ICT

Key Unit Competency:
To be able to explain principles, standards and purposes of computer network

Read the following scenario and answer to the asked questions.

In the school computer labs, choose a classmate and send him/her an email that
has “Computer Network “as the email subject and the email body contains names of
previous units already covered in senior 5 computer science. Ask him/her to reply
immediately to your email.

After receiving the reply, answer the following questions:

1. List all possible elements that make this communication possible

2. What devices are used to facilitate sending email successfully?

3. Discuss what made possible the sending and receiving of emails

4. Do you like using email?

5. How do you value the factor of sending and receiving an email

6. Describe what you see in the photo below?

3.1. Fundamental of computer Networ

3.1.1. Computer Network Definition

ACTIVITY 3.1

Observe computers in the computer lab and answer the following question?

1. Describe what you see?

2. What are transmission media used to connect computers in the
    computer labs?

3. Are all devices connected?

A computer network is a system of interconnected computers for the purpose of
sharing data and resources.

Computers on a network are called nodes. Nodes can include hosts such as personal
computers, phones, servers as well as networking hardware. Two devices are
networked together when one device is able to exchange information with the
other device. The computer can be connected to another in the two ways.

Wired network: Computers are connected using cable media. Most commonly
Ethernet Cable, coaxial cable and optic fiber.

Wireless network: Computers are connected using wireless media. Radio waves are
used in wireless mode.

3.1.2 Properties of Computer Network

• Easy Sharing of Resources: Computers are able to share various resources
easily over a network. Shared resources can be Internet, files, printer, storage
and others.

• Performance: It is achieved by measuring the speed of data transmission
with number of network users, connectivity used and the software used. The
commonly measured qualities in the network performance are Bandwidth
and Latency.

• Reliability: It means that computer network provides assurance of the
delivery of data to the intended recipient.

• Scalability: The possibility of adding new computer without affecting the
network performance.

• Security: computer network must be secured for the benefit of the user and
data protection. The security is achieved by protecting data from unauthorized
access.

• Quality of Service (QoS): Quality of Service refers to the mechanism that
   manage congested network traffic.

• Fault tolerant: A fault tolerant network limits the impact of hardware or
software failure and recovers quickly when a failure occurs

APPLICATION ACTIVITY 3.2

1. Investigate what happen when a shared resource is disconnected from
the computer network?

2. Imagine other areas where computer network is used?

3.1.3 Advantages and Disadvantage of Computer Networking
       The common advantages of computer network

Activity 3.2

1. Discuss the disadvantages of using computer network within your school?

2. In class of senior 5 MPC, Computer Science Teacher decides to share notes
   for students to use on our school network. The mathematics teacher decides
   to print notes of 100 pages and distributes to each member of senior 5 MPC
   class.

i. Evaluate the cost impact for both teachers

ii. Both teachers, whom save money in giving notes.

The common advantages of computer network

1. Enhanced communication and availability of information: It allows access
   to a vast amount of useful information.

Example: Population data, newsletters, online businesses, contents,
Applications.

2. Allow resource sharing: Fewer resources are needed when an organization
uses a computer network.
Example: only one printer is needed instead of buying a printer for each office.

3. File sharing made easy: computer network allows people to share files, which
    helps to save more time and effort.
    Example: A teacher can share homework to all students through school
    network

4. Improve storage capacity: since you are going to share information, files and
    resources to other people, you have to ensure that all data and content are
    properly stored in the system.

5. Cost efficiency: on computer network, you can share software license installed
on the server and can then be used by various workstations.

6. Security of information and resources: users cannot see other users' files
unlike on stand-alone machines.

7. Backup of data is easy as all the data is stored on the file server.

The common disadvantages of computer networking

1. Lack of independence: people rely on computer network and when the
system is down, people get stack. Most of organizations depend on the
computer networks.

2. Security issues: huge number of people use a computer network to get and
share their files and resources, a certain user’s security would be always at
risk. Viruses can spread to other computers throughout a computer network.
There is a danger of hacking, particularly with wide area networks. Security
procedures are needed to prevent such abuse, Examples: The use of Antivirus
and firewall.

3. Lack of robustness: computer network’s main server breaks down, the entire
system would become useless

APPLICATION ACTIVITY 3.2

1. Investigate what happen when a shared resource is disconnected from
    the computer network?

2. Imagine other areas where computer network is used?

3.1.4 Types of computer networks

Activity 3.3

With two or more Bluetooth enabled devices available in the classroom:

1. Turn on the Bluetooth feature on both devices

2. Share and receive files such images and documents between the
   devices

3. Turn off Bluetooth feature in the two devices.

A computer network is classified basing on the size of the area covered, the number
of users connected and the number & types of services available.

The followings are type of computer networks:

1. Personal Area Network (PAN)

A personal area network (PAN) is a network that connects devices, such as mice,
keyboards, printers, Smartphone, and tablets within the range of an individual
person. PAN has connectivity range up to 10 meters. PAN may include wireless
computer keyboard and mouse, Bluetooth enabled headphones, wireless printers
and TV remotes. All of these devices are dedicated to a single host and are most
often connected with Bluetooth technology.

Bluetooth is a wireless technology that enables devices to communicate over short
distances. A Bluetooth device can connect up to seven other Bluetooth devices.

2. Local Area Network (LAN)

Traditionally, a LAN is defined as a network that covers a small geographical area.
However, the distinguishing characteristic for LANs today is that they are typically
owned by an individual, such as in a home or small business, or wholly managed
by an IT department, such as in a school or corporation. This individual or group
enforces the security and access control policies of the network. LAN uses Ethernet
IEEE 802.3 as its standard.

A Wireless LAN (WLAN) is a LAN that uses radio waves to transmit data between
wireless devices. In a traditional LAN, devices are connected together using copper
cabling. In some environments, installing copper cabling might not be practical,
desirable, or even possible. In these situations, wireless devices are used to transmit
and receive data using radio waves. As with LANs, on a WLAN, you can share resources,
such as files, printers, and Internet access. WLAN uses Ethernet IEEE 802.11 as its
standard.

