Spanning Tree Protocol

The Spanning Tree Protocol, or STP, is a network protocol that builds a loop-free logical topology for Ethernet networks. Its basic job is to prevent bridge loops and the broadcast radiation they cause, while still letting a network design include backup links that provide fault tolerance if an active link fails. It works by computing a spanning tree over the connected layer-2 bridges and disabling the links that are not part of that tree, leaving a single active path between any two nodes. The underlying algorithm was invented by Radia Perlman while she worked for Digital Equipment Corporation. STP was standardized as IEEE 802.1D, was followed by the faster Rapid Spanning Tree Protocol in 2001, and is now incorporated into IEEE 802.1Q-2014.