A, B, C, D-OSN3500 equipment in the network is a bureau also built a new project equipment, power commissioning is uploaded to the T2000 transmission network management, a day access network equipment ONU-UA5000 power commissioning, and B-OSN3500 equipment using 2M link docking, access network HONET network management frequently reported signal out-of-step alarms, transmission T2000 network management reported pointer adjustment. The access network HONET network management frequently reported signal out-of-step alarms, and the transmission T2000 network management reported pointer adjustment alarms, link docking failed, and the automatic telephone service could not be opened.

Alarm information

Transmission T2000 network management B network element reported: pointer adjustment alarm; access network HONET network management frequently reported signal out of step alarm.

Processing

Processing

Query the "clock configuration" of A, B, C, D-OSN3500 devices and find that: the first and the last are connected, SSM protocol is not enabled, resulting in a ring.

A. "Clock Priority List" is configured as follows: 1 clock signal is extracted from westward STM-16 optical port (priority order 1); 1 clock signal is extracted from eastward STM-16 optical port (priority order 2), and internal clock source (priority order 3). The following is an example of the internal clock source (Priority 3).

B. "Clock subnet setting", standard SSM and extended SSM are not enabled to prevent loop formation protocol.

C. Check A, B, C, D-OSN3500 device "clock view", four network elements are connected to each other, forming a ring network.

D, D-OSN3500 device did not extract the "topology cloud" network "external clock source".

Root cause

Root cause analysis

Pointer adjustment is the adjustment of the pointer according to the actual need to accommodate the rate desynchronization and phase difference of the net load signal. In other words, the net information load is rate-adjusted by the pointer adjustment to synchronize it with the STM-N frame.

The pointer is used as a frequency tracking calibration when the network is out of synchronization and different network elements are operating in a frequency-differentiated state. Frequency jitter and drift in the network can also be accommodated by pointer adjustment.

The reasons for this are analyzed as follows.

- Due to the inconsistency between the system clock and the receiving clock, the demultiplexing process generates TU pointer adjustment.

- The upstream network elements through which the service passes generate pointer adjustments, and the TU pointer adjustment is generated in the demultiplexing process after the service passes through to this station.

- The clock configuration is not reasonable, and the standard SSM and extended SSM protocols are not enabled to prevent ring formation.

After one by one elimination, we found that the root cause is item 3.

Solution

1. For D-OSN3500 devices, configure the "Clock Priority List": 1 external clock source for "Topology Cloud", and set the priority to 1.

2. In order to avoid changing the clock configuration one by one, which may cause the service to flash off frequently, for A, B, C, D-OSN3500 devices, use "Network Element Batch Configuration Function" - "Clock Configuration" to enable "Extended SSM" and "Clock Priority List". - At the same time, enable the "extended SSM protocol" to realize the clock to split the ring; refresh the clock view found that: A, B, C-OSN3500 network elements to track the clock signal of D network elements.

3. Refresh the "Alarm Information", the pointer adjustment alarm is gradually eliminated, and the signal out-of-step alarm frequently reported by the HONET network management of the access network is eliminated.

4. 2 hours of observation, the alarm does not reappear, test the automatic telephone service is normal, processing is complete.

Recommendations and summary

Maintenance personnel need to find the root cause of the problem based on the "clock into a ring" triggers; after determining the failure point, to develop safe and efficient disposal methods, so as to minimize the impact on the network, to provide a stable and reliable transmission channel for the business system, troubleshooting.

This chapter of related technical information and SDH equipment troubleshooting process by Shenzhen Optical Transmission Network Technology Co., Ltd (www.opticaltrans.com), reproduced please retain! Huawei SDH Optical Transmission Equipment, SDH Transmission Equipment Sales