A ToR switch (Top-of-Rack switch) is a network switch installed at the top or upper section of a server rack. It connects all servers within the rack using short copper or optical cables and aggregates their traffic before sending it upstream to aggregation or core switches. While the name TOR implies that the switch is deployed at the top of the server cabinet, in reality, as shown in Figure 2-1, the switch can also. Knowing the roles of core, aggregation, and access switches in contemporary network topology becomes essential to create effective and scalable networks.