Network topology is at the heart of building a functional wired or wireless network. For optimum performance, networked devices are arranged in specific topologies that safeguard the effective flow of data between them. Knowing the key types of network topology is essential for understanding or building networks. In this article, 7 types of network topology are explained with examples.
What is network topology?
Network topology is how participating computers, antennas, sensors, and other devices are arranged and interact in a network. Several types of topology can be used to organize and direct the flow of data within networks.
Selection of the most appropriate topology is a critical part of network design and takes into consideration:
- The type of devices in the network (e.g. computers, antennas, phones, sensors)
- The network application
- Expected network throughput and capacity
- The technologies used to connect devices
- Management and maintenance demands
The 7 types of network topology
These are the predominant network topologies. They may be wired or wireless and are used in telecommunications, IT, and any other practical arrangement of nodes where data flows or is exchanged:
1. Point-to-point network topology
This is the most basic type of network connection and can be used as a building block for the more complex network topologies below.
What is a point-to-point network?
A point-to-point network connection is a single wired or wireless linkage that connects two computers, devices, or nodes. There is a uni or bi-directional data exchange between the two points and the data stream can be secured against interference.
Depending on the bandwidth available a point-to-point link can exchange large amounts of data with high-speed, high-throughput connectivity.
Characteristics of a point-to-point connection
In a point-to-point connection:
- There are only two participating devices
- Data can flow uni- or bidirectional
- There is no network hub or controller
- Exchanged data does not have to be specifically managed or packaged
Pros and cons of a point-to-point connection
Pros of a point-to-point connection:
- Fast and reliable connection, capable of providing a high-speed data link.
- Simple and cheap to install over short distances.
- Long distances can be covered with a wireless link.
- Point-to-point linkages can connect multiple devices to form other network topologies.
Cons of a point-to-point connection:
- Interference or attack of the connection affects both devices.
- Data is only shared between two devices.
Examples of point-to-point network topology
A successful application of point-to-point network topology is the use of wireless links for home broadband connectivity. In locations where cable or fiber internet connectivity is unavailable, wireless internet companies can set up a wireless link that provides high-speed data exchange between an internet company’s backhaul and a remote or rural domestic residence.
2. Star network topology
Star network is one of the original and most common network topologies. It became widespread through use in ARCNET and Ethernet local area networking.
What is a star network?
A star network is an arrangement of connected nodes, where each participating node is individually and directly connected to a central hub or switch. Graphically represented, it looks like a star or the spokes of a wheel.
The hub is the network controller and the main conduit for the exchange of data. Data cannot be exchanged between nodes, everything must pass through the hub which directs the flow of information. Star networks can be wired or wireless.
Characteristics of a star network
In a star network:
- All connections (wired or wireless) terminate at a central point.
- Star networks can be scaled by connecting or disconnecting nodes from the central hub.
- Any loss of connectivity to the hub only affects an individual node rather than the entire network.
Pros and cons of star networks
Pros of star networks include:
- A failed connection in a node does not cause downtime across the entire network.
- Devices can be connected and disconnected without requiring downtime.
- Large networks can be supported in this arrangement with centralized control.
Cons of star networks include:
- The hub is the most vulnerable part of the network. If it fails, the entire network goes down.
Example of star network topology
ZigBee networks for smart home management rely on a single controller which devices individually connect to for monitoring and control.
3. Bus network topology
Bus or line topology is closely associated with the development of Ethernet in 1972 by Robert Metcalfe. Ethernet continues to be one of the main network technologies that use this topology.
What is a bus network?
A bus (or line network) is a network topology where all participant devices in the network are connected to a common linear length of cable, known as a bus. The cable is usually an RJ-45 network cable or coax and forms a backbone or trunk for the network.
There are two types of bus topology:
- Linear bus topology with all nodes connected to an end-to-end length of cable
- Distributed bus topology, where the nodes are connected to a branched cable that has multiple endpoints.
In bus networks, network traffic moves along the linear backbone, which may form a wired internet backhaul. Each node in a bus network is called a station, with all stations receiving the network traffic and having equal transmission priority. To prevent collisions the network uses an access control technology like carrier-sense multiple access (CSMA).
Characteristics of a bus topology
In a bus network:
- Devices are connected linearly along one or more cables.
- The cable ends must be carefully terminated with signal absorbers to prevent signal reflection. Unterminated bus cables echo, producing an interference phenomenon called ringing.
Pros and cons of bus networks
Pros of bus networks include:
- Low cost
- Efficient topology for small, contained networks
- Easy to add or remove devices
- Less cabling required
- The loss of one node does not impact the other nodes in the network
Cons of bus networks include:
- Damage to the backbone cable brings down the entire network.
- Because all devices are using a single cable connection, troubleshooting problems become difficult.
- These networks scale poorly and can become slow if network traffic is high.
- Because all of the devices share the bus, if a single node becomes infected or hacked, all nodes can become compromised.
Example of bus network topology
The earlier forms of Ethernet networking (the 1970s and 80s) used bus network architecture. It is not prevalent today, except for networks that interface with legacy systems.
4. Ring network topology
Ring network topology is another of the earlier LAN topologies that were introduced by IBM in 1984.
What is a ring network?
A ring network consists of nodes connected in a ring formation, with each node connected to two other nodes. A ring network forms a single continuous pathway for the flow of data, which passes through each node sequentially.
The data flow in ring networks can be uni- or bidirectional. Unidirectional data flows can be clockwise or anticlockwise. Practical deployments of ring networks may use the ring as a high-speed backbone and use a hub or concentrator to direct the network.
Characteristics of a ring network
In a ring network:
- Devices are connected in a ring at the logical level.
