WEEK 4: COMMUNICATIONS AND NETWORKS

Question 1

What is a computer network?

Answer 1

Computer network - consists of two or more computing devices that are connected to each other. This is to pass information and share resources.
-> can start with only two computers, and as more devices join in, the network becomes bigger.

Question 2

What is a communication system and what are the four basic elements?

Answer 2

• Involves electronic systems that exchange data from one location to another.
• Data transmission can be made through a wired or wireless connection.

Four basic elements of a communications system:

• > Sending and receiving devices.
• > Communication devices.
• > Communications channel.
• > Data transmission specifications.

Question 3

This is how a communication system functions with its elements.

Answer 3

Sending device -> modem -> communication device -> packets of a communication channel -> communication device -> modem -> receiving device.

Question 4

What are sending and receiving devices?

Answer 4

• All types of computers and mobile devices acts as sending and receiving devices in a communications system.
  Eg. personal laptop, printers, game consoles, mainframe computers, servers, etc.

Question 5

What are communication devices?

Answer 5

• Hardware that is capable of transferring data or information between a sending and receiving device.
• At the sending point, a communication device relays the signal from the sending device to a communications channel.
• At the receiving point, a communications device accepts the signal from the communications channel.
• Signals can be digital or analog signals, based on the channel used.

Question 6

What are modems?

Answer 6

Modem is short for modulator and demodulator.

• Converts digital signals to analog signals and vice versa.
• Modulation - convert from digital to analog.
• Demodulation - convert from analog to digital.
• Speed of a modem is called data transfer rate or the symbol bit/s, sometimes abbreviated “bps”.
• Modern broadband modems are typically described in megabits.

Telephone lines relay and accept analog signals. Computers only relay and accept digital signals.

Question 7

What are the types of modems?

Answer 7

• > Dial - up modem.
• > DSL or Digital Subscriber Line modem.
• > Cable modem.
• > Wireless modem.

Question 8

How does a communication channel function?

Answer 8

• Carry the data from one comp to the other; essential element of every communication system.
• Physical and Wireless Connections.

Question 9

What are the physical connections?

Answer 9

• > Twister pair cable - two pairs of copper wire are twisted together.
• up to 1Mbps to 10Gbps.
• Telephone lines, Ethernet cables.
• > Coaxial cable - single solid copper wire.
• 80X more transmission capability than twister pair cables.
• Television cable.
• > Fibre optic cable - bundle of glass threads that use light to transmit data.
• 40 Gbps / 26,000X more transmission capability than twisted pair cables - but also a much higher cost.
• Widely used in high speed communications system.

Question 10

What are the wireless connections?

Answer 10

Infrared - use infrared light waves.
-> Within the range of 10 feet and in straight line.

Bluetooth - short range radio technology standard.
-> Range of 10 meters or 33 feet.

WiFi - uses radio wave to provide wireless high speed internet and network connections. Based on IEEE standard 802.11x.
-> Widely used in home, schools, campus and offices.

WiMAX (Worldwide Interoperability for Microwave Access) - use microwave connections to extend Wifi range. Based on IEEE standard 802.16.
-> Long-range wireless networking spanning distances miles or kilometers away.

LTE (Long Term Evolution) - cellular wireless connection, synonym to 4G for marketing purposes.
-> Theoretically data speed are 10 times faster than 3G.

Cellular radio - wireless transmission media that are used for mobile devices and mobile phones to transfer voice and data.
-> As long as a mobile phone in the network coverage is within a cell.

Microwave - used radio waves; a microwave transfer signal to another via straight line.
-> Installed on top of a building, towers or hills to avoid any obstruction.

Satellites - specialised wireless receiver-transmitter and sent to space by rocket and stationed in orbit around the earth.
-> More than 2000 satellites in orbit which was used by both government and private organisations.

Question 11

What are some communication services?

Answer 11

• Service provider that provides infrastructures for information to be transported from one device to another or through a network on the internet.
• > Leased Line - Telekom Malaysia.
• > Fiber-optic Service - Fibre Comm.
• > Satellite Connection Service - Thuraya.
• > Cellular Service Providers - Celcom, Maxis, Digi.

Question 12

How did the revolution of the cellular radio progress?

Answer 12

1980s 1G - analogue voice calls; mobile connectivity.
1990s 2G - digital voice calls; text messaging; basic data services.
2000s 3G - mobile broadband; introduction of smartphones.
2010s 4G - fast mobile broadband; uses internet protocol.
2020s 5G - enhanced mobile broadband; wireless for the industry.

Question 13

Why do computers need IP Addresses?

