Spanning tree elevation protocol: Enhancing metro Ethernet performance and QoS

Abstract

The economics and familiarity of Ethernet technology is motivating the vision of wide-scale adoption of Metro Ethernet Networks (MEN). Despite the progress made by the community on additional Ethernet standardization and commercialization of the first generation of MEN, the fundamental technology does not meet the expectations that carriers have traditionally held in terms of network resiliency, load management, and Quality of Service (QoS). We propose a new concept of Spanning Tree Elevation Protocol (STEP) that increases MEN performance while supporting QoS including traffic policing and service differentiation. STEP manages multiple Spanning Trees as a means to control the traffic flow rates and to differentiate classes of traffic. Whenever a service level agreement is compromised, STEP redirects frames of affected flows to the next spanning tree in sequence utilizing the alternate paths. As a result, the capacity in terms of network throughput is greatly enhanced while almost avoiding any reconvergence time in the case of failures. The gain ranges from 1.7% to 7.3% of the total traffic in the face of failure; while load balancing increases an additional 12.8% to 37% of the total throughput. At the same time, STEP maintains the required bandwidth for high priority traffic class during the failure scenarios and the high congestion scenarios.