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CS6: Data Communication and Networking

Communication is one of the fundamental aspects of life. In this regard, electronic communication means have been developed on top of the traditional manual and mechanical modes of communication for individuals and organisations to communicate more effectively. A person can now communicate through contemporary media like mobile phones and over the internet. It is therefore important that learners are introduced to basic data communication and ICT networking infrastructure and services in order to come to terms with contemporary data communication facilities. Learning Outcome: The learner should develop basic skills, knowledge and expertise in the use of contemporary communication facilities like computers, mobile telephones, the Internet, among others.

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DATA COMMUNICATION AND NETWORKING

Sub Topic 11.1: Introduction to Data  Communication

Sub-topic Objectives:

a. defining data communication.

b. explaining the elements of data communication (sender, receiver, messages, transmission media and protocol).

c. defining data communication tools

d. describing types of electronic data communication tools like computers, mobile phones, the Internet, among others.

e. comparing electronic and manual data communication tools (manual drums, bells and messengers).

f. defining data transmission media.

g. differentiating between physical transmission media and wireless transmission media.

h. describing services offered by data communication tools like E-mail, Skype, News groups, and instant messaging.

i. explaining the implications of using data communication services.

Definition of terminologies

Computer Network And Internet Communication Concept Stock Photo, Picture  And Royalty Free Image. Image 27719029.Computer communication is the transmission of data and information over a channel between two computers. Communications between computers can be as simple as cabling two computers to the same printer.

A computer Network is a collection of two or more computers and devices connected by channels so that they can communicate with each other and share resources: Examples of resources

  • data, a single internet connection,
  • software,
  • peripheral devices, processing power.

Encoding: This is the process through which Information (e.g. data, text, voice or video) from the sending device is converted into signals which the communication medium can carry.

Transmission: This is the process through which the signals are broad cast/ sent out through the medium to the receiving device.

Decoding: This is the process through which the signals are converted back into the information in its original form in the receiving device.

Telecommunication refers to transmission of data and information over a long-distance, eg television

Teleprocessing: This refers to access and modification of computer files located elsewhere.

Downloading: To Download is to transfer a file to your computer from another.

Uploading means to transfer a file from your computer to another.

Throughput refers to the rate of how much data is moved during a certain amount of time. The amount of signals that can travel over a communications channel sometimes is called the Bandwidth. The higher the bandwidth, the more data and information the channel can transmit.

Data Encryption: This is Process of converting data into coded form (cypher text) to prevent it from being read or understood by unauthorized people. Encrypted data is difficult to decode without a secret key

Communications Software: This refers to a set of instructions (software) needed by a computer before it starts sending and receiving data from other computers.

Importance of computer communication

  • It allows sharing of hardware like printers.
  • It allows sharing of software between two or more computers, hence reducing on cost.
  • It allows sharing and transfer of data and information stored on other computers on the network.
  • Facilitate communications between people e.g. through electronic-mail, Mobile phones,e.t.c.
  • Computer communication has security & tight control measures over data access.
  • It enables online learning and collaborative research.
  • It allows access to common databases for example in banks.
  • Has enabled improved travel service through e-bookings and e-reservation.
  • Provides for online employment e.g. telecommuting.

Limitations of computer communication

  • Data theft. If a computer is a standalone, physical access becomes necessary for any kind of data theft. However, if a computer is on a network, a computer hacker can get illegal access.
  • Rapid Spread of Computer Viruses: If any computer system in a network gets infected by computer virus, there is a possible threat of other systems getting infected.
  • Expensive Set Up: The initial set up cost of a computer network can be high depending on the number of computers to be connected.
  • Dependency on the Main File Server: In case the main File Server of a computer network breaks down, the system becomes useless.
  • Exposure to External Exploits. Someone on a different computer can send data to the computer in such a way as to attack it – make it lock up or crash, make it slow down, or even take control of it.
  • Automatic Downloads. If a computer is connected to a network, it’s easier to download and install software from the network onto the computer without any human intervention. If the new software hasn’t been tested, it could cause unpredictable behavior.
  • Computer Networks can Fail. Computer networks can be so powerful and useful that it is very vital for them to be used. All of the computers in an office building might become completely useless if a single network component fails.

Transmission media (Channels)

Transmission media refers to the physical materials that are used to transmit data between computers. For communications between computers that are linked by cable, there are three choices:

  • Twisted wire,
  • Coaxial cable,
  • Fiber optic line.

