Networking and topologies


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Industrial Communications Handbook

By Mick Crabtree

Chapter 2: Networking and topologies


The physical layout (or topology) of a network is usually implemented as one of four forms: Bus (or multi-drop), star, ring or mesh.

Bus: In bus topology, all nodes connect to a common media – often called the backbone.

Star: In the star topology, each node has its own network segment that links it back to a central host – called the hub – which controls all communications.

Ring (or loop): In ring topology, all the nodes are connected to a single cable that forms a closed loop or ring. Data flows only in one direction – with each node passing the data onto the next node on the line.

Tree: A tree topology combines the characteristics of star and bus topologies. In its simplest form, a hub connects directly to the bus – with each functioning as the root of a tree of devices.

Mesh: In a mesh network, each node is connected to several others and involves the concept of routes – such that a message can take any of several possible paths from source to destination.