Performance of rapid spanning tree protocol in access and metro networks

Ethernet provides a simple and low-cost solution at high bandwidth for access and metropolitan networks. The failover performance of bridges is indispensable of their applicability. Therefore, new IEEE protocols were developed and deployed in support of fast recovery. Rapid Spanning Tree Protocol (RSTP) is the current fault handling mechanism for generic topologies, which is included in the standards and implemented in each Ethernet bridge nowadays. There are many different statements about the recovery time of RSTP from the order of seconds down to the order of ten milliseconds. Most of these analyses only rely on simulation results assuming ideal conditions. This paper reports on the performance of RSTP in real environment. It presents an experimental performance analysis of RSTP based on measurement results from test networks comprising Ethernet bridges from various vendors. Basic processing times and hardware delays are deeply analyzed for small topologies and the performance of RSTP is then characterized for larger network topologies.