The world of networks

Introduction

Communication has evolved greatly. Traditional communication methods such as mail have been overtaken by more sophisticated forms. Electronic Communication methods offer higher speeds; more efficiency, reliability, integrity, security; scale across larger geographical areas and require less resources to use. Tools and services such as e-mail, blogs, podcasts, instant messaging, and social networks among other multimedia methods have changed the way we communicate to a great extent.

In this chapter, we give an overview of the world of networks: we will discuss the following:

1. The role of networks in our lives
   
2. Explain the qualities and elements of a network
   
3. Define key terms and diagrams used in this course
   
4. Explain what a converged network is
   
5. Give a brief history of computer networks
   

This chapter is crucial since some of the concepts learned in it will be useful in understanding the rest of the course.

The role of networks.

The need to communicate is human nature. Communication has evolved over the years, from carvings on rocks to more complex forms. The diagram below is an apt description of this evolution.

Modern communication methods are as a result of the evolution of computer networks. Since the first e-mail was sent back in 1965, communication has come a long way.

We are no longer restricted with face to face communication. And with the internet the world has become more interconnected than ever before.

Computer networks are not just responsible for communication, but our entire way of life has evolved. The way we work, the way we interact, among other ways have changed significantly.

Some of the ways we use computer networks include:

• Business – online banking, e-mail, e-commerce.
  
• Entertainment – online movies, online games.
  
• Social interactions – instant messaging, social networking sites.
  

Clearly, therefore, networks play a central role in our lives.

Elements of a network

In order to understand networks we need to understand the elements of a network. There are four main elements that define how communication over networks works.

• Rules or agreements to govern how the messages are sent, directed, received and interpreted – examples include protocols.
  
• The messages or units of information that travel from one device to another – these may be packets, frames among others.
  
• A means of interconnecting these devices – a medium that can transport the messages from one device to another – such as copper cables, fibre optic among others.
  
• Devices on the network that exchange messages with each other – these may include ip phones, computers, servers, routers among others.
  

In this course, we will use several network devices, from these, we will create simple and complex topologies, based on the requirements. Keep these in mind because they will be used throughout the course as well as the exams. These are shown below.

Device symbol	Device name
	Branch office
	Cloud, ISP, internet
	CSU/DSU
	Server
	Firewall
	Head office
	Layer 3 switch
	Ip phone
	Modem
	Router
	Hub
	Wireless router
	Switch
	LAN media
	WAN media

These are some of the icons that will be used in this course.

Converged network

The world of networks has grown over the years. We are finding more and more ways to use computer networks. Communication over networks today is not just limited to transmitting static data, rather new applications such as teleconferencing, video, news and other multimedia applications can be found on computer networks.

In yester years, communication was segmented. There were different networks for each application.

• For voice, there were telephone networks,
  
• For video, there were TV and cable service providers
  
• For data there were internet service providers.
  

However, all these services can be provided over the same network and this has been attributed to the growth of computer networks. Therefore, a converged network is one in which all these services; data, voice, and audio, are provided over the same network. 

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This essentially eliminates the need for multiple service providers for each of these services.

Other concepts.

Fault tolerance and scalability – this means that networks should be able to recover from down time or other faults and should be able to expand as needed.

Quality of service – this is a measurement instituted in networks so as to ensure that the services provided in a converged network work optimally. For example communication would be poor, if a network had only video and not audio when a business executive is in a video conference call. To ensure quality of service, different services are given different priorities.

Security – the network should be safe from intrusions from unauthorized access. This would ensure that communication is effective and confidentiality, integrity and availability of information is maintained.

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