what is a network topology definition

The network topology is the schematic arrangement or relationship of the network devices, including its nodes and connecting lines. The network has two shapes or two types of network topology; one is physical network topology, and the other is logical network topology.

The physical network topology

The physical topology of a network is the actual physical and geometric layout of the network that we can see, such as devices like routers, switches, wireless access points, nodes, and cables. So, there are several common physical topologies, like point-to-point, ring, bus, star, and mesh. The physical topology has two different categories: WAN and LAN topologies.

Common Physical WAN Topologies

WAN are generally interconnected using the following physical topologies:

Point-to-Point

Point-to-point (PTP) network topology connects two nodes directly to one another. Only two devices are involved in a point-to-point connection, with one wire (or air, in the case of wireless) sitting between them. This is the simplest topology in networking. For this reason, this is a very popular WAN topology. The figure below illustrates the physical point-to-point topology.

Hub and Spoke

A hub-and-spoke network is a traditional and widely used network topology for all types of networks, also known as a star topology. In this topology, a central site interconnects branch sites using point-to-point links. The Central site is known as the hub, and branch sites are known as spokes. Communication between two spokes always travels through the hub. The figure below illustrates the physical hub-and-spoke topology.

Mesh Topology

A mesh network is a network topology in which each node relays data for the network. This topology provides high availability but requires that every end system be interconnected to every other system. Therefore, the administrative and physical costs can be very high. Each link is essentially a point-to-point link to the other node. Variations of this topology include a partial mesh in which some but not all of the end devices are interconnected. The figure below illustrates the physical mesh topology.

Physical LAN Topologies

Physical LAN topologies define how the end systems physically connected. We can connect devices in LAN using the following physical topologies as illustrated in the figure below:

Star topology

In Star topology, all end devices are connected to the central device. Early star topologies interconnected end devices using Ethernet hubs. However, star topologies now use Ethernet switches. The star topology is easy to install, scalable (add and remove end devices), and easy to troubleshoot.

All the data on the star topology passes through the central device before reaching the intended destination. The hub/Switch acts as a junction to connect different nodes present in the Star Network, and at the same time, it manages and controls the whole of the network. Depending on which central device, “hub” and “Switch” can act as repeaters or signal boosters. The central device can also communicate with other hubs and switches of a different network.

Extended Star Topology

In an extended star topology, additional Ethernet switches interconnect other star topologies.

Bus Topology

Bus Topology is the simplest of network topologies. All end systems (computers and servers) are connected and terminated in some form on each end. Infrastructure devices such as switches are not required to interconnect the end devices. Bus topologies use coax cables in legacy Ethernet networks because they are inexpensive and easy to set up.

Ring Topology

In the ring topology, end systems are connected to a single circle of cable. Unlike the bus topology, the ring does not need termination. The signals travel around the loop in one direction and pass through each computer, which acts as a repeater to boost the signal and send it to the next computer. Ring topologies are used in legacy Fiber Distributed Data Interface (FDDI) and Token Ring networks.

The logical network topology

The logical topology is the way that signals proceed on the network media or the way that data passes through the network from one device to the next without regard to the physical interconnection of the devices. In other words, it defines how a network transfers frames from one node to the next.

This topology also consists of virtual links between a network’s nodes. Data link layer protocols define these logical paths. The data link layer deals with the logical topology of a network when controlling data access to the media. The logical topology influences the type of network framing and media access control used.