Bandwidth sensitive fast failure recovery scheme for Metro Ethernet

Restoration in Ethernet has evolved over the years as specified in various standards: first the classical reconstruction of spanning trees was proposed in 802.1d; later 802.w specified RSTP to reduce the convergence time required in the STP protocol. Recently, the use of multiple spanning tree was suggested in 802.1s standard. In addition, there have been several proposals to implement multiple tree based restoration. Even though the results are promising they fall short of elevating Ethernet to a carrier grade technology. In this paper, we develop a distributed fast failure recovery spanning tree scheme, which restores lost facilities within tens of milliseconds. Recovery algorithm is localized around the point of failure on the spanning tree, thus avoiding disruption of the entire network. Failures are repaired using pre-configured sub spanning trees which are computed based on traffic requirements and resource availability. This paper also proposes possible enhancements to the failure recovery method using IEEE link aggregation standard to further reduce restoration time and provide differentiated survivability.