CHAPTER TWELVE (12)

INTRODUCTION TO COMPUTER NETWORKING

LESSON OBJECTIVES
The student will be able to:
• Explain concepts of networking.
• State the types of networks.
• Identify types of network topology.
• Identify various Network Architecture.
• Discuss the media used in network transmission.
• Configure a simple network.
• Explain data communication and its related concepts.
• Discuss the role of hardware, software and communication channels play in data communication.
• Discuss the various directions for transmitting data.
• Discuss the various forms of data transmission signals.
• Discuss the various forms of data communication.
• Discuss the ways of data security over a transmission media.

COMPUTER NETWORK
A computer network is a system of interconnected devices that can communicate using some common
standard (called protocol). These devices communicate to exchange resources (e.g., files and printers) and
services. Here is an example network consisting of two computers connected together:

In the example above, the two computers are directly connected using a cable. This small network can be
used to exchange data between just these two computers.
What if we want to expand our network? Then we can use a
network device, either a switch or a hub, to connect more
than two computers together: Now all of the devices on the
network can communicate with each other.
Networking
The act of linking computers so that users can exchange
information or share access to a central store of information.

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 REASONS FOR USING A NETWORK
1. Communication – When connected to the internet, network users can communicate with people
around the word. Example, talking or chatting with your brother outside your country.
2. File Sharing – Networks offer a quick and easy way to share files directly, instead of using disk or
USB. Example, using Xender App to share files on phones.
3. Sharing Resources – It easy to share resources such as printers. More than one computer in an
office could share one printer.
4. Sharing Software – it possible to stream software using web applications. Example, using google
doc, etc.

TERMINOLOGIES ASSOCIATED WITH NETWORKING

• Server – is a computer hardware or software that provides resources, data, services, or programs
to other computers known as clients, over a network.
• Client – is a computer hardware or software that accesses a service made available by a server.
• Connection – is a term that describes the link between a plug into a port or jack. This generally
infers that a connection is built before the data transfer and then deconstructed at the end of the
data transfer.
• Packet – is a data unit in computer network. Meaning is a message or part of a message packaged
as a fixed-size segment of data for transmission through a computer network.
• Network Interface – is any kind of software interface to networking hardware. It may be
associated with a physical device, or it may be a representation of virtual interface.
• Protocol – is a set of rules and standards that basically define a language that devices can use to
communicate. Some level protocols are TCP, UDP, IP, and ICMP.
• Port – is an endpoint to a logical connection. It is an address on a single machine that can be tied
to a specific piece of software.
• Firewall – is a system designed to prevent unauthorized access to or from a private network. You
can implement firewall in either hardware or software form, or a combination of both.
• Gateway – is a hardware device that acts as a ‘gate’ between two networks. It may be a router,
firewall, server, or other device that enables traffic to flow in and out of the network. While a
gateway protects the nodes within network, it is also a node itself.
• Node – is a connection that can receive, create, store, or send data along distributed network
routes. It either a redistribution point or communication endpoint.
• Network Address Translation (NAT) – is a process of changing the source and destination IP
addresses and ports. Address translation reduces the need for IPv4 public addresses and hides
private network address ranges. Routers or firewalls usually do the process.
• Virtual Private Network (VPN) – is an encrypted connection over the internet from a device to a
network. Hence, a means of connecting separate LANs through the internet, while maintaining
privacy.
• Domain Name Server (DNS) – translates internet address (such as www.ashts.com) to IP address
(such as 208.215.179.146) so routers can find websites on the internet.

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 • Dynamic Host Configuration Protocol (DHCP) – is a network protocol that automatically assigns IP
addresses to the devices on your network.
• Ethernet - is a networking standard.
• Internet Protocol (IP) Address – is a numerical label assigned to each device connected to a
computer network that uses the Internet Protocol for communication.
• Internet Service Provider (ISP) - is a company that provides individuals and other companies’
access to the Internet and other related services for a fee.
• Wi-Fi Protected Access (WPA and WPA2) – are wireless security standards for protecting your
wireless network and the data on your wireless network.
• Sneaker-net – is a slang term that refers to the transfer of data and electronic files between
computers through removable media (like hard drives, flash drives, etc.) which are physically
transported between computers and on foot.

NETWORK DEVICES
HUBS
A hub serves as a central point to which all of the hosts in a network connect to. It receives a signal from
one port and sends it out to all other ports. Sometimes it is called a multiport repeater.

SWITCHES
Like hubs, a switch is used to connect multiple hosts together, but it has many advantages over a hub.
Each port on a switch is a separate collision domain and can run in a full duplex mode.

