Ethernet, when evolving through time, has presented the need of a better perform ance in data traffic. Proposals such as the implementation of protocol 802.1p offer to some extent a control of quality of services (QoS), but when Ethernet net grows to metropolitan environment (e-man), new challenges arise. This work evaluates performance parameters need to characterize e-man net, and analyzes a new pro cedure to approach the problem of quality of services. This work also analyzes the performance behavior of a simulation model based on the backbone nucleus of a metropolitan net rpr.