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Unit# 4 DATA COMMUNICATION AND COMPUTER
NETWORK
A. Choose the right answer:
1. Wired Media is also called: a) targeted media b) directed media c) guided media d) unguided media 2. Communication system is made up of: a) three components b) four components c) five components d) six components 3. Both Physical and Logical addresses are: a) different b) unique c) permanent d) temporary 4. If you are an electrical or electronic engineer, you should join: a) IEEE b) IETF c) ITU d) ANSI 5. The topology in which all computers are connected to a central device called hub is: a) Bus b) Star c) Ring d) Tree 6. Change in the shape of signal between sender and receiver is called: a) attenuation b) interruption c) noise d) distortion 7. Router determines data path to transfer data packets which is the: a) shortest b) longest c) cheapest d) optimal 8. Converting digital signal to analog is called: a) modulation b) modification c) bandwidth d) multiplexing 9. The number of bits used in an IPV 4 address are: a) 16 b) 32 c) 64 d) 128 10. The loss of energy in transmission signal refers to: a) Attenuation b) Distortion c) Noise d) Jitter
B. Respond the following:
- List the properties of a good communication system. Explain any one. The effectiveness of a data communications system depends on following fundamental characteristics: Delivery Accuracy Timeliness.
1. Delivery: the data should be delivered to the correct destination and correct user.
2. Accuracy: the communication system should deliver the data accurately, without introducing any
errors. The data may get corrupted during transmission effecting the accuracy of the delivered data.
3. Timeliness: Audio and video data has to be delivered in a timely manner without any delay; such a data
delivery is called real time transmission of data. 2. Explain components of communication using single example. The five components are :
1. Message
It is the information to be communicated. Popular forms of information include text, pictures, audio, video etc. Text is converted to binary, number doesn’t converted, image is converted to pixels, etc.
2. Sender
It is the device which sends the data messages. It can be a computer, workstation, telephone handset etc.
3. Receiver
It is the device which receives the data messages. It can be a computer, workstation, telephone handset etc.
4. Transmission Medium
It is the physical path by which a message travels from sender to receiver. Some examples include twisted-pair wire, coaxial cable, radio waves etc.
5. Protocol
It is a set of rules that governs the data communications. It represents an agreement between the communicating devices. Without a protocol, two devices may be connected but not communicating.
Example When a person directly talks with another person, then the speaker is called transmitter conveying the message in the form of the waves of sound through a communication channel, the air around and person who is listening the message is the receiver. If the distance between transmitter and receiver is large, therefore sound waves cannot reach directly from the transmitter to the receiver and communication is not possible. We have to change the communication channel and method to make communication possible.
3. Write the function of following network devices. Amplifiers, Routers, Switch, Hub
Amplifier:
An amplifier is an electronic device that increases the voltage, current, or power of a signal. Amplifiers are used in wireless communications and broadcasting, and in audio equipment of all kinds. They can be categorized as either weak-signal amplifiers or power amplifiers.
Router:
A router is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions on the Internet. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey.
Switches:
Most business networks today use switches to connect computers, printers, phones, cameras, lights, and servers in a building or campus. A switch serves as a controller, enabling networked devices to talk to each other efficiently.
Hub:
A hub, also called a network hub, is a common connection point for devices in a network. Hubs are devices commonly used to connect segments of a LAN. The hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.
4. List the causes of signal impairments. Explain any one. Below are the causes of the impairment.
Causes of impairment:
- Attenuation
- Distortion
- Noise
Attenuation:
It means loss of energy. The strength of signal decreases with increasing distance which causes loss of energy in overcoming resistance of medium. This is also known as attenuated signal. Amplifiers are used to amplify the attenuated signal which gives the original signal back and compensate for this loss. Attenuation is the loss of signal strength in networking cables or connections. Amplifiers are used to overcome attenuation and make signal stronger again. It is measured in decibels.
Distortion
Distortion is a term used to describe an interruption of transmitting signals that cause an unclear reception. When it travels through a medium different component of signal may reach at different time at destination because each component has different speed in that medium. This is called distortion.