ROUTERS
A router is a device that routes packets from one network to another. It connected to at least two
networks, commonly to LAN’s or WAN’s or a LAN and its ISP’s network.

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REPEATER
A network device used to regenerate or replicate a signal. Repeaters are used in transmission systems to
regenerate analog or digital signals distorted by transmission loss.

BRIDGE
A network bridge is a device that divides a network into segments. Each segment represents a separate
collision domain, so the number of collisions on the network is reduced.

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 TYPES OF NETWORKS
There are various types of computer networks available. We can categorize them according to their size as
well as their purpose.

Some of the most popular network types are:

• Personal Area Network (PAN)

• Local Area Network (LAN)
• Metropolitan Area Network (MAN)
• Wide Area Network (WAN)

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PERSONAL AREA NETWORK (PAN)
PAN is a computer network formed around a person. It generally consists of a computer, mobile, or
personal digital assistant. PAN can be used for establishing communication among these personal devices
for connecting to a digital network and the internet.
Characteristics of PAN

• It is mostly personal devices network equipped within a limited area.

• Allows you to handle the interconnection of IT devices at the surrounding of a single user.
• PAN includes mobile devices, tablet, and laptop.
• It can be wirelessly connected to the internet called WPAN.
• Appliances use for PAN: cordless mice, keyboards, and Bluetooth systems.
Advantages of PAN

• PAN networks are relatively secure and safe

• It offers only short-range solution up to ten meters
• Strictly restricted to a small area
Disadvantages of PAN

• It may establish a bad connection to other networks at the same radio bands.
• Distance limits.

LOCAL AREA NETWORK (LAN)

A Local Area Network (LAN) is a relatively small
network that is confined to a small geographical
area such as a single office, a building, a school,
laboratory, or a home. It is a widely useful
network for sharing resources like files, printers,
games, and other application. The simplest type
of LAN network is to connect computers and a
printer in someone's home or office.
It is a network which consists of less than 5000
interconnected devices across several buildings.

Characteristics of LAN

• It is a private network, so an outside regulatory body never controls it.

• LAN operates at a relatively higher speed compared to other WAN systems.
• There are various kinds of media access control methods like token ring and Ethernet.

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Advantages of LAN

• Computer resources like hard disks, DVD-ROM, and printers can share local area networks. This
significantly reduces the cost of hardware purchases.
• You can use the same software over the network instead of purchasing the licensed software for
each client in the network.
• Data of all network users can be stored on a single hard disk of the server computer.
• You can easily transfer data and messages over networked computers.
• It will be easy to manage data at only one place, which makes data more secure.
• Local Area Network offers the facility to share a single internet connection among all the LAN
users.
Disadvantages of LAN

• LAN will indeed save cost because of shared computer resources, but the initial cost of installing
Local Area Networks is quite high.
• The LAN admin can check personal data files of every LAN user, so it does not offer good privacy.
• Unauthorized users can access critical data of an organization in case LAN admin is not able to
secure centralized data repository.
• Local Area Network requires a constant LAN administration as there are issues related to software
setup and hardware failures.

METROPOLITAN AREA NETWORK (MAN)

A Metropolitan Area Network or MAN is
consisting of a computer network across an
entire city, college campus, or a small region.
This type of network is larger than a LAN, which
is mostly limited to a single building or site.
Depending upon the type of configuration, this
type of network allows you to cover an area
from several miles to tens of miles.

Characteristics of MAN

• It mostly covers towns and cities in a maximum 50 km range

• Mostly used medium is optical fibres, cables
• Data rates adequate for distributed computing applications.

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Advantages of MAN

• It offers fast communication using high-speed carriers, like fibre optic cables.
• It provides excellent support for an extensive size network and greater access to WANs.
• The dual bus in MAN network provides support to transmit data in both directions concurrently.
• A MAN network mostly includes some areas of a city or an entire city.
Disadvantages of MAN

• You need more cable to establish MAN connection from one place to another.
• In MAN network it is tough to make the system secure from hackers

WIDE AREA NETWORK (WAN)

WAN (Wide Area Network) is another important
computer network that which is spread across a
large geographical area. WAN network system
could be a connection of a LAN which connects
with other LAN's using telephone lines and radio
waves. It is mostly limited to an enterprise or an
organization. The internet is the largest WAN,
spanning the Earth.

