Abstract: A method for automatic protection switching in a ring network detects a link failure at a first interface of a node, generates a first link down message and sends the first link down message along the second direction of the ring network. Upon generation or receipt of the first link down message by the redundancy manager, the redundancy manager is unblocked such that non-control frames of the at least one automatic protection switching domain are no longer blocked by the redundancy manager. Upon generation or receipt of the first link down message by one of the nodes, the node having at least one entry assigning an address to the second interface IF2, deletes only the entries in the forwarding database of the node which assign an address to the first interface of said node. Deleted entries are then updated in the forwarding database.

Abstract: Test packets (TP1, TP2) are emitted from redundancy managers (RM1, RM2) containing a source address and a rank number (RN) in information fields. Another redundancy manager (RM1) replaces this rank number only if its own rank number is lower (higher priority) than the rank number in a received test packet. All redundancy managers (RM2) with a higher rank number switch to a passive mode and only the redundancy managers (RM1) with the lowest rank number remains active.

Abstract: In a system comprising nodes linked in a ring structure where data flows between the nodes, a method of operating the system after a link has become broken, comprising recovering the broken link and the system treating the recovered link as still broken and operating the system so as to block the recovered link. One of the nodes in the ring system is a redundancy manager node which sends messages to the other nodes to implement blocking of the recovered link. Only when another link becomes broken does the system start to use the previously recovered link.

Abstract: There is described a method of operating a node in a ring network. A first loop avoidance protocol, for example, a Spanning Tree Protocol (STP) is run at the node together with a protocol adaptation process. The protocol adaptation process performs processes that enable the first loop avoidance protocol to run over a second loop avoidance protocol, for example, the Ethernet Ring Protection Protocol (ERP), operating in the ring. This makes it easier for network operators to incorporate in networks running STP, equipment manufactured to run ERP.

Abstract: The invention relates to a method for protection switching in a data network network including at least two rings (ERA, ERB) with a shared span (SP2,3) and a plurality of nodes (1-4). Each ring (ERA, ERB) has an associated ring manager (RMA, RMB) for checking its associated ring (ERA, ERB) and the ring managers (RMA, RMB) have dedicated different priorities (PR1, PR2). When a failure (interruption) occurs in a shared span, a shared span node (2, 3) sends a failure message (FSP2,3) to a ring manager (RMB) of higher priority (PR1) of an associated ring (ERB), and the ring manager (ERB) unblocks its port (PB2) while the ring manager (RMA) of lower priority (PR1) maintains its port (PA2) blocked.