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Learning Outcome

At the end of this lessons, students should able to :

Explain the concept of network (L)
Explain example of communication devices and type of transmission media used in a network (L)
Describe the advantages and disadvantages of a network (L)

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Explain the concept of network (L)

A collection of computers and devices connected together via communication device and transmission media to share resources (Shelly,2018).

What is a network?

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Computer network?

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Communication

The process in which two or more computers or devices transfer data, instruction and information.
Some communication involve cables and wires; others are sent wirelessly through the air.
Sometimes called telecommunications.

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Communication System

Figure10-1: A simplified example of communications system which consist of some devices that serve as sending, receiving devices and communication devices to transmit data

over communication channel.

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Communication System

Sending devices	Devices that initiate an instruction to transmit data, instructions, or information.
Receiving devices	Devices that accept the transmission of data, instructions, or information
Communication Device	Any type of hardware capable of transmitting data, instructions, and information that connect the sending device and a receiving device to transmission media. Example: modem, hub, switch, router, wireless access point, network card

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Communication System

Transmission Media / communication channel	Transmission media consist of materials or substances capable of carrying one or more signals (Shelly, 2018). 2 types of transmission media

Wired / Physical / Guided	Wireless/Unguided/Logical
Physical transmission media use wire, cable and other tangible materials to send communications signals. Example: Twisted pair cable, coaxial cable, fiber optic cable	Wireless transmission media send communications signals through the air or space The sender and receiver are not connected by any electrical or optical wires/cables Example : infrared, broadcast radio, cellular radio, microwaves, communication satellite

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b) Explain example of communication devices and type of transmission media used in a network (L)

Communication device	Function
Modems	Digital Modems A broadband modem / digital modem is a communication device that sends and receives data and information to and from a digital line. 3 types of broadband modems : - Cable modems , DSL modems, ISDN modems

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(b) Communication Device

Communication device	Function
Modems	Cable modems Sends and receive digital data over the CATV network. DSL modems Sends digital data and information from a computer to a DSL line. Receives digital data and information from a DSL line. ISDN modems Sends digital data and information from a computer to an ISDN line. Receives digital data and information from an ISDN line.

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Cable Modem

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(b) Communication Device

Communication device	Function
Modems	2. Wireless Modems Some mobile users have a wireless modem that uses a mobile service provider’s network to connect to the Internet wirelessly from a computer or mobile device Wireless modems, which have an external or built-in antenna, are available as USB adapters and other devices Some smartphones also can function as a wireless modem, called a mobile hotspot, when tethered to a personal computer or mobile device

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Wireless Modem

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(b) Communication Device

Communication device	Function
Wireless Access Point	Is a central communications device that allows computers to transfer data wirelessly among themselves or to transfer data wirelessly to a wired network. Wireless access points have high-quality internal or external antennas for optimal signals For the best signal, some manufacturers suggest positioning the wireless access point at the highest possible location and using a device to strengthen your wireless signal

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(b) Communication Device

Communication device	Function
Routers	Is a communication device that connects multiple computers or other routers together and transmit data to its correct destination on a network

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Wireless Router

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(b) Communication Device

Communication device	Function
Network Cards / Network interface card (NIC)	Is a communication device that enables a computer or device that does not have built-in networking capability to access a network The network card coordinates the transmission and receipt of data, instructions, and information to and from the computer or device containing the network card

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(b) Communication Device

Communication device	Function
Hub and Switch	Is a device that provides a central point for cables in a network Smaller networks typically use a hub, while larger networks use a switch Some hubs and/or switches include routers. That is, the hub or switch receives data from many directions and then forwards it to one or more destinations

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Transmission media consist of materials or substances capable of carrying one or more signals (Shelly, 2018).

A communications channel, or transmission media on which the data, instructions, or information travel

(b) Transmission Media

“

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(b) Transmission Media

Types	Wired Media	Wireless Media
Definition	Wired network connects computers and other devices together via physical media such as cable.	Wireless networks connect computers and other devices together via air space such as radio waves.
Example of communication devices	Hub, switch , router, DSL modem, FTTP modem, Network Interface Card	wireless router, wireless access point, wireless modem
Example of transmission media	Twisted pair cable, Coaxial cable, Fibre optic cable	Microwaves, infrared, cellular radio, broadcast radio and communication satellite.