Characteristics of LAN:

• The software files will be shared among all the

users; therefore, all can access to the latest files.
• Any organization can form its global integrated
network using WAN.
Advantages of WAN

• WAN helps you to cover a larger geographical area. Therefore, business offices situated at longer
distances can easily communicate.
• Contains devices like mobile phones, laptop, tablet, computers, gaming consoles, etc.
• WLAN connections work using radio transmitters and receivers built into client devices.
Disadvantage of WAN

• The initial setup cost of investment is very high.

• It is difficult to maintain the WAN network. You need skilled technicians and network
administrators.
• There are more errors and issues because of the wide coverage and the use of different
technologies.

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 • It requires more time to resolve issues because of the involvement of multiple wired and wireless
technologies.
• Offers lower security compared to other types of networks.

NETWORK TOPOLOGY
A network topology refers to the layout of a network and how different nodes in a network are connected
to each other and how they communicate. Topology can be physical or logical.

• Physical Topology – is the physical layout of nodes, workstations, and cables in the network.
• Logical Topology – is the way, information flows between different components.
Five (5) commonly used network topologies are;
Most networks, including the Internet, use combinations of these topologies.
STAR TOPOLOGY
On a star network topology, all of the computers and devices (nodes) on the network connect to a central
device, thus forming a star. It consists of one central node, typically a switch or hub, which acts as a
conduct to transmit messages. In star topology, every node is connected to a central node.
A star network contains a single, centralized hub or
switch through which all the devices in the network
communicate.
Advantages of a Star Topology

• Easy to install and wire

• No disruptions to the network when
connecting or removing devices.
• Easy to detect faults and to remove parts.
Disadvantages of a Star Topology

• Requires more cable length than a linear

topology
• If the hub, switch, or concentrator fails, nodes
attached are disabled.
• More expensive than linear bus topologies because of the cost of the hubs, etc.

BUS TOPOLOGY
Bus topology is the physical arrangement of computers or nodes in a network such that each
computer/node in the network is connected to a common shared transmission medium.

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A bus network topology consists of a single central cable, to which all computers and other devices
connected. The bus is the physical cable that connects the computers and other devices. In a bus network
transmission data, instructions, and information in both directions.
Advantages of a Bus Topology

• Easy to connect a new node

(computer or peripheral) to a linear bus.
• Requires less cable length than
a star.
Disadvantages of a Bus Topology

• Entire network shuts down if

there is a break in the main cable.
• Terminators are required at both ends of the backbone cable.
• Difficult to identify the problem if the entire network shuts down.
• Not meant to be used as a stand-alone solution in a large building.
TREE TOPOLOGY
A tree network topology combines characteristics of bus and star topologies. It consists of groups of star-
configured workstations connected to a linear bus backbone cable. Tree topologies allow for the
expansion of an existing network, and enables schools to configure a network to meet their needs. It is
also called an Expanded Star Topology.
Advantages of a Tree Topology

• Point-to-point wiring for individual

segments.
• Supported by several hardware and
software venders.
Disadvantages of a Tree Topology
• The types of cabling used limit overall
length of each segment.
• If the backbone line breaks, the entire
segment goes down.
• More difficult to configure and wire
than other topologies.

RING TOPOLOGY
In a ring topology, all devices in the network are connected via a cable that loops in a logical ring or circle.
In ring topology, the data circulates in a logical ring shape within the network. When a computer or device
sends data, the data travels to each computer on the ring until it reaches its destination. Ring topologies
are used in both local area network (LAN) and wide area network (WAN) setups.

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On a ring network, all connected devices form a continuous loop.
Advantages of a Ring Topology

• All the traffic flows in only one direction

at very high speed.
• Even when the load on the network
increases, its performance is better than that of
Bus topology.
• Additional components do not affect
the performance of network.
• Each computer has equal access to
resources.
Disadvantages of a Ring Topology

• Each packet of data must pass through all the computers between source and destination. This
makes it slower than Star Topology.
• If one workstation or port goes down, the entire network gets affected.
• Network is highly dependent on the wire, which connects different components.

MESH TOPOLOGY
Is a network set up where each computer and network device is interconnected with one another,
allowing most transmissions to be distributed, even if one of the connections goes down. Mesh
technology comes into two types:
Full Mesh – Every computer in the network has a connection to each of the other computers in that
network. The number of connections in this network can be calculated using this formula: n(n-1)/2 (n is
the number of computers in the network).
Partial Mesh – Not all hosts have point-to-point connection to every other host. This topology exists
where we need to provide reliability to some hosts out of all.
Advantages of a Mesh Topology

• Redundancy of paths is the main advantage of full-mesh

topology. If a connection between two devices failed, there is
always an alternate path available to reach the destination.
Disadvantages of full-mesh topology
• The cabling costs of full-mesh topology-based network can be
very high.
• It is not easy to troubleshoot a large full-Mesh topology-based
network.

