Networking and Telecommunication

 Information and Communication Technology is increasingly at the core of strategies aimed at securing the goals of sustainable development and stimulating economic growth around the world.

Hotel booking, air ticketing, banking, email and Internet, etc. are services provided by use of computer and telecommunication after 1995 AD. 

The group of computers all over the world is inter-connected through different media to transfer information. 

The process of sending and receiving data and information between two or more than two people is known as communication.

Data communication Mode

Data communication is the process of transferring data and information between computers and other electronic devices. The two types of data communication are as follows: 

a. Simplex Mode 

Simplex mode is the transmission of data and information that takes place in only one direction. It is a unidirectional mode of data transmission. Radio, newspaper, television broadcasting, books etc. are examples of simplex mode. 

                                                    Simplex Transmission Mode

b. Duplex Mode 

Duplex is mode of data transmission in which data and information flow in both directions. It is bi-directional mode of data transmission. The two types of duplex modes are:

i. Half Duplex :Half-duplex is the mode of data communication where data and information  flows in both directions but only one direction at a time. Walky-talky and wireless handset are examples of half-duplex mode.

ii. Full Duplex In full duplex mode, data and information flow in both direction simultaneously on the transmission path. Mobile and landline phones are examples of full duplex mode.

Components of  Data communication

The five basic components (data, sender, medium, receiver and protocol) are required to make data communication. 

Data (message) : Data is to be communicated between sender and receiver. It is simply a piece of information.

Sender : Sender is a device used to transfer data. 

Medium: Medium is a channel through which sender and receiver make communication. 

Receiver: Receiver is a device used to receive data. 

Protocol: Protocol is a set of rules followed by sender and receiver

Communication Media 

A channel or path through which data and information are transmitted between connected devices in a network environment is called communication media. Communication media is also called transmission media. It acts as a communication channel for connecting different devices. Wire or wireless media is used for communication. The two main types of communication media are: 

1. Guided (Wired/bounded) communication media 

2. Unguided (Wireless/unbounded) communication media\

1. Guided (Wired/bounded) Communication Media 

The media which uses cable or wire to transfer data and information among computers are called guided communication media. This is an easy, fast and secure way to transfer data and information from one computer to another. The different types of wire or cable are used for a computer network. The three types of wire or cable are: 

a. Twisted pair   
                                                                                                                                            

b. Co-Axial Cable     

                                                                                                                                   

c. Fiber Optic Cable 

a. Twisted Pair 

Twisted pair wire is made of copper and a pair of wires are twisted together and insulated with plastic. It is commonly used in communication media. This is also widely used in landline telephone. RJ-45 connector is the most popular connector used in twisted-pair wire. The two types of twisted pair wire are: 

i. UTP (Unshielded Twisted Pair) 

Unshielded twisted pair cable or wire is most popular wire. This is used to transfer data and information in telephone connection. The cable without a shield is called unshielded twisted pair. Its grade starts from cat1 to cat7. It is easy, cheap and can cover a distance of 100 meters. The capacity of wire to transfer data from one computer to other is called bandwidth. Unshielded twisted pair has low bandwidth and measures in Mbps (Megabits per second). 

ii. STP (Shielded Twisted Pair) Shielded twisted pair is a wire woven with a copper shield. Cabling is more difficult to install and more expensive than UTP. Its bandwidth is 10 to 500 Mbps (Megabits per second). RJ 45 connector is used in STP. It provides better protection against EMI (Electromagnetic Interference) than UTP

b. Co-Axial Cable 

Co-axial cable is made of copper or aluminum wire with an inner conductor surrounded by an insulating layer and again surrounded by conducting shield. So it consists of two conductors inner and outer conductors. It has high bandwidth and noise immunity. It is widely used in long-distance telephone lines. BNC and T connectors are the most popular connector used in co-axial cable.

c. Fiber Optic Cable Fiber optic cable is made of plastic or glass fiber to transmit data. It uses light wave to carry data signal from one end of the cable to other end. It is of high quality and transmits data signals at very high speed. It is more powerful than twisted pair cable and co-axial cable. So it is widely used cable especially in ISP (Internet Service Provider). ST (Straight Tip) connector, SMA (Screw-Mounted Adaptors), SC (Subscriber Connector) etc. are the common connectors used in fiber optic cable.

