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Rules for Calculating and Generating the Parity Bit for a Path Trace Byte on the OptiX OSN NEs

Publication Date:  2012-07-25 Views:  126 Downloads:  0

Issue Description

An access network board is connected to a piece of optical network equipment. Although both ends use the same J0 and J1, they report the J0_MM and HP_TIM alarms. What is the cause of the alarms? 


Alarm Information


Handling Process

The alarms do not affect the services. Mask the alarms. 

Root Cause

Both ends use the same J0 and J1. The optp command, however, shows that the optical network equipment receives a character string different from the character string that the optical network board sends.
The optical network equipment processes bytes J0, J1, and J2 by ITU-T G.831.
●In single-byte mode, the equipment sets the byte simply into the chip.
●In 16-byte mode, the equipment calculates a parity bit by the CRC-7 algorithm and places the parity bit in the first byte. The optp command can display the J0, J1, or J2 received with the parity bit.
-Byte J0: :optp:bdid,0,9b,1,08,9f,laser
-Byte J1: :optp:bdid,0,9b,1,08,a3,laser,0,byPath,au3path
-Byte J2: :optp:bdid,0,9b,1,1a,53,LowPath
●In 64-byte mode, the equipment supports only byte J1 and does not support byte J0 or J2. The string is a 64-byte sequence ended in 0d 0a without a parity bit.
The access network boards developed earlier, however, generate a parity bit by a different rule. They calculate the parity bit by a different algorithm and place the parity bit in the last byte.
Both ends check the parity bit when they check bytes J0 and J1. Therefore, they report the mismatch alarms.