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Two-way digital television network fault analysis

In Electronic Infomation Category: T | on February 09,2012

1 independent optical transceivers and HD63C03YF datasheet and three switches do not match data is a major cause dropped packets.

Symptom: a residential user can not access on-demand video on demand page.

Failure Analysis: field test client computer Ping gateways, packet loss seriously, to BAN-port switch, and HD63C03YF price and community room light switch test, substitution phenomenon is still exist, but the community room of the optical transceiver through five lines directly connected with the computer display properly. Initially speculated that the possibility of failure: a loop exists within the cell network; community room or room light on hair associated receiver equipment failure; community room to connect the optical transceiver and HD63C03YF suppliers and the switch has five line connector crimp problem; community room three faulty switch.

one by one according to conclude our investigation, the first crystal re-crimping head, the fault still exists. Then replace the optical transceivers and three switches, and in order to exclude the area inside the loop switch, we switch to three-connected with all five lines, all pulled out the second line, the fault still exists. This, our initial failure to lock the switch in the optical transceiver with compatibility issues, then changed the existing optical transceiver form of cascaded transmission switch to switches, integrated optical modules in the form of replacement, adjustment test, the network returned to normal, no substitution phenomenon.

can be seen from this failure, the network equipment from different manufacturers may be an incompatible mix of problems, such as:

(1) communication operating mode (full duplex or half duplex);

(2) to support different service levels and network (VLAN, AG ING, Q oS, CoS, etc.);

(3) the actual supported network protocols are different;

(4) curing the actual design of the manufacturers of different functions (such as the design of some special features, etc.).

2 L2 switch software problems caused by the substitution failure

Symptom: part of the district consumer complaints network is not normal, seriously affecting the Internet and video on demand.

Failure Analysis: field testing 50% of users take away bag, but the community room of the network as usual. Based on past experience of many similar failure investigation, we found the existence of such failure is a common phenomenon that occurred in the end of the power switch at the mouth, the general solution is to replace a new two-story floor BAN switch or end switch United mouth set on strong 10M bandwidth by adjusting the fault is resolved, but the replacement switch mounted down test is normal. We think you can not rely on the joint replacement device, or a strong set 10M-bandwidth interface to solve the problem, but should find a deeper reason, then contact the equipment supplier to discuss the issue of common analysis.

with our equipment suppliers and technicians to the site to test and found that the problem is rooted in the switch software. We also found that these problems of the community, using the two-story BAN is a lot of switch products, that is with a software version of the switch. Switch to other batches of different versions of the software switch is an increase of loop detection and self-healing function, but this feature is not stable, there may be the end of the switch is on the second floor BAN associated optical switch intermittently closed port communication, resulting in users can not access and video on demand.

the Center for the failure to maintain personnel to spot network of organizations within the jurisdiction of the relevant software upgrades and switch for system reset.

3 community room is not well grounded due to network failure

Symptom: with a switch on a cell associated with S2224 engine room of the S3424 switch suburban network. From S2224 to S3424 to send P ing packet, packet loss rate of 30% to 40%. S2224 in the middle of the interface device together the LINK / ACT lamp lit. Through the console port to the S2224, S2224 corresponding to the display port debug interface to constantly switch between the Down and Up states.

Failure Analysis: local switch hardware failure; transmission line failure; software configuration error.

first check for hardware failure, will switch ends at the local switch back to back testing with the other, that switch is working properly. The community room on the joint use of stand-alone transceiver circuit connected to the computer, P ing server gateway, does not appear substitution, indicating normal transmission line. Carefully check both ends of the switch configuration, no errors. Touch that switch housing with discharge, check the voltage switch grounding and found the switch and the public to discharge voltage difference of up to 110 V. The investigation found that power supply voltage leakage, the switch is working properly grounded.

with the failure makes us aware of the switch is powered on before the configuration data, you must check the following:

(1) around the switch if there is enough space for heat dissipation;

(2) whether the switch then the power requirements of power line;

(3) switch ground wire is connected properly;

(4) switches and other devices with the configuration of the terminal is correctly connected.

4 network broadcast storm caused by network failure

Symptom: a residential user often can not get network access is slow or the case, Ping from a computer directly to the core switch, there will be packet loss, such as pull a Building A root connected to the cable will be able to return to normal, not draw a line on the normal, A BAN floor there are only three sets of switches, one switch and two optical ports S2024BF mouth S2024B electrical switch, switch S3424 through the community room fiber-optic transceiver connected to S2024BF, S2024BF following cascade of other two S2024B also switches work properly.

Failure Analysis: A building maintenance staff to switch connected, Ping packet loss will soon be the gateway, the control lines connected to the S3424, the CPU usage found rate reached 50%, soon after pulled maintained at about 10% of normal, view port status that connected the port broadcast packets Building A growth rate of more than 10,000 per second. Thus, we come to the A building connections directly connected to unplug the network cable that comes with laptop, to get caught, arrested for 20 seconds, there are 320,000 broadcast packet, source IP and MAC address are the same, so number of broadcast packets is obviously not normal, the CPU of the switch a very great impact. A building maintenance personnel arrived to find the problematic computer, killing virus, Trojan horse, the light from the second floor of the mouth and BAN-port switch on the power set arp block and broadcast storm control, MAC address of the problem to bind the computer monitor, final problem is resolved.

the face of such failures, we must first see the CPU and the aggregation layer switch port information relevant to observe whether there is abnormal growth of the number of packages, if you see broadcast or unicast packets or multicast packets grew very fast, use the capture software to capture, identify the source address, then te lnet or console port connected to the S3424 to view the MAC address table to see if the problem connected to which port the computer, the timely processing.

5 breakdown maintenance summary

(1) to strengthen the network equipment routine maintenance. Through the usual inspection, maintenance and routine maintenance, you can discover problems, eliminate hidden dangers of equipment failure, the equipment has been in good working condition.

(2) Always check switch alarm records. Some soft fault occurs on the switch will not affect the normal work, but the switch will record the corresponding alarm. So always check the alarm record will find some problems, prevent the occurrence of a larger failure.

(3) should be more communication between maintenance personnel. In the usual maintenance work, we often share their experience if the failure problems, explore solutions, we can reduce the future maintenance troubleshooting time.

(4) strengthen the technical training of personnel. Digital cable TV technology is developing rapidly, increasingly high demand for technical personnel, and only continue to enhance training, technical personnel in order to keep up with the pace of technological development, to provide users with better service.

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