Noise
Noise is unwanted electrical or electromagnetic energy that degrades the quality of signals and data. Noise occurs in digital and analog systems, and can affect communications of all types, including text, programs, images, audio, and telemetry.
5. What is the difference between radio wave and microwave?
Radio waves
Radio waves are a type of electromagnetic radiation best-known for their use in communication technologies, such as television, mobile phones and radios. These devices receive radio waves and convert them to mechanical vibrations in the speaker to create sound waves.
Microwaves
Microwaves are widely used in modern technology, for example in point-to-point communication links, wireless networks, microwave radio relay networks, radar, satellite and spacecraft communication. These are mostly used for mobile phone communications tower and television broadcast. Terrestrial and Satellite are two types of microwave transmissions.
QUESTIONS OTHER THAN EXERCISE
11. Define the following terminology of data communication. i) Data ii) Data communication iii) Data Transmission iv) Analog signals v) Digital signals.
i) Data
Data communication is simply the exchange of data between two or many users through the transmission media like twisted pair cable, coaxial cable, optical fibers, radio wave, satellite microwave, etc. The user or device that sends the data is the source and the user that receives the data is a receiver. Data can be defined as a representation of facts, concepts, or instructions in a formalized manner, which should be suitable for communication, interpretation, or processing by human or electronic machine. Data is represented with the help of characters such as alphabets (A-Z, a-z), digits (0-9) or special characters *(+, - , /, , <, >, = etc.)
ii) Data communication
Communication is the process of sharing a message. A conversation between two people is an example of communication. Data communications refers to the sharing of a virtual message. Electronic communications, like emails and instant messages, as well as phone calls are examples of data communications.
iii) Data transmission
Data transmission refers to the process of transferring data between two or more digital devices. Data is transmitted from one device to another in analog or digital format. Basically, data transmission enables devices or components within devices to speak to each other.
iv) Analog signal
An analog signal is signals and wavelengths transmitted over communications lines such as the sound of a voice over the phone line. With computers, a dial-up modem is an example of a device that takes digital data and converts it to an analog signal to transmit over phone lines.
14. Differentiate between Analog and digital signals.
Difference between Analog and Digital Signals
Analog signal Digital signal
An analog signal is a continuous wave that changes by time period. A digital signal is a discrete wave that carries information in binary form. Analog signal has no fixed range. Digital signal has a finite number i.e. 0 and 1. An analog signal can easily be disturbed by other signals or waves. A digital signal is less prone to other signals disturbance. The human voice is example of an analog signal. Signals used by computer are the digital signal. An analog signal is represented by a sine wave. A digital signal is represented by square waves. Analog signals are long term waves need to be boosting. Digital signals are short term signals remain within digital devices / electronic.
15. Differentiate between Data Rate and Baud Rate.
Difference between Data Rate and Baud Rate
Data Rate Baud Rate
Bit rate tells the number of bits transmitted per unit of time (Second). Baud rate is used when we want to know the number of signal units transmitted per unit of time (Second). Bit rate is the number bits (0's and 1's) transmitted per second. Baud rate is the number of times a signal is traveling comprised of bits. One signal can represent more than one bit. Bit rate = baud rate x the number of bits per signal unit Baud rate = bit rate / the number of bits per signal unit
BASICS OF DATA COMMUNICATION
Data communications means the exchange of data between two devices via some form of transmission medium such as a wire cable. Communication is the process of sharing a message. 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). Electronic communications, like emails and instant messages and phone calls are examples of data communications. Basic Terminologies of Data Communication In order to understand the data communication, it is good to know some basic terms related to it.
Data
Collection of raw facts and figures is called data. The word data is derived from Latin language and it is plural of Datum. The text, numbers, symbols, images, voice and video which are processed by computers and digital devices are called data. Data can be considered as unorganized information.
Data Communication
Data Communication is the process of transferring data electrically from one place to another. It is the process of exchange of data and information between two parties such as human and electronic or computing device.
Data Transmission
Data transmission refers to the process of transferring data between two or more digital devices. Data is transmitted from one device to another in analog or digital format. Basically, data transmission enables devices or components within devices to speak to each other
Analog Signals
An analog signal is a continuous signal in which one time-varying quantity (such as voltage, pressure, etc.) represents another time-based variable. In other words, one variable is an analog of the other. An analog signal can be used to measure changes in some physical quantities such as light, sound, pressure or temperature.
