of FIG. 2 will be described later.

FIG. 3 shows an embodiment of the pseudo test apparatus according to the present invention. In FIG. 3, reference numeral 2 denotes a dummy test apparatus.

Reference numeral 21 denotes a LAN monitoring device. 25 is LA
N transmission path A. 26 is a LAN transmission path B.

In the pseudo test apparatus 2, reference numeral 31 denotes a path conversion unit. 32 is a line state setting unit.

Reference numeral 33 denotes a path conversion table (corresponding to the path conversion table in FIG. 1). 35 is an input / output processing unit. A control unit 36 controls each unit of the pseudo test apparatus.

Reference numeral 37 denotes a packet receiving unit for receiving a packet (verification data). Reference numeral 38 denotes a packet transmitting unit for transmitting a packet (verification data).

Reference numeral 41 is an A port. 43 is a B port. Reference numeral 51 denotes a pseudo terminal device.

Reference numeral 52 denotes a console. Reference numeral 53 denotes a parameter input unit for inputting a conversion address of the path conversion table 33 and the like.

A display unit 54 is a display or the like. Reference numeral 91 denotes a real device, which represents a relay device connected to the transmission line B, an actual terminal device (real device), or the like.

The operation of the configuration shown in FIG. 3 will be described later. FIG. 4A shows a configuration of the verification data before and after the route of the verification data output from the monitoring device is changed to the pseudo terminal device.

Reference numeral 110 denotes verification data (packets) issued by the LAN monitoring device. It has a destination address (xxxx) which is an address of a test target device (it is an actual device such as an actual relay device and a terminal device) and a source address (address (aaaa) of a LAN monitoring device). FCS is a check code.

Reference numeral 111 denotes verification data (packets) to be transmitted to the pseudo terminal device. The destination address (xxxx) of the verification data 110 is replaced with a pseudo terminal address (bbbb). The replaced destination address (xxxx) is recorded in the verification table as shown in the figure. The FCS recalculates.

FIG. 4B shows the configuration before and after the conversion process of the source address of the verification data returned from the pseudo terminal device. Reference numeral 112 denotes verification data returned from the pseudo terminal device. It has the address (aaaa) of the LAN monitoring device as the destination address and the address (bbbb) of the pseudo terminal device as the source address. Also, the original destination address (xxx) included in the transmission to the pseudo terminal device is included.
x).

Reference numeral 113 is for transmitting the verification data returned from the pseudo terminal device to the LAN monitoring device. The source address of the verification data returned from the pseudo terminal device 2 is replaced with the original destination address (xxxx). The FCS recalculates.

FIG. 4C shows an example of the path conversion table.
Each destination address has a destination address of a real device whose route is changed to the pseudo terminal device and a symbol indicating whether or not the route is changed. In FIG. 4 (c),
Represents an address to perform conversion (conversion is valid), and X represents an address not to perform conversion (translation is invalid). Addresses not recorded in the destination address are not converted.

FIG. 5 is an explanatory diagram of the operation of the line state setting means of the present invention, and is an explanatory diagram of generation of a band / delay / fluctuation. In FIG. 5, reference numeral 1 denotes a LAN monitoring device.

Reference numeral 22 denotes a monitoring unit. 23 is a retransmission unit. Reference numeral 2 denotes a simulated test device.

Reference numeral 131 denotes a test-related device or a pseudo terminal device. The operation of the configuration of FIG. 5 will be described. The monitoring unit 22 transmits the verification data to the simulated test device. The dummy test device discards the verification data. In the LAN monitoring device 1, since the completion notification of the verification data does not come, the retransmitting unit 23 retransmits the verification data after t1 seconds. The pseudo test apparatus 2 discards the verification data again. Therefore, after t2 seconds, the retransmission unit 23
Resend the verification data. Again, the pseudo test apparatus 2 discards the verification data. The retransmitting unit 23 transmits the verification data again after t3 seconds. The simulated test device 2 transmits the received verification data to the test-related device or the simulated terminal device. The test related device or the pseudo terminal device responds to the reception of the verification data. A response to the reception of the verification data is transmitted to the LAN monitoring device 2 via the pseudo test device 2. Therefore,
The delay time of the verification data in this case is t1 + t2 + t3.

