What Caused Occasional NE Unreachability

Keywords: WDM products, OptiX OSN 6800, OptixOSN 8800

Summary:

For an NE of a version earlier than OptiX OSN 6800 V100R004C04SPC800 or OptiX OSN 8800

V100R002C02SPC800, there is a low probability that the NE is unreachable by the NMS due to the

QFull count error in the DCN communication.

[Problem Description]

Trigger condition:

The problem may occur when either of the following conditions is present:

l The NE version is earlier than OptiX OSN 6800 V100R004C04SPC800 and the TN11SCC or

TN51SCC board is installed on the NE, or the NE version is between V100R004C00 and V100R004C04SPC800

(excluding V100R004C04SPC800) and the TN52SCC board is installed on the NE.

l The NE version is earlier than OptiX OSN 8800 V100R002C02SPC800 and the TN11SCC or TN51SCC board is

installed on the NE, or the NE version is between V100R002C00 and V100R002C02SPC800 (excluding

V100R002C02SPC800) and the TN52SCC or TNK2SCC board is installed on the NE.

Symptom:

The NE is unreachable by the NMS. If the NE is a gateway NE (GNE), all its subtending NEs will be unreachable

by the NMS.

Identification method:

1. Check whether the version of an unreachable NE is one of the versions listed in the preceding table.

2. Use the UpgradeKit tool to log in to the GNE of the NE in the same way as how you log in to a GNE using the

Navigator. Click Login on the tool main menu, and then select Gateway IP and click OK in the Login dialog

box that is displayed.

 

 

3. On the tool main menu, click Comm. In the dialog box that is displayed, select the unreachable NE and its

GNE, and then click Check. In the example shown in the following figure, NE 9-226 is unreachable. Therefore,

both NE 9-226 and its GNE 9-228 are selected. Click OK in the Select Check Items dialog box that is displayed.

 

 

4. View the Check QFull on the NE item in the output results. If the check result is not “OK”, the NE has a

QFull count error.

 

 

Note: The methods of using the UpgradeKit and Navigator tools are the same. Both tools can be used to remotely

log in to a subtending NE through its GNE. When the UpgradeKit tool is directly connected to a GNE using a

network cable or through Ethernet, the tool does not communicate with the GNE over a DCN channel. Therefore,

communication between the tool and NEs are not affected regardless of whether the NEs are unreachable.

The UpgradeKit tool can log in to the GNE when it is directly connected to the GNE. Generally, a remote login can

be implemented using the above-mentioned method if a faulty NE is not severely unreachable. If the GNE fails to

be logged in to, directly connect the UpgradeKit tool to an unreachable NE on site and then log in to the NE.

 

[Root Cause]

The product software has a bug in collecting statistics on the sending queues of DCN channels. When the sending

queue count reaches the maximum value, the queue buffering capability fails and subsequent packets are directly

discarded. Consequently, the QFull count of the DCN channel on an involved NE becomes abnormal, causing the

NE to become unreachable by the NMS.

 

[Impact and Risk]

When the fault occurs, the NE becomes unreachable and the DCN communication cannot be automatically restored.

The NMS cannot manage the NE through DCN or monitor service alarms and performance in real time.

 

[Measures and Solutions]

Recovery measures:

Perform a warm reset on the system control board.

Workarounds:

Perform a warm reset on the system control board.

Preventive measures:

You are advised to upgrade the NE to the target version:

l For OptiX OSN 6800: OptiX OSN 6800 V100R004C04SPC800 (5.51.05.35) or later

l For OptiX OSN 8800: OptiX OSN 8800 V100R002C02SPC800 (5.51.05.35) or later