On building multiple spanning trees and VLAN assignment in metro ethernet networks

Abstract

While most of today's research effort is being devoted to wireless technologies involving the tiniest and most sophisticated devices, Ethernet is evolving from a best effort, plug-and-play LAN technology, towards a carrier-grade WAN technology. Most of the new Ethernet standards rely on spanning tree protocols (STP) such as Rapid STP (RSTP) and multiple STP (MSTP). RSTP offers faster convergence than the legacy STP but like its predecessor, it uses a single tree to carry all the traffic offered to the network, seriously impacting throughput and bandwidth usage. MSTP however supports multiple spanning tree instances but does not provide generic methods to build those instances. Moreover, MSTP does not provide efficient methods to map between spanning trees and virtual LANs (VLAN). Operators must manually provision this mapping which seriously affects network operation expenditures and network performance. In this paper, we introduce a multiple spanning tree generation algorithm (MSTGA) and a VLAN-spanning tree mapping algorithm (VSTMA) aimed at helping operators leverage their networks, save bandwidth, and support service level agreements with their customers. These algorithms can be used to extend and/or work with MSTP. We show that MSTGA maximizes throughput while VSTMA minimizes bandwidth usage. We also show that combining edge-disjoint spanning trees with VSTMA constitutes the best bandwidth/throughput tradeoff. © 2012 Wiley Periodicals, Inc. NETWORKS, 2013