3. Metropolitan Area Network (MAN)

A metropolitan area network (MAN) is a network that spans across a large organization
like campus or a city. The network consists of various buildings interconnected
through wireless or fiber optic backbones.

A backbone is the part of the computer network infrastructure that interconnects
different LAN networks and provides a path for exchange of data between these
different networks

The communication links and equipment are typically owned by a network service
provider who sells the service to the users. A MAN can acts as a high-speed network
to enable sharing of regional resources.

4. Wide Area Network (WAN)

A WAN connects multiple networks that are in geographically separated locations.

The distinguishing characteristic of a WAN is that it is owned by a service provider.
Individuals and organizations contract for WAN services. WAN network provides
connectivity to MANs and LANs. The most common example of a WAN is the
Internetwork or Internet in short. The Internet is a large WAN that is composed of
millions of interconnected networks.

Example: Kigali and Nairobi networks are connected through the Internet

APPLICATION ACTIVITY 3.3

1. Discuss the role ISP services for LANs?

2. Do an observation in the school computer lab and categorize the
computer network type available at your school? Justify your answer.

3. Using clear examples, Distinguish Personal Area Network and Local Area
Network?

4. Using an arrow match the following in Group A with their
corresponding in Group B

Group A                                               Group B
a. Radio waves                                     1. Qualities of Computer network
Performance

b. Millions of interconnected network    2. Disadvantages of Computer network

c. Sharing resources                             3. Wireless

d. Hacking attacks                                 4. WAN

e. Bandwidth and Latency                     5. Advantages of Computer network

3.2 Computer Network Concept and Technology

ACTIVITY 3.4

You are browsing a website on the internet while the speed is okay and suddenly you
find that the page is loading slowly. Investigate the reason behind slowness?

3.2.1 Network metrics

Network metrics are defined as standards of measurement by which efficiency,
performance, progress, or quality of a plan, process can be assessed. Network metric
are used by a router to make routing decisions.

When data is sent over a computer network, it is broken up into small chunks called
packets. Each packet contains source and destination address information. Packets
are sent across a network one bit at a time.

      a. Bandwidth

Bandwidth is the amount of data that can be transmitted in a fixed amount of time.
Bandwidth is measured in the number of bits that can be sent every second.
The following are examples of bandwidth measurements:

• b/s - bits per second

• kb/s - kilobits per second

• Mb/s - megabits per second

• Gb/s - gigabits per second

                b. Latency
Latency is the time between requesting data and receiving data. More simply put,
the time it takes to establish a connection between your computer and the server
hosting the website you requested. The important thing to take away here is that
latency is not speed. Data is delayed by network devices and cable length. Network
devices add latency when processing and forwarding data.

                 c. Throughput:
Throughput is the actual rate at which information is transferred. It measures the
amount of completed work against time consumed and may be used to measure
the performance of a processor, memory and/or network communications.

                   d. Error rate:
Error rate is the number of corrupted bits expressed as percentage or fraction of the
total sent.
                    e. Jitter:
Jitter is variation in packet delay at the receiver of information. For measuring the
capacity of all of these metrics above, we focus on capacity of message and this one
change into different form depending on the network devices where this message
is located.

               3.2.2 Data Transmission model

The term transmission mode is used to define the direction of signal flow between
two linked devices. The data that is transmitted over the network can flow using one
of three modes: simplex, half-duplex and full-duplex.

1. Simplex: it is a single one-way transmission. In a simplex transmission
mode, the communication between sender and receiver occurs only in one
direction. That means only the sender can transmit data, and receiver can
receive that data. The receiver cannot transmit any information back to the
sender.

The keyboard to monitor transmission is an example of simplex transmission
mode. Other examples are communication between a computer and a
printer, listening to the radio and the signal that is sent from a TV station to
your home TV.

2. Half-Duplex: data flows in one direction at a time. In half-duplex, the
    channel of communications allows alternating transmission in two
   directions, but not in both directions simultaneously. An Example of Halfduplex
   is the Talkie- Walkie used by the police.

3. Full-Duplex: data flows in both directions at the same time. In a full duplex
   transmission mode, the communication between sender and receiver can
  occur simultaneously. Sender and receiver both can transmit and receive
  simultaneously at the same time.

A telephone conversation is an example of full-duplex communication. Both people
can talk and be heard at the same time.

APPLICATION ACTIVITY 3.4

1. Examine 2 reasons that cause latency in computer network.

2. What is your school download bandwidth and upload bandwidth?

3. Contrast upload bandwidth and download bandwidth?

4. Categorize following devices according to their transmission modes

                     a. TV

                     b. Radio

                     c. Walkie -Talkie

                     d. Phone

                     e. Computer

3.2.3. Internetwork (Internet, Intranet, Extranet)

ACTIVITY 3.5

Using computer network, an organization’s employees can access data when
they are inside the organization buildingand when they are physically outside.
Investigate technologies that can be used to allow employees inside and outside
to access organization’s data.

A network of networks is called an internetwork, or simply the Internet. The Internet,
extranets, and intranets all rely on Transport Control Protocol / Internet Protocol
(TCP/IP). However, they are different in terms of the levels of access they allow to
various users inside and outside the organization and the size of the network.

1. An Intranet is a private computer network that uses Internet Protocol to
   securely share any part of an organization’s information or operational
   systems within that organization. Only users inside the organization are
    only allowed to access it.

2. An Extranet is a private network that uses Internet protocols, network

connectivity. An extranet can be viewed as part of a company’s intranet
that is extended to users outside the company, the connectivity is made
possible by the Internet.

3. The Internet is a global system of interconnected computer networks that
use the standard Internet Protocol suite (TCP/IP) to serve billions of users
worldwide.

The difference between the Internet and Extranets is that while the extranet allows
limited access to non-members of an organization, the Internet generally allows
everyone to access all network resources.

