Overview EIPS

In the Ethernet L2 network, STP is adopted for network reliability. STP is a standard ring protection protocol developed by the IEEE and extensively applied, but it is restricted by the actual network capacity and the convergence time is affected by the network topology. The STP convergence time is in the unit of second and a larger network diameter results in longer convergence time.

To reduce the convergence time and eliminate the impact of the network capacity, the EIPS (Ethernet Intelligent Protection Switching) emerges. The EIPS is a link layer protocol applied to the Ethernet ring and it can prevent the broadcast storm caused by the data link. When a link on the Ethernet ring is disconnected, a backup link can be used immediately to recover the communications among different nodes on the ring network. Compared with the STP, the EIPS is characterized with faster topology convergence speed (less than 50s) and convergence time irrelevant with the number of the nodes on the ring network.

The EIPS supports the sub ring and hierarchical modes. In the sub ring mode, two intersecting rings are divided into a main ring and a sub ring. A common link exists between the main ring and sub ring. In the hierarchical mode, a main ring is selected from the intersecting rings. The low-level link is formed by the ring connected to the main ring excluding the common link with the main ring. Generally, the sub ring mode divides the intersecting rings to the main ring and sub ring, and the hierarchical mode divides the intersecting rings to the main ring and low-level link. In both modes, there is only one main ring and multiple sub rings or multiple low-level links.