2. Unguided (Wireless/unbounded) Communication Media Unguided communication is a communication channel in which data and information transferred between two devices without using wire or cable. Nowadays, wireless technology is used in communication technology. It uses radio signal for receiving and transmitting electronic data. 

Permission for the use of wireless technology is to be taken from Nepal government. The three types of wireless communication are: 

 Radio Wave 

 Micro Wave 

 Satellite Communication  

Radio Wave

Radio wave is an electronic magnetic wave. In Nepal, radio wave transmission is used in rural and hilly areas. The data and information can be changed into audio signals using high frequency wave on the basis of frequency, amplitude and phase modulation. The wave is modulated due to its frequency change known as FM (Frequency Modulation). The wave is modulated due to its amplitude change known as AM (Amplitude Modulation). The wave is modulated due to its phase change known as PM (Phase Modulation). So, radio wave is wave or pattern received after modulation of signals.

Microwave 

Microwave is high frequency wave which is used to transfer signals through atmosphere. It is also called line of sight communication. The microwave signal cannot bend or pass obstacles like hill and tall buildings. So transmitting and receiving devices should be in a clear line of sight fitted on very high towers, repeaters until to amplify the signal for long-distance communication in microwave. Digital modem and antenna are the important microwave devices.

fig: Microwave communication

Satellite Communication 

Satellite communication is used to transfer information wirelessly worldwide after 1965. It is an artificial satellite placed in outer space for the purpose of telecommunication, radio, television, Internet, etc. Text, photo, video, etc. can be transferred worldwide using satellite communication. It is like microwave relay stations in the space or sky. 

Nowadays, most of the countries use their own satellite to communicate.

fig: satellite communication

Computer Network 

Computer network is a group of two or more computers and devices connected to each other through wired or wireless media to exchange data and information and share hardware, software and other resources. In other word, the interconnection of many computers to share information is called computer network. It can share resources like scanner, printer, hard disk, operating system software, application software, etc. within the networking computer. The services provided by computer network are print service, message service, application service, file service, database service, etc. 

Advantage of Computer Network 

1. A network connected computers can share hardware devices such as scanner, printer, hard disk, etc. 

 2. It can communicate and share information all over the world through Internet.

3. Computer network supports centralized administration.                      

4. Networking also provides the facility of data and software backup system. 

Disadvantage of Computer Network 

1. Computer network can be route for computer virus and malware transmission.   

2. Skilled manpower is required to manage and operate computer network.                                              

3. The initial setup cost is very high to build computer network.                 

4. Cybercrimes are originated from computer network.

Basic Elements of the Network 

Nowadays, the use of computer network is growing all over the world. So a computer network is used for Internet, e-mail, chat, e-banking, etc. The hardware, software and medium are components of computer network. NOS (Network Operating System) and application software are the software used as network software. The hardware used in the network are computer set, modem, hub, NIC card, bridge, repeater, etc.

1. NIC Card 

NIC stands for Network Interface Card. It connects all computers in network. It is placed on expansion slot of the motherboard. It provides a port on the back of system unit to connect a computer in network. It controls flow of data to and from computers in network environment. It is used in LAN (Local Area Network). Token ring and Ethernet are the examples of NIC card.  

2. Connectors 

Connectors are used to connect communication media with network devices. It provides data communication through NIC card. The different types of connectors are: 

 RJ- 45 connector for UTP cable 

 BNC connector for co-axial cable 

 ST connector for fiber optics cable

3. Hub 

Hub is a network connectivity device with multiple ports for connecting different computers on network. It connects computers in star topology. It is simple, easier to install, low in cost, as compared to other devices. It can receive or send information between the computers. Nowadays, hub is replaced by a switch.