APPLICATION ACTIVITY 3.5

General supply Ltd. sell various services online and offline. It has various partners such
as suppliers, sellers, buyers and clients in different Districts of Rwanda. Each partner
wants to access the General supply data from its servers located at the main office in
Ruhango District.

Examine in details the appropriate technology for each user to access the General
supply Ltd. data to avoid the user location problem

3.3 Local Area Networks (LANs)

ACTIVITY 3.6

By definition, computer network is said to be a group of computers connected together
and share resources. Using your school environment, observe followings:

1. The range covered by your school network?

2. The number of users on your school network?

3. Resources shared on your school network?

3.3.1 Definition

Local Area Networks (LANs) are networks usually confined to a geographic area, such
as a single building or a college campus. LANs can be small, linking as few as three
computers, but often link hundreds of computers used by thousands of people.

3.3.2 LAN Categories

1. Peer-to-Peer Network

A peer-to-peer (P2P) network is created when two or more computers are connected
and share resources without going through a separate server computer. In a peerto-
peer network, there is no hierarchy among the computers, nor are there any
dedicated servers.

Each device on the network, also called a client, has equivalent capabilities and
responsibilities. A user is responsible for its own resources and can decide which
data and devices to be shared with other computers. Because individual users are
responsible for the resources on their own computers, the network has no central
point of control and no central administration. Peer-to-peer networks work best in
environments with ten or fewer computers.

Advantages of peer to peer network are as follows:

• The main advantage of peer to peer network is that it is easier to set up

• In peer-to-peer networks all nodes are act as server as well as client therefore
  no need of dedicated server

• The peer to peer network is less expensive

• Peer to peer network is easier to set up and use this means that you can spend
 less time in the configuration and implementation of peer to peer network.

Disadvantages of peer to peer network

• A computer can be accessed anytime

• Network security has to be applied to each computer separately

• Backup has to be performed on each computer separately

• No centralized server is available to manage and control the access of data.

2. Client-Server Network

In a client-server network, the client requests information or services from the server
and the server provides the requested information or service to the client. Servers
on a client-server network commonly perform some of the processing work for
client machines.

In a client-server network, resources are controlled by a centralized network
administration. The network administrator implements data backups and security
measures. The network administrator also controls user access to the server
resources.

Note: In a home or small business, a single server can run multiple types of server
software, it may be necessary for one computer to act as a file server, a web server,
and an email server. A client computer can also run multiple types of client software.
There must be client software for every service required. With multiple client software
installed, a client can connect to multiple servers at the same time.

Advantages of Client-Server Network

• Centralization of control: Access, resources and integrity of the data are
  controlled by the dedicated server so that a program or unauthorized client
  cannot damage the system.

• Scalability: You can increase the capacity of clients and servers separately.
  Any element can be increased (or enhanced) at any time, you can add new
  nodes to the network (clients or servers).

• Easy maintenance: Distribute the roles and responsibilities to several
  standalone computers, you can replace, repair, upgrade, or even move a server,
  while customers will not be affected by that change (or minimally affect).

Disadvantage of Client Server Networks

• There is a reliance on the central server, if it fails, no work can be done

• A network manager is required and this costs money

• The server costs money, as does the network operating system

• Servers are powerful, thus expensive

• Lots of network traffic.

Advantages of Client Server Networks over Peer to Peer Networks

• Centralization: Unlike Peer to Peer, where there is no central administration,
  Client Server Networks have a centralized control.

• Proper Management : All the files are stored at the same place. Therefore,
management of files becomes easy and it is easier to find files.

• Back-up and Recovery possible: As all the data is stored on server it is easy to
  make a back-up of it. Also, in case of some break-down if data is lost, it can be
  recovered easily and efficiently. While in peer to peer network, we have to take
  back-up at every workstation.

• Upgrade and Scalability in Client-server set-up: Changes can be made
  easily by just upgrading the server. Also new resources and systems can be
   added by making necessary changes in server.

• Accessibility: From various platforms in the network, server can be accessed
  remotely.

• Security: Rules defining security and access rights can be defined at the time of
set-up of server.

Disadvantages of client server network over the Peer to peer network

• Congestion in Network: Too many requests from the clients may lead to
  congestion, which rarely takes place in Peer to Peer network. Overload can
  lead to breaking-down of servers. In peer-to-peer, the total bandwidth of the
  network increases as the number of peers increase.

• Client-Server network is not as robust as a Peer to Peer network and if the
  server fails, the whole network goes down.

• Cost: It is very expensive to install and manage client server network.

APPLICATION ACTIVITY 3.6

Respond the following questions by True or False and justify your answer

• Peer to Peer network is only implemented by computers which run same
operating system.

• In Server-Client network, Server respond to service only requested by the
Client.

• Limit number of hosts in the Peer to Peer network are 10 computers.

• Client requests only the service available on the server in Server-Client
  network.

• Peer to Peer network is more secure than Server-Client network.

• There is a dedicated computer in Peer to Peer network.

• In Client- Server network, both client and server must run the same Operating
 System.

3.4. Physical Components

 ACTIVITY 3.7

In the computer lab observe devices that are directly participating in the
network. Examine the role of each device you have identified.

3.4.1. Definition of network device

A network host or a node is a computer or any other device that is directly connected
to a computer network. A network host may offer information resources, services,
and applications to users.

i. Network Interface Card (NIC)

Network Interface card is a component that allows the computer to communicate
across a network. This component is frequently built into the motherboard of today’s
computers, but it can also be a separate card for use in a PCI slot.

Network Interface cards can be either wired or wireless. However, some cards do
support both wireless and wired networking

APPLICATION ACTIVITIES 3.7

NIC Card installation in a desktop computer:

Step 1: Shut down your Computer and disconnect it from the power source

Step 2: Remove the case cover. Then remove the cover of the available slot.

Step 3: Install NIC in proper slot and secure it

Step4: Replace the case cover.

