Description of the problem

A bureau's fiber-optic cable outage causes the 10GMSP ring of Huawei OSN3500 equipment to be inverted, and when the fiber-optic cable is restored, the service of the NE40 equipment that is docked with transmission is interrupted. The customer tests 1+1MSP protection inversion, and when the optical path is interrupted, the service of NE40 equipment docked with transmission is interrupted.

warning message

The disappearance or appearance of R-LOS on the primary link of the transmission link is accompanied by an automatic shut down of the NE40 port.

Processing

Change the BFD value greater than 50 ms, retest the inversion, and the NE40 device has no interruption.

Root cause

From the definition of MSP, multiplexing segment protection refers to a protection method that completes a series of protocol handshaking processes with the help of K bytes in the multiplexing segment in the overhead, so that the service signals that were originally transmitted on the damaged fiber are transferred to the protection route for transmission, thus allowing the original service to continue to be transmitted without interruption.MSP is divided into linear multiplexing segment protection and ring multiplexing segment protection.LMSP automatically switches the service that passes through the primary link to the backup link the instant the primary optical link fails. LMSP automatically switches the services passing through the primary link to the backup link at the moment of the failure of the primary link.G.814 recommendation stipulates that the inversion time of the linear multiplexing segment is 50ms.The bureau here sets it as a restoration type.RMSP has no dedicated primary and backup fibers.The first half of the time slot of each fiber is the primary channel, and the second half of the time slot is the backup channel, and the services flow in the opposite direction on the two fibers.G.814 recommendation stipulates that the inversion time of the linear multiplexing segment is 50ms.G.814 recommendation stipulates that the linear multiplexing segment is 50ms.G.814 recommendation specifies the inversion time of the primary and backup fibers. The multiplexing segment inversion time is 50ms. the bureau here sets it to recovery.

BFD is a standard protocol used to realize fast fault detection, BFD has two operation modes: asynchronous mode and query mode. At present, our company only supports asynchronous mode. In this mode, both ends of the session send BFD control messages periodically, and the status of the session is detected according to whether or not the BFD control message of the other end can be received. The purpose of adding BFD protocol to NE40 device is to allow the routing protocol to calculate new routes as soon as possible after getting the BFD notification, so as to shorten the convergence time. However, because BFD detects link messages for 10 ms at a time, in this case, when MPS protection inversion occurs in transmission, the NE40 will detect the link message interruption at the instant of inversion, which leads to automatic shut down of the NE40 device ports.

Recommendation and Summary

When adding new protocols to the docking equipment, if it involves detecting the transmission link, you should communicate with the transmission engineer and make relevant tests in time to avoid the occurrence of failures.