Local area network loop rapid detection positioning system

Abstract

A local area network loop rapid detection positioning system comprises a loop detection engine, an alarm module, an application module, a database, a data analysis module and a data acquisition module. The data acquisition module is deployed in a local area network and acquires port traffic, mac address and LDT information of a switch in the local area network, the data analysis module performs standardized analysis on original data and stores the data into the database, and the database uploads the data to the loop detection engine through the switch for further analysis; and the loop detection engine performs deep analysis detection on the acquired analysis data of the switch to finally judge whether a loop exists in the network, and when the loop condition is detected, the alarm module performs alarm notification, and the network state is displayed through the application module. According to the invention, the network state can be monitored in real time, the loop fault in the local area network can be accurately identified, and operation and maintenance personnel can be timely notified through an alarm mechanism. Through the system, operation and maintenance personnel can quickly position a fault point, and the troubleshooting time is greatly shortened.

Description

Technical Field

[0001] The invention relates to the technical field of network management and maintenance, and in particular to a local area network loop rapid detection and positioning system. Background Art

[0002] As the scale and complexity of local area networks (LANs) continue to expand, the number of network devices and connection nodes has increased dramatically, resulting in a significant increase in the probability of network loop problems. A network loop refers to the cyclic transmission of the same data frame within a LAN, which results in a large consumption of network bandwidth, increased device load, and even serious faults such as broadcast storms and network congestion, which directly affects the normal operation of services and the stability of the network.

[0003] Traditional loop detection methods rely on manual troubleshooting or simple network protocols, which are inefficient, difficult to accurately locate loops in complex network environments, and time-consuming troubleshooting. The existing technology urgently needs an automated and intelligent loop detection system that can monitor network status in real time, accurately identify and quickly locate loop problems in the network, thereby improving network operation and maintenance efficiency, reducing network failure time, and ensuring efficient network operation. Summary of the invention

[0004] In view of the technical problems that loop faults in the above-mentioned existing networks are difficult to locate quickly and have low detection efficiency, this technical solution provides a local area network loop rapid detection and positioning system, which integrates a loop detection engine, an alarm module, an application module, a database, a data analysis module, and a data acquisition module. Through automated data acquisition, intelligent analysis and processing, and the collaborative work of multiple detection algorithms, it is possible to monitor the network status in real time, accurately identify loop faults in the local area network, and promptly notify the operation and maintenance personnel through the alarm mechanism. Through this system, the operation and maintenance personnel can quickly locate the fault point, greatly shorten the troubleshooting time, improve the availability and stability of the network, and ensure the normal operation of the business; it can effectively solve the above-mentioned problems.

[0005] The present invention is achieved through the following technical solutions: A local area network loop rapid detection and positioning system comprises a loop detection engine, an alarm module, an application module, a database, a data analysis module and a data acquisition module; the data acquisition module is deployed in the local area network, collects switch port traffic, MAC address table, link discovery protocol LDT information, transmits the data to the data analysis module, and the data analysis module performs standardized analysis on the original data and stores it in the database; the loop detection engine is a core component, performs in-depth analysis and detection on the network data stored in the database, determines whether there is a loop fault in the local area network, and when a loop fault is detected, the alarm module issues an alarm notification, and displays the network status through the application module.

[0006] Furthermore, the data analysis module uses hash mapping to use the data fields of the switch port traffic, MAC address table, and link discovery protocol LDT information collected by the data acquisition module as key values, stores the hash values ​​of the data, and quickly finds and removes duplicate data; at the same time, the data analysis module sets a threshold range detection, defines a reasonable traffic range or packet loss rate, and those exceeding the range are regarded as abnormal and marked or removed; at the same time, the data analysis module normalizes the collected raw data.

[0007] Furthermore, the specific operation method of the data analysis module for normalizing the collected raw data is: first, remove redundant, repeated and abnormal data through data cleaning, and correct or complete missing data; then, standardize the data from different sources according to timestamps, units and field names; at the same time, the data analysis module performs consistency, integrity and logic checks; the processed data is stored in the database, and after index optimization and partition management, it is convenient for subsequent efficient query and in-depth analysis.