In this way, the traffic on the transmission line can be set in a pseudo manner. It is also possible to artificially set the traffic fluctuation by changing the number of times from discarding to transmitting the verification data with time. Alternatively, for example, by discarding and transmitting the verification data once, the pass verification data can be halved. This is equivalent to halving the transfer rate of the verification data passing through the transmission line, and therefore, it is equivalent to halving the pass band of the transmission line. In this way, the bandwidth of the transmission path can be set in a pseudo manner.

The operation of the configuration shown in FIGS. 2 and 3 will be described (see FIGS. 4 and 5 as necessary). LAN monitoring device 21
Issues verification test data (see Fig. 4 (a)) to each test-related device (relay device such as router, terminal device, etc.) to acquire the information (device ID, connection information, failure information, etc.) I do. The verification data is for verifying system configuration information of the LAN monitoring device 21, generating system configuration information, or verifying that a failure of a test-related device can be reliably detected when a failure occurs. It is.

In the pseudo test apparatus 2, the verification data is A
The packet is received by the packet receiving unit 37 via the port 41.
The received verification data is passed to the path conversion unit 31. The path conversion unit 31 refers to the path conversion table 33 and checks whether it is necessary to change the destination address to the address of the pseudo terminal device, and if it is necessary to change the destination address, changes the destination to the address of the pseudo terminal device. . At that time, the destination address of the original real device is included in the verification data and held (see FIG. 4B). Next, the verification data is passed to the line state setting unit 32. The line state setting unit 32 discards verification data that needs to be discarded for traffic adjustment and the like, and packet transmission is performed when the traffic adjustment is not necessary or when the traffic adjustment is performed. To the unit 38 (see FIG. 5). The verification data is transmitted from the packet transmitting unit 38 to the test-related device or the pseudo terminal device 51 according to the destination address.

The test-related device or the pseudo terminal device is
According to the contents specified by the verification data, device information, device status information, and the like are created as return data, and are returned to the pseudo test device 2. Return data from the test related device is received by the packet receiving unit 37 via the B port. The return data from the pseudo terminal device 51 is received by the packet receiving unit 37 via the A port 41. The received reply data is passed to the path conversion unit 31.

In the path converter 31, the reply data whose source address is the address of the pseudo terminal device 51 is the original destination address (L) contained in the reply data.
The source address is replaced with the destination address assigned when issued by the AN monitoring device 21 (see FIG. 4B).
The reply data is sent to the LAN monitoring device 21 via the A port 41.
Sent to.

The LAN monitoring device creates a system configuration diagram based on the received reply data. Alternatively, verification of the configured system configuration diagram, verification of information collection when a failure occurs, and the like are performed.

For setting parameters such as creation and updating of the path conversion table, data is input by the parameter input unit 53 in the console 52. Then, the anthropomorphic test device 2 creates or updates the path conversion table 33 via the input / output processing unit 35.

FIG. 6 shows the configuration of the traffic fluctuation control table and the line setting unit according to the present invention. FIG. 6A shows an example of the traffic fluctuation control table.

Reference numeral 135 denotes a traffic fluctuation control table, which is a table for holding conditions for traffic control. 136 is a counter A, which gives the current fluctuation value. For example, for the address jjjj, it indicates that the current fluctuation is 25% of the delay value. In the range from the minimum value of fluctuation to the maximum value of fluctuation, for example, the fluctuation is set at regular time intervals by increasing or decreasing stepwise with time (for example, when the fluctuation is ± 30%, the current counter value of −30% is set. The delay value at this time is set to 70, and the current counter value is increased by 5%.
0 is the maximum delay value + 30%). Alternatively, it may be determined at random using a random number or the like.

The traffic fluctuation control table 135 is
It has a traffic delay value (ratio or the number of packets to be discarded (verification data)) for the destination address, a fluctuation value (fluctuation rate) when a fluctuation is given, and a minimum value and a maximum value of the fluctuation.

FIG. 6B shows the configuration of the line state setting unit.
In FIG. 6B, reference numeral 32 denotes a line state setting unit.

