Differences between Physical and Logical topology
Network topology defines how the network is structured and how the devices on the network communicate. It consists of two parts: physical and logical. The physical part describes the physical layout of the network, while the logical part describes how data flows in the network. Both physical and logical parts are also known as physical topology and logical topology.
Physical part (topology) + Logical part (topology) = Network topology
Physical topologies
Physical topology describes how the devices in the network are physically connected and what happens when a node fails. It also specifics the cabling arrangement and how cables connect one device to another. The most common physical topologies are the following.
Bus Topology
In this topology, devices connect in a line. It uses two types of coaxial cables to connect devices in the sequence. It uses a thick coaxial cable as the primary or backbone cable. It uses a thin coaxial cable to connect an end device to the backbone cable. It terminates both ends of the backbone cable with terminators. A BNC connector connects an end device's thin cable with the backbone cable.
Star topology
In this topology, devices connect to a centralized device. It uses a Hub or a switch as the centralized device. It uses twisted pair cables to connect end devices with the hub. There are two types of twisted pair cables: UTP and STP. STP is expensive but provides several advantages over UTP.
Mesh Topology
In this topology, devices connect directly. There are two types of mesh: partial and full. In partial mesh, only necessary devices have a direct connection. In full mesh, all devices have direct connections.
The following video explains network topologies in detail. You can watch it to learn more about network topologies.
Topology in Computer Networks
The following tutorial provides the text version of the above video and describes all network topologies in depth.
Network Topologies Explained with Examples
Logical topologies
Logical topology defines the logical layout of the network. It describes how the devices in the network communicate with each other and how data is transmitted. The three main logical topologies are bus, ring, and switched.
Bus topology
Bus topology uses the one-to-all method. In this method, when a device transmits a message, the message reaches all the nodes on the same link. All nodes read the message and determine whether it is for them. A node processes the message only if it belongs to it. A node uses the message's destination address to determine whether the message is for it. Each message has a destination address. A node discards the message if the message is not for it.
Ring topology
Ring topology uses the one-to-one method. In this method, each node receives data only from one node and transmits data only to one node. Data is passed sequentially from node to node. It uses a token mechanism to determine the node that can transmit data. Only one node can transmit data at a time. A node can transmit data only if it has the token. After transmitting data, the node passes the token to the next node. When a node receives data, it checks whether it belongs to it. If not, the node passes it to the next node.
Switched logical topology
It is also called point-to-point topology. It creates end-to-end connections on demand. When the switch receives a data packet, it checks the source and destination addresses and makes a logical connection between the sender and the receiver nodes. When the transmission is over, the switch terminates the logical connection.
Differences between physical and logical topologies
| Network Topology | Physical Topology | Logical topology | Description |
| Ethernet (Coaxial cables) | Bus | Bus | It is a classical implementation of Ethernet network topology. It uses coaxial cables to connect all devices in a sequence. Data sent by one device reaches all devices, creating a logical bus topology. |
| Ethernet (Hub-based) | Star | Bus | It uses a hub as the central device to connect to all devices, creating a physical star topology. It uses a logical bus topology to transmit data. |
| Wireless LANs | Star | Bus | In this implementation, devices connect through a central access point. Only one device transmits data at a time. All other devices listen to it. Since data transmitted by one device reaches all other devices, it is a logical bus topology. |
| Token Ring (IBM) | Star | Ring | This implementation uses an MAU (Multi-station access unit) to connect devices. MAU creates a logical ring, so data is passed from node to node in a pre-defined sequence until it reaches the destination device. |
| Token Ring (FDDI) | Ring | Ring | This implementation uses fibre optical cables to connect devices. It connects the first device to the second, the second to the third, and so on. It connects the last device to the first, creating a physical ring. Logically, it uses ring topology for data transmission. |
| Ethernet (Switch-based) | Star | Switched | It is the modern implementation of Ethernet network topology. It uses a physical star topology running a switched logical topology. In this implementation, the switch dynamically creates logical circuits between two devices whenever they exchange data. Almost all modern networks use this implementation. |
Conclusion
Network topology defines the layout of the network. It consists of physical topology and logical topology. Physical topology describes the physical layout of the network, while logical topology illustrates data flows on the physical layout.
Author Laxmi Goswami Updated on 2026-04-26