Twisted wire

Twisted pair cable comes in two varieties: Shielded and Unshielded Twisted Pair (UTP). UTP is the most popular

TWISTED-PAIR CABLE UTP/K6/305M/PE - UTP, FTP Cables - Delta

Advantages:

  • It is of low cost
  • small in size
  • easy to install
  • It is the most popular and generally the best for schools.

Disadvantage:

    • Subject to interference
    • limited distance, usually less than 100 meters

Coaxial cable

What is a coaxial cable? A definition from WhatIs.comCoaxial cable consists of a single copper wire surrounded by at least three layers:

  • An insulating material
  • A woven or braided metal
  • A plastic outer coating.
  • Cable TV wiring often uses coaxial cable because it can be cabled over longer distances than twisted-pair cable

Advantages

  • Coaxial cable is insulated more heavily than twisted-pair cable. So it is highly resistant to signal interference.
  • Used for longer distances (300 – 600 meters)
  • Transmits faster than UTP

Disadvantages

    • Heavy & bulky
    • Needs booster over longer distances

Fiber Optic Cable

What's the Difference Between Copper Cable and Fiber Optic Cable?

Each strand, called an optical fiber, is as thin as a human hair. Each optical fiber is surrounded by an insulating glass cladding and a protective coating. Fiber-optic cables are used by many local and long-distance telephone companies, cable TV, and in high-traffic networks or as the main cable in a network.

Advantages:

  • Carry significantly more signals than other cables.
  • Faster data transmission.
  • Less vulnerable to electrical noise from other devices
  • Better security for signals during transmission.
  • Smaller size, and much thinner and lighter than other cables.

Disadvantages:

    • Expensive as compared to other media
    • Harder to install and modify.

Wireless telecommunications technologies transport digital communications without cables between communications devices. Wireless transmission media used in communications include broadcast radio, cellular radio, microwaves, communications satellites, and infrared & bluetooth.

Wireless transmission is more convenient than installing cables but it has Slower data transfer than hard-wired methods and it is also Subject to interference.

Microwave

Microwave transmission - WikipediaMicrowaves are high-frequency radio waves that are sent through the atmosphere and space to deliver telecommunications services, including TV distribution. It is dependent on line of sight.

Advantage:

  • Speed of light
  • Microwave signals can carry thousands of channels at the same time

Disadvantage:

  • Line-of-sight only- (there is need for radio transmitters  in networks using air interface (radio waves) to be positioned free of obstacles)

Satellite communication Vectors & Illustrations for Free Download | FreepikSatellite

A satellite is basically a microwave station placed in outer space. The satellite receives a signal from the earth, amplifies it, and then rebroadcasts it at a different frequency to any number of earth-based stations.

  • Advantage: Always in sight
  • Disadvantage: Expensive uplink and downlink facilities

Satellite In The Rays Of Light. 3D Scene.

Infrared and Bluetooth IrDA (Infrared Data Association) ports transmit data via infrared light waves. As long as the devices are within a few feet and nothing obstructs the path of the infrared light wave, data can be transferred without the use of cables.

Bluetooth® Technology WebsiteBluetooth port is an alternative to IrDA. Bluetooth technology uses radio waves to transmit data between two devices. Many computers, peripherals, smart phones, PDAs, cars, and other consumer electronics are Bluetooth-enabled, which means they contain a small chip that allow them to communicate with other Bluetooth-enabled computers and devices.

Physical transmission media and wireless transmission media

Advantages of physical over wireless transmission media

  • Physical media support higher bandwidth
  • They can carry voice, data and video signal simultaneously.
  • They are more resistant to radio and electromagnetic interference.

Disadvantages of physical transmission media

  • Installation is difficult because the cables must be carefully handled.
  • They are relatively complex to expand as compared to wireless
  • Cover short distance since they use the physical wires
  • Inconvenience due to inflexibility of restrictive cables.

Services offered by data communication tools

Data communication tools offer services like Telephone, SMS, E-mail, Skype, Newsgroups and instant messaging.

  • Telephone voice calls help keep people talking even when they are distant and mobile.
  • Short Messaging Services SMS facilitate sending and receiving of brief text messages
  • Electronic mail and fax : An electronic mail is the message transmitted electronically over the internet, from one user to another. A fax machine is a device that transmits and receives typed or hand written documents over telephone lines.
  • Skype supports voice and video calls, text, instant messaging and sharing conversation with (someone) over the Internet using the software application Skype, frequently also viewing by webcam.
  • Newsgroups are organized group of internet users who wish to share ideas and interests through discussion forums and debates.
  • Instant messaging: This is a more enhanced messaging service that allows two or more people to chat directly in real time.
  • Social networking e.g. Facebook and Twitter create digital societies through linking people of common interests.

