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Star network layout

Star networks are one of the most common computer network topologies. In its simplest form, a star network consists of one central switch, hub or computer which acts as a conduit to transmit messages. If the central node is passive, the originating node must be able to tolerate the reception of an echo of its own transmission, delayed by the two-way transmission time (i.e. to and from the central node) plus any delay generated in the central node. An active star network has an active central node that usually has the means to prevent echo-related problems.

The star topology reduces the chance of network failure by connecting all of the systems to a central node. When applied to a bus-based network, this central hub rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, sometimes including the originating node. All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only. The failure of a transmission line linking any peripheral node to the central node will result in the isolation of that peripheral node from all others, but the rest of the systems will be unaffected.

Strictly speaking only networks that use switches have a true star topology. If the network uses a hub, the network topology has the physical appearance of a star, but is actually a bus.

• Good performance.
• Easy to set up and to expand.
• Any non-centralised failure will have very little effect on the network, whereas on a ring network it would all fail with one fault.
• Easy to detect faults
• Data Packets are sent quickly as they do not have to travel through any unnecessary nodes.

• Expensive to install
• Extra hardware required
• If the hub/switch fails the entire system is affected.

• Bus network
• Ring network
• Mesh network
• Tree and hypertree networks