Handling Double-Link Failures in Metro Ethernet Networks Using Fast Spanning Tree Reconnection

Ethernet is becoming a preferred technology to be deployed in metro domain due to its low cost, simplicity and ubiquity. However, traditional spanning tree based Ethernet protocol does not meet the requirement for metro area networks in terms of network resilience. In the work of Qiu et al. (2009), we proposed a fast spanning tree reconnection (FSTR) mechanism for metro Ethernet networks to handle single link failures. Upon failure of a link on a spanning tree, FSTR mechanism activates a reconnect-link to reconnect the broken spanning tree. FSTR mechanism has the features of fast recovery, simplicity, and guaranteed protection. However, when more than one link fail in the network, the FSTR mechanism would generate unexpected loops and cannot function properly. In this paper, we propose a fast spanning tree reconnection mechanism to handle double-link failures with protection grade guarantees. The mechanism is distributed and can alleviate the problem in previous FSTR mechanism. We formulate the reconnect-link pre-configuration problem for double-link failures as an integer linear programming problem. Through numerical results we demonstrate that the proposed mechanism can satisfy the protection grade required for each connection by efficiently utilizing the network capacity.