Types of Topology

 

Introduction

 

A series of points or nodes interconnected by communication paths is usually referred to as a Network in Information Technology.

Networking thus can be defined as the construction, design, and use of network, including the physical (cabling, hub, bridge, switch, router, and so forth), the selection and use of telecommunication protocol and computer software for using and managing the network, and the establishment of operation policies and procedures related to the network.

In connecting computers together to form a Network, the structure and layout of the computers and the cabling required to link them together must be taking into consideration. The pattern of computer nodes and the way they are interconnected is referred to as the Topology.

 

Network can be of any of the following three types:

 

• Local Area Network:  Which is a series of nodes connected to work and communicate together within a limited geographical area. There are a number of topologies that are common to LAN; they are Star, Bus and Ring topologies.

 

• Metropolitan Area Network: This is the connection of devices that covers a geographical area or region that is larger than that of Local Area Network (LAN) but smaller than Wide Area Network (WAN).  It implies the interconnection of network in a city into a larger network.  For example the different combination of the boroughs of London Networks.

 

• Wide Area Network:  The interconnection of devices across a wide geographical are.  The connection spans from country to country.  Example is the internet which is the interconnection of networks.

 

NETWORK TOPOLOGIES

 

When we talk of topologies, we are talking of the manner in which network devices are organized.

Topology is a term that refers the shape of the network and the layout of cabling from a bird's eye view, much as a floor plan identifies the layout of offices and hallways in a building. (www.marconi.com)

The different topologies available to LAN are discussed in the following pages:

 

STAR TOPOLOGY

This is a form of LAN architecture is which nodes on a network are connected to a common central hub or switch, and this is done by the use of dedicated links.

The Star topology is now emerging as the most common network layout used today in LAN layout. Each workstation is connected point-to-point to a single central location.

 

BUS TOPOLOGY

In the bus topology the server is at one end, and the client PCs (devices) are connected at different points or positions along the network.  All signals pass through each of the devices. Each device has a unique identity and can recognize those signals intended for it. It is easy and simple to design and implement.

The Mesh topology is a variation of the bus, in which all devices are connected to one another in a daisy-chain fashion, as opposed to connecting in sequence to a single network cable. Each node is capable of transmitting, receiving, and routing data. (www.Marconi.com)

 

LAN Ring Topology

This topology is a simple design and consists of a single cable that forms the main data path in the shape of a ring. Each device is connected to a closed loop of cable. Signals travel in one direction from one node to all other nodes around the loop.

 

LAN Tree Topology

The Tree topology is essentially a hybrid of the bus and star layouts. The basic topology is similar to that of a bus, with nodes connected in sequence to a linear central cable. But tree networks may have "branches" that contain multiple workstations that are connected point-to-point in a star-like pattern. Signals from a transmitting node travel the length of the medium and are received by all other nodes.

 

Popular Networks:

 

Ethernet: 10/100Mbps

Most popular network method.

 

Wireless 802.11b: 11 Mbps

802.11b is now the standard for wireless networking in both the home and business. 

 

Wireless 802.11a: 54 Mbps

A new standard for wireless ethernet, 802.11a is incompatible with 802.11b and g.  

 

HomePNA 2.0 (Phone Line): 10Mbps

 

Alternative Technologies

 

Ethernet: Gigabit - 1000TX

Wireless 802.11g: 22 Mbps

Firewire Networking - 400Mbps

Bluetooth

Wireless HomeRF 2.0: 10Mbs

Powerline Networking

The Chart

Technology	Speed	Wireless	Range	Support	Cost
Ethernet 10/100	100Mbs	N	A	A	A
802.11b	11Mbps	Y	B	A	B
802.11a	52/72 Mbps	Y	C	B	C
PhoneLine 2.0	10Mbps	N	A	B	B
Gigabit Ethernet	1000Mbps	N	A	D	D
802.11g	22/54Mbps	Y	C	NA	NA
Firewire	400Mbps	N	D	C	A
Bluetooth	1.5Mbps	Y	D	C	C
HomeRF 2.0	10Mbps	Y	B	C	C
PowerLine	14Mbps	N	A	C	C

Chart Explanation - D is poor or inappropriate, A is best