Troubleshooting and solving method of campus integrated wiring

With the deepening of education informationization in our country, the network construction of colleges and universities is becoming more and more perfect. After more than 10 years of construction, the rapid expansion of campus network coverage, the level of construction gradually increased, the application of continuous expansion, today's campus network and the majority of teachers and students work, learning and life closely linked together. On the one hand, campus network is convenient for teachers and students through the Internet to understand the information at home and abroad, to improve the teaching level; On the other hand, optimize and integrate resources on the basis of campus network, set up data center, provide the basic platform for the information construction of university. Campus Network has created a good supporting environment for college Digital campus, and has exerted far-reaching influence on administration, scientific research, talent training, subject construction and after-school life of staff and students.

With the continuous construction of campus network and the expansion of college enrollment, network users are increasing, and the problems brought by network failures are becoming more and more prominent. Therefore, to ensure the stable operation of campus network, familiar with a variety of possible points of failure, rapid positioning and troubleshooting, to ensure the normal teaching, research and management of the university is of great significance.

1 Campus network operation and Maintenance overview

1.1 Logical Structure of campus network

Campus network generally adopts core layer, convergence layer and access layer model structure. The core layer is responsible for the access of the convergence layer, the fast forwarding of the data, and the interconnection of the backbone network of the Internet operators. The aggregation layer handles all traffic from the Access layer device and provides the uplink to the core layer. The access layer provides an interface for end users to access campus networks.

1.2 Campus network integrated wiring System

Campus Network Cabling System is an important foundation of campus network, it is a kind of modular and highly flexible information transmission channel between buildings and complex. It enables voice, data, imaging, and switching devices to connect with other information management systems, as well as to external communication networks. In order to ensure the function and development demand of the campus network integrated wiring system, and to study the common troubleshooting and solving methods of the high campus network integrated wiring

2 Integrated Wiring Troubleshooting

In the Daily network maintenance, the campus network integrated wiring failure rate is relatively high, according to incomplete statistics, accounting for more than 70% of the total number of failures. Once the network failure, rapid and accurate analysis of the cause of failure, timely resolution of the fault, so as to protect users to restore normal use, not only to master the basic theoretical knowledge of computer network, but also in the operation and maintenance of accumulated experience.

Comprehensive wiring failure is based on the network integrated wiring system and construction technology, from the fault phenomenon, through the network diagnostic tools to help troubleshoot information, analyze the reasons, determine the fault point, troubleshoot, and restore the normal operation of the campus network process.

2.1 Network Troubleshooting step Process

General troubleshooting steps for the network are as follows:

1) Observe and describe the phenomenon of malfunction.

Visit the site to observe the user to demonstrate the failure, to ask the user the action before the failure occurred, the first time, frequency of the failure, the scope of impact and whether the node or network changes before the failure, sorting out and recording the fault phenomenon.

2 collect information that may cause the failure.

Review the network maintenance log and learn more about recent fault area changes to other administrators. Through network management system, network equipment diagnostic commands, operating system diagnostic commands, protocol analysis tools, and network testing instruments to collect fault-related information. For example, observe whether the twisted pair is connected to the crystal head; Check the status of the switch port through the show interface command, and log on to the network management system to view the statistical records of the network monitoring system before and after the failure.

3 Analyze the cause of the failure.

Based on the information gathered, the analysis enumerates the possible causes of the failure.

4) Develop solutions.

According to the cause of the failure, sorted by priority, from the possibility from large to small to work out the solution, improve the efficiency of the investigation.

5) Implementation of the solution.

Implement the solution individually and observe the network status until the failure returns to normal. In the actual cabling troubleshooting, we can use the Piecewise method to determine the fault point, and then flexibly apply the combination of replacement method and other troubleshooting, so as to improve the efficiency of troubleshooting.

6 record good troubleshooting process.

The troubleshooting process should carefully record the results of each change in one parameter. After dealing with the fault, we should make clear the cause of the fault, draw up the corresponding countermeasures, avoid the recurrence of similar failures as far as possible, and record the network management log for future reference and accumulate operation and maintenance experience.

2.2 General wiring troubleshooting common diagnostic tools

General wiring Troubleshooting common diagnostic tools include: Hardware troubleshooting tools, software troubleshooting tools, as well as Network Diagnostics commands.

