Huawei OTN Equipment Fails to Transparently Transmit Ethernet Clock Signals

Symptom Clocks between PTN equipment must be synchronized. Network AM using the OTN network architecture is configured between PTN equipment to transparently transmit clock signals from upstream PTN equipment to downstream PTN equipment or to implement network-wide clock synchronization. After the network is set up according to the network topology, the clock synchronization fails. The following figure shows the network topology. Figure 1 The Network Topology of AM Network  Cause Analysis The OptiX OSN 6800/OptiX OSN 8800 earlier than V100R006C01 cannot directly restore clock signals from 10GE services transmitted from PTN equipment. Therefore, clock signals are transparently transmitted from the upstream PTN equipment to the downstream PTN equipment. According to the network topology, PTN equipment transmits 10GE LAN services to the OTN network that consists of NG WDM equipment. The TN52TQX board is configured on the OptiX OSN 6800/OptiX OSN 8800 equipment and is set to the MAC Transparent Mapping (10.7G) mode. This network topology, however, cannot implement clock transparent transmission because of the MAC Transparent Mapping (10.7G) mode and Bit Transparent Mapping (11.1G) mode when clock signals are processed. 10GE LAN services can be set to 10GE LAN MAC Transparent Mapping (10.7G) mode or 10GE LAN Bit Transparent Mapping (11.1G) mode. The differences are as follows: ·         In the 10GE LAN MAC Transparent Mapping (10.7G) mode: 10GE LAN signals are encapsulated in the GFP-F mode and then mapped into standard OTU2 frames. In this mode, 10GE MAC frames are transparently transmitted. In addition, the equipment working in this mode supports standard OTU2 frames at the rate of 10.71 Gbit/s and can be interconnected with all equipment that supports standard protocol rates. In this mode, the local clock is traced and service clock signals cannot be transparently transmitted. ·         In the 10GE LAN Bit Transparent Mapping (11.1G) mode: Client 10GE LAN signals are directly mapped into OTU2 frames and transmitted at the rate of 11.1 Gbit/s. The transmission is implemented by extending the OTU2 frame structure and the transmission rate is higher than standard OTU2 signals. In this mode, the service clock is traced, and service clock signals can be transparently transmitted after the line rate is set to speed-up mode for the TN52TQX board. ·         To transmit link information in client services, you must set the MAC Transparent Mapping (10.7G) mode and enable the LPT function or set the Bit Transparent Mapping (11.1G)mode for the TN52TQX board. Procedure 1.    Set the Working Mode to Bit Transparent Mapping (11.1G) mode and the line rate to Speed-up Mode for the service board. Result The problem is resolved. Reference Information The NG WDM equipment traces the local clock or service clock based on the service type. Generally, the service clock is traced, and clock transparent transmission is supported when OTN boards are configured with the maximum supported cross-connect granularity and are set to the Speed-up Mode. Clock synchronization can be achieved by means of transparent transmission and network-wide clock synchronization. The OptiX OSN 6800/OptiX OSN 8800 earlier than V100R006C01 can only transparently transmit 10GE services and clocks between PTN equipment. The same is true for SDH services (transparent transmission is implemented using SDH boards). Network-wide clock synchronization can be achieved only when the TN52TOG board is interconnected to PTN equipment to transmit GE services. On the OTN network, the boards that support the IEEE 1588 feature can transmit physical clocks.