This thesis elaborates one of the most important protocol in modern computer networks – Spanning Tree Protocol. Development and characteristics are described from the early begining of the protocol and until today's implementations in modern environments. Potential updates to existing STP are also mentioned, such as: RSTP – Rapid Spanning Tree Protocol and MST – Multiple Spanning Tree Protocol. For each of these technologies it is highlighted in detail where and how it is used and what benefits it brings to the classic STP. Flaws and also advantages of the STP are shown in this thesis. Moreover, different variations and possibilities of detection, correction and monitoring protocol itself is well described and explained. In the end, there is a part related to a completely new approach to the aggregation network - TRILL. TRILL is a new protocol, which brings large and significant changes into the network segments that affects packet forwarding. Higher speeds and better utilization of bandwidth are just a few of these advantages.