# Network Topology and Types

Introduction

The word Network Topology is use to explain the manner in which a network is physically connect. Devices or nodes in a network get connect to each other via communication links and all these links are related to each other in one way or the other.

The geometric representation of such a relationship of links and nodes is known as the topology of that network. Topologies can be classified as Peer to peer and Primary-secondary.

Peer to peer is the relationship where the devices share the link equally. The examples are Ring and Mesh topologies. In Primary-secondary relationship, one device controls and the other devices have to transmit through it. The examples are Star and Tree topology.

#### Types of Network Topology

There are five basic network topologies are as follows:

#### (1) Bus Topology

The bus topology is usually use when a network under consideration is small, simple or temporary. On a typical bus network is a simple cable, which we can use without additional electronics to amplify the signal or pass it along from computer to computer. Therefore the bus is a passive topology.

The speed of the bus topology is slow because only one computer can send a message at a time. A computer must wait until the bus is free before it can transmit. The bus topology requires a proper termination at both the ends of the cable in order to avoid reflections. Since the bus is a passive topology, the electrical signal from a transmitting computer is free to travel over the entire length of the cable.

The bus topology is easy to understand, install, and use for small networks. The cabling cost is less as the bus topology requires a small length of cable to connect the computers.

#### (2) Ring Topology

In a ring topology, each computer is connect to the next computer, with the last one connected to the first. Rings are use in high performance networks where large bandwidth is necessary.

In this topology, every computer is connect to the next computer in the ring and each retransmits what it receives from the previous computer hence the ring is an active network. The message flow around the ring in one direction. There is no termination because there is no end to the ring.

Some ring networks do token passing. A short message called a token is passed around the ring until a computer wishes to send information to another computer. That computer modifies the token, adds an electronic address and data and sends it around the ring. In this topology, every computer gets an equal access to the token and there are no standing waves produced.

#### (3) Star Topology

In a star topology all the computers are connect via cables to a central location where they are all connected by a hub. There is no direct connections among the computers. All the connections are made via the central hub.

Stars are use in concentrated networks, where the endpoints are directly reachable from a central location, when network expansion is expected and when the greater reliability of a star topology is needed.

Each computer on a star networks communicates with a central hub. The hub then resend the message to all the computers in a broadcast star network. It will resend the message only to the destination computer in a switched star network. If the central hub fails, the whole network fails to operate.

#### (4) Mesh Topology

In a mesh topology every device is physically connect to every other device with a point to point dedicated link. The term dedicated means that the link carries data only between two devices connected on it. The use of dedicated links guarantees that each connection can carry its own data reliably.

Too many cables are require in mesh topology. A mesh topology is a robust because the failure of any one computer does not bring down the entire network. It provides security and privacy because every message sent travels along a dedicated line.

#### (5) Tree Topology

A tree topology is a variation of a star topology. As in a star, nodes in a tree are connect to a central hub that controls the entire network. However, every computer is not plugged into the central hub. Most of them are connected to a secondary hu which in turn is connected to the central hub.

The Central hub in the tree is an active hub which contains repeater. The repeater amplify the signal and increase the distance a signal can travel.

Tree topology allows more devices to be attach to a single hub and can therefore increase the distance of the signal. It allows the network to isolate and attach priorities to the communications from different computers.