Reference numeral 135 denotes a traffic fluctuation control table. 136 is a counter A for counting the number of times the verification data is discarded.

Reference numeral 141 denotes a destination address table.
This holds the address of the real device. Reference numeral 142 denotes a delay value holding unit that holds a delay value.
Is a fluctuation value holding unit that holds the fluctuation rate of the fluctuation.

Reference numeral 144 denotes a fluctuation maximum value holding unit which holds the maximum value of the fluctuation. A fluctuation minimum value holding unit 145 stores the minimum value of the fluctuation.

Reference numeral 151 denotes a fluctuation width calculator for calculating a fluctuation minimum value and a fluctuation maximum value in accordance with the delay value and the fluctuation value. Reference numeral 152 denotes a discard number determination unit that determines the number of times the verification data is discarded based on the result of the delay value, maximum fluctuation value, minimum fluctuation value, and fluctuation value determination unit 153.

Reference numeral 153 denotes a fluctuation delay value determination unit which determines the magnitude of the fluctuation between the maximum value and the minimum value of the fluctuation stepwise between the maximum value and the minimum value.
153 'is a counter B which holds the current fluctuation counter value.

A verification data discarding unit 154 discards the verification data for the number of times specified by the discard number determination unit 152, discards the specified number of times, and transmits the verification data input later to the packet transmission unit. To pass.

The operation of the configuration shown in FIG. 6 will be described. The fluctuation width calculation unit 151 inputs the delay value held by the delay value holding unit 142 and the fluctuation value held by the fluctuation value holding unit 143,
The maximum fluctuation value and the minimum fluctuation value are obtained and stored in the fluctuation maximum value holding unit 144 and the fluctuation minimum value holding unit 145, respectively.

The discard number determination unit refers to the destination address of the verification data, and obtains a delay value and a fluctuation value recorded in the traffic fluctuation control table of the destination address. If the fluctuation value is 0, the number of packets to be discarded is calculated according to the delay value, and the packet is notified to the verification data discarding unit 154.
If the fluctuation value is not 0, the fluctuation delay value determination unit 1
53 determines the fluctuation value between the fluctuation maximum value and the minimum value,
The fluctuation ratio at that time is held in the counter B (153 '). The discard number determination unit 152 obtains the discard number based on the determined delay value, and notifies the verification data discard unit 154.

The verification data discarding unit discards the verification data by the notified number of times, and passes the verification data transmitted thereafter to the packet transmitting unit. FIG. 7 shows an embodiment of the system configuration of the present invention.

In FIG. 7, reference numeral 25 denotes a LAN transmission line A. 26 is a LAN transmission path B.

Reference numeral 161 denotes a computer A, which is a LAN
It operates as a monitoring device. 162 is a LAN monitoring program.

A computer B 163 operates as a pseudo terminal device. A pseudo terminal program 164 is a program for creating a pseudo terminal device.

Reference numeral 165 denotes a computer C which serves as a pseudo test device. Reference numeral 166 denotes a computer pseudo test program, which is a program for performing the pseudo test of the present invention.

A storage medium driver 171 loads the contents stored in the storage medium 172 into the computer C (165). 172 is a storage medium, a CD
It is a storage medium such as an optical storage medium such as a ROM and a magnetic storage medium such as a magnetic disk.

173 is a path conversion program. 17
4 is a line state setting program. 180 is a test-related device.

FIG. 8 is a flowchart of the verification data transmission of the pseudo test apparatus of the present invention. The flowchart in FIG. 8 will be described according to the step numbers in FIG. S1 The verification data is received from the LAN monitoring device.

S2, S3, S4 Referring to the path conversion table, if the destination address is in the path conversion table and is valid, the destination address is changed to the address of the pseudo terminal device. The original destination address is recorded in the verification data. Further, the check address is calculated again.

S2, S3, S5 Referring to the path conversion table, the destination address is not described in the path conversion table, or even if described, the destination address is not changed unless it is valid.

S5 The processing of the line state setting unit is performed. S6 Transmit the verification data to the device at the destination address. FIG. 9 is a flowchart of the verification data receiving process of the pseudo test apparatus of the present invention.

