Network topology relates to a layout pattern of interconnections of the various network elements, such as nodes and links, of a computer network. Network topologies may be physical or active. Physical topology refers to the physical design of a network including the devices, location and cable installation. Active topology refers to how data is transferred in the network from one device to the next, without regard to the physical design. Though a path electrical signals take between nodes in the physical topology may at least somewhat match a flow of data in the active topology.
For example, the physical topology of the network may be defined by a layout of cabling, the locations of nodes, and the interconnections between the nodes and the cabling. However, the active topologies may be determined by network protocols, such as the Spanning Tree Protocol (STP), Rapid Spanning Tree Protocol (RSTP), VLAN Spanning Tree Protocol (VSTP) and Multiple Spanning Tree Protocol (MSTP).
The network protocols may apply graph theory and algorithms associated therewith to create a minimum spanning tree for the routing of data through the network. The spanning tree may define a tree composed of all the nodes and at least some of the edges of a connected, undirected graph, in which no cycles or loops are formed. For example, the STP may ensure a loop-free topology for any bridged Ethernet LAN. As a result, network planning may be significantly simplified as a network administrator need not be concerned about the resulting cabling of the physical topology, which may readily create loops.