Optimizing QoS aware Ethernet spanning trees

Ethernet is gaining in importance in both access and metro networks. As a layer 2 technology, Ethernet gives a basic framework for routing, QoS and traffic engineering (TE), as well as a protocol for building up trees. IEEE 802.1 standards define default configuration parameters considering the topology only. We propose methods for resource management in Ethernet networks through spanning tree optimization for both STP (spanning-tree protocol) (IEEE 802.1D) and MSTP (multiple spanning-tree protocol) (IEEE 802.1s). As a result of optimization, we assign costs to the bridge ports in the network to build trees based on these costs via STP and MSTP. These trees yield optimized routing, TE and support for different QoS classes. We show on typical metro-access networks that, through optimization, the total network throughput can be significantly increased for both enforcing fairness or allowing starvation of some demands. This gain can be realized by simultaneously assigning demands to trees and routing these trees.