A network topology is how computers, printers and other devices are connected, and describes the layout of wires;, devices and routing path on a network. When referring to topology through the lens of the “Internet of Things”;, it is how sensors, actuators and gateways communicate with one another. To decide which network is best for your smart application;, you need to know the advantages and disadvantages of each. There are number of common topologies;, point to point, bus, star and mesh. I will be discussing some of which today
- Point to Point
Mesh topology is a type of networking where all nodes cooperate to distribute data in a network. This topology is typically used for things like home automation;, smart HVAC control, and smart buildings. The industry standards that rely on mesh network topology include ZigBee, Z-Wave, and Thread.
A mesh network consists of three types of nodes:
- A gateway node as in a star network, provided so data can reach the outside world;
- Simple sensors nodes; and
- Sensor/router nodes, which are sensor nodes with repeater/routing capability.
Sensor/router nodes must not only capture and disseminate their own data, but also serve as relays for other nodes.
Mesh network nodes are deployed so every node is within transmission range of at least one other sensor/router node. Data packets pass through multiple sensor/routers nodes to reach the gateway node.
Mesh is a growing network topology commonly found in IoT deployments;, some of its advantages include:
- Data can be transmitted from different devices simultaneously. This topology can withstand high traffic;
- Even if one of the components fails there is always an alternative present. So data transfer doesn’t get affected; and
- Expansion and modification in topology can be done without disrupting other nodes.
In local area networks with a star topology;, each network host is connected to a central hub with a point-to-point connection;, with every computer indirectly connected to every other node with the help of the hub.
The switch is the server and the peripherals are the clients. The network does not necessarily have to resemble a star to be classified as a star network;, but all of the nodes on the network must be connected to one central device. All traffic that traverses the network passes through the central hub.
The advantage of star topology is that all the complexity in the network is driven to a central node;, so all the other nodes only need to communicate in their time or frequency slot.
How they communicate depends on whether wireless multiplexing is done through frequency-division multiple access (FDMA);, time-division multiple access (TMA);, or code-division multiple access (CDMA).
The primary disadvantage of star topology is that the radio link between; the gateway and the end node or terminal can be very long;, which means the further a node is away from the gateway;, the more energy it has to expend relaying a message.
But unlike a mesh node that has to be constantly “awake,” ;star nodes are able to rest between message transmissions, helping conserve the total amount of energy expended by each node.
3. Point to Point
A point-to-point network establishes a direct connection between two network nodes.
Communication can take place only between these two nodes, or devices. An example of this type of network is a Bluetooth link between a cellphone and an ear piece. The advantages of point-to-point networking are its simplicity and low cost. The primary limitations spring from the one-to-one relationship that exists between two devices; the network cannot scale beyond these two nodes, therefore it is not a widely used topology for industrial IoT.
The advantage of point-to-point network topology is that it is much simpler than mesh or star;, because the topology simply tunnels a flow of data either unidirectionally or bidirectionally between two points.
The disadvantage is that point-to-point networks are not very useful for IoT. They are still used in some SCADA systems, traffic data systems;, or in point-to-point broadcast systems (like police or fire radios);, but it rarely makes sense in IoT to have a receiver talk to a single node instead of multiple nodes.
In local area networks where bus topology is used;, each node is connected to a single cable with the help of interface connectors. This central cable is the backbone of the network and is known as the bus.
A signal from the source travels in both directions to all machines; connected on the bus cable until it finds the intended recipient. If the machine address does not match the intended address for the data, the machine ignores the data.
Alternatively, if the data matches the machine address, the data is accepted. Because the bus topology consists of only one wire, it is rather inexpensive to implement when compared to other topologies. However, the low cost of implementing the technology is offset by the high cost of managing the network.