NGL01-3: Multiple Spanning Tree Generation and Mapping Algorithms for Carrier Class Ethernets

Ethernet is evolving from a plug-and-play LAN technology towards a carrier grade WAN technology. In order to support Service Level Agreements (SLA) over Public Ethernets, extensions to STP include RSTP and MSTP. RSTP offers faster convergence than STP but uses a single tree for the entire network. In order to achieve a better utilization of the network links, MSTP supports multiple spanning trees, one tree per VLAN group. However, MSTP does not provide efficient methods to build those spanning trees. Furthermore, MSTP does not provide methods to perform efficient VLAN-Spanning-Tree Mapping. Operators must manually provision this mapping which might seriously impact OPEX and network performance. In this paper, we propose very simple and yet easy to use spanning tree generation and mapping algorithms; which can be used to extend and/or work with the 802.1s MSTP. We show that these algorithms yield optimal bandwidth utilization and enhanced network throughput compared to existing methods.