The IEEE 802.1D Spanning Tree Protocol
Defined with the IEEE 802.1 Bridge Standard (IEEE 802.1D) – note bridge is the old name used to describe what we now call switches - to detect data loops between switches and to logically break these loops to create a final topology in which only one active route is maintained. This final topology is referred to as a spanning tree. Procedures are also included to detect link failure and to restore links in order to maintain connectivity.
A switch is simply a multi-port bridge and so switching hubs support the IEEE 802.1 Spanning Tree Protocol.