Note: A wireless NIC has an antenna connected to the back of the card or attached
with a cable so that it can be positioned for the best signal reception. You must
connect and position the antenna.

     ii. Media Access Control Address

Media Access Control Address (MAC address) of a device is a unique identifier
assigned to network interfaces for communications at the data link layer of a
network segment. MAC address is a physical address of Network Interface Card. In
other words MAC addresses are linked to the hardware of network adapters. A MAC
address is given to a network adapter when it is manufactured.
Example of a MAC address: 00:0a:95:9d:68:16.

iii. Modem

A modem is a hardware device that enables a computer to send and receive data
over a telephone line or a cable or satellite connection. Modem is used to transmit
digital information via analog systems. The word “modem” is derived from the term
“Modulator - Demodulator.”

The essential functions of a modem are:

• Modulate: an analog carrier signal to carry digital information, it means to
   convert the analog signal to digital signal.

• Demodulate: a similar signal so as to decode the digital information from
the analog carrier signal and it means to convert the same signal back to the
analog signal then transmitted through telephone line.

They are two types of modems:

Internal modem which are circuit boards that plug into a computer’s motherboard and
external modems which are discrete units housed in a separate case. Typically, an external
modem is connected to the telephone line and the computer via cables or USB.

APPLICATION ACTIVITY 3.8

Find the Mac address of your computer

Step1: Click the Run button in the windows 10 Start Menu

Step 2: Type cmd in the Open prompt of the Run menu and click OK to launch a
             command prompt window

Step 3: Type ipconfig /all at the command prompt to check the network card
             settings.

Step4: MAC address is listed by ipconfig under Physical Address

iv. RJ 45 Connector and Port

A registered jack (RJ) is a standardized physical network interface for connecting
telecommunications or data equipment. The physical connectors that registered
jacks use are mainly of the modular connector and 50-pin miniature ribbon connectortypes

The RJ45 port is the network port on a computer. This socket has many names. It is
also known as the Ethernet port, the network adapter, the network jack or the RJ45jack.

3.5. Network Devices

ACTIVITY 3.8

Observe the connection between network devices that make your school network.
Then answer following questions:

1. Examine how computers are connected together in order to exchange
    data?

2. Investigate how data / message is forwarded from the Computer A (as
     source) to Computer B (as destination)?

3. The equipment used to connect devices within a LAN has evolved from
     hub to bridge to switch. Contrast both devices?

3.5.1 Hub

A hub is a network hardware device for connecting multiple devices together and
making them act as a single network segment.

Definition:A network segment is a portion of a computer network that is separated from
the rest of the network by a network device.

Hub receives message on one port and then send it out to all other ports, this means
that when hub receives message, the received message is regenerated or duplicated
and sent to all computers connected to the hub, each computer on the network
receives the message, if it is not the destination message is destroyed, if it is the
destination it reads the message.

Note: Hubs are used less often today because of the effectiveness and low cost of
switch. Hub do not segment network traffic. When one device sends traffic, the hub
floods that traffic to all other devices connected to hub. The devices are sharing the
bandwidth.

3.5.2 Switches

Switch filters and segments network traffic by sending messages only to the device to
which it is sent. This means that when a switch receives a message do not duplicated
it, it sends it directly to the destination computer. This provides higher dedicated
bandwidth to each device on the network.

A switch maintains a switching table, the switching table contains a list of all MAC
addresses of computers on the network and a list of switch port which are used to
reach a computer with a given MAC address.
When message arrives that is destined for a particular MAC address, the switch uses
the switching table to determine which port to use to reach the MAC address. Then message is forwarded to the destination.

3.5.3 Bridge

A network bridge is a computer networking device that creates a single aggregate
network from multiple communication networks or network segments. This function
is called network bridging

Bridges keep a record of all the devices on each segment. A bridge can then filter
network traffic between LAN segments. This helps reduce the amount of traffic
between devices

3.5.4 Access point

The Access Point is connected to a switch using UTP cable, therefore it can provide
access to the rest of the network. Instead of providing copper cabling to every
network host, only the wireless access point is connected to the network with
copper cabling and spread radio waves to the rest of network.
The range (radius of coverage) for Access Point indoors is 98.4 ft (30 m) and too
much greater distances outdoors depending on the technology used.

APPLICATION ACTIVITY 3.9

1. Justify why outdoor range is better that indoor range?

2. Discuss how a switch perform micro-segmentation?

3. Analysis why Switch is much preferred than a HUB

4. Examine the difference between Access Point and Bridge?

5. Identify the purpose of switching table in the switch?

6. Using the internet search for the diagram representation of hubs,
    switches and bridges in a network

3.6 Network Transmission Medium

ACTIVITY 3.9

Draw a computer network of 10 computers
This is the physical mean of communication between network computers.
Data transmission media are the physical materials used to transmit data between
computers. Packet of data can be transmitted on network as electrical signals
in electric wire, light signal in fiber optic cables or as electromagnetic waves
through space.
There are two main types of data communication media used in network:

1. Bounded or Guided media: which transmit signals by sending electricity
   or light over a cable wire. Common examples of bounded media are
  twisted cables, Coaxial cables and fiber optic cables.

2. Unbounded media: which transmit data through the air, radio waves,
layer or infrared signal and satellite based microwaves, etc.

3.6.1 Guided transmission media

A wide variety of networking cables are Coaxial, Fiber optic and twisted-pair
cables which use electrical signals over copper to transmit data while Fiber-optic
cables use light signals to transmit data. These cables differ in bandwidth, size, and
cost.

It is used by both cable television companies and satellite communication systems
and it carries data in the form of electrical signals. There are several types of coaxial
cable:

• Thicknet or 10BASE5 - used in networks and operated at 10 Mb/s with a
maximum length of 1640.4 ft. (500 m.)

• Thinnet 10BASE2 - used in networks and operated at 10 Mb/s with a maximum
length of 607 ft. (185 m.)

      b. Twisted-pair copper cabling

Twisted-pair is a type of copper cabling used for telephone communications and
most Ethernet networks. The pair is twisted to provide protection against crosstalk,
which is the noise generated by adjacent pairs of wires in the cable.
The use of this cable is limited by two factors:

a. Attenuation: the strength of signal reduces as the distance increases i.e the
cables loose signals strength when they exceed their maximum length stated
in network specification.

b. Crosstalk: this refers to interference generated by cables when they are too
close to each other. Signals from one line get mixed with signals from another.