- Data packets are handled by each node in the network.
- Links between nodes can be uni or bidirectional.
- Ring networks can be strengthened and protected against faults by using a backup ring (dual-ring network). The secondary ring may be counter-rotating (C-ring network).
Pros and cons of bus networks
Pros of ring networks include:
- The network is not monopolized by any single node.
- Nodes have equitable access to the transmission and receipt of data.
- Can cope with heavier network loads than a bus network.
- Installation and configuration are easy.
- The point-to-point connectivity between each participating node makes it easy to identify and repair faults.
Cons of ring networks include:
- Damage to the ring network’s backbone will shut down the entire network.
- Ring networks don’t scale well, and slow down if there is excessive network traffic.
- A single hacked or infected node can compromise the entire network.
- Adjustment of ring networks usually requires downtime for the entire network.
Examples of ring network topology
IBM Token Ring networks (IEEE 802.5) are the most well-known example of ring networks. The feature is a proprietary three-byte frame called a token which is exchanged by the participating devices in the network.
Other examples of ring networks include:
- The PSTN telephony systems network Signaling System No. 7
- SONET networks
- Fiber Distributed Data Interface (FDDI)
5. Mesh network topology
Mesh networks were developed by the defense sector in the 1980s. Its wider adoption was delayed because of its high cost and complexity. The adoption of mesh networks has increased steadily since the late 1990s.
What is a mesh network?
Mesh networks consist of multiple nodes that are all interconnected. The links between individual nodes are non-hierarchical, bidirectional, and dynamic, allowing data to spread across the entire network and nodes to send and receive data from nodes they are not directly connected to.
These networks can be wired or wireless. Wireless mesh networks are also known as wireless ad hoc networks. Mesh networks can be partial, with fewer interconnections between devices and a controller, or full, with all devices in the network connection.
Mesh networks are resilient because the network is not reliant on any single node. Though mesh networks often have a controller they are capable of self-organization and self-configuration.
Characteristics of a mesh network
In a mesh network:
- Nodes are non-hierarchical
- Data can be routed through the network in multiple ways
- Mesh topology has the appearance of a fishing net, due to the interconnection of participating devices.
Pros and cons of mesh networks
Pros of mesh networks include:
- Highly scalable and robust
- New nodes can be added and configured without disturbing the rest of the network
- Failure or compromise of one node does not shut down the entire network
- Point-to-point linkages between individual nodes are resilient
Cons of mesh networks include:
- Complex network architecture
- Higher cost compared to older and legacy network topologies
- Cabled mesh networks are extremely expensive because of the amount of cable required to make the connections
- Implementation can be complicated.
Examples of mesh network topology
Mesh network technology has entered the consumer market with the introduction of mesh Wi-Fi. Rather than relying on a single router at a fixed location in the property, mesh Wi-Fi consists of multiple nodes that are interconnected, exchanging data wirelessly throughout large buildings or campuses.
6. Tree network topology
Tree network topology was developed in 1971 by Rudolf Bayer and Ed McCreight at Boeing Labs. This network topology is also known as B-tree and Bus and Star topology.
What is a tree network?
Tree networks have a topology that has a root node with subsequent nodes connected in a hierarchy. The root or ‘parent’ node is often a controller that relays data through several generations of ‘child’ nodes. An alternate arrangement has several star topologies connected to a single bus, leading to the name Star Bus topology.
Characteristics of a tree network
In a tree network:
- Nodes are arranged in a hierarchical topology
- Data is routed through the network from a primary, parent, or controller node
- Contained star networks can be arranged along a branched-like bus network cable
Pros and cons of tree networks
Pros of tree networks include:
- Network resilience – if one node fails the rest of the network can continue to function.
- Easily scaled
- Straightforward error detection
- IT teams can manage and maintain these networks
Cons of tree networks include:
- Wired tree networks require a lot of cables
- Loss of the hub or controlling node takes down the entire network
Example of tree network topology
B-trees that are used in computer programming, file systems, and databases are an example of this topology.
7. Hybrid network topology
Hybrid topology is the most varied of these network topologies and can include elements of the topologies described above.
What is a hybrid network?
A hybrid network combines at least two distinct network topologies to create a novel network structure. The development of hybrid networks is credited to the work of Wittie et al who developed the bus-spanning hypercube.
Types of a hybrid network include:
- Star-ring networks are composed of several star networks arranged in a ring.
- Hypermesh networks are where a bus connects each node to all the other nodes in the network.
- Snowflake networks with multiple star networks arranged in a star!
- Hierarchical star networks are composed of star networks arranged in a hierarchy.
An exception is the use of a tree network in a combination, as any network that includes a tree network is a tree network.
Characteristics of a hybrid network
In a hybrid network:
- Multiple network topologies are combined to create a network with maxim robustness, utility, and performance.
Pros and cons of hybrid networks
Pros of hybrid networks include:
- A high degree of customization is possible
- The strengths of individual network types can be maximized and weaknesses minimized
- Easy scaling and high flexibility
- Unless an individual node is a controller, the network is resilient against downtime
Cons of hybrid networks include:
- High cost
- Complex development and implementation
Example of hybrid network topology
Fifth-generation or 5G cellular networks have a hybrid network topology. This is because 5G RAN technology is unconventional and uses multiple telco technologies, including small-cell, distributed antenna networks, and open-source network access to achieve its coverage and performance.
The majority of networks are organized using these conventional topologies to ensure that they perform competently and remain resilient. The successful network design will use these 7 types of network topology as a foundation, making changes and adaptations, directed by the real-world requirements of the network.
The image featured at the top of this post is ©Mikko Lemola/Shutterstock.com.