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In a mesh topology there is no central connection point. Instead, each node is connected to at least one other node and usually to more than one. Each node is capable of sending messages to and receiving messages from other nodes. The nodes act as relays, passing on a message towards its final destination.

There are two types of mesh topology:

• fully connected mesh topology
• partial mesh topology

In a fully connected mesh, each node is directly connected to every other node. This enables a message to be sent along many individual routes.

In a partially connected mesh, not all nodes are connected directly to each other. A partially connected mesh therefore has fewer routes for a message to travel along than a fully connected mesh but is simpler to implement.

Wired mesh networks tend to be uncommon, mainly because connecting all nodes to all other nodes is expensive and impractical. However, wireless mesh networks are increasingly being used since it is far simpler and cheaper to connect using radio signals.

Advantages and disadvantages of using a mesh topology

The advantages of a mesh topology are:

• messages can be received more quickly if the route to the intended recipient is short
• messages should always get through as they have many possible routes they can travel along
• multiple connections mean - in theory - that no node should be isolated
• multiple connections mean each node can transmit to and receive from more than one node at the same time
• new nodes can be added without interruption or interfering with other nodes

The disadvantages of a mesh topology are:

• fully connected mesh networks can be impractical to set up because of the high number of connections needed
• many connections require a lot of maintenance

Mesh topologies in use

Mesh topologies are used where the reliability of network communication is very important:

• military organisations often use mesh topologies to avoid breakdowns in communication
• cities are increasingly using wireless mesh networks to help monitor traffic flow, sewage treatment and to help control street lighting
• emergency services, such as police and fire services, also use wireless mesh networks to ensure that communication is reliable
• some utility companies who provide gas and electric use mesh networks to enable smart meters to send readings automatically
• the internet is a huge partially connected mesh network