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HYBRID TOPOLOGY
Hybrid topology is a type of network topology, which is made of two or more different topologies. Hybrid
topology is the combination of two or more of the primary topologies (i.e., bus, star, ring and mesh) to
form a new network.
A hybrid network topology can be made of different network topologies. Hybrid topologies are often
made using combination of bus topology, star topology, mesh topology (full-mesh topology or partial-
mesh topology), ring topology or wireless topology as per the requirement of the organization.
An example of hybrid topology is star-bus topology. Below image shows a star-bus hybrid network
topology.

Another example of hybrid topology is star-ring topology. Below image shows a star-ring hybrid network
topology.

Factors to consider when selecting a network topology

Network designers consider several factors when determining which topology or combination of
Topologies to use. They include
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 i. The type of computers to be installed (High Specification)
ii. The type of cables needed.
iii. The cost of various components (Nodes).
iv. The services required to implement the network.
v. The distance between each computer.
vi. The speed with which data must travel around the network.
vii. The future growth or expansion of the network.

NETWORK ARCHITECTURE
Every component of the network must be planned very well so that information can travel fast from one
point of a network node to the other. The components of a network are;

• Hardware – Computers, Printers, Scanners.

• Software – Databases, Operating System, Applications, Internet.
• Connecting Devices – Hub, Switch, Router, Modem, Cables, Wireless Devices.
• Communication Protocol – guidelines for implementing networking communications.
• Transmission – Wired or Wireless.
The design and arrangement of these network components such as Hardware, Software, Connecting
Devices, Communication Protocol and Transmission Media like cables or wireless is termed Network
Architecture.
There are three (3) main types of Network Architecture, these are;

• Peer-to-peer (P2P)
• Client – server.
• File – Sever.

PEER-TO-PEER ARCHITECTURE
A peer-to-peer (P2P) network is a simple, inexpensive network architecture that typically connects fewer
than 10 computers. Each computer or mobile device, called a peer, has equal access shared resources
found on other computers on the network.

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For example, you might set up a P2P network between an Android tablet and a Windows Laptop so that
they can share files using Bluetooth or so that you can print from the tablet to a printer accessible to all
devices on the network.
Both wired and wireless networks can be configured as a peer-to-peer network. Connections can be wired
or wireless and may occur through a communications device.

CLIENT-SERVER ARCHITECTURE
On a client/server network, one or more computers acts as a server, and the other computers on the
network request services from the server.
For example, a server might store an organisation’s information system. Client on the network, which
include any user connected computers or mobile devices, access the information system’s database on
the server.
Both wired and wireless networks can be configured as a client/server network. Most client/server
networks required a person to serve as a network administrator because of the large size of the network.

FILE –SERVER ARCHITECTURE

File server is a computer responsible for the central storage and management of data files so that other
computers on the network can access the files. A file server allows users to share information over a
network without having to physically transfer files by pend drive or some other external storage device.
Any computer can be configured to be a host and act as a file server unlike the client-server where the
server requires a computer with very high specifications.
The file server acts like a storage where information is retrieved from the network.

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 NETWORK TRANSMISSION MEDIA
Networking systems deliver data using a number of different transmission media, including copper wires,
fibre-optic cables, communication satellites, Bluetooth and microwave radio, etc.
TYPES OF NETWORK TRANSMISSION MEDIA
Transmission medium is a physical connection or an interface between the transmitter and the receiver.
There are two major categories of transmission media, namely;
1. Guided Transmission Medium (Cabling system) – twisted pair, coaxial cable. Fibre optic etc.
2. Unguided Transmission Medium (Wireless system) – Bluetooth, infrared, Wireless Fidelity (Wi-Fi),
satellite etc.

GUIDED MEDIA
Guided means those that provide a conductor from one device to the other device. A signal travelling by
this media means is directed and contained by the physical limits of the medium.
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Twisted Pair Cable
A twisted-pair cable has four pair of wires. These wires are twisted around each other to reduce crosstalk
and outside interference (noise/electro-magnetic interference). This type of cabling is common in most
current LANs.
Twisted-pair cabling can be used for telephone and network cabling. It comes in two versions,
1. UTP (Unshielded Twisted-Pair) and
2. STP (Shielded Twisted-Pair)
The difference between these two is that an STP cable has an additional layer of insulation that protects
data from outside interferences.

