Communication Systems: How is data organized for transferal over the Internet?

Question 1

Twisted-pair

Answer 1

consists of two copper conductors of a single circuit are twisted together for the purposes of cancelling out EM interference from external sources.

Question 2

Coaxial cable

Answer 2

A single copper wire surrounded by at least three layers: (1) an insulating material

(2) a woven or braided metal
(3) a plastic outer coating.

A coaxial cable has a solid copper or copper- clad- steel center conductor surrounded by a non- conductive dielectric insulating material.

Question 3

Fibre Optic Cable

Answer 3

Dozens or hundreds of thin strands of glass or plastics that use light to transmit signal.

made of optical fibres that can transmit large amounts of information at the speed of light.

Question 4

Microwave

Answer 4

Radio waves that provide a high-speed signal transmitting.

Terrestrial microwave transmission:

• When information is transmitted via radio waves.

- Used in radio broadcasting, using a satellite microwave system.

• microwaves do require line of sight.

Question 5

Satellite

Answer 5

Provides high-speed Internet connections via a satellite to a satellite dish that communicates with a satellite modem.

Question 6

Infrared (IR)

Answer 6

A wireless transmission medium that sends signals using infrared light waves.

EM energy of wavelengths longer than red light

Question 7

Braodcast Radio

Answer 7

A wireless transmission medium that distributes radio signals through the air over long distances e.g. between cities and countries and over short distances e.g. within an office or home.

Broadcast radio is slower and more susceptible to noise than physical transmission media but it provides flexibility and portability.

Question 8

Broadcast radio: Bluetooth

Answer 8

Uses short-range radio waves to transmit data over a standard network between two bluetooth devices.

Question 9

Broadcast radio: Wi-Fi (Wireless Fidelity)

Answer 9

A type of broadband Internet connection that uses radio signals to provide high-speed Internet connections to compatible wireless devices.

Commonly found in schools, coffee shops and at home.

Question 10

Broadcast Radio: Cellular Radio

Answer 10

provides high-speed Internet connections to devices with built in compatible technology.

used widely for mobile communications, specifically cell phones.

A cell phone is a device that uses high-frequency radio waves to transmit voice and digital data messages.

Because only a limited number of radio frequencies exist, cellular network providers re-use frequencies so that they can accommodate the large number of users.

Other computers or devices can also connect to a cell phone to access the Web.

Cellular radio is based on a network of transmitters each serving a small area known as a cell: the mobile receiver switches frequencies automatically as it passes from one cell to another.

Question 11

Cellular Radio: 2G (2nd Generation)

Answer 11

refers to the second generation of wireless mobile telephone networks, which were the first to feature purely digital technology.

Typical characteristics of 2G include:
- roaming

• better high bit-rate voice quality
• improved security with different levels of encryption
• the ability to convey some data (e.g. SMS) as well as speech
• a wider selection of subscriber services.

Question 12

Cellular Radio: 3G (3rd Generation)

Answer 12

Third generation of wireless technologies.

It comes with enhancements over previous wireless technologies, like:

• high-speed transmission
• advanced multimedia access and global roaming

3G is mostly used with mobile phones and handsets as a means to connect the phone to the Internet or other IP networks in order to make voice and video calls, to download and upload data and to surf the net.

Question 13

Cellular Radio: 4G (4th Generation)

Answer 13

Fourth generation of mobile phone communication technology standards.

It is a successor to the third generation (3G) standards.

It transmits digital data at speeds up to 15 Mbps.

Wireless internet at higher speeds than 3G

Question 14

ISDN (Integrated Services Digital Network)

Answer 14

Set of communication standards for simultaneous digital transmission of:

• voice
• video
• data
• other network services over the traditional circuits of the public switched telephone network

Question 15

DSL (Digital Subscriber Line)

Answer 15

Family of technologies that are used to transmit digital data over telephone lines.

A digital subscriber line (DSL) modem is a device used to connect a computer or router to a telephone line which provides the digital subscriber line service for connectivity to the Internet, which is often called DSL broadband.

Question 16

ADSL (Asymmetric Digital Subscriber Line)

Answer 16

Type of digital subscriber line (DSL) technology, a data communications technology that enables faster data transmission over copper telephone lines rather than a conventional voiceband modem can provide.

