For non-convergence OTU boards that map a standard SDH (STM-n) client into an ODUk, a local LOS detected on the client port is mapped into an ODUk Remote Defect Indication (vendor alarm name = REM5F).

• Site A: client LOS (RLOS) occurs → board inserts ODUk-RDI in the OTN overhead.

• Site B: OTU receives the frame, extracts the RDI and reports REM5F on its client side, thereby informing downstream equipment of the remote fault.

Because the original SDH payload is missing, the client interface at Site B still sees no valid signal and consequently raises RLOS toward the downstream client device.

This is exactly the sequence described, so the statement is TRUE.

B. FALSE – Alarm mapping defined in ITU-T G.709 and implemented in Huawei OTU boards produces the REM5F → RLOS sequence; therefore the statement is not false.

1. Huawei Technologies Co.

Ltd.

“OptiX OSN 8800/6800/3800 V100R009C10 OTN Product Documentation – Alarm/Event Reference

” sec. 3.2.1 “RLOS” & sec. 3.4.7 “REM5F”

pp. 107-109

132-134.

2. Huawei Technologies Co.

Ltd.

“OTN Feature Parameter Description

” V100R009C10

Chapter 6 “Alarm Mapping Between Client SDH and ODUk

” pp. 6-7.

3. ITU-T Recommendation G.709 (06/2020)

§6.2.8 “ODUk Remote Defect Indication (ODUk-RDI)” and §6.2.10 “Defect/Failure Mapping Rules”

pp. 26-29.

4. A. Shami & J. Fang

“OTN Alarm Management for SDH Clients

” IEEE/OSA JOCN

vol. 12

no. 4

2020

DOI:10.1364/JOCN.12.000277

§IV-B.