Overview ULFD

In the traditional Ethernet, we usually use the fiber and other physical medium to connect the devices. In the actual networking, the fiber crossover connection (Figure 2-1), or one fiber not connected or disconnected (Figure 2-2) may result in the uni-directional communication. This kind of faulty link is called uni-directional link. The uni-directional link causes a series of problems. For example, the spanning tree detection failure results in the topology calculation error.

Figure 2-1 Fiber crossover connection

Figure 2-2 One fiber is not connection or disconnected

ULFD (Unidirectional Link Fault Detection) can monitor whether the fiber or twisted-pair has the uni-directional link. When ULFD detects the uni-directional link, it is responsible for closing the physical and logical uni-directional connection, sending the alarm information to the user and blocking the failure of other protocols.