Spanning Tree Protocol

The Spanning Tree Protocol (STP) is a network protocol that

ensures a loop-free topology for any bridged Ethernet local

 area network. The basic function of STP is to prevent bridge 

loops and the broadcast radiation that results from them. 

Spanning tree also allows a network design to include spare 

(redundant) links to provide automatic backup paths if an 

active link fails, without the danger of bridge loops, or the 

need for manual enabling/disabling of these backup links.

Spanning Tree Protocol (STP) is standardized as IEEE 

802.1D. As the name suggests, it creates a spanning tree 

within a network of connected layer-2 bridges (typically 

Ethernet switches), and disables those links that are not part 

of the spanning tree, leaving a single active path between 

any two network nodes.

STP is based on an algorithm that was invented by Radia 

Perlman while she was working for Digital Equipment 

Corporation.