[0008] Furthermore, the data analysis module needs to define a mapping table for data standardization, map the data units and formats of different devices to a unified standard, and use regular expressions to verify the consistency of MAC addresses and other formats of data; finally, the data analysis module uses a B-tree index to index the timestamp, device ID, and port ID fields, and partitions the database table by time period to improve query efficiency.

[0009] Furthermore, the loop detection engine performs loop detection through the collaborative work of traffic anomaly analysis, CPCAR packet loss analysis, MAC address drift monitoring, and LDT loop monitoring. First, the traffic anomaly analysis identifies the situation of abnormal and substantial increase in traffic by monitoring the traffic changes of the switch port, and preliminarily marks the possible loop risk. Then, the CPCAR packet loss analysis makes an in-depth comparison of the control plane rate limit packet loss data of the port to detect whether the packet loss exceeds the normal range, and further confirms the loop risk when the packet loss is too large. At the same time, the MAC address drift monitoring analyzes the frequent changes or drifts of MAC addresses in network devices. Finally, the LDT loop monitoring detects the newly added loop information in the core device by continuously monitoring the link discovery protocol data, and further confirms whether there is a loop.

[0010] Furthermore, the traffic anomaly analysis monitors the traffic changes of the switch port by monitoring the switch port traffic, collects the inbound and outbound traffic data of the port, calculates the increase in traffic through a sliding window, identifies the situation where the traffic increases significantly, marks the possible loop risk, sets a reasonable traffic threshold, and marks it as a potential loop risk when it exceeds this threshold.

[0011] Furthermore, the CPCAR packet loss analysis obtains packet loss data through the display cpu-defend arp-requeststatistics command, and makes an in-depth comparison between the CPCAR (control plane rate limiting) packet loss data Drop(Packets) of the port and the preset value to detect whether the packet loss exceeds the normal range. When the packet loss is too large, the loop risk is further confirmed.

[0012] Furthermore, the MAC address drift monitoring is performed by monitoring the MAC address drift of the switch trap log. Once the MAC_FLAPPING_ALARM log type is found, it indicates that the MAC address in the network device changes or drifts frequently, which is one of the key signals that the loop causes path confusion.

[0013] Furthermore, the application module provides a graphical interface to display information on network status and loop detection results; through this interface, network administrators can view key information on network status and loop detection results to fully understand the health of the network; at the same time, the application module also supports troubleshooting and performance tuning functions to help network administrators better manage and maintain the LAN environment.

[0014] Furthermore, when the loop detection engine detects a loop, the alarm module is immediately triggered to send an alarm notification to the network administrator through various methods such as system pop-up windows, etc. This function ensures that the network administrator can understand the changes in network status in a timely manner and quickly take corresponding measures to solve the problem.

[0015] Furthermore, the database storage system collects, analyzes and generates all data during the detection process.

[0016] Furthermore, the operation steps of the detection and positioning system include: Step 1: The data acquisition module establishes a connection with the network device through SSH to collect port traffic, CPCAR packet loss data, MAC address drift information, and LDT loop information in real time; after preliminary processing, the collected data is transmitted to the data analysis module for further analysis and stored in the database to ensure the integrity and accuracy of the data; Step 2: The loop detection engine reads the port traffic data from the database and continuously monitors traffic changes. If it detects that the traffic of a port increases abnormally and exceeds the normal range, the device is temporarily marked as having excessive traffic, indicating a loop risk. Step 3: After finding traffic anomalies, the loop detection engine further compares and analyzes the CPCAR packet loss data of the port. It calculates the difference between the CPCAR packet loss data and the normal packet loss data and takes the absolute value. If the difference exceeds the preset threshold, it is further confirmed that the device has excessive packet loss, which increases the risk of loops. Step 4: The loop detection engine retrieves the syslog log of the device at the same time, focusing on monitoring whether there is any log information related to MAC address drift. If the MAC address is found to drift frequently between different ports, it is confirmed that the device has a loop problem and the device is marked. Step 5: The loop detection engine continuously monitors the LDT link discovery protocol data of the core device and analyzes the loop topology changes in real time; if LDT detects new loop information, the system immediately marks the device as having a loop to further verify the loop problem. Beneficial Effects

