Ethernet protection switching ring (EPSR)

To ensure the continuity of Ethernet technology, which is traditionally a bus or star topology, in the core area, Ethernet itself must support ring-shaped interconnections of switches as they occur in the core area. Such ring configurations of Ethernet switches increase the resilience and stability of networks and their resilienceto failure.

Ring-shaped Ethernet switches are fault-redundant and can be protected by spanning tree procedures( STP). The disadvantage here is that recovery times are extremely long and can be 30 seconds or more for reconfiguring links with the conventional Spanning Tree Protocol. These long downtimes are unacceptable when transmitting audio, video, or real-time because any discernible or audible interruption in these transmissions is disruptive.

As an alternative to STP methods with much shorter interruption times in the millisecond range, Allied Telesis has developed Ethernet Protection Switching Ring (EPSR). Alternatively, there is Ethernet Automatic Protection Switching( EAPS) from Extreme Networks, Resilient Ethernet Protocol (REP) from Cisco, Rapid Ring Protection Protocol( RRPP) from Huawei, and others.

Ethernet Protection Switching Ring (EPSR) is a protocol that operates in physical ring configurations and is characterized by short recovery times in case of failure. When a node fails, the method recovers the configuration in about 50 ms, depending on the ports and configuration. If all Ethernet switches in the ring are powered up, EPSR prevents a loop from forming by blocking traffic on a port. In the event of a node failure, EPSR detects the failure and unblocks the blocked port so that data can be transmitted over the ring. In an EPSR configuration, there is one master node and several transit nodes that are connected to the ring via two ports.