Application Scenarios for ERPS
Generally, redundant links are used on an Ethernet switching network to provide link backup and enhance network reliability. The use of redundant links, however, may produce loops, causing broadcast storms and rendering the MAC address table unstable. As a result, communication quality deteriorates, and communication services may even be interrupted.
To prevent loops caused by redundant links, enable ERPS on the nodes of the ring network. ERPS is a Layer 2 loop-breaking protocol defined by the ITU-T, and provides fast convergence of carrier-class reliability standards.
As shown in Figure 1, SwitchA through SwitchE constitute a ring. The ring runs ERPS to provide protection switching for Layer 2 redundant links and prevent loops that cause broadcast storms and render the MAC address table unstable.
Generally, the RPL owner port is blocked and does not forward service packets, preventing loops. If a fault occurs on the link between SwitchA and SwitchB, ERPS will unblock the blocked RPL owner port and traffic from User network1 and User network2 is forwarded through the path SwitchC ->SwitchD ->SwitchE.