What is network topology?
A network topology is the physical and logical arrangement of nodes and connections in a network. Nodes usually include switches, routers and software with switch and router features. Network topologies are often represented as graphs showing node connections.
Network topologies describe the arrangement of networks and the relative location of traffic flows. Administrators can use network topology diagrams to determine the best placements for each node and the optimal path for traffic flow. With a well-defined and planned-out network topology, an organization can more easily locate faults and fix issues, improving its data transfer efficiency and security.
Network geometry can be defined as the physical topology and the logical topology. Network topology diagrams are shown with devices depicted as network nodes and the connections between them as lines. The type of network topology differs depending on how the network needs to be arranged.
Why is network topology important?
Network topology plays a major role in how a network functions. Namely, the topology has a direct effect on network functionality. Choosing the right topology can help increase performance, as a properly selected and maintained network topology increases energy efficiency and data transfer rates.
A well-defined network topology makes it easier for network admins to locate faults, troubleshoot issues and allocate network resources. Diagrams, which can represent physical and logical layouts, are an important reference point in helping to diagnose network issues.
Topology design also affects how easily a network can scale to accommodate more devices over time. The type of topology design can also influence security considerations. A more centralized topology might make network security easier to implement, but it can also act as a single point of failure. More decentralized topologies provide security through path diversity but at the expense of increasing the attack surface.
Physical topology vs. logical topology
Both physical and logical topologies are essential parts of network infrastructure.
Physical network topologies refer to the physical connections of nodes in a network. They focus on the placement of hardware, or nodes, that can be visibly seen.
Logical topologies refer to how data travels through a network. They focus on the communication paths and data transmissions between devices. Because data does not always flow in a single defined path, a logical network topology diagram can help administrators visualize how data should flow and the number of nodes it must flow through.
What are the types of network topologies?
Network topologies are categorized as either physical or logical. A network's physical topology is the physical layout of nodes and connections. Connections include the lines in diagrams that connect nodes, such as Ethernet or digital subscriber line wires, fiber optics and microwaves. Logical network topologies define how a network is set up, including which nodes connect and how, as well as the pattern of data transfers.
Point-to-point is the most basic type of network topology. In this setting, a single link connects two nodes, making a direct connection. This is a simple topology where data only travels back and forth between these two points.
Several other types of physical topologies include the following:
- Bus network. In the bus network topology, every node is connected in series along a single cable. This arrangement is often found in cable broadband distribution networks.
- Ring network. The nodes are connected in a closed-loop configuration in the ring network topology. Some rings pass data in one direction only, while others can transmit in both directions. These bidirectional ring networks are more resilient than bus networks because traffic can reach a node by moving in either direction. Metro networks based on Synchronous Optical Network, or SONET technology, are the primary example of ring networks.
- Mesh network. The mesh network topology links nodes with connections to make multiple paths between at least some network points available. A network is considered fully meshed if all nodes are directly connected to all other nodes and partially meshed if only some nodes have multiple connections to others. Meshing multiple paths increases resiliency but also increases cost. However, dedicated links require more space.
- Star network. In the star network topology, a central device connects to all other nodes through a central hub. Switched local area networks are based on Ethernet switches, and most wired home and office networks have a physical star topology.
- Tree network. The tree network topology consists of one root node, with all other nodes connected in a hierarchy. The tree topology itself is connected in a star configuration. Many larger Ethernet switch networks, including data center networks, are configured as trees.
- Hybrid network. A hybrid network topology is any combination of two or more topologies. Hybrid topologies typically provide exceptional flexibility, as they can accommodate several setups. For example, different departments in the same organization might opt for personalized network topologies more adaptable to their network needs.
A logical topology for a network refers to the relationship between nodes and logical connections -- defining how data should transfer.
A logical connection differs from a physical path when information can take an invisible hop at intermediate points. In optical networks, optical add-drop multiplexers create logical optical paths because the arrow diagramming method hop is not visible to the endpoint nodes. Networks based on virtual circuits or tunnels have a physical topology based on the real connection medium -- fiber, for example -- and a logical topology based on the circuits and tunnels.
Sometimes, the logical topology refers to the topology as the user sees it. Internet Protocol (IP) and Ethernet networks are two common examples. They are fully meshed at the connection level, as any user can connect with any other user. This is true unless some means of blocking unwanted connections, like a firewall, is introduced. Full connectivity is a property of the network protocols used -- IP and Ethernet -- not of the network topology itself.
For example, logical bus and logical ring topologies can be used to define data transmission flows. A logical bus topology features nodes that broadcast data to the entire network. Other nodes on the network check to see if the data is meant for them. A logical ring topology only allows one node at a time to transfer data.
How do you diagram a network topology?
Before constructing a network, diagrams of the network topology should be made. This way, network admins know what components constitute the network and how they interact. Creating the diagram includes the following steps:
- Create a list of all the devices in the network, including routers, firewalls and servers.
- Choose the type of network topology and sketch out the diagram. Devices should be placed in areas that make the most sense, considering data flows.
- Draw lines from network devices. These lines are the connections the network nodes make. Avoid having too many lines cross over each other and strive to make the diagram clear and easy to read. Scalability and future modifications should also be considered when creating the diagram.
- After constructing the sketch showing a rough general input, diagram software can help map out everything. The software might include a network diagram template to follow. The network nodes should be named, and lines can be color-coded to make the diagram more understandable and clearer.
What are examples of network topology tools and software?
Many network topology tools are available, including configuration and management tools, network performance software and network mapping software.
For instance, network configuration software helps configure networks while automating repetitive tasks. These tools are often used to configure complicated network topologies and can auto-detect network nodes and highlight apparent vulnerabilities.
Network performance monitoring and troubleshooting tools keep track of and alert users to network-related performance issues and outages. Some of these tools might track performance using a visual display of the network topology. After setting baseline performance settings, users can track, locate and troubleshoot issues.
Network topology mapping software aids in creating network topology diagrams. According to Capterra and Gartner Peer Insights, examples of mapping tools and features include the following:
- Datadog.
- Dynatrace.
- ManageEngine OpManager.
- Microsoft Visio.
- Nagios XI.
- netTerrain Logical.
- Paessler PRTG Network Monitor.
- SolarWinds Network Topology Mapper.
- UVexplorer.
- WhatsUp Gold.
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