4. Switch 

Switch is a network connectivity device which joins multiple computers together to share information among them. It co-ordinate file server and computers. The selected computer can get information through switch. It works faster than hub. 

Difference between hub and switch

HUB	Switch
It is cheaper than switch.	It is more expensive than hub.
It transmits data slower than switch.	It transmits data faster than hub.
It is not intelligent	It is intelligent device
It broadcasts the information packets to all computer connected network.	It transfers packets to only those selected computers connected in network
It is half duplex device.	It is full duplex device.

5. Bridge 

Bridge is a network connectivity device that interconnects two computer networks having similar protocol. It inspects incoming signals and decides whether to forward or discard it. It connects similar networks.

6. Router Router is a network connectivity device that joins multiple wired or wireless networks together. Like a bridge, router also inspects and forwards data among different networks having similar protocol. It works on the principle of IP (Internet Protocol) address. It is an intelligent device that has ability to determine the best possible path for data transmission. Nowadays, different types of router are available in market.

7. Gateway Gateway is a network connectivity device that interconnects two networks having dissimilar communication protocols. It is also called protocol converters. It sends data in any network layer. Generally, it is more complex than a switch or router.

8. Repeater 

Repeater is a network connectivity device that accepts weak signals and convert into stronger signal. It makes possible for long-distance data transfer. So it boosts the data signals that are received from network.

9. MODEM

MODEM stands for Modulator and Demodulator. The MODEM turns the computer's digital signals into analog signals which are then transmitted across the phone line is called modulation phase. The MODEM receives analog signals from phone line and converts into digital signals for the computer is called demodulation phase. It can convert analog signal to digital signal and the vice versa. So, it is a device which connects computers to ISP (Internet Service Provider) by the help of telephone line or router device. The MODEM which is placed inside the CPU Casing is called internal modem. MODEM which is placed outside the Casing is called an external modem.

Bandwidth 

The amount of data that can be carried from one point to another in a given time period is called bandwidth. It is measured in bits per second (bps). A MODEM that works at 57600 bps has twice the bandwidth of a MODEM that works at 28800 bps.

Network Software 

Network software is an important software which controls and manages computer network. It is also called NOS (Network Operating System). Novell Netware is a popular NOS. Windows NT, Windows XP, Linux, Banyan Vinex, etc. are other example of NOS. The main functions of NOS are:

• It helps to setup and install network
• It allows administration to add or remove user from the network
• It enables user to have access to network resources
• It manage and control all the resources of the computer network

Protocol 

A set of rules followed for interconnection and communication between computers in a network is called a protocol. So it is rules followed while sending and receiving information using network software. NCP (Network Control Protocol) was the first protocol. Some common protocols are as follows: 

 TCP/IP (Transmission Control Protocol/Internet Protocol) is used in Internet. 

 HTTP (Hypertext Transfer Protocol) is used to transfer HTML documents in WWW. 

 SMTP (Simple Mail Transfer Protocol) is used in sending e-mail.

 POP (Post Office Protocol) is used to retrieve e-mail from a mail server. 

 FTP (File Transfer Protocol) is used to transmitting files between computers.

Types of Network Computer 

network can be classified according to its area covered. The main three types of computer network on the basis of geographical location (area covered) are: 

1. LAN (Local Area Network)

2. MAN (Metropolitan Area Network) 

3. WAN (Wide Area Network) 

1. LAN (Local Area Network) 

Local Area Network is a network limited within a small area like a room, a building, school, college, etc. generally connected through wire media. It can cover up to one kilometre for transferring data and information between the computers. It has high speed data transfer capacity than MAN and WAN. Computer in LAN can be connected through wireless media and is referred to as WLAN (Wireless Local Area Network). Computer lab networking and cyber networking are examples of LAN.