Digital Signals
A digital signal is a signal that is being used to represent data as a sequence of discrete values; at any given time, it can only take on, at most, one of a finite number of values. Simple a digital signal is an electrical signal that is converted into a pattern of bits to represent a sequence of discrete values, at any given time. It can only be one of the finite numbers represented as 0 or 1.
Data Rate / Bit Rate
Data rate is the rate at which data is transferred. It is normally measured in bits per second. Bit is the actual binary digit which is the basic unit of data transmission. Bit can hold either 0 or 1. Data rate can be ranging from bps (bits per second) for smaller values to kbps (kilobits per second) and mbps (megabits per second). It is also called bit rate. Data rate becomes faster when more bits are transferred in one second.
Baud Rate
The baud rate is the number of signals transmitted per second and one signal can represent one or more bits. It is used to describe the maximum change in an electronic signal. For example, if a signal changes 1200 times in one second, it would be measured at 1200 baud.
Signal to Noise Ratio
ii) Microwaves
Microwaves are widely used in modern technology, for example in point-to-point communication links, wireless networks, microwave radio relay networks, radar, satellite and spacecraft communication. These are mostly used for mobile phone communications tower and television broadcast. Terrestrial and Satellite are two types of microwave transmissions.
Terrestrial:
Terrestrial microwaves have both stations having antennas on earth.
Satellite:
In satellite system, some antenna are on satellite in orbit and others are on stations on earth. They work at remote places so it can be used in mobile devices.
(iii) Infrared:
Infrared radiation (IR), or infrared light, is a type of radiant energy that's invisible to human eyes but that we can feel as heat. All objects in the universe emit some level of IR radiation, but two of the most obvious sources are the sun and fire. Wireless infrared communications can be used to establish short range wireless links or wireless Local Area Network. Transmission Impairments The signal received may differ from the signal transmitted. The effect will degrade the signal quality for analog signals and introduce bit errors for digital signals. There are three types of transmission impairments: i) Attenuation, ii) Delay distortion iii) Noise. COMMUNICATION DEVICES A communication device is any type of hardware capable of transmitting and receiving data, instructions and information.
Switch
A network switch (also called switching hub, bridging hub, is networking hardware that connects devices on a computer network by using packet switching to receive and forward data to the destination device. A switch or network switch is a networking device that connects computers and other devices like printers, scanners and cameras on a network. Data cables from all computers and other devices of network are plugged into the switch to enable communication between them.
Router
A Router is a device that connects two or more networks. Routers are a combination of hardware and software. The main function of a router is to determine the optimal data path and transfer the information through that path, also known as network traffic controller.
Modem
Modem is short for Modulator and Demodulator. Modulation is the process of converting digital signals into analog signals. Demodulation is quite opposite; it converts analog signals into digital signals. Modem has the ability of sending and receiving signals that allows computers to share information with each other. This sharing of information is possible over phone lines, cables or satellite connections.
Dialup Modem
Dialup modems use standard telephone lines to transmit and receive information. A dialup modem can be internal or external. It is important to remember that telephone lines carry only analog signals, whereas data packets sent by the computer are in digital form. In order to send these packets across a telephone line, modem converts digital signals into analog.
DSL Modem
DSL stands for Digital Subscriber Line. Like dial-up modem DSL modem also uses telephone lines to transfer digital signals. DSL modem has a built-in network switch which enables use of twisted pair wires to deliver data and voice at high speed as compare to dial-up modem. Some DSL modems also have wireless communication functionality.
ISDN Modem
Integrated Services Digital Network is a digital phone connection that can transmit data, voice and video over a normal telephone line at the same time which was not done before. It is faster and expensive technology. Since ISDN work on digital transmission it converts analog voice to digital signals before transmission.
Network Interface Card (NIC)
Network cards also known as Network Interface Cards are hardware devices that connect a computer with the network. They are installed on the mother board. They are responsible for establishing a physical connection between the network and the computer. Computer data is translated into electrical signals and sent to the network via Network Interface Cards. Modern motherboards have built-in NICs. Define computer network.
