DCC resource reallocation after hard reset of optical interface board leads to network element decontrol

When upgrading or expanding the capacity of a network element, the DCC resources are reallocated after the hard reset of the optical interface board, and the low-rate multi-optical interface board seizes the DCC resources of the high-speed optical interface board, resulting in a shortage of DCC resources, which triggers the de-regulation of the network element. Troubleshoot this fault by releasing the DCC resources of the low-rate optical interface board.

Products

OptiX OSN3500

Fault category

DCN Failure

DCC_CHAN_LACK

Phenomenon Description

Before the network element is upgraded or expanded, there are no abnormal alarms reported by the network element, and the DCC communication between the network elements is normal. After the network element is upgraded or expanded, the optical interface board reports the DCC_CHAN_LACK alarm, and the network element goes offline.

Cause Analysis

During the process of network element upgrade or capacity expansion, DCC resources are reallocated because the operation of hard resetting the optical interface board occurs. The low-speed optical interface board seized the DCC resources of the high-speed optical interface board, resulting in insufficient DCC resources, and the high-speed optical interface board could not obtain the DCC resources, which triggered network element de-regulation.

Procedure

Check the DCC bytes sent and received by the network elements on both sides of the docking. The sending end sends DCC bytes, but the receiving end does not receive the byte information, so the possibility of DCC error codes is ruled out.

Go to the equipment site to check the status of the network elements.

Connect the PC directly to the network element and log in to the network element.

Check the ECC protocol settings are normal, so the possibility of an error in the ECC protocol configuration is ruled out.

Perform a master-standby reversal on the master control board. When the service is inverted to the backup master control, the alarm DCC_CHAN_LACK still exists and the fault is not removed, so the possibility of a faulty master control board is ruled out.

Pull out the low-speed optical interface board, the high-speed optical interface board immediately resumes normal data transmission, the alarm disappears, and normal communication between network elements resumes. Preliminary judgment is that the low-speed optical interface board has seized the DCC resources of the high-speed optical interface board, which has led to network element de-regulation.

Description:

The main control board generally supports multiple DCC working modes, and you can modify the DCC working modes to obtain more DCC resources.

By default, the DCC working mode of the N1GSCC board is: using D1 to D3 bytes as the physical transmission channel, supporting 10DCC optical interface resources.

Most of the low-speed optical interface boards are multi-optical interface circuit boards, for example: the SLT1 single board is a 12-channel optical interface board. When the DCC resources are reallocated after hard resetting the optical interface board, the low-speed optical interface board immediately seizes the DCC resources released by the high-speed optical interface. This results in the high-speed optical interface board not being able to acquire DCC resources, and the network element is decontrolled.

Reinsert the low-speed optical interface board.

After the network element operates normally, query whether the DCC_CHAN_LACK alarm still exists on the network management. The DCC_CHAN_LACK alarm is still reported by the optical interface board, and the network element is again decontrolled.

After releasing the DCC resources of the optical ports of the low-speed optical interface board one by one, the DCC optical ports of the high-speed optical interface board also resume data sending and receiving one after another, and the alarm disappears, and normal communication between the network elements resumes. Thus, it is sure that the low-speed optical interface board has seized the DCC resources of the high-speed optical interface board, resulting in network element de-regulation.