2.2.1 Hardware Troubleshooting Tool

1) Digital Multimeter

For direct measurement of voltage, current and resistance of electrical values. Using the ohmmeter of multimeter, it can be tested that each core of twisted pair is connected, and it can be found that the first core of one end connector corresponds to the first core of the other end of the twisted pair cable.

2 double stranded Wire network tester

The most commonly used in the campus network operation is the broken twisted pair tester, the price is cheap, used to test the end of twisted pair of wires to the other end of the path, short circuit, open circuit. And the more advanced network tester mostly uses the digital technology, able to fully certify the electrical characteristics of twisted pair, quickly, accurately and intuitively indicate the fault point, report its length, short circuit, string winding, bridging, reverse connection, and more conveniently store all test results to generate test reports.

3) Digital Line Finder

A line finder that combines digital audio with analog audio. can help network administrators quickly determine the exact position of twisted pair in the wiring racks, switch ports, walls, and bundles of slots, even if the cables are connected to a running network. To eliminate the signal interference factors between strapping cables, accurately identify the cable or line pairs.

4) Optical Power meter

Apparatus for measuring absolute optical power or relative loss of optical power through a section of fiber. Using the combination of a light power meter and a stable source, it can measure the connection loss, continuity of inspection, and help to evaluate the quality of the fiber link transmission.

5) Light Time domain reflector

It is applied to the maintenance and construction of optical cable lines, which can be used to measure fiber length, transmission attenuation of optical fiber, joint attenuation and fault location.

6) Wireless Network tester

Ability to quickly perform wireless network discovery, comprehensively evaluate current wireless network security and availability settings, and test results include network availability, connectivity, utilization, security settings, malicious device capture, interference detection, and more.

2.2.2 Software Troubleshooting Tool

The network management system is used to monitor connected network devices. You typically use Simple Network Management Protocol (SNMP) to collect information about the performance and utilization of your network, and use this information to help you determine whether your network is functioning properly through a variety of statistics. Commonly used network management tools are CiscoView, solarwinds and so on.

Diagnostic commands for 2.2.3 networks

Network equipment vendors provide a rich diagnostic command that can be used to troubleshoot, troubleshoot, and perform performance testing. Common commands are: show--View system Status and system information. debug--gets the details of the messages and frames exchanged in the router for debugging information. ping--checks to see if the network is connected and normal communication. tracer-oute--track routing, provide path information, confirm link latency.

3 Campus Network integrated wiring system common troubleshooting and resolution cases

3.1 Twisted pair cable fault

Twisted pair is the most common transmission medium of campus network access layer, and the main fault of the line is mainly single point fault and small influence surface. Common failures are line interruption, the ends of the connector line is not in accordance with wiring standards, crystal Head and network module contact oxidation, electromagnetic interference. 3.1.1 Interrupted due to physical damage to the line

Failure phenomenon: Campus network as a whole normal operation, a dormitory or office can not be connected to the network, information outlets connected to the network cable after the hint "net cables are not plugged."

Cause analysis: After the replacement of the normal UTP jumper, through the pass-and-Break tester detection information module to the floor cabinet wiring frame of the circuit state for the open circuit, the network module after the 1-2, 3-6-line pair still have a core does not pass. Because of the long life link length and aging or bitten by rats and other reasons, the twisted pair may appear open circuit phenomenon.

Solution: Find the distance between the breakpoint and the test point through the twisted pair network tester (e.g. Fluck link) if the breakpoint off the line at both ends of the distance, you can easily find the breakpoint, you can break all the core line of the breakpoint, respectively, after the production of Crystal Head, with the docking module for direct connection. If the distance is far, because the twisted-pair line in the building shaft and the line groove, the single line replacement is more difficult. In the case of ensuring that no more than two pairs of broken cores (the two cores with each other winding are a pair of lines), the two pairs of core lines can be adjusted to 1, 2, 3 and 6 at both ends.

3.1.2 Electromagnetic interference caused by the network can not communicate

Failure phenomenon: The school living area newly renovated teacher's apartment, some teachers reflect the internet speed is slow.

