Efficient building method of multiple spanning tree for QoS and load balancing

Current traffic patterns are far removed from the traffic trends seen during the early days of Ethernet technology. Therefore, the current IEEE 802.1 standard and its extensions to the spanning tree protocol fall short of providing-satisfactory quality of service for traffic which has a significant amount of QoS-sensitive traffic. In addition, they do not provide a mechanism for stabilizing the traffic load among a whole bridged network where usually the root switch has to handle all the traffic from its child switches. In the current and near-future scenario of switching networks with significantly large layer-2 clusters and numerous VLANs, we show significant shortcomings of the basic spanning tree and the multiple spanning tree protocols with regard to QoS and load balancing. We propose to incorporate a bridge ID scheme of a regional root identifier which is used in multiple spanning tree instance (MSTI) to provide an efficient MSTI building method for QoS and load balancing. Through this scheme, the traffic source of a point-to-multipoint (P2MP) application can set itself as the root of MSTI satisfying the QoS constraint while roots of several regular MSTIs are built in a distributed way. We discuss the problem of building MSTI for P2MP applications and regular MSTIs and present in detail our proposed scheme. Our experiments for two cases show good improvement of QoS in terms of delay and load balancing of the whole bridge network.