Introduction to Computer Networks - Study Notes

Chapter Summary

A computer network is a group of computers and other devices connected so they can share resources, exchange data and communicate. Networks have changed how businesses, homes, schools, hospitals and governments work, because they give quick access to information and to online services. This chapter also traces the history of the Internet, from ARPANET, a research network funded by the US Department of Defense, to the worldwide network we use now, along with the growth of mobile networks and social media.

Learning Objectives

• Define a computer network and explain what a node is.
• Recall the main milestones in the history of the Internet, including ARPANET and the development of TCP/IP.
• Describe how networks are used in business, at home and in mobile communication.
• Discuss the social side of networks, including the advantages and disadvantages of social media.
• Identify common network problems, such as hacking, viruses and online arguments known as flame wars.

Key Concepts and Definitions

• Computer Network: Two or more computers or other hardware devices connected through a communication medium, such as cables or wireless signals, so that they can exchange information and share resources.
• Node: Any device connected to a network, such as a computer, printer, server, mobile phone or tablet. Each node is identified by a network address such as an IP address.
• Internet: The worldwide system of interconnected networks that links academic, government, private and commercial organisations.
• Base Station: A fixed transmitter and receiver in a mobile network that serves one area, called a cell, and carries voice, data and multimedia to and from the phones in that cell.
• E-Governance: The use of information and communication technology by government departments to run their work, deliver public services and deal with citizens and businesses.
• Flame Wars: Long, angry exchanges of messages and personal insults between users on message boards, discussion forums or social media.
• Hacker: In this chapter, a person with strong technical skills who breaks through network security to get into private accounts or confidential data without permission.

Worked Methods

Method 1: Resolving a Domain Name to an IP Address

When you type a domain name into a browser, the Domain Name System (DNS) finds the matching IP address. The browser first looks in its own cache. If the name is not there, it asks the local name server, usually run by your Internet Service Provider (ISP). That server asks a root server, then the top-level domain (TLD) server, such as the one for .in, and finally the authoritative name server for the domain, which gives the IP address. The address is sent back to your computer, and the browser connects to the site.

Method 2: Mobile Network Handoff and Cellular Routing

A mobile network divides its area into small, adjoining regions called cells, and each cell has its own base station. If you move from one cell to the next during a call or data session, the network passes your connection from the current base station to the neighbouring one with the stronger signal. This is called handoff (or handover), and it is why a call does not drop as you travel.

Common Exam Traps

• Internet vs. WWW: They are not the same thing. The Internet is the worldwide network of connected computers. The World Wide Web is one service that runs on it, just as email is another.
• Node vs. host: A node is any connected device, including routers, switches and printers. A host is an end device, such as a PC or server, that runs applications for users.
• What flame wars are: Flame wars are not a technical attack or a hacking method. They are arguments between people in online communities.

Exam Tips

• Learn the main uses of a network: communication, resource sharing and information sharing. Be ready to give an example of each.
• Remember that ARPANET began in 1969 and that TCP/IP became the standard protocol suite of the Internet.
• Be able to explain and compare network applications in business, at home, in mobile networks and in social media.
• Prepare short notes on hackers, viruses and the security problems that businesses face on networks.