Beware of Using a Single Cross-connect Board for OSN 7500

[Problem Description]
Trigger condition:

The problem described in this pre-warning is occasionally triggered when the following conditions are all met:
1. More than 16 processing boards are used on an NE.
2. Only one cross-connect board is powered on.
Problem Description
The NE reports a COMMUN_FAIL alarm, or MSP switching fails.

Huawei corss-connected board

Identification Methods:
Check the following:
Whether there is any COMMUN_FAIL alarm that has a parameter whose value is 01 or 02.
Whether only one cross-connect board is powered on.
Whether the number of service processing boards in the line slots is more than 15.

Parameters of the COMMUN_FAIL alarm:
725127 COMMUN_FAIL  SA NEW_BOARD  MJ start 2012-11-07 09:42:33+08:00 None SA NEW_BOARD board=10;01 00 01 ff ff;

725127 COMMUN_FAIL SA  NEW_BOARD  MJ start 2012-11-07 09:42:33+08:00 None SA NEW_BOARD board=3;01 00 02 ff ff;

The first parameter indicates a slot number which may be any slot. You need to pay attention to the fourth parameter. A fault will occur if the value of the fourth parameter is 01 or 02 which indicates a 485 communication failure on the first or second channel.

[Root Cause]
The problem was caused by the related components on cross-connect and service processing boards on the OptiX OSN 7500 NEs which were delivered before October, 2012. Specifically, the delay in the transmit and receive directions on the 485 bus is long; however, the data driving capability of the 485 bus is mainly driven by the circuit on the cross-connect board. When only one cross-connect board is inserted and used, the driving capability of the bus decreases by 50%. In this case, if multiple processing boards are used, there is a high probability that a fault or conflict occurs in the communication data. As a result, communication between boards on an NE fails. In some cases, a COMMUN_FAIL alarm (485 communication) may occur. Therefore, in this case, the use of single cross-connect board for an OptiX OSN 7500 is not allowed. The relevant components manufactured after October, 2012 have been technically improved. The 485 components on all boards are replaced with components with shorter delay. In addition, their circuits are optimized. Therefore, no such problem will exist on the boards which are delivered after October, 2012.

  OptiX OSN 7500 Equipment Delivered Before    OptiX OSN 7500 Equipment
  October, 2012    Delivered After October, 2012
Scenario If more than 16 service processing boards are used,two cross-connect boards must be configured.     No such problem exists.

However, because newly delivered boards may work with old NEs and boards, it is recommended that you not use a single cross-connect board on all Huawei optical network products like OptiX OSN 7500 NEs.

[Impact and Risks]
1. The NE reports a COMMUN_FAIL alarm.
2. MSP switching may occasionally fail.
Measures and Solutions
Recovery measures:
Insert a cross-connect board on the idle slot for cross-connect boards. For more boards you can search from Huawei network product distributor.
Workaround
Do not use single cross-connect board on the OptiX OSN 7500 NE on the entire network.
Corrective Action
Boards which were deliveried after October, 2012 do not have this problem.

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