3.6.2. Types of twisted pair cables

There are two types of twisted pair cables: unshielded and shielded cables

a. Unshielded twisted-pair (UTP)

Unshielded twisted-pair (UTP) cabling is the most common variety of twisted-pair
cabling.

UTP cable consists of four pairs of color-coded wires that are twisted together and
then encased in a flexible plastic sheath that protects from minor physical damage.
The twisting of wires helps protect against crosstalk. However, UTP does not protect
against electromagnetic interference (EMI) or radio frequency interference (RFI).
EMI and RFI can be caused by a variety of sources including electric motors and
fluorescent lights.

There are two different wiring schemes called T568A and T568B. Using the T568A
and T568B wiring schemes, two types of cables can be created: a straight-through
cable and a crossover cable.

1. A straight-through cable is the most common cable type. It maps a wire
    to the same pins on both ends of the cable. The order of connections (the
    pin out) for each color is the exact same on both ends.

Two devices directly connected and using different pins for Transmit and Receive
are known as unlike devices. They require a straight-through cable to exchange
data. For example, connecting a PC to a switch requires a straight-through cable.

2. A crossover cable uses both wiring schemes. T568A on one end of the
cable and T568B on the other end of the same cable.
Devices that are directly connected and use the same pins for transmit and receive,
are known as like devices. They require the use of a crossover cable to exchange
data. For example, connecting a PC to another PC requires a crossover cable.

Note: The most used cable standards are below:

• 100Base-TX: known as Fast Ethernet, it uses category 5, 5E, or 6 UTP cable and
it wires u to 100 meters long.

• 1000Base-T means that the speed of the network is up to 1000
Mbps, baseband signaling is sed, T stands for twisted-pair as UTP cable used

b. Shielded twisted-pair (STP)

The STP type similar to UTP cable except that there is a metal foil or braided metal-
mesh cover that encases each pair of insulated wires. The extra covering in shielded
twisted pair wiring protect the transmission line from electromagnetic interference
( EMI) leaking into or out of cable. However this can make cables quite bulky
 and harder to install.
The basic difference between UTP and STP is that UTP is a cable with wires that are twisted
together to reduce noise and crosstalk. On other hand, STP is a twisted pair cable confined
in foil or mesh shield that guards the cable against electromagnetic interference.

APPLICATION ACTIVITY 3.10

Requirements:

1. Unshielded twisted pair (UTP) patch cable

2. Modular connector (8P8C plug, aka RJ45)

3. Crimping tool

4. Cable tester (optional, but recommended

Step 1: Strip the cable jacket about 1.5 inch down from the end.

Step 2: Spread the four pairs of twisted wire apart.

Step 3: Untwist the wire pairs and neatly align them in the T568B orientation.

Step 4: Cut the wires as straight as possible, about 0.5 inch above the end of the jacket.

Step 5: Carefully insert the wires all the way into the modular connector, making sure
            that each wire passes through the appropriate guides inside the connector.

Step 5: Carefully insert the wires all the way into the modular connector, making sure
            that each wire passes through the appropriate guides inside the connector.

Step 6: Push the connector inside the crimping tool and squeeze the crimper all the
            way down.

Step 7: Repeat steps 1-6 for the other end of the cable.

Step 8: To make sure you›ve successfully terminated each end of the cable, use a cable
            tester to test each pin.

APPLICATION ACTIVITY 3.11

Step 1: Open the Network and Sharing Center:

Step 2: Select the Control Panel from the Start menu.

Step 3: Select Open Network and Sharing Center and click Network and Sharing Center

3.6.3 Fiber optic cables

An optical fiber cable, also known as a fiber optic cable, is an assembly similar to an
electrical cable, but containing one or more optical fibers that are used to carry light
signals

Advantages of fiber optic

a. Since they transmit light rather than electronic signal, the problem of electrical
    interference is eliminated , therefore they are not affected by radio interference
     or cross talk

b. They have become the standard for connecting networks between buildings due
     to their immunity the effects of moisture and lighting.

c. Fiber optic can transmit signal over much longer distance than coaxial cable and
    twisted cables

d. They can carry information at high rate speed between

e. The distance can be up to 2000 meters without repeater

f. Security: it is difficult to tap into optical fiber line. If this is happen it will be
    noticed immediately.

g. Low transmission loss

h. Data can be transmitted digitally

i. They are more resistant to adverse weather conditions.

3.6.4 Unguided transmission media

Unguided media transport electromagnetic waves without using a physical
conductor. This type of communication is often referred to as wireless communication.
The mediums used in wireless communications are air, vacuum and even water. Air
is the most commonly used medium.

      a. Wireless Transmission

Wireless transmission can be categorized into three broad groups namely radio
waves, microwaves, infrared

      1. Radio waves

Radio waves are normally omnidirectional. When an antenna transmits radio
waves, they are propagated in all directions. This means that the sending and
receiving antennas do not have to be aligned. The omnidirectional characteristics
of radio waves make them useful for multicasting, in which there is one sender but
many receivers. Our FM radio stations, cordless phones and televisions are examples
of multicasting.

     2. Infrared

Infrared is used in devices such as the mouse, wireless keyboard and printers. Some
manufacturers provide a special port called the IrDA port that allows a wireless
keyboard to communicate with a PC.

Infrared signals have frequencies between 300 GHz to 400 THz. They are used for
short-range communication. Infrared signals have high frequencies and cannot
penetrate walls. Due to its short-range communication system, the use of an infrared
communication system in one room will not be affected by the use of another system
in the next room. This is why using an infrared TV remote control in our home will
not interfere with the use of our neighbor’s infrared TV remote control.

The disadvantages of using infrared

• Infrared signals cannot be used for long distance communication.

• Infrared waves can not be used outside of a building because sun’s rays contain
infrared waves that can interfere with communication.