[0017] Compared with the prior art, the local area network loop rapid detection and positioning system proposed by the present invention has the following beneficial effects: The present invention integrates a loop detection engine, an alarm module, an application module, a database, a data analysis module, and a data acquisition module. Through automated data acquisition, intelligent analysis and processing, and the collaborative work of multiple detection algorithms, it is possible to monitor the network status in real time, accurately identify loop faults in the local area network, and promptly notify the operation and maintenance personnel through the alarm mechanism. Through this system, the operation and maintenance personnel can quickly locate the fault point, greatly shorten the troubleshooting time, improve the availability and stability of the network, and ensure the normal operation of the business; it is intended to quickly locate the network loop fault when there is a loop fault scenario in the local area network business, and the operation and maintenance personnel can quickly locate the fault point, reduce the troubleshooting time, and improve the availability and stability of the network.

[0018] The loop detection engine in the present invention performs loop detection through the collaborative work of traffic anomaly analysis, CPCAR packet loss analysis, MAC address drift monitoring, and LDT loop monitoring. It can detect loop problems in the local area network in real time and accurately, and quickly locate faulty equipment or ports, significantly reducing troubleshooting time.

[0019] The data analysis module in the present invention avoids false positives or negative positives caused by a single factor by comprehensively judging multiple indicators such as traffic, packet loss, and MAC address changes. Multi-dimensional data analysis and detection methods work together to effectively improve the accuracy and sensitivity of detection.

[0020] The alarm module of the present invention is set up so that once a loop problem is detected, the system can send an immediate alarm to the network administrator through various means (such as desktop pop-up windows, text messages, emails, etc.), ensuring that the problem can be handled in a timely manner to avoid network interruption and business loss. The system has a high degree of automation and can continuously monitor the network status in real time. It can automatically detect and alarm loop problems without manual intervention, significantly improving the efficiency of network operation and maintenance and reducing the risk of errors in manual operations.

[0021] The setting of the application module in the present invention enables operation and maintenance personnel to intuitively view network status, fault information and loop detection results through the graphical interface of the application module, which improves the convenience of network management and user experience, and helps to optimize network performance and quickly troubleshoot faults.

[0022] The loop problem in the local area network of the present invention can be quickly identified and solved at an early stage, preventing the loop from causing a wider range of network paralysis, significantly improving the overall availability and stability of the network, and ensuring the normal operation of network services. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the overall structure of the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Under the premise of not departing from the design concept of the present invention, various modifications and improvements made by ordinary persons in the art to the technical solutions of the present invention should all fall within the protection scope of the present invention. Example

[0025] like Figure 1 As shown, a local area network loop rapid detection and positioning system includes a loop detection engine, an alarm module, an application module, a database, a data analysis module and a data acquisition module. The data acquisition module is deployed in the local area network, collects switch port traffic, MAC address table, link discovery protocol LDT information, and transmits the data to the data analysis module, which performs standardized analysis on the original data and stores it in the database; the loop detection engine is a core component, which performs in-depth analysis and detection on the network data stored in the database to determine whether there is a loop fault in the local area network. When a loop fault is detected, the alarm module issues an alarm notification, and the network status is displayed through the application module.

[0026] Data collection module: The main function is to collect port traffic information, MAC address table data, link discovery protocol (LDT) and other key network status indicators of these network devices in real time and accurately. It is deployed in the local area network and is responsible for real-time collection of port traffic, MAC address, link discovery protocol (LDT) and other information of network devices. By continuously monitoring and recording these data, the data collection module provides a solid data foundation for subsequent analysis and detection of the system.

[0027] The data acquisition module obtains raw data, including switch port traffic, MAC address table, Link Discovery Protocol (LDT) information, etc., and transmits the data to the data analysis module.

[0028] Data analysis module: Use hash mapping to take data fields (switch port traffic, MAC address table, link discovery protocol LDT information, equipment ID, port ID, and timestamp collected by the data collection module) as key values, store the hash value of the data, quickly find duplicate data and remove it; at the same time, the data analysis module sets the threshold range detection, defines a reasonable traffic range or packet loss rate, and those outside the range are considered abnormal and marked or removed. At the same time, the data analysis module normalizes the collected raw data, defines a mapping table, and maps the data units and formats of different devices to a unified standard. The data analysis module uses regular expressions to verify the consistency of MAC addresses and other formats of data. Finally, the data analysis module uses B-Tree Index to index fields such as timestamps, equipment IDs, and port IDs, and partitions the database table by time period to improve query efficiency.