S1 Reply data is received. S2, S3 Based on the source address of the received verification data, it is determined whether the data is received from the pseudo terminal device or from the real device. If it is received from the pseudo terminal device, the process of S4 is performed, and if it is received from the real device, the process of S6 is performed.

S4 Since the data is received from the pseudo terminal device, the source address is replaced with the original destination address included in the reply data. Then, the error check code is calculated again.

S5 The original destination address contained and held is deleted. S6: Send reply data to the LAN monitoring device. FIG.
Is a flowchart of the line state setting unit.

S1 The verification data is input. S2: Reference the destination address of the traffic fluctuation control table that is the same as the destination address of the verification data.

S3: It is determined whether a traffic condition is set for the destination address. If it is set, the process of S4 is performed, and if the traffic condition is not set, the process of S5 is performed.

S4: The count value is compared with the number of discards. If they match, the verification data is discarded in S5. If they do not match, the counter value is incremented by one in S6. S5 The verification data is transmitted to the destination address.

S6 The verification data is discarded. S7 Increment the counter value by one.

[0081]

According to the present invention, since it is not necessary to perform verification using an actual device, network verification can be easily performed. In addition, since it is possible to select whether to perform verification using an actual device or to perform verification using a pseudo device, the verification can be performed flexibly. In addition, since the condition can be set by allocating the bandwidth, delay, and traffic fluctuation of the transmission path of the network for each path of the network, verification that the performance of the transmission path is affected can be easily performed.

According to the present invention, since it is not necessary to prepare an actual device for verification, it is possible to greatly reduce the network verification cost. In addition, since the pseudo test apparatus of the present invention can be performed using a personal computer or the like, it is economical.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of the present invention.

FIG. 2 is a diagram showing an embodiment of the present invention.

FIG. 3 is a diagram showing an embodiment of a pseudo test apparatus of the present invention.

FIG. 4 is a diagram showing a path conversion and a path conversion table according to the present invention.

FIG. 5 is an explanatory diagram of band / delay / fluctuation generation according to the present invention.

FIG. 6 is a diagram illustrating a configuration of a traffic fluctuation control table and a line state setting unit according to the present invention.

FIG. 7 is a diagram showing an embodiment of a system configuration of the present invention.

FIG. 8 is a view showing a flowchart (transmission) of the pseudo test apparatus of the present invention.

FIG. 9 is a view showing a flowchart (reception) of the pseudo test apparatus of the present invention.

FIG. 10 is a flowchart of a line state setting unit of the present invention.

[Explanation of symbols]

 1: Monitoring device 2: Pseudo test device 3: Device A 4: Device B 5: Transmission line 11: Route conversion means 12: Line status setting means 13: Path conversion table 15: Pseudo device

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI H04L 12/56 29/14

Claims (5)

[Claims] 1. A simulated test device that receives verification data from a monitoring device that monitors a transmission line and transmits the verification data to an actual device connected to the transmission line or a simulated device that simulates the actual device. The destination address A of the verification data addressed to the actual device is converted into the address of the pseudo device, the destination address before the address conversion is included in the verification data and transmitted to the pseudo terminal device, and the reply data from the pseudo device is transmitted. A pseudo test apparatus for a transmission path monitoring apparatus, wherein the source address of the transmission path is converted into the destination address A before the conversion. 2. The pseudo test apparatus for a transmission path monitoring apparatus according to claim 1, wherein the original destination address A is deleted from the reply data after converting the source address of the reply data. 3. A route conversion table for holding a destination address for changing a route to a pseudo device, wherein when the destination address recorded in the route conversion table is valid, the destination address is converted to an address of the pseudo device. 3. The pseudo test device for a transmission line monitoring device according to claim 1, wherein 4. The apparatus according to claim 1, further comprising a line state setting means for changing a pass band of the transmission path in a pseudo manner by discarding a part of verification data issued from the monitoring apparatus. Pseudo test equipment for transmission line monitoring equipment. 5. The communication system according to claim 1, further comprising a line state setting unit for changing a traffic on a transmission line in a pseudo manner by discarding a part of the verification data issued from the monitoring device. Simulated test equipment for transmission path monitoring equipment.