       3. Bluetooth

Bluetooth technology is designed to serve as a new way of connecting devices.
Bluetooth technology has an advantage of being low investment and low energy
consumption demanding.

The difference between Bluetooth and infrared is that Bluetooth allows communication
when there is a barrier or a wall.

4. Wi-Fi (Wireless Fidelity)

Wi-Fi (Wireless Fidelity) is a standard that certifies that wireless devices in Wireless
LAN to work together. It supports IEEE802.11b Ethernet standard.

Wi-Fi uses radio signals to transmit high speed data over the wireless network, the
Access Point is used to connect devices and it acts as the central device for Wireless
LAN. Wireless devices can be: smartphones, PDAs, IPad, laptop and notebook.

APPLICATION ACTIVITY 3.11
General steps to connect to a WI-FI network near you
The following steps run through the general steps that anyone needs to take to get
connected to the internet via WI-FI. (Do this exercise and discover the corresponding
windows for every step. What is the meaning of different icons forms that a wireless
network take?)

Step 1: Locate yourself in a property or public space that has a wireless router.

Step 2: Make sure that the device you›re going to use is:

          • Capable of connecting to the internet and

         • Capable of connecting to WI-FI.

Step 3: Find out the name of the WI-FI network that the router in your location is
           transmitting.

Step 4: Once you know the name of the WI-FI network, use your chosen device to find
            it.

       3.7. IP Address

       3.7. IP Address

The fingerprint and addressed letters are ways of identifying and addressing a person.
A person's fingerprints usually do not change. They provide a way to physically identify
people. The mailing address of a person can change, as it relates to where the person
lives or picks up mail. Do network devices have addresses? Justify your answer.

    3.7.1 Understand IP Addresses

An IP address is an address used in order to uniquely identify a device on a computer
network.

      IP Versions

There are two versions of IP addressknown as IP version 4 and IP version 6

      a. IP version 4

IP version 4 is the common used IP address,

    a.1 Structure of IP address

• An IP address is simply a series of 32 binary bits. Because it is difficult for human
   to read a binary IP address, the 32 bits are grouped into fout-8-bits bytes called
    octets.

• When a computer is configured with an IP address it is entered as doted decimal
   number such as 192.168.1.5

• When a host receives an IP address , it looks at all 32 bits as they are received by
   the NIC

• Each octet is made up with 8 bits an each bit has a value. The four groups of 8 bits
   have same set of value.

• Parts of the IP address
 The logical 32 bits IP address is made up two parts which are network part or network
 address and the second one is host address .

 a.2 Classes of IP version 4

There are five classes of available IP ranges: Class A, Class B, Class C, Class D and Class
E, while only A, B, and C are commonly used classes D and E are reserved.
Here is a listing of these addresses:

Class A

In class A the first bit of the first byte is always 0

0xxxxxxx where x stand for any value (either o or 1)

Minimum: 00000000
Maximum: 01111111

The valid range in class A =

The range of IPs 127.x.x.x is reserved for the loopback or localhost, for example,
127.0.0.1 is the common loopback address. Range 255.255.255.255broadcasts to

all hosts on the local network.
The first byte in class A represent Network address while the three remaining
represent the host address thus class A=Network. Host-Host-Host

Class B

In class B the first bit of first byte is always 1 and the second bit of first byte is always
0

10xxxxxx

Minimum: 10000000=128
Maximum: 10111111=191

Valid range[ 128-191]

The two first byte in class B represent Network address while the two remaining
represent the host address thus class B=Network-Network-Host-Host

Class C

The first bit of first byte is always 1, the second bit of first byte is always 1 and the
third bit of first byte is always 0 i.e 1100000

Minimum: 11000000= 192
Maximum: 11101111= 223
Valid range: 192-223
The three first bytes in class C represent Network address while the last byte remaining
represent the host address thus class C=Network. Network -Network -Host

a.3 Subnet Masks

A subnet mask help to know which portion of the address identifies the network
and which portion of the address identifies the host. Class A, B, and C networks have
default masks, also known as natural masks, as shown here:

Class A: 255.0.0.0

Class B: 255.255.0.0

Class C: 255.255.255.0

Devices that are attached to a network have two addresses that are similar to a
person’s fingerprints and a person’s mailing address. These two types of addresses
are the Media Access Control (MAC) address and the IP address. The MAC address is
hard coded onto the network interface card (NIC) by the manufacturer and it does
not change. The IP address is assigned to a host to the network and may change.

  b. Internet Protocol Version 6 (IPv6)

IPv6 (Internet Protocol Version 6) also called IPng (Internet Protocol next generation)
is the newest version of the Internet Protocol reviewed to replace the current version
of IPv4. IPv6 is designed to allow the Internet to grow steadily, both in terms of the
number of hosts connected and the total amount of data traffic transmitted.

IPv6 shows a 128-bit address in eight 16-bitblocks separated by colons

Example: 3ffe:1900:4545:3:200:f8ff:fe21:67cf.

FE80:0000:0000:0000:0202:B3FF:FE1E:8329

  b.1 Features of IPv6

• Supports source and destination addresses that are 128 bits (16 bytes) long.

• No more NAT (Network Address Translation)

• Auto-configuration

• No more private address collisions. Requires IPSec support to provide two
   security headers which can be used separately

• Those security headers are Authentication Headers(AH) and Encrypting
   security payload(ESP)

• Uses Flow Label field to identify packet flow for Quality of Service handling by
   router.

• Allows the host to send fragments packets but not routers.

• Does not require manual configuration or DHCP.

• Moves optional data to IPv6 extension headers.

• Uses Multicast Neighbor Solicitation messages to resolve IP addresses to linklayer
   addresses.

• Uses Multicast Listener Discovery (MLD) messages to manage membership in
   local subnet groups.

• Uses ICMPv6 Router Solicitation and Router Advertisement messages to
  determine the IP address of the best default gateway

Why there is no different classes in IP v6?