BASICS OF COMPUTER NETWORKS
Computer networks are just like a highway on which data can travel. A computer network connects parts of distributed system including hardware and software. It shares common functions and features like data and devices which is very important nowadays.
Computer Network
A computer network is a group of computers and related equipment connected by a communication links to share data and other resources. The related equipment may be printer, scanners, fax machines, server, etc. The resources may include a file server, internet connection, etc.
Networking
Networking is the act of joining computers and its accessories so that exchange of information and sharing of resources take place. In today's world, networking plays a vital role in computers and telecommunication fields. Modern organizations create a networking environment and device connectivity for fast, inexpensive and reliable communication. Describe the types of computer network.
Types of Computer Networks
Computer networks can be categorized by their size as well as their purpose. The size of a network can be expressed by the geographical area they occupy and the number of computers that are part of the network. Networks can cover anything from a handful of devices within a single room to millions of devices spread across the entire globe. There are three types of computer networks:
**1. Local Area Network (LAN)
- Metropolitan Area Network (MAN)
- Wide Area Network (WAN)**
1. Local Area Network (LAN)
A local-area network (LAN) is a computer network that spans a relatively small area. Most often, a LAN is confined to a single room, building or group of buildings, however, one LAN can be connected to other LANs over any distance via telephone lines and radio waves. LAN is a group of computer and peripheral devices which are connected in a limited area such as school, laboratory, home and office building.
2. Metropolitan Area Network (MAN)
A Metropolitan Area Network (MAN) is a large computer network on the large geographical area that include several buildings or even the entire city (metropolis). It is also often used to provide public available connection to other networks using a WAN connection. Therefore, only large business organization or universities set up MAN. It also requires security measures to prevent unauthorized access.
3. Wide Area Network (WAN)
A WAN can cover country, continent or even a whole world. Internet connection is an example of WAN. Other examples of WAN are mobile broadband connections such as 3G, 4G etc.A Wide Area Network is used for long distance transmission of data. WAN helps to cover a larger geographical area and connect cities, provinces or even countries. Using WAN technology, computers may be linked together in different countries using satellites, microwaves or telecommunication links. Therefore, large business, research and educational organizations situated at longer distances use WAN. A WAN may include multiple MANs and LANS. Define topology. Explain the different types of topology.
Fundamental of Topologies
The physical layout in which computers are connected is called topology. The topology of network describes the way computers are connected. Topology is a major design consideration for computer networking.
Bus Topology
layer architecture. It defines seven layers or levels in a complete communication system. It characterizes and standardizes the communication functions of a telecommunication and computing network.
TCP/IP Model
The TCP/IP Reference Model. TCP/IP means Transmission Control Protocol and Internet Protocol. It is the network model used in the current Internet architecture as well. These protocols describe the movement of data between the source and destination or the internet. They also offer simple naming and addressing schemes. TCP/ IP is a suite of communication protocols used to interconnect network devices on the internet. These are set of rules and procedures. TCP/IP specifies how data is exchanged over the internet by providing end-to-end communications. With reference to OSI layers, we can understand the functions of TCP/IP layers.
NETWORK ADDRESSING
A network address is also known as the numerical network part of an IP address. This is used to distinguish a network that has its own hosts and addresses. For example, in the IP address 192.168. 1.0, the network address is 192.168. Network addresses are like our house addresses. They must be unique and distinctive. This avoids confusion for the postman. A network address is any Logical or Physical Address that uniquely identifies it from others. This address is needed to distinguish a network node or device on a computer network.
IPV4 Address
The IPv4 address is a 32-bit number that uniquely identifies a network interface on a machine. An IPv4 address is typically written in decimal digits, formatted as four 8-bit fields that are separated by periods. Each 8-bit field represents a byte of the IPv4 address. The device could be a computer, printer, smart phone, tablet, etc. Every device connected to the internet must have an IP address to communicate with other devices. IP address acts as a telephone number or a car registration number. It shows ownership and location. The network portion of the address mentions the computer network and the host portion identifies the computer or any other computing device. IP version 4 (IPV4) addresses are comprised of four number segments separated by dots. Example of an IP address is 192.168.108.105.