Question 17

What is a Protocol?

Answer 17

A set of standards and agreements for exchanging information between computers.

Protocols define how the communications link is established, how information is transmitted and how errors detected and corrected.

Using the same protocols, different types and makes of computers can communicate with each other.

Question 18

Protocol: TCP/IP

Answer 18

Transmission Control Protocol/Internet Protocol

Defines how data is routed from one end of a network to the other, ensuring the data arrives correctly.

Made up of 4 layers:

• Application
• Transport
• Internet
• Network

Question 19

OSI Model compared to TCP/IP Model

Answer 19

Question 20

TCP/IP Model

Answer 20

Question 21

Protocol: IP

Answer 21

(Internet Protocol)

Layer: Internet

Uniquely identifies each computer or device that is connected to the internet

Question 22

Protocol: IPX/SPX

Answer 22

(Internetwork Packet Exchange/Sequenced Packet Exchanged)

Layer: IPX – Network layer of the OSI Model

SPX – Transport layer of the OSI Model

IPX and SPX are used primarily on networks using the Novell NetWare operating systems.

IPX and SPX both provide connection services similar to TCP/IP, with the IPX protocol having similarities to IP, and SPX having similarities to TCP.

Question 23

Protocol: NetBEUI

Answer 23

(NetBios Extended User Interface)

Layer: Application

Provides a small network with the ability to translate user-friendly computer names to an IP address

Question 24

Protocol: FTP

Answer 24

(File Transfer Protocol)

Layer: Application

Permits file uploading and downloading with other computers on the Internet

An Internet standard that allows you to exchange files with other computers on the Internet.

Computers that contain files avaialble for FTP are called FTP sites or FTP servers.

Question 25

Protocol: SMTP

Answer 25

(Simple Mail Transfer Protocol)

Layer: Application

Communications protocol used by some outgoing mail servers

Question 26

Protocol: POP3

Answer 26

(Post Office Protocol)

Layer: Application

The POP3 service makes e-mail messages available for download from a server

Question 27

Protocol: HTTP

Answer 27

(Hypertext Transfer Protocol)
Layer: Application

A set of rules that defines how pages transfer on the internet

Question 28

Protocol: Ethernet

Answer 28

Layer: Network Access

A network standard that specifies no central device on the network should control when data can be transmitted; instead, each node attempts to transmit data when it determines the network is available and if a collision occurs because 2 nodes are attempting to transmit at the same time, they must attempt to send their messages again.

Question 29

What is a packet?

Answer 29

A formatted unit of data carried by a packet-switched network.

Computer communications links that do not support packets, such as traditional point-to-point telecommunications links, simply transmit data as a bit stream.

When data is formatted into packets, the bandwidth of the communication medium can be better shared among users than if the network were circuit switched.

Question 30

What is circuit switching?

Answer 30

A methodology of implementing a telecommunications network in which two network nodes establish a dedicated communications channel (circuit) through the network before the nodes may communicate.

The circuit guarantees the full bandwidth of the channel and remains connected for the duration of the communication session.

The circuit functions as if the nodes were physically connected as with an electrical circuit. T

he defining example of a circuit-switched network is the early analog telephone network.

When a call is made from one telephone to another, switches within the telephone exchanges create a continuous wire circuit between the two telephones, for as long as the call lasts.

Question 31

Bandwidth

Answer 31

The amount of data that can be transmitted in a fixed amount of time.

For digital devices: bits per second(bps) or bytes per second.

For analog devices: cycles per second, or Hertz (Hz).

Analogy: Pipe width, or no.of lanes on a highway

Question 32

Throughput

Answer 32

The amount of material or items passing through a system or process.

Question 33

Encryption

Answer 33

Encryption is the process of encoding data and information to an unreadable form

When an authorised user attempts to read the data, it is automatically decrypted, or converted back into a readable form

Question 34

Encapsulation

Answer 34

The process of data moving down through each of the four TCP/IP layers to be packaged ready for transfer across the Internet.

Question 35

Decapsulation

Answer 35

the reverse process of encapsualtion; it is the process of extracting the data for the end-user. This is achieved as it becomes ‘unwrapped’ as it moves up through each of the four layers at the reciever’s end.