In IPv4 we have class A, B, C,D and E. In IPv6 we have only global prefix and interface
id

IP v6 has three types of addresses, which can be categorized by type and scope:

Unicast addresses: a packet is delivered to one interface.

Multicast addresses: a packet is delivered to multiple interfaces.

Anycast addresses:a packet is delivered to the nearest of multiple interfaces (in
terms of routing distance).

3.7.2. IP address assignment1. Static IP assignment

 The manual configuration of a host in a network, allows to assign the static IP address
 and the following information has to be specified:

• IP address - identifies the computer on the network

• Subnet mask - is used to identify the network on which the computer is
   connected

• Default gateway - identifies the device that the computer uses to access the
Internet or another network

Optional values - such as the preferred Domain Name System (DNS) server
address and the alternate DNS server address

Note that host on the same network should have the same Network ID

APPLICATION ACTIVITY 3.12

Go through all these steps to assign to your computer a static IP address

STEP 1: Go to Network Connections.

STEP 2: Go to the network connection your computer is currently using, then
             select Properties.

STEP 3: Go to Internet Protocol Version 4 (IPv4) from the list and click the Properties
             button
STEP 4: Choose Use the following IP address option

NOTE: When assigning a static IP address, make sure to set a value that will not
            conflict with others on your network. You may refer to your router documentation
           for the range of IP address that it assigns to its devices.

STEP 5: Next to the IP address field, enter the IP address value you want to assign
              to the computer.

NOTE: If the DHCP range of your router is from say 192.168.1.100-200, you can use
any range from 192.168.1.2-99 for example.

STEP 6: In the Subnet mask field, enter “255.255.255.0.”

STEP 7: In the Default gateway field, enter the IP address of your router or gateway
              device.

NOTE: Usually, the default gateway address for most routers is 192.168.1.1. Again,
you may refer to your device documentation to determine the correct IP address
of your router.

STEP 8: For the Preferred DNS server and Alternate DNS server fields, you can take
             a look for the exact DNS values that your router is getting from your ISP, which can
             be usually found by accessing your router’s configuration page.

STEP 9: Click OK on all windows to save your changes.

3. Dynamic IP configuration

A DHCP (Dynamic Host Configuration Protocol) server automatically assigns IP
address to host. It simplifies the addressing process. DHCP server can automatically
assign to a host an IP addres, Subnet mask, Default gateway and Optional values,
such as a DNS server address

APPLICATION ACTIVITY 3.13

Go through all the steps to assign an IP address using DHCP

Step 1: Go to network connections

Step 2: Select “View network connections”.

Step 3: Locate the “Network connection” you want to view

Step 4: After locating connection, right –click on it and select “Properties”

Step 5: Double-click “Internet Protocol Version (TCP/IPv4)”

Step 6: Select the followings:

          • Obtain an IP address automatically

          • Obtain DNS server addresses automatically
          • OK

Step 7: Select “OK” and restart your computer.

3.7.3 Some common protocols

A protocol is defined a set of rules and procedures that control communication
between computers or other network devices on a network.

a. Internet control message protocol (ICMP)

Internet Control Message Protocol (ICMP) is used by devices on a network to send
control and error messages to computers and servers. There are several different
uses for ICMP, such as announcing network errors, announcing network congestion,
and troubleshooting.

b. HTTP (Hypertext Transfer Protocol)

e.g. http://www.reb.rw/
http:stands for hypertext transfer protocol used to connect computer to the server.
It provides a standard web browser to communicate with a server FTP (File Transfer
Protocol)

This protocol allows you to transfer files between two computers on internet.

     c. TCP and UDP

Transmission Control Protocol and User Datagram Protocolare most common
transport layer both protocols that manage the communication of multiple
applications. The difference between the two are the specification function that
each protocol implements.

d. SMTP (Simple mail Transfer protocol)

The SMTP stands for Simple mail Transfer protocol is a TCP/IP used in sending and
receiving e-mails. However, since it is limited in its ability to queue message at the
receiving end, it is used with one of two other protocols POP or IMAP that let users to
save messages in server mailbox and download them from the server once needed.

e. POP (Post Office Protocol)

Post Office Protocol is a protocol designed to allow single user computer to retrieve
electronic mail from a POP server via TCP/IP.

3.7.4 Commands used to verify computer connection on a network

3.7.4.1 Ping

The command Ping is commonly used to test connections between computers.
Ping is a simple but highly useful command-line utility used to determine whether a
specific IP address is accessible.

3.7.4.2 ipconfig

The ipconfig command is used to find out your current local IP address, default
gateway, TCP/IP settings and more.

All Ipconfig commands explained:

          i. ipconfig/all: it displays all current IP information for all adapters.

          ii. ipconfig /release: Used to release current IP information and obtain a
              new IP Address from the DHCP server.

        iii. ipconfig /renew: it is used to renew IP Address if you have it set to

           obtain IP Address automatically.

 3.8. Data and device sharing

   ACTIVITY 3.10(b)

1. Share a folder with your classmate on your school computer network

2. Identify how resource are shared on computer network

3.8.1 Workgroup

A workgroup is a collection of computers and servers on a LAN that are designed
to communicate and exchange data with one another. Each individual workstation
controls its user accounts, security information, and access to data and resources.

APPLICATION ACTIVITY 3.14

Go through the steps below in order to create a WorkGroup

Step 1: Open the Start menu, do a search for HomeGroup and press Enter.

Step 2: Click Create a HomeGroup.

Step 3: Click Next.

Step 4: Choose what to share on the network. By default Windows sets Pictures, Videos,
Music, and Printers & Devices as Shared. However, the Documents folder is marked as
not shared.

Note: The sharing options you choose will only apply to devices connecting with
different accounts. If you sign-in with the same user account on another computer,
you will have access to all files regardless of what you chose to share.

Step 5: Once you've decided what content to share, click Next.

Step 6: The wizard will complete the setup, and you'll be presented with a HomeGroup
password, which is needed to allow other computers to access files and printers. Write
down or click the link to print the password.

