Function Implementation

Trigger Conditions

The trigger conditions for the DLAG automatic switching are as follows:

• The board is offline, including the following situations: Removing or cold resetting the board.
• A warm reset is performed on the board.
• The board hardware fails: EQPT-SA and RMV.
• The link is faulty or the following alarms are reported on the board: LINK-ERR, LOS and LOF.
• Loopback is configured at the working ports.
• In the revertive mode, the system priority or port priority is changed.

Working Principle

The DLAG protection can work with the SW SNCP protection.

Figure 1 and Figure 2 shows the principle of the DLAG when it works with the SW SNCP protection.

Figure 1 Principle of the DLAG when working with the SW SNCP protection (normal)

: Direction of the working signal flow

: Direction of the protection signal flow

Figure 2 Principle of the DLAG when working with the SW SNCP protection (switching)

: Direction of the working signal flow

: Direction of the protection signal flow

NOTE:

• An SW SNCP protection group and a DLAG protection group are configured at station A. An SW SNCP protection group is configured at station B.
• In Figure 1 and Figure 2, the boards numbered 1 and 2 are the TBE boards. Board 1 is the working board of the DLAG protection and board 2 is the protection board of the DLAG protection. The boards numbered 3 and 5 are the protection OTU boards. The boards numbered 4 and 6 are the working OTU boards. The OptiX OSN 6800A implements dual fed and selective receiving by using a centralized cross-connect board (XCS board), which is not shown in Figure 1 and Figure 2. The OptiX OSN 3800A implements dual fed and selective receiving by using mesh cross-connections.
• The SCC and the line boards communicate through the backplane, which are not shown in Figure 1 and Figure 2.

The working and protection tributary boards interconnect to the digital subscriber line access multiplexer (DSLAM) by using the link aggregation control protocol (LACP). When a fault occurs between the DLAG protection and the DSLAM, the LACP detects the fault of the corresponding port and re-select a working port. In addition, the SCC informs the cross-connection to making connection changes accordingly.

• In the transmitting direction, the client services that require protection are input through two ports of the DSLAM and then sent to the TBEs numbered 1 and 2. In normal situations, the OTUs numbered 3 and 4 in the SW SNCP protection group at station A have cross-connections only with the TBE numbered 1 in the DLAG protection. When a fault occurs between the DLAG protection and DSLAM, the DLAG protection switching occurs. At station A, the OTUs numbered 3 and 4 in the SW SNCP protection group have cross-connections only with the TBE numbered 2 in the DLAG protection.
• In the receiving direction, the cross-connection of the OTU numbered 6 takes effect and the cross-connection of the OTU numbered 5 is disabled. When the working channel is faulty, the cross-connection of the OTU numbered 6 is disabled and the cross-connection of the OTU numbered 5 takes effect. The services are transmitted over the protection channel.
• After the working channel is recovered, the services can be switched to the specified OTU according to the revertive mode that is preset on the U2000 Web LCT.