A twisted-pair cable uses RJ45 connector (8P8C connector).

Coaxial cable
Coaxial cable has an inner conductor that runs down the middle of the cable. The conductor is
surrounded by a layer of insulation which is then surrounded by another conducting shield, which makes
this type of cabling resistant to the outside interference.
This type of cabling comes in two types,
1. Thinnet.
2. Thicknet.
Both types have a maximum transmission speed of
10 Mbps. Coaxial cabling was used for computer
networks, but today are largely replaced by twisted-
pair cabling.

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Fibre-optic cabling
This type of cabling uses optical fibres to transmit data in the form of light signals. The cables have strands
of glass surrounded by a cladding material.

This type of cabling can support greater cable lengths

than any other cabling type (up to a couple of miles).
The cables are also immune to electromagnetic
interference. As you can see, this cabling method has
many advantages over other methods but its drawback
is that it is the most expensive type of cabling.
There are two types of fibre-optic cables:
1. Single-mode fibre (SMF) – uses only a single ray of light to carry data
2. Multi-mode fibre (MMF) – uses multiple rays of light to carry data
Two types of connectors are commonly used:
1. ST (Straight-tip connector)
2. SC (Subscriber connector)

UNGUIDED MEDIA
Unguided transmission transmits the electromagnetic waves without using any physical medium. In
unguided media, air is the media through which the signal flows.

Radio Waves
Electromagnetic waves ranging in frequencies between 3 KHz and 1 GHz are normally called radio waves.
Radio waves are omnidirectional. When an antenna transmits radio waves, they are propagated in all
directions. The omnidirectional characteristics of radio waves make them useful for multicasting in which
there is one sender but many receivers.
Micro Waves
Electromagnetic waves having frequencies between 1 and 300 GHz are called microwaves. Microwaves
are unidirectional. When an antenna transmits microwaves, they can be narrowly focused.

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Infrared Waves
Infrared waves, with frequencies from 300 GHz to 400 THz, can be used for short-range communication.
Infrared waves, having high frequencies, cannot penetrate walls.

OSI & TCP/IP MODELS

OSI MODEL
The International Organization for Standardization (ISO) created OSI (Open Systems Interconnection)
model. It was designed to be a reference model for describing the functions of a communication system. It
has seven layers, with each layer describing a different function of data traveling through a network.
Here is the graphical representation of these layers:

The layers are usually numbered from the last one, meaning that the Physical layer is consider to be the
first layer. Most people learn the mnemonic “Please Do Not Throw Sausage Pizza Away”

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Purpose of The Layers
Vendors most commonly use them. They enable them to implement some functionality into a networking
device, which then enables easier interoperability with devices from other vendors. It mainly describes
general guidelines for designing and implementing computer protocols.
Brief Description of Each of The Layers
Physical
Defines how to move bits from one device to another. It details how cables, connectors and network
interface cards are going to work and how to send and receive bits.
Data Link
Encapsulates a packet in a frame. A frame contains a header and a trailer that enable devices to
communicate. A header, most commonly, contains a source and a destination MAC address. A trailer
contains the Frame Check Sequence field, which is used to detect transmission errors. The data link layer
has two sublayers:
1. Logical Link Control – used for flow control and error detection.
2. Media Access Control – used for hardware addressing and controlling the access method.
Network
Defines device addressing, routing, and path determination. Device (logical) addressing is used to identify
a host on a network (e.g., by its IP address).
Transport
Segments great chunks of data received from the upper layer protocols. Establishes and terminates
connections between two computers. Used for flow control and data recovery.
Session
Defines how to establish and terminate a session between the two systems.
Presentation
Defines data formats. Compression and encryption are defined at this layer.
Application
This layer is the closest to the user. It enables network applications to communicate with other network
applications.

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The table shows which Data Name, Network Devices and Mnemonic reside on which layer:

TCP/IP MODEL
Défense Advance Research Project Agency (DARPA) created the TCP/IP model in the 1970s. Like the OSI
model, it describes general guidelines for designing and implementing computer protocols.
It consists of four layers: Network Access, Internet, Transport, and Application.

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The table below shows the comparison between the TCP/IP model and OSI model:

TCP/IP Model OSI Model

Application Application
Presentation
Session
Transport Transport
Internet Network
Network Access Data Link
Physical
As you can see, the TCP/IP model has fewer layers than the OSI model.