APPLICATION ACTIVITY 3.15

Go through these steps to add computers to a HomeGroup

Step 1: Open the Start menu, do a search for HomeGroup and press Enter.

Step 2: Click the Join now button.

Note: If you don't see the Join now button, there is something wrong, make sure
you're connected to the network and restart your computer.

Step 3: Click Next.

Step 4: Select the content you want to share on the network by using the drop
down menu for each folder and click Next.

Step 5: Enter your HomeGroup password and click Next.

Note: If you're signed into another computer, but you're using your Microsoft
Account, then you won't be prompted to enter a password.

Step 6: Click Finish to complete the task.

3.8.2 Network Resource Sharing

First determine which resources will be shared over the network and the type of
permissions users will have to the resources. Any device which is connected to a
host /node is called a Network Peripheral in other word network peripheral is any
device that is indirectly connected to the network. Examples of network peripheral
are: printer, scanner

APPLICATION ACTIVITY 3.16

Go through the steps below to add new folders to shared HomeGroup libraries

Step 1: Use the Windows key + E keyboard shortcut to open File Explorer.

Step 2: On the left pane, expand your computer’s libraries on HomeGroup.

Step 3: Right-click Documents.

Step 4: Click Properties.

Step 5: Click Add.

Step 6: Select the folder you want to share and click Include folder.

Step 7: Click Apply.

Step 8: Click OK.

Application activity 3.17

Go through these steps to add new folder via Windows network share to your
HomeGroup

Step 1: Right-click the folder you want to share.

Step 2: Select Share with and click the Homegroup (view) option.
Users can access the newly shared folder by:

Step 3: Using the Windows key + E keyboard shortcut to open File Explorer.

Step 4: Clicking Network on the left pane.

Step 5: Double-clicking the computer name with shared content, and browsing the
            folder location.

By default, every HomeGroup folder shared on the network are set with read only
permissions. It has to be this way to prevent accidental deletions and modification to
your files by other users.

3.9. Network Topology

ACTIVITY 3.11

Draw a Peer-to-peer network and assign each host an IP address. Network must have 1
switch, 8 computers, one printer which has NIC card and a printer.

The network topology describes the configuration of network, the physical and
logical arrangement of nodes that form a network. Network topologies are classified
as physical, logical and signals topologies.

Physical topology describes the mapping of network nodes and physical connection
between them. Signal topology describes the paths which signals take while they
pass over network that mapping of the paths taken by data as they travel over
network. A logical topology is the way data signals pass from one device to another.

There exist different types of network topologies which are Bus topology, Ring
topology, Star topology, Mesh topology, Tree topology and Hybrid topology,

3.9.1 BUS Topology

Bus topology is a network type in which every computer and network device is
connected to single cable. When it has exactly two endpoints, then it is called Linear
Bus topology.

It is the most used and employed in LAN architecture. All devices are connected to a
central cable, called the bus or backbone. This topology is relatively inexpensive and
easy to install for small networks.

Features of Bus Topology

1. It transmits data only in one direction.

2. Every device is connected to a single cable

3.9.2 RING Topology

It is called ring topology because it forms a ring as each computer is connected to
another computer, with the last one connected to the first. Exactly two neighbors
for each device. In a Ring topology each device is connected directly to two other
devices, one on either side of it, to form a closed loop. This topology is relatively
expensive and difficult to install, but it offers high bandwidth and can span large
distances

A ring topology is a computer network configuration in which computer connections
create a circular data path. Each networked computer is connected to two others
like points on a circle.

In a ring network, data travel from one device to the next until they reach their
destination. Most ring topologies allow data to travel only in one direction called
a unidirectional ring network. Others permit data to move in both directions called bidirectional.

3.9.3 STAR Topology

In this type of topology all the computers are connected to a single hub or a switch
through a cable. This hub or switch acts as the central device and all others nodes
are connected to the central device.

So, in a Star topology all devices are connected directly to a central computer or
server. Such networks are relatively easy to install and manage

Features of Star Topology

      1. Every node has its own dedicated connection to the hub.

      2. Hub acts as a repeater for data flow.

     3. Can be used with twisted pair or coaxial cable.

3.9.4 MESH Topology

• It is a point-to-point connection to other nodes or devices. All the network
nodes are connected to each other. A Mesh topology can be either a full mesh
or a partial mesh. In the former, each computer is connected directly to each
of the others.

Types of Mesh Topology

1. Partial Mesh Topology: In this topology some of the systems are connected
in the same fashion as mesh topology but some devices are only connected to
two or three devices.

2. Full Mesh Topology: all devices are connected to each other which is very
expensive but provides the best redundancy as a failure of a single does not
affect the network connectivity.

Features of Mesh Topology

1. Fully connected.

2. Robust.

3. Not flexible.

3.9.5 Tree Topology

It has a root node and all other nodes are connected to it forming a hierarchy. It is
also called hierarchical topology. It should at least have three levels of hierarchy.

Features of Tree Topology

1. Ideal if workstations are located in groups.

2. Used in Wide Area Network.

3.9.6 Hybrid Topology

Hybrid, as the name suggests, is mixture of two different things. Similarly in this
type of topology that integrate two or more different topologies to form a resultant
topology which has good points (as well as weaknesses) of all the constituent
basic topologies rather than having characteristics of one specific topology. This
combination of topologies is done according to the requirements of the organization.

For example, if there exists a ring topology in one office department while there is a bus
topology in another department, connecting these two will result in hybrid topology.
However, connecting two similar topologies cannot be termed as Hybrid topology.

Notice that the cost of technology, network devices, and transmission mediums to
be used in the computer network has to be considered while choosing the network
topology to use.

APPLICATION ACTIVITY 3.18

Using clear example, compare computer network devices, network peripherals
and computer peripherals?

1. In an organization there are 20 computers distributed into different offices
    and all offices share one printer .The managements wants to build a
     computer network that connects all the computers and printer.

     i. Identify a topology to use in this situation

     ii. Draw arrangement of computers using identified topology

2. Draw a hybrid topology