Partial spatial protection for provisioning differentiated reliability in FSTR-based Metro Ethernet networks

摘要

Fast Spanning Tree Reconnection (FSTR) is a newly proposed restoration method by us to handle link failures in Metro Ethernet networks. Compared with other methods existing in the literature, FSTR has the advantages of lower signaling overhead, faster recovery and lesser rerouted traffic. However, FSTR.lacks its own mechanism to support differentiated reliability (DiR), which is required by voice and data services, as well as a variety of emerging multimedia applications such as video conferencing and online gaming. In DiR, a traffic request is guaranteed a minimum reliability/protection degree in the event of a link failure, according to clients' requirements. Unnecessary redundant/backup network resources are thus eliminated in DiR and, as a result, the blocking probability of traffic requests decreases, compared to that in full protection where 100% reliability is guaranteed for all traffic requests. In this work, we propose to use partial spatial protection (PSP) mechanism at the spanning tree layer to provision DiR in FSTR-based Metro Ethernet networks. The basic idea of PSP to provide DiR is that a traffic request is protected using backup bandwidth against failure of only a subset of the links on its route, according to the specified reliability requirement. To the best of our knowledge, this is the first work on the problem of PSP at the spanning tree level, a layer unique to Ethernet where traffic requests are required to be mapped onto different trees and the protection mechanisms usually involve tree restoration/reconstruction. We formulate the optimal PSP problem in FSTR-based Metro Ethernet networks as a mixed integer linear programming (MILP) model. We develop a heuristic algorithm to reduce the computational complexity in implementing PSP. The heuristic algorithm is designed based on a known 1/2-approximation approach to the Knapsack problem. We describe the recovery operations of PSP in the event of a link failure. The numerical results demonstrate that the proposed PSP solution can significantly reduce the blocking probability of traffic requests in an FSTR-based Metro Ethernet network, compared to full protection.