Differences between OSI and TCP/IP model

There are some other differences between these two models, besides the obvious difference in the
number of layers. OSI model prescribes the steps needed to transfer data over a network and it is very
specific in it, defining which protocol is used at each layer and how. The TCP/IP model is not that specific.
It can be said that the OSI model prescribes and TCP/IP model describes.

NETWORK PROTOCOLS

Protocol is a set of rules and standards that basically define a language that devices can use to
communicate. Some level protocols are TCP, UDP, IP, and ICMP.

Transmission Control Protocol

TCP is a connection-oriented protocol that facilitates the exchange of data between computing devices in
network. NB: It guarantees the delivery of data.

User Datagram Protocol

UDB is a connectionless oriented protocol that facilitates the exchange of data between computing
devices in network. NB: It does not guarantee the delivery of data, hence faster than TCP.

File Transfer Protocol

FTP is a standard protocol use by web users to upload and download files between computers through the
internet. NB: It mainly uses the TCP for file transfer.

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Trivial File Transfer Protocol

TFTP is a simple protocol that is use to transfer files within the same network. NB: It connectionless
protocol that uses UDP.

Secure File Transfer Protocol

SFTP is just like FTP it just adds a layer of security. Data is encrypted using secure shell during transfer.

Simple Mail Transfer Protocol

SMTP is the protocol use to send email. It uses the TCP protocol. Mnemonic to remember the use;
Sending Mail To People.

Post Office Protocol Ver. 3

POP3 is a protocol use for receiving email. It only downloads the email. NB: No copy is left on the Mail
Server after downloading using POP3 protocol.

Internet Message Access Protocol Ver. 4

IMAP4 is similar to POP3 but keeps copies of the email you download from the Mail Server.

HyperText Transfer Protocol

HTTP is the protocol that is use to view web pages on the internet. It the most commonly use protocol.

Secure HyperText Transfer Protocol

HTTPS is just like HTTP but with security feature. Data is encrypted using http.

Telnet
Telnet is a terminal emulation program that is use to access remote servers. Due to it insecurity it mostly
use to access to access devices within a LAN and not on the internet.

Secure Shell

SSH is a better alternative to Telnet. It adds up a security layer around the passage and protects it from
potential threats.
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Address Resolution Protocol

ARP is a protocol that is use to resolve IP addresses to MAC addresses. Computers use MAC addresses for
communication between each other.
Computers search their ARP cache first to find the target MAC address. If the MAC address is not in the
ARP Cache, the computer will broadcast a message asking for it.

Reverse Address Resolution Protocol

RARP is just the opposite of ARP. It uses to resolves MAC addresses to IP addresses.

IP ADDRESSES

IP Address is an identifier for a computer or a device on a network. It a numeric address.

Every Device on a network needs to have an IP address to communicate.
Consists of 2 parts

 Network Address

 Host Address

Types of IP Address

 IPv4

 IPv6

IPv4

IPv4 is the current version of IP addresses. It’s a 32bit numeric address written as four numbers separated
by periods.

The number range is from 0 – 255.

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 IPv6

IPv6 is the next generation of IP addresses. It’s a 128bit hexadecimal address. Hexadecimal uses both
numbers and alphabets.

76DC:4F59:34CF:71CD:9DCD:45D6:
Reserved IP Addresses

127.0.0.0 is reserved for IP traffic local to your host [Loopback Address]

NETWORK CONFIGURATION

• Setting up a Home Network.

• Components and Structure.
Most home and small office networks will use a wireless network or mixed networks, as most people use
Smart phones, and tablets which don’t have Ethernet support.
The main components required to build a typically home/small office are:

• Router or wireless router – connects the network to the internet.

• Wireless Access Point – used to connect Wi-Fi equipped devices to the network.
• Ethernet Hub or Switch – used to connect Ethernet equipped devices.
• Cable cat5, cat5e or cat6 with RJ45 connectors.
• Telephone cable with RJ10 connectors.
The home network diagram below shows the structure of a typical small home network.

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 • Home Wireless Networks – use Wi-Fi and are quick and easy to install, but generally slower than
wired networks.
• Home Wired Networks – use Ethernet over UTP cable and tend to be faster than wireless
networks.

DATA COMMUNICATION
Data communications are the exchange of data between two devices via some form of transmission
medium such as a wire cable. For data communications to occur, the communicating devices must be part
of a communication system made up of a combination of hardware (physical equipment) and software
(programs).
The effectiveness of a data communications system depends on these fundamental characteristics:

• Delivery – The system must deliver data to the correct destination. Data must be received by the
intended device or user and only that device or user.
• Accuracy – The system must deliver the data accurately. Data that have been altered in
transmission and left uncorrected are unusable.
• Timeliness – The system must deliver data in a timely manner. Data deliver late are useless.
There are five components of the data communications system, these are;

• Message – is the information or data to be communicated.

