Load Balanced Spanning Tree (LBST) in Metro Ethernet Networks

Spanning Tree Protocol (STP) is a link management protocol that provides path redundancy while preventing undesirable loops in the Ethernet networks. In fact, STP defines a tree that spans all switches in the network such that the sum of the costs of the chosen links is minimized. Deploying the STP to manage the topology autonomously is inadequate and do not meet the requirement for Metro Area Networks because STP blocks redundant links leaving traffic on a single path, running the risk of congestion, especially close to the root. As a result, STP provides poor support for load balancing. A solution for this problem is using the multi-criteria Minimum Spanning Tree by considering criterions such as load balancing over links and switches. In our previous work, we proposed an algorithm named Best Spanning Tree (BST) to find the best spanning tree in a Metro Ethernet network. BST is based on the computation of total cost for each possible spanning tree. Therefore, it is very time consuming especially when our network is large. In this paper we propose an algorithm named Load Balanced Spanning Tree (LBST) to find the near-optimal Balanced Spanning Tree to reduce the computational complexity of BST algorithm.