The reason analysis: through the network Test Instrument's field test, discovers the network speed slow family internal networks has the near-end crosstalk phenomenon; View the status of the switch's corresponding port and error detection information. Building in the campus living area of the teacher's apartment, by the school unified planning integrated wiring, access to campus network, each family has reserved a 4-meter twisted pair from the weak well into the family.

In the decoration, some of the family's internal wiring is by the lack of network knowledge of the electrician to complete, when it is necessary to extend the length of twisted pair, the copper core one by one corresponding to both ends of the two segments corresponds to the winding connection, but without welding and sealing of the outer skin, there are many high power home appliances near the contact, which produces electromagnetic interference, affect the communication quality of twisted-pair wires.

Solution: The cable will be reserved at the junction cut, according to the standard production network module, problem solving.

Network fault caused by lightning 3.1.3

Failure phenomenon: One to thunderstorm weather, the campus built on the backer of some network equipment and terminal devices susceptible to the damage caused by lightning.

Reason analysis: As the school is built on the mountain, is located in the mine area, the early years of construction of the campus network of integrated wiring Most of the use of overhead twisted-pair line or fiber transceiver conversion, the cabinet grounding and building protection against the lack of necessary precautions, whenever the thunderstorm season, network equipment susceptible to lightning, This may cause damage to devices such as fiber transceivers, Access layer switches, broadband routers, and computer network cards connected by twisted-pair wires.

Solution: For separate buildings using overhead twisted-pair line cascaded, to optical fiber cascade to reduce the impact of lightning. For the use of overhead twisted-pair wire access to terminal equipment, replaced by metal pipe after the laying of the break-in. If there is trouble in burying the home, the twisted pair shall be laid in a metal pipe and connected to a potential connection of each separate building [5]. The more economical way to replace the optical transceiver with the optical module is to increase the RJ45 network signal Lightning Protection device between the twisted pair and the fiber transceiver.

3.2 Fiber fault

Optical fiber is the main network of campus network transmission medium, fiber fault is generally a regional fault, involving a wide range of generally. Common faults are fiber optic connectors, terminal box contaminated, cable, jumper, tail fiber interruption.

Failure caused by damage to 3.2.1 optical cable

Failure phenomenon: Campus Network A convergence switch in the area of all users can not access the Internet. On-site observation of the core switch corresponding to the parallel port and Convergence Switch Connector Fiber module Connection LEDs are not lit.

Cause analysis: After replacing the good SFP light module, the new fiber jumper and the redundant two-core fiber, the network did not return to normal, so the fault may appear on the cable between the core switch and the converging switch.

Reason 1: Campus network backbone optical cables are mostly laid in the ground, separated by a distance between a communication well, with a manhole cover. In the construction of the campus infrastructure, the mud-head car through the communication well when the pressure is too large, roller pressure caused the damage to the cover, the manhole cover slipped caused by the compression of optical cable or construction unit accidentally cut the cable.

Reason 2: The campus because of the complex geographical structure, some of the cable using steel stranded support structure overhead erection, if the erection height does not meet the standard height of large trucks or ultra-high trucks are likely to be hung up cable.

Solution: Use the time domain reflector (OTDR) to measure the line through the connector, the distance between the fault point and the test end is calculated, then the basic data such as the maintenance detail Chart of the cable can be determined, the approximate position of the fault point, the approximate location along the road, the accurate fault point and the optical cable are fused.

The maintenance of optical cable line facilities should be standardized management to ensure a good direct buried line of the standard stone, signs, billboards, pipelines, hand holes and other facilities. For the aerial cable located in the traffic arteries, it is best to bury it underground or raise the aerial height of the cable.

Fault caused by 3.2.2 jumper

Failure phenomenon: A convergence switch in the computer room transformation, the replacement volume of a larger switch cabinet, the lower part of several access layer switches have network connectivity instability.

Cause Analysis: Ping Gateway in the access layer is seriously lost, so that the optical power meter test access layer to the convergence layer of the line, light power is low. Due to the adjustment of switch cabinet position, the distance between the switch cabinet and the fiber distribution rack is increased, which leads to the original 3 m fiber jumper tension from the wiring frame to the converging switch, plus the tie strap of the jumper bundle is too tight, causing the jumper to deform and damage the optical fiber.