• Sender – is the device that sends the data message. It can be a computer, workstation, telephone
handset, video camera, etc.
• Receiver – is the device that receives the message. It can be a computer, workstation, telephone
handset, television, etc.
• Transmission Media – is a physical connection or an interface between the transmitter and the
receiver.
• Protocol – is a set of rules that govern data communication.

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Forms of Data Communication

• Information Services
• Electronic Funds Transfer
• Telecommuting
• The Internet services
• E-mail (Electronic Mail)

DATA TRANSMISSION MODE/DIRECTIONS

The term transmission mode defines the direction of data flow between two linked devices. The way in
which data is transmitted from one place to another is called Transmission Mode.
There are three ways of transmitting data from one location to another. These are;
1. Simplex Mode – the communication can take place in only one direction. In this mode, a terminal
can only send data and cannot receive it or it can only receive data but cannot send it. It means
that this mode of communication is unidirectional. Examples of simplex communication modes are
Radio and TV transmissions.
2. Half-Duplex Mode – the communication can take place in both directions, but only in one
direction at a time. In this mode, data is sent and received alternatively. In half-duplex mode, at a
time only one end transmits data while other end receives information. The internet browsing is
an example of half-duplex. Another example is Walkie-talkie.
3. Full-Duplex Mode – the communication can take place in both directions simultaneously, i.e., at
the same time on the same channel. It is the fastest directional mode of communication. Example
of this mode is conversation of the persons through telephone.

DATA TRANSMISSION SIGNALS

When data is sent over physical medium it needs to be first converted into electromagnetic signals. There
are two main forms of Data Transmission Signals namely;
1. Analog Signal – is any continuous signal for which the time varying feature (variable) of the signal
is a representation of some other time varying quantity, i.e., analogous to another time varying
signal. There are many examples of analog signals around us. The sound from a human voice is
analog, because sound waves are continuous.
2. Digital Signal – is described as using binary (0s and 1s), and therefore, cannot take on any
fractional values. Computers in contrast send and receive digital signals. Digital signal just refers to
an electrical signal that is converted into pattern of bits.

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 DATA SECURITY AND CONTROL
Unfortunately, many companies do not deal with data security and network management problems until
there is a crack in the network. To protect vital information, the companies must set up a sound security
system before the network is intruded. This involves;

• Identification of the security risks,

• Applying sufficient means of security, and
• Teaching the users data security awareness.

COMPUTER SECURITY RISK

A computer security risk is any event or action that could cause loss of or damage to computer:

• Hardware
• Software
• Data
• Information, or
• Processing capability
While some breaches to computer security are accidental, many are intentional. Any illegal act involving a
computer generally is referred to as a computer crime.
The term cybercrime refers to online or internet-based illegal acts. Software used by cybercriminals
sometimes called crime ware.
Some examples of computer security risks.

• Unauthorized access and use (intercepting wireless communications).

• Hardware theft (stolen computer or parts).
• Information theft (Stolen Identity).
• Software theft (Illegal Copying).

DATA SECURITY
Data Security is a practice of keeping data protected from unauthorized access and corruption. The focus
behind data security is to ensure privacy while protecting personal or corporate data.
Computer Systems pose four main securities:
1. Password Protection
2. Destination Code
3. Error Code
4. Encryption

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Password Protection
Password protection is a security process protects information accessible via computers that needs to be
protected from certain users. Password protection allows only those with authorized password to gain
access to certain information.
Passwords are used commonly to gain entry to networks and into various internet accounts in order to
authenticate the user accessing the website.
Destination Code
The destination code feature provides destination codes for basic telephone service. The destination code
will be used for a call if dialled or modified (in PAC) digits and Nature of Address are matching. This field
specifies the number configured for this Destination Code. Destination Code can be of length 1-15.
Encryption
To encrypt a file or other information stored in a computer means to convert it into a secret code so that
it can’t be used or understood until it is decoded or decrypted.
This is a process of encrypting data to prevent unauthorized person from viewing or modifying it. The
main features of data encryption are:
1. Prevents unwanted access to documents and email messages.
2. Strongest levels of encryption are very difficult to break.
The Process of Data Encryption consists of certain steps. The data passes through a mathematical formula
called an algorithm, which converts it into encrypted data called cipher-text. These algorithms create a
key and then encapsulate the message with this key.