[0029] The specific operation method of the data analysis module for normalizing the collected raw data is: first, remove redundant, duplicate and abnormal data through data cleaning, and correct or complete missing data; then, standardize the data from different sources according to timestamps, units and field names; at the same time, the data analysis module performs consistency, integrity and logic checks; the processed data is stored in the database, and after index optimization and partition management, it is convenient for subsequent efficient query and in-depth analysis.

[0030] The data analysis module needs to define a mapping table to standardize the data, map the data units and formats of different devices to a unified standard, and use regular expressions to verify the consistency of MAC addresses and other formats of data; finally, the data analysis module uses B-tree indexes to index the timestamp, device ID, and port ID fields, and partitions the database table by time period to improve query efficiency.

[0031] Database: stores all data generated during the system's collection, analysis and detection processes.

[0032] Loop detection engine: As a core component, it is responsible for in-depth analysis of network data stored in the database to determine whether there is a loop fault in the LAN. The engine ensures efficient and accurate loop detection through the collaborative work of multiple detection algorithms. The engine performs loop detection through the collaborative work of traffic anomaly analysis, CPCAR packet loss analysis, MAC address drift monitoring, and LDT loop monitoring to ensure efficient and accurate loop detection.

[0033] The operation mode of the collaborative work of the traffic anomaly analysis, CPCAR packet loss analysis, MAC address drift monitoring, and LDT loop monitoring is as follows: First, the traffic anomaly analysis monitors the traffic changes at the switch port, identifies the abnormal and substantial increase in traffic, and preliminarily marks the possible loop risks. Specifically, the switch port traffic is monitored, the inbound and outbound traffic data of the port is collected, the traffic increase rate is calculated through the sliding window, the traffic anomaly is identified, the possible loop risks are marked, and a reasonable traffic threshold (1000) is set. When this threshold is exceeded, it is marked as a potential loop risk.

[0034] Then, CPCAR packet loss analysis makes an in-depth comparison with the control plane rate limiting packet loss data of the port to detect whether the packet loss exceeds the normal range. If the packet loss is too large, the loop risk is further confirmed. Specifically, the display cpu-defend arp-request statistics command is used to obtain the packet loss data, and the CPCAR (control plane rate limiting) packet loss data Drop(Packets) of the port is compared with the preset value to detect whether the packet loss exceeds the normal range. If the packet loss is too large, the loop risk is further confirmed.

[0035] At the same time, MAC address drift monitoring analyzes the frequent changes or drifts of MAC addresses in network devices. Specifically, by monitoring the MAC address drift of the switch trap log, once the MAC_FLAPPING_ALARM log type is found, it indicates that the MAC address in the network device has frequent changes or drifts, which is one of the key signals that the loop causes path confusion.

[0036] Finally, LDT loop monitoring detects new loop information in core devices by continuously monitoring Link Discovery Protocol (LDT) data, further confirms whether a loop exists, and ultimately determines the loop situation.

[0037] Alarm module: When the loop detection engine detects a loop, the alarm module is immediately triggered, and an alarm notification is sent to the network administrator through various methods such as system pop-up windows. This function ensures that the network administrator can understand the changes in network status in a timely manner and take corresponding measures to solve the problem quickly.

[0038] Application module: provides a graphical interface to display information about network status and loop detection results. It is a bridge between the system and the user, and provides an intuitive and easy-to-use graphical interface; through this interface, network administrators can view key information about network status and loop detection results, and fully understand the health of the network; at the same time, the application module also supports troubleshooting and performance tuning functions, helping network administrators better manage and maintain the LAN environment.

[0039] The operation steps of the detection and positioning system include: Step 1: The data acquisition module establishes a connection with the network device through SSH to collect port traffic, CPCAR packet loss data, MAC address drift information, and LDT loop information in real time; after preliminary processing, the collected data is transmitted to the data analysis module for further analysis and stored in the database to ensure the integrity and accuracy of the data.