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(b) Wired/Guided Transmission Media

Example	Function / Purpose	Protocol / Application
Twisted pair cable	Consists of one or more twisted-pair wires bundled together Each twisted-pair wire consists of two separate insulated copper wires that are twisted together	UTP cable PC to PC PC to modem / hub Telephone line
Coaxial cable	Consists of a single copper wire surrounded by at least three layers :- An insulating material A woven or braided material A plastic outer coating Connected computer to modem	Cable Internet CCTV system DTV HDTV Smart TV
Fiber optic cable	Consists of dozens or hundreds of thin strands of glass or plastic that use light to transmit signals Each strand, called an optical fiber, is as thin as a human hair Inside the fiber-optic cable, an insulating glass cladding and a protective coating surround each optical fiber Longer distance to carry data as pulse of light.	Unifi, Maxis Fiber Nation

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(b) Wired/Guided Transmission Media

Twisted pair cable

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(b) Wired/Guided Transmission Media

Coaxial cable

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(b) Wired/Guided Transmission Media

Fiber optic cable

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(b) Difference between Twisted Pair Cable, Coaxial cable , Fibre Optic Cable

Comparison	Twisted pair cable	Coaxial cable	Fiber Optic cable
Bandwidth	The lowest among the cable	moderately higher than Optical Fibre cable	The highest
Data rate	lowest	higher than Twisted pair cable	The highest
Diameter of cable	larger than fibre optic cable	The largest among three cable	smaller than twisted pair cable

Bandwidth	Data Rate
It is the number of bits per second that a link can send or receive.	It is the speed of data transmission.

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(b) Wireless / Unguided Transmission Media

Example	Function / Purpose	Protocol / Application
Infrared	Infrared (IR) is a wireless transmission medium that send signals using infrared light waves Mobile computers and devices, such as mouse, printer and smartphones often have an IrDA port that enables the transfer of data from one device to another using infrared light waves.	TV remote control Infrared mouse
Broadcast Radio	Is a wireless transmission medium that distributes radio signals through the air over long distances, such as between cities, regions, and countries, and short distances, such as within an office or home	Bluetooth UWB Wi-Fi Wi-Max Hot spots use Wi-Fi

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(b) Wireless / Unguided Transmission Media

Example	Function / Purpose	Protocol / Application
Cellular radio	Is a form of broadcast radio that is in wide use for mobile communications, specifically wireless modems and mobile phones.	mobile communication mobile phone
Microwaves	Are radio waves that provide a high-speed signal transmission. Microwave transmission, often called fixed wireless, involves sending signals from one microwave station to another
Communication Satellite	Is a space station that receives microwave signals from an earth-based station, amplifies (strengthens) the signals, and broadcasts the signals back over a wide area to any number of earth-based stations.

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(b) Wireless / Unguided Transmission Media

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Facilitating communications	People communicate efficiently and easily via email, Internet messaging, chat rooms, blogs, wikis, online social networks, video calls, online meetings, video conferencing, VoIP, text messaging and more
Easy in sharing hardware	Each computer or device on a network can be provided access to hardware on the network
Easy in sharing data and information	Any authorized user can access data and information stored on a network
Easy in sharing software	Users connected to a network can access to the software on the network
Easy in transferring funds	Electronic funds transfer (EFT ), allows users connected to a network to exchange money from one account to another via transmission media

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Attack by viruses	When computers are connected by a network, the virus can spread itself electronically, at computer speeds
Network failure	If the file server fails then no-one on the network can access any files or folders. This means that nobody can do any work. For an organization, this would be extremely costly and disruptive
Slow service	As more users log onto the network and request files, send things to be printed and open more software applications, the network can start to slow down
High cost	Every workstation needs a network interface card to enable it to be connected to the network. Other hardware such as hubs, switches and routers are often needed
Expert support required	Networks need constant monitoring to ensure that the performance is maintained and that all of the components are working properly.