The convergence time for legacy Spanning Tree Protocol (STP) IEEE 802.1D standard is 30 to 50 seconds. When the network is converging on a topology change, no traffic is forwarded to or from any of the network bridges and switches. In modern networks this convergence time gap is not acceptable and Cisco enhanced the original Spanning Tree Protocol (STP) 802.1D specification with features such as PortFast, UplinkFast and BackboneFast to speed up the convergence time. But these were proprietary enhancements.
The Rapid Spanning Tree Protocol (RSTP) IEEE 802.1W standard is available to address the convergence time gap issue. Rapid Spanning Tree Protocol (RSTP) enables root ports and designated ports to change from the blocking to forwarding port state in a few seconds.
