Huawei transmission equipment SNCP multirings are cut, and upstream SNCP inversion triggers SNCP multilevel inversion. Use the meter to test this service, and the meter reflects the inversion overrun.

Analysis of the inversion principle: The SNCP multi-ring tangency network diagram is shown in the following figure:

Among them, four sites, A, B, C, and D, form the SNCP multi-ring tangent, S1 and S2 are two SNCP services at site B, and S3 and S4 are two SNCP services at site C. It is assumed that the current SNCP services are all working on the working channel. The two SNCP services S1 and S2 are configured as: working W, protecting P, that is, S1 and S2 have the same working and protection path configuration.

When fiber break reversal occurs between sites A and B, analyze the reversal instantaneous actions of each site at that time as follows:

(1) The working channel of site B detects SF and triggers SNCP inversion, and the inversion time is within 50ms.

(2) A reversal within 50ms at Site B, for downstream Sites C and D, there is actually a transient bad and then good process in the working and protection paths (for the reason why RLOS fiber breakage between A and B triggers AIS alarms at downstream Sites C and D, please refer to the subsequent section of "Supplementary Explanation"). In this way, for the downstream sites, there are two scenarios of bad detection of working and protection channels as follows:

For scenario 1, since the working path is detected as bad first, the single board reports to the protocol through the interrupt, and the SNCP protocol finds that the working path is bad, the protection path is good, and the current working path is working, so it triggers the inversion of the two groups of SNCPs, S1 and S2, at the same time.

For Scenario 2, since the protection path detects bad first, the veneer reports to the protocol through interrupt, the SNCP protocol finds that the work is good, the protection is bad, and the current work is working, so it does not trigger the SNCP inversion.

It should be noted that for the inversion of scenario 1, since the inversion is triggered by an interrupt at site C, its inversion action and the inversion action at site B are almost simultaneous, i.e., there will be no superposition of SNCP inversion time, and the inversion time can be guaranteed to be within 50ms.

(3) Continuing to analyze the subsequent instantaneous changeover scenario of (2), assuming that the downstream site is still working on the working path after (2), and since the line veneer of the current NGSDH detects and reports the changeover status through the 50ms inspection task, there are also two scenarios as follows:

For scenario 3, the working path is first detected to be good, the veneer is reported to the protocol through the timed patrol, and the SNCP protocol finds that the work is good, the protection is bad, and the current work is working, so the SNCP inversion is not triggered.

For Scenario 4, the protection path is detected as good first, and the single board reports to the protocol through timed inspection, and the SNCP protocol finds that the work is bad, the protection is good, and the current work is working, so it triggers the SNCP inversion of the two groups of S1 and S2 protection again.

It can be seen that for the process of SNCP state becomes good, may also trigger a SNCP inversion, and this inversion is in the upstream SNCP inversion is completed, that is, there is a possibility of SNCP inversion time superposition, the inversion time can not be guaranteed within 50ms.

Solution Analysis: From the above analysis of the inversion principle, it can be seen that the real reason that may lead to long SNCP inversion time is due to the SNCP state by the work of the protection path are bad and then successively become good (the above scenario 4), therefore, only need to consider how to avoid this scenario, you can solve the problem of SNCP multi-ring tangent inversion exceeding the standard.

As shown in the figure above, the B site configuration is modified, two SNCP services: W1 P1 --- S1, W2 P2 --- S2, S1, S2, the work of the S1, S2, the protection path is configured to the opposite, and S1, S2 is configured as a recovery type. In this way, S1 works on the upper W1 path by default, and S2 works on the lower W2 path by default.

When the above fiber break occurs between A and B network elements, for S1 service, it will trigger an SNCP inversion, and for S2 service, since the broken protection path is the protection path, it will not trigger an SNCP inversion.

That is, through this configuration modification, although it is not possible to avoid simultaneous inversion of multiple rings in one fiber break, it can ensure that the inversion time of all rings is within 50ms.

The configuration method is summarized:

Configuration requirements for SNCP multi-ring tangent sites:

(1) Configure the working and protection paths of the two sets of homologous SNCP protection at the SNCP ring tangency site to be opposite.

(2) Configure the SNCP service of the two homologous SNCP services at the SNCP ring tangency point to be restored.

Supplemental Description:

In the presence of an upstream RLOS alarm, an AUAIS alarm is interpolated downstream, and this processing is required by the ITUT Recommendation, see ITUT G.806 section 6.3.1, with the following description:

The all-ONEs (AIS) signal replaces the received signal under certain detected near-end defect conditions in order to prevent downstream The all-ONEs (AIS) signal replaces the received signal under certain detected near-end defect conditions in order to prevent downstream failures being declared and alarms being raised.

The all-ONEs (AIS) signal replaces the received signal sent downstream under certain detected near-end defect conditions in order to prevent downstream failures being declared and alarms being raised.

Termination sink functions: aAIS¬dAIS or dUNEQ/dLOS or (dTIM and not TIMAISdis)

Termination sink functions: aAIS ¬dAIS or dUNEQ/dLOS or (dTIM and not TIMAISdis) will be inserted downstream when AIS, LOS, etc. are detected.

Solution Limitations Description:

The above solution can solve the scenario of SNCP multi-ring cut, but there are some scenario limitations, and the following scenarios cannot be solved:

(1) Chaining exists between SNCP rings;

(2) MSP rings and SNCP rings are tangent;

Example screenshot of network management configuration method:

For the following tangent network elements, the board configuration is as follows:

The configuration method is to configure Service 1 from left to right first:

Operation: 26-SLQ64-2-17, Protection: 26-SLQ64-4-17 à17-SLQ64-1-17

Then configure operation 2 from left to right:

Work: 26-SLQ64-4-17, Protection: 26-SLQ64-2-17 à26-SLQ64-1-17

Configure right-to-left operation 3 again:

Work: 17-SLQ64-1-17, Protection: 26-SLQ64-1-17 à26-SLQ64-2-17

Configure right-to-left operation 4 again:

Work: 26-SLQ64-1-17, Protection: 17-SLQ64-1-17 à26-SLQ64-4-17

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