Positive Implications

  • Have led to faster, simpler communications between people e.g. through electronic-mail, mobile phones, social networks etc.
  • Communications costs have become lower e.g. Making cheap internet calls, for example via Google talk and Skype
  • Community mobilization now easier – its now very simple to send a message to many people in one go e.g using Mailing lists and group chats.
  • Data communication tools like the internet have facilitated emergence of the world wide web where there is a wealth of information, such as news, weather reports, and airline schedules.
  • Data communication tools like telephones and SMS Have revolutionised the way people transact businesses e.g access to mobile money services using phones.

Negative Implications

  • Security and privacy: data communication services have made it easy access private information e.g. on social networks, hence posing security concern.
  • Spamming is high especially by advertisers who send unwanted e-mails in bulk, such as email adverts.
  • There has been emergency of new kinds of crimes facilitated by data communication services, such as cyberbullying.
  • Inaccurate information on the internet can be misleading and lead to dire consequences to the users.
  • Data communication services have facilitated the digital divide in society, hence disadvantaging the computer illiterate people when it comes to opportunities like jobs and government services.

DATA TRANSMISSION

Telecommunications involves the transmission of data, information, and instructions among computers. Any transmissions sent during these communications can be categorized by a number of characteristics including the signal type, transmission mode, transmission direction, and transmission rate.

Signal Type: Recall that computers produce digital signals yet telephone equipment originally was designed to carry only voice transmission in the form of an analog signal.

26,617 Analog Signal Images, Stock Photos & Vectors | Shutterstock

Analog Signals

An analog signal uses variations which are represented by a continuous waveform to convey information.  It is particularly useful for wave data like sound waves. Analog signals are what normal phone line and sound speakers use.

Digital Signals

A digital signal is a series of discrete (discontinuous) bits which are simply the presence or absence of an electric pulse. The state of being on or off represents the binary digit of 1 or 0, respectively.

Advantages of digital signals include:

  • Digital signals can be copied exactly without any loss of quality
  • Digital signals can be further processed by computer.

Transmission Modes

When two devices exchange data, the data flows between the devices as a continuous stream of bits.

There are two basic transmission techniques for separating the groups of bits: asynchronous transmission and synchronous transmission

Asynchronous transmission

Asynchronous transmission transmits one byte at a time over a line at random intervals. Each byte is framed by controls—a start bit for marking the beginning of the byte, a stop bit for marking the end of the byte, and a parity bit for error checking. Asynchronous transmission is relatively slow and used for low-speed transmission.

Synchronous transmission

Synchronous transmission transmits groups of bytes simultaneously at regular intervals. The beginning and ending of a block of bytes is determined by the timing of the sending device and receiving devices.

Although synchronous transmission requires more complicated and expensive communications devices, it provides much higher speeds and greater accuracy than asynchronous transmission.

Transmission Direction

What is Data Transmission Modes? - The Study Genius

The direction in which data flows along transmission media is characterized as

  • simplex,
  • half-duplex,
  • full-duplex or
  • multiplex

Simplex transmission

Do you know what differences are between simplex, half duplex and full  duplex in telecommunication network?

Simplex transmission sends data in one direction only. Simplex transmission is used only when the sending device does not require a response from the receiving device. One example of simplex transmission is television broadcasting.

Half-duplex transmission

Simplex, Half duplex, Full-duplex Data Transmission Modes | T4Tutorials.comHalf-duplex transmission allows data transmission in either direction, but only one way at a time. Many fax machines, police radio calls, credit card verification systems and automatic teller machines use half-duplex transmission.

Full-duplex transmission

In full-duplex transmission, data can flow in both directions at the same time. A regular telephone line, for example, supports full-duplex transmission, allowing both parties to talk at same time.

Multiplex transmission

In multiplex transmission, several different types of signals can be carried at once through the same line. E.g. During Video calls where Images

Assignment

CS6: Assignment on Data Communication and Networking

ASSIGNMENT : CS6: Assignment on Data Communication and Networking MARKS : 25  DURATION : 45 minutes

 

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