Features of LAN (Local Area Network) Coverage area is a generally small geographical area such as room, building and few kilometers. 

 LAN runs the multiple devices to share a transmission medium

 The different topology used mainly bus and ring in LAN 

 The communication quality is better in LAN, the transmission error rate are low as compare to WAN

LAN supports a variety of communications transmission medium such as an Ethernet cable (thin cable, thick cable, and twisted pair), fiber and wireless transmission.

2. MAN (Metropolitan Area Network) 

Metropolitan Area Network (MAN) is a network within the area like valley, city, metropolitan, etc. connected through wire or wireless technology or media. It covers more area than LAN and less area than WAN. It has high speed data transfer capacity than WAN and is slower than LAN. It is used in medium size organization having various branches within city or valley. Cable TV network and telephone networks providing high-speed DSL lines are examples of MAN. 

Features of MAN (Metropolitan Area Network) 

 Network size up to 50 km. It may be as small as a group of buildings in a campus to as large as covering the whole city

 It is normally owned by single or multiple organizations. 

 It facilitates sharing of regional resources. 

 They provide uplinks for connecting LANs to WANs and Internet.

3. WAN (Wide Area Network) 

Wide Area Network is a network that is extended to a large area i.e. world in which computers are connected through wireless technology or media as satellite communication. It is the largest computer network. Internet, 4G Mobile Broadband Systems and satellite communication are the best examples of WAN.

Features of WAN (Wide Area Network) 

 It covers the whole world and cannot be restricted to any geographical location. It uses satellite and microwave communication. 

 It is normally owned by multiple organizations. 

 Communication links are provided by public carriers like telephone networks, satellites, network providers, cable systems, etc. 

 They have low data transfer rate and high propagation delay so they have low communication speed.

Network Architecture/Model 

Network architecture defines how the computer communicates and interacts with each other on network. It is combined form of topologies and data transmission mode between the different computers in the network. The three types of network architecture are: 

1. Peer to Peer Network 

In this type of network, all nodes on the network have an equal relationship with each other. It is also called workgroup. It can share data, hardware and software with each other. It is suitable for a small area such as small offices, small room, building, etc. It uses many operating systems such as Windows 2000, Windows 8, Macintosh Operating System etc., have built-in features to support peer to peer network. 

Advantage of Peer to Peer Network 

 Everything can be shared in this network. 

 System administrator is not required and each user can control their shared resources. 

 The failure of one computer doesn't affect the functioning of other peers. 

Disadvantages of Peer to Peer Network 

 It is difficult for administrator and control as resources are decentralized in this network. 

 Security is very low in this system. 

 Data recovery or backup is very difficult.

Client-Server Network 

A network model where one or more powerful computers (servers) provide the different network services and all other users of computer network (clients) access those services to perform user's tasks is known as client-server network. In such networks, there exists a central controller called server. A server is a specialized computer that controls the network resource and provides services to other computers in the network. 

Novell Netware, Windows NT, Linux, etc. are the common examples of an operating system of client-server network.

Advantages of Client-Server Network 

 Centralized back up is possible in client-server computer network. 

 The use of dedicated servers also increases the speed of sharing resources. 

 Security is better in this network as all the shared resources are centrally administered. 

Disadvantages of Client-Server Network 

 It requires specialized servers with large memory. This leads to an increase in the cost. 

 The cost of network operating system that manages the various clients is also high. 

 It requires network administrator.

Centralized Network

In this network, the main computer is known as host or server computer. Workstation is just used for input/output operations, which has no processing capabilities and are connected to server or host computer. Linux or UNIX operating system is used in centralized network. 

Advantages of Centralized Network 

 It saves cost of installation of network system. 

 It secures all data and information on host computer which works on IPOS (input process output system). 

 Host Computer gives facilities like Disk storage and software to workstation.

Disadvantages of Centralized Network 

 The malfunctioning of host computer affects other workstation. 

 It takes long time for data processing. 

 It is difficult to add more workstation.

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