Best Multiple Spanning Tree in Metro Ethernet Networks

Current Ethernet networks rely on IEEE Spanning Tree Protocol (STP), which provides a loop-free connectivity across various network nodes. STP does this task by reducing the topology of a switched network to a tree topology where redundant links are pruned. In STP, all customers need to use the same spanning tree and there isn´t any traffic engineering mechanism for load balancing. Currently, one of the main approaches to address this issue is IEEE Multiple Spanning Tree Protocol (MSTP), in which, a spanning tree instance is run separately for each Virtual LAN (or group of Virtual LANs). This standard does not provide any generic method to select the spanning trees and to map the VLANs to the spanning tree. This paper presents a scheme for MSTP that considers all of the possible Edge-disjoint spanning trees and all of the possible VLANs grouping and finds the best solution based on load balancing on links and switches. Actually, we define three major criterions: load balancing over links, load balancing on switches and shortest path selection. We can weight the importance of each criterion based on our goal.