A rapid protection switching method in carrier ethernet ring networks

Abstract

Abstract: Ethernet is the most important Local Area Network (LAN) technology since more than 90% data traffic in access layer is carried on Ethernet. From 10M to 10G, the improving Ethernet technology can be not only used in LAN, but also a good choice for MAN even WAN. MAN are always constructed in topology because the network could provide resilient path protection by using less resource (fibre or cable) than other network topologies. In layer 2 data networks, spanning tree protocol (STP) is always used to protect transmit and preventing the formation of logic loop in networks. However, STP cannot guarantee the efficiency of service convergence when happened. In fact, convergent time of networks with STP is about several minutes. Though Rapid Spanning Tree Protocol (RSTP) and Multi-Spanning Tree Protocol (MSTP) improve the STP technology, they still need a couple of seconds to achieve convergence, and can not provide sub-50ms protection switching. This paper presents a novel rapid protection method (RRPM) for carrier Ethernet. Unlike other link-fault detection method, it adopts distributed algorithm to detect rapidly (sub-50ms). When networks restore from fault, it can revert to the original working state. RRPM can provide single protection and interconnected protection without the formation of super loop. In operation, the master node blocks the secondary port for all non-RRPM Ethernet frames belonging to the given RRPM Ring, thereby avoiding a loop in the ring. When happens, the node on which the failure happens moves from the ring normal state to the ring fault state. It also sends link down frame immediately to other nodes and blocks broken port and flushes its forwarding database. Those who receive link down frame will flush forwarding database and master node should unblock its secondary port. When the failure restores, the whole will revert to the state. That is block secondary port on master node for loop avoidance. Ethernet rings may be interconnected through dual nodes with a shared link. In this case, we should fix that which on the share is ctrl-ring, and only ctrl-ring can deal with the failure happens on the share link. Carrier Ethernet is an alternative for traditional MAN technologies. Ethernet network which can make CE more reliable is one of the hottest topics in recently years. RRPM can provide protection switching in sub-50ms and process on single and interconnected rings.