star topology
In network technology, terminal devices and switching nodes are interconnected in various physical constellations. These constellations are called topologies. There are various topologies, all of which have their own application-specific advantages. In the star topology, the end stations are connected in a star configuration to a central node.
In terms of topology, a distinction is made between physical and logical topologies. For example, a physical star topology may well represent a logical ring topology, or a bus topology and also a tree topology. Since the cabling standard makes a physical star topology mandatory in some areas, all logical network concepts can be mapped on such a topology: Ring, Bus, Tree, Star.
In the star topology, the end stations always exchange their data via the central node. The switching node is active or passive and can distribute access rights to the transmission medium to the individual end stations. In the active configuration, the switching node is a computer that manages the access rights and handles the retransmission of messages. Its performance determines the performance of the network. A typical example of such an active node is a private branch exchange. Passive star systems have only one passive node in the middle, which combines the paths. This node does not perform any switching tasks, but at most serves for signal regeneration. Passive star systems can be operated, for example, with Time Division Multiple Access( TDMA), CSMA/ CD or a token method. An example of such a star network configuration is StarLAN according to IEEE 802.3.
If further star configurations occur in the star topology instead of the connected terminal equipment, this is referred to as double stars.
The star topology has the disadvantage that all connections run via the central switching node. If this fails, the terminal stations can no longer communicate with each other. In addition, the transmission rate is determined by the number of terminals and the switching node.