LESSON ASSESSMENT
OBJECTIVES
1. The form of data transmission that sends start signal, followed by a group of message bits for a
character of data, followed by a stop signal is called
A. Asynchronous
B. Character based
C. Multiplexing
D. Synchronous
2. Local Area Networks are intended to:
I. Restrict physical movement of personnel
II. Share programs among connected computers
III. Share data among connected computers
IV. Share peripheral devices among connected computers
A. I and II only
B. II and III only
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 C. III and IV only
D. I, II, III and IV
3. Which of the following is the same as http://127.0.0.1 in the address bar of a web client?
A. http://hostip
B. http://local
C. http://localhost
D. http://www.local.com
4. Which of the following is not a factor to be considered when selecting network type for an organisation
to implement?
A. Size of the organisation
B. Amount of network traffic
C. Location of the organization
D. Level of administrative support available
5. The OSI model, repeaters operate at the
A. Data link layer
B. Network layer
C. Physical layer
D. Transport layer
6. Which of the following cables transmit data at the least speed?
A. Category 2 UTP
B. Category 3 UTP
C. Category 4 UTP
D. Category 5 UTP
7. The cable that is best suitable for implementing a bus topology is
A. Coaxial
B. Fibre optic
C. Shielded twisted pair
D. Unshielded twisted pair
8. Communication media such as copper wire, coaxial cables or wireless systems that are used to
interconnect the other components of telecommunication network are referred to as
A. Channels
B. Modem
C. Processors
D. Servers
9. The following are examples of wireless technology except
A. Bluetooth
B. Infrared
C. Fibre optics
D. Communication satellites
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10. The following are network resources except
A. Applications
B. Cache
C. Files
D. Printers
11. BNC-T connector is associated with which type of cable?
A. Coaxial
B. Ethernet
C. Fibre-optic
D. Twisted-pair
12. Which of the following reasons justifies the use of a layered approach to networking?
A. Allows for large networking
B. Makes creation of networks easy
C. Allows many programmers to implement a network
D. Permits computer on different platforms to communicate
13. The internet service that allows users to connect to remote computers and run applications is referred
to as
A. Gopher
B. Hypertext
C. Switching
D. Telnet
14. A system of connected computers, telephones or other communications devices that communicate
with one another is called a
A. Closed network
B. Circuit network
C. Packet switching
D. Communications network
15. The layer responsible for dialogue in the OSI model is the
A. Data link layer
B. Network layer
C. Physical layer
D. Session layer
16. Networks that use different communications architecture are interconnected by using
A. Bridge
B. Gateway
C. Hub
D. Protocol
17. To prevent intruders from tapping into a network, it is advisable to use
A. Coaxial cable
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 B. Twisted pair
C. Optical fibre cable
D. Untwisted pair cable
18. Which of the following protocols uploads files to a host machine?
A. FTP
B. PGP
C. POP
D. TCP
19. The following network media are for guided communications except
A. Coaxial cable
B. Fibre optic
C. Satellites
D. Twittered pair cable
20. A bridge is used in a computer network to
A. Control the network speed
B. Connect local area networks
C. Separate local area networks
D. Fluctuate network communications
21. Which of the following media is immune to electromagnetic signals?
A. Coaxial cabling
B. Fibre optic cabling
C. Shielded twisted pair
D. Unshielded twisted pair
22. Which of the following offers the longest possible segment length?
A. Coaxial cabling
B. Fibre optic cabling
C. Shielded twisted pair
D. Unshielded twisted pair
23. Computer networking can achieve all the following except
A. Reduce cost
B. Increase efficiency
C. Centralize administration and support
D. Increase the number of computers in the organisation
24. Logical topology describes how computer networks
A. Message travel
B. Cables are run
C. Resources are arranged
D. Run faster or slower
25. A physical star topology consists of several workstations connected to a central device called
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 A. Bridge
B. Hub
C. Modem
D. Repeater

SUBJECTIVE
1. A) State one function each of the following computer network devices:
I. Bridge
II. Repeater
III. Router
B) Name the layer of the OSI model at which each of the devices listed in 1(a) operates.
C) List two types of network transmission media.

2. A) Explain the term bandwidth?

B) State two uses of a USB internet modem.
C) List three examples of computer network protocols.

3. A) What is physical topology with respect to computer networking?

B) Identify the following network topologies:
I.

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 II.

C) Explain the topologies identified in 3(b).

4. A) What is computer network?

B) Define the following types of networks.
I. LAN
II. MAN
III. WAN
C) State four main reasons for creating a network within an organisation.

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