Local restoration with multiple spanning trees in metro ethernet

Ethernet is becoming a preferred technology to be extended to Metro Area Networks (MAN) due to its low cost, simplicity and ubiquity. However, current Ethernet lacks fast failure recovery mechanism. It reconstructs the spanning tree after the failure is detected, which commonly requires tens of seconds. Some researchers have proposed fast failure handling methods based on multiple spanning trees, but these approaches are either centralized or require periodic message broadcasting over the entire network. In this paper, we propose a local restoration mechanism for Metro Ethernet, which is distributed, fast, and does not need failure notification. Upon failure of a single link, upstream switch locally restores traffic to pre-configured backup spanning trees. We propose two approaches for backup tree selection (connection based and destination based), and formulate the working spanning tree assignment and backup spanning tree configuration problem as an integer linear programming problem. We also develop heuristics for each strategy to reduce computation complexity. The simulation results show that our algorithms have comparable performance close to the optimal solutions, and both strategies can efficiently utilize the network bandwidth to handle single link failure.