[0040] Step 2: The loop detection engine reads the port traffic data from the database and continuously monitors traffic changes. If it detects that the traffic of a port increases abnormally and exceeds the normal range, the device is temporarily marked as having excessive traffic, indicating a loop risk.

[0041] Step 3: After finding traffic anomalies, the loop detection engine further compares and analyzes the CPCAR packet loss data of the port; by calculating the difference between the CPCAR packet loss data and the normal packet loss data, the absolute value is taken; if the difference exceeds the preset threshold, it is further confirmed that the device has excessive packet loss, which increases the risk of loops.

[0042] Step 4: The loop detection engine retrieves the syslog log of the device at the same time, focusing on monitoring whether there is any log information related to MAC address drift; if the MAC address is found to drift frequently between different ports, it is confirmed that the device has a loop problem and the device is marked.

[0043] Step 5: The loop detection engine continuously monitors the LDT link discovery protocol data of the core device and analyzes the loop topology changes in real time; if LDT detects new loop information, the system immediately marks the device as having a loop to further verify the loop problem.

[0044] The specific operation methods of the detection and positioning system include: Step A: The operation and maintenance personnel deploy data collection modules on key network nodes in the LAN to ensure that the modules can cover all core devices and ports and monitor the traffic, MAC address table and link status of network devices in real time.

[0045] Step B: The data collection module establishes a connection with the switch through a secure SSH protocol, regularly collects indicators such as port traffic, MAC address table, CPCAR packet loss rate, LDT loop information, and transmits these data to the data analysis module efficiently and accurately to ensure real-time synchronization of information.

[0046] Step C: After receiving the collected raw data, the data analysis module performs data cleaning, format unification, and anomaly filtering according to predefined rules. The processed data is stored in the database through an optimized storage strategy, providing a clear and structured analysis basis for subsequent loop detection.

[0047] Step D: The loop detection engine extracts the latest network data from the database and performs deep correlation analysis on the data through multiple algorithms such as traffic anomaly analysis, CPCAR packet loss monitoring, MAC address drift detection, and LDT loop monitoring to determine whether there is a loop. Once a loop is detected, the alarm module is immediately triggered.

[0048] Step E: After confirming the loop problem, the alarm module promptly sends an alarm notification to the network administrator. The alarm is presented in a variety of ways, including desktop pop-up windows, SMS or email notifications, ensuring that the administrator can respond quickly and take measures.

[0049] Step F: The application module displays the loop detection results and network status in intuitive forms such as charts and topology diagrams, provides real-time network health monitoring, fault location and detailed loop analysis reports, and helps administrators quickly troubleshoot problems and optimize the network.

[0050] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the present invention.

Claims

1. A local area network loop rapid detection and positioning system, characterized in that: It includes a loop detection engine, an alarm module, an application module, a database, a data analysis module and a data acquisition module; the data acquisition module is deployed in the local area network, collects switch port traffic, MAC address table, link discovery protocol LDT information, and transmits the data to the data analysis module, which performs standardized analysis on the original data and stores it in the database; The loop detection engine is a core component that performs in-depth analysis and detection on the network data stored in the database to determine whether there is a loop fault in the local area network. When a loop fault is detected, the alarm module issues an alarm notification and displays the network status through the application module.

2. A local area network loop rapid detection and positioning system according to claim 1, characterized in that: The data analysis module uses hash mapping to use the data fields of the switch port traffic, MAC address table, and link discovery protocol LDT information collected by the data acquisition module as key values, stores the hash value of the data, and quickly finds and removes duplicate data; at the same time, the data analysis module sets a threshold range detection, defines a reasonable traffic range or packet loss rate, and those exceeding the range are regarded as abnormal and marked or removed; at the same time, the data analysis module normalizes the collected raw data.

3. A local area network loop rapid detection and positioning system according to claim 2, characterized in that: The specific operation mode of the data analysis module for normalizing the collected raw data is as follows: first, redundant, repeated and abnormal data are removed through data cleaning, and missing data is corrected or supplemented; then, data from different sources are standardized according to timestamps, units and field names; At the same time, the data analysis module performs consistency, integrity and logic checks; the processed data is stored in the database, and after index optimization and partition management, it facilitates subsequent efficient query and in-depth analysis.