Solution: Re-customize the 5-meter fiber jumper to replace the original short 3-meter jumper, and redesign the line to troubleshoot. In the future, select jumper length, depending on the distance of the equipment connected, the length of the route, and the proper margin of natural bending is appropriate; the jumper bundle should be empty and should not be real, only play the role of wrapping, not too much force.

Failure of 3.2.3 Fiber terminal box

Failure phenomenon: A staff dormitory network suddenly impassability, and other local network normal. Through the network management system monitoring records query, this node has lost packet phenomenon occurred.

Reason analysis: To the scene to replace the switch and optical module after the failure has not been resolved, to determine the possibility of a larger line failure. Use the optical power meter to test the line of the node to the converging switch, no light power. After replacing the redundant two-core fiber, the network is multiplexed, but the packet loss rate is high. Observe the inside of the network cabinet, found that the fiber jumper has mouse bite marks, network cabinets accumulated dust serious, open the fiber terminal box to see a core bare fiber has been bitten by rats.

Due to the old staff dormitory building network cabinets in a relatively dark and humid environment, the tenants piled up the place is also close to the cabinet, over time the cabinet will become a mouse habitat.

Fiber jumpers and bare fibres in incompletely sealed fiber terminal boxes may suffer from mouse bites, while the clutter and dust accumulated by mice can affect the communication quality of the fiber.

Solution: Re-weld the fiber core of the disconnected tail fiber and optical cable, replace the new fiber jumper, and clean the network cabinet, at the bottom of the cabinet and the rear end of the optical fiber terminal box to prevent the mouse from being blocked with fireproof mud.

3.3 Wireless Network

With the increasing popularity of laptops, smartphones, tablets and other wireless terminals, WLAN access has become more and more popular with campus network users. The common fault of campus network is the problem of signal instability and slow network speed.

3.3.1 signal Normal, slow surfing speed

Fault Description: When the wireless signal is normal, unable to connect to the AP or connected successfully, but the speed still does not reach the corresponding rate of the operator's claim.

Cause Analysis: Although the major network operators have built a wireless network covering the whole campus, however, because the number of AP in the student dormitory area is still insufficient, a large number of users access, causing the air interface competition, resulting in the delay, or even inaccessible, can access the average speed of the user's Internet is not ideal.

Solution: If operators can increase input, can increase the number of AP and increase the total bandwidth in the user-intensive area. And for those who need wireless connection can also purchase the wireless AP, through the bedroom network plug into the campus network use, thereby reducing the operator to provide access points and insufficient bandwidth problems.

3.3.2 signal when good and bad, internet speed is not stable

Failure Description: According to the single teachers dormitory area using a part of the teacher reflects the use of wireless connection to the network speed is slow, and the use of wired access without lines from the normal usage.

Cause analysis: Because WLAN uses the common frequency band of 2.4 GHz, it is susceptible to outside interference, the equipment that causes disturb includes microwave oven, cordless telephone and earphone, Bluetooth equipment. The IEEE802.11 b/g standard only supports channels 1, 6, 11, or 13 of these 3 non-overlapping transport channels. The distance between the residents of the single faculty dormitory area is close, almost every home uses no line, most users of the wireless device channel using the default configuration of 1 or 6, and the same or similar channel settings are prone to channel conflict, so that no lines from each other interference, resulting in the overall performance of wireless network decline.

Solution: No line by the placement of the location, should be as far as possible to avoid the microwave ovens and other household appliances, avoiding in the frequent use of wireless Internet access and no line between the signal source to generate other transmission channels. Through wireless network tester, operating system of wireless management software, Net-stumbler and other software to find out the most powerful wireless signal SSID channel, will be no line from the channel to the adjacent channel is not similar to the frequency band, the general channel number by adding five or minus five settings.

4 Summary

University Campus Network is a complicated information system engineering, and the integrated wiring is an important part of campus network, and it is also one of the infrastructure with the longest cycle. In the daily running of the campus network, the occurrence of integrated wiring fault is unavoidable, only master the basic principle of network cabling system and construction technology and accumulate experience through operation and maintenance practice, gradually perfect management mode, perfect technical document, can improve the efficiency of solving fault, make the campus network toward fast, safe, Improve the direction of development, thus better for the vast number of teachers and students to provide quality network services.