4. A local area network loop rapid detection and positioning system according to claim 3, characterized in that: The data analysis module needs to define a mapping table to standardize the data, map the data units and formats of different devices to a unified standard, and use regular expressions to verify the consistency of MAC addresses and other formats of data; Finally, the data analysis module uses B-tree index to index the timestamp, device ID, and port ID fields, and partitions the database table by time period to improve query efficiency.

5. A local area network loop rapid detection and positioning system according to claim 1, characterized in that: The loop detection engine performs loop detection through the collaborative work of traffic anomaly analysis, CPCAR packet loss analysis, MAC address drift monitoring, and LDT loop monitoring. First, the traffic anomaly analysis identifies the situation of abnormal and substantial increase in traffic by monitoring the traffic changes of the switch port, and preliminarily marks the possible loop risk. Then, the CPCAR packet loss analysis makes an in-depth comparison of the control plane rate limit packet loss data of the port to detect whether the packet loss exceeds the normal range, and further confirms the loop risk when the packet loss is too large. At the same time, the MAC address drift monitoring analyzes the frequent changes or drifts of the MAC address in the network device. Finally, the LDT loop monitoring detects the newly added loop information in the core device by continuously monitoring the link discovery protocol data, and further confirms whether there is a loop.

6. A local area network loop rapid detection and positioning system according to claim 5, characterized in that: The traffic anomaly analysis monitors the traffic changes of the switch port by monitoring the switch port traffic, collects the inbound and outbound traffic data of the port, calculates the increase in traffic through a sliding window, identifies the situation where the traffic increases significantly, marks the possible loop risks, sets a reasonable traffic threshold, and marks it as a potential loop risk when it exceeds this threshold.

7. A local area network loop rapid detection and positioning system according to claim 5, characterized in that: The CPCAR packet loss analysis uses the display cpu-defend arp-request statistics command to obtain packet loss data, and compares the CPCAR (control plane rate limiting) packet loss data Drop(Packets) of the port with the preset value to detect whether the packet loss exceeds the normal range. If the packet loss is too large, the loop risk is further confirmed.

8. A local area network loop rapid detection and positioning system according to claim 5, characterized in that: The MAC address drift monitoring is performed by monitoring the MAC address drift of the switch trap log. Once the MAC_FLAPPING_ALARM log type is found, it indicates that the MAC address in the network device changes or drifts frequently, which is one of the key signals that the loop causes path confusion.

9. A local area network loop rapid detection and positioning system according to claim 1, characterized in that: The application module provides a graphical interface to display information on network status and loop detection results. Through this interface, network administrators can view key information on network status and loop detection results to fully understand the health of the network. At the same time, the application module also supports troubleshooting and performance tuning functions to help network administrators better manage and maintain the LAN environment.

10. A local area network loop rapid detection and positioning system according to any one of claims 1 to 9, characterized in that: The operation steps of the detection and positioning system include: Step 1: The data acquisition module establishes a connection with the network device through SSH to collect port traffic, CPCAR packet loss data, MAC address drift information, and LDT loop information in real time; after preliminary processing, the collected data is transmitted to the data analysis module for further analysis and stored in the database to ensure the integrity and accuracy of the data; Step 2: The loop detection engine reads the port traffic data from the database and continuously monitors traffic changes. If it detects that the traffic of a port increases abnormally and exceeds the normal range, the device is temporarily marked as having excessive traffic, indicating a loop risk. Step 3: After finding traffic anomalies, the loop detection engine further compares and analyzes the CPCAR packet loss data of the port. It calculates the difference between the CPCAR packet loss data and the normal packet loss data and takes the absolute value. If the difference exceeds the preset threshold, it is further confirmed that the device has excessive packet loss, which increases the risk of loops. Step 4: The loop detection engine retrieves the syslog log of the device at the same time, focusing on monitoring whether there is any log information related to MAC address drift. If the MAC address is found to drift frequently between different ports, it is confirmed that the device has a loop problem and the device is marked. Step 5: The loop detection engine continuously monitors the LDT link discovery protocol data of the core device and analyzes the loop topology changes in real time; if LDT detects new loop information, the system immediately marks the device as having a loop to further verify the loop problem.

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