Answer 13

• Networks, and the internet, does not identify computers by the name user assigned to them.
• Computers prefer numbers, and the numbers they use as identifiers are called IP addresses.
• IP stands for “internet protocol” which is part of Transmission Control Protocol/internet Protocol (TCP/IP). IP for short and ICP/IP is how data is delivered.
• Domain Name Server (DNS) translates domain name into IP address.

Examples of IP Address - 255.255.255.255; to check = command prompt -> ipconfig.

Question 14

What are the specifications of data transmissions?

Answer 14

• Refers to the rules and procedures that coordinate the message transmitted between sending and retrieving devices across the channel.
• Several factors that affect data transmission which include bandwidth and network protocol.

Bandwidth

• > Refers to the amount of data that can pass through the communication channel in a given amount of time.
• > Measured in bits per second, most internet connections have a bandwidth on the scale of megabits per second.

Network protocols

• > Sets of established rules that dictate how to format, transmit and receive data.
• > From servers and routers to endpoints.
• > Transmission Control Protocol or Packetization is the process whereby:
• • Information are broken up into smaller packets.
• • Travel on different route (fast transmission).
• • Reassembled at the destination.

Question 15

What is a network?

Answer 15

• Interconnection between all devices in a network.
• Individual devices are known as a node.
• Computer not part of a network is called a stand alone computer.

Question 16

What are some basic network terms?

Answer 16

Nodes - any device connected to a network; laptop, printers, servers.

Clients - computers that access and use the network and share network resources.

Host - when there are two computer systems connected by modems and telephone lines.

• > System that contains the data is the host.
• > While the computer is at where the user requested data it is called the remote terminal.

Servers - computers that hold shared files, programs, and the one installed with network operating system.

Network administrator - person who is responsible to coordinate, maintain and ensure that a network is in an organization that is running smoothly and is up to date.

Question 16

What are some basic network terms?

Answer 16

Nodes - any device connected to a network; laptop, printers, servers.

Clients - computers that access and use the network and share network resources.

Host - when there are two computer systems connected by modems and telephone lines.

• > System that contains the data is the host.
• > While the computer is at where the user requested data it is called the remote terminal.

Servers - computers that hold shared files, programs, and the one installed with network operating system.

Network administrator - person who is responsible to coordinate, maintain and ensure that a network is in an organization that is running smoothly and is up to date.

Question 17

What are the advantages of a network?

Answer 17

1) Sharing resources: network makes it easy for everyone to access the same file and work on it together
2) Communication and collaboration: allows employees to share files, view other people’s work, and exchange ideas more efficiently.
3) Organization: variety of scheduling software is available that makes it possible to arrange meetings without constantly checking everyone’s schedules. Software includes other helpful features - shared address books and to-do lists.
4) Remote access: users are able to access the same file, data and messages even when they’re not in the office. This access can even be given to handheld devices.
5) Data protection: important task to back up a computer data regularly. Network makes it easier to back up all the company’s data at once, either to put them on an offsite server, a set of tapes, CDs or other backup system.

Question 18

What are the different types of networks?

Answer 18

Personal Area Network (PAN) -
covers a very small area, connects devices within a certain range and if a user moves outside that range, connection can be lost.
-> Connecting a smartphone to a laptop, tablet or other wireless devices.

Local Area Network (LAN) - computer network that links devices within a building or group of adjacent buildings. Especially with a radius less than 1km.
-> WLAN allows devices to communicate via WiFi but still within certain range.

Wireless LAN (WLAN) - LAN without using cables; alternative to a LAN that uses Ethernet cables.

• > Common in an office or large campus; wireless access point is used.
• > Any node that has a wireless connection devices such as a wireless network card will get into the WLAN by receiving the broadcast signal from the wireless access point.
• > WLAN would normally need a strong password - to avoid anyone from using it without permission.

Metropolitan Area Network (MAN) - used to link between office buildings in a city; comprises of several LANs working together.

• > Covers larger area than a LAN but smaller area than a WAN.
• > MAN may span in the range of 5 to 50 km in diameter.
• > MAN is operated by a service provider that provinces an Internet connection or cable television to a city.

Wide Area Network (WAN) - exists over a large-scale geographical area.

• > Biggest and widest network.
• > Connects all over the world.

Question 19

What are the hardware requirements for a Network?

Answer 19

Network interface card - connects computers to a local data network or the internet.

Network access point - a device that connects to a wired router, switch, or hub via an Ethernet cable, and projects a Wi-Fi signal to a designated area.

Wireless access point - device that broadcasts radio signals so that other wireless devices can receive the signals in order to access the network and the Internet.

• > Allows data from wireless devices to be transferred to wired devices.
• > Important to position the wireless access point at a strategic place so that surrounding devices can capture the signals.

Router - device that forwards data packets between computer networks - can connect networked computers to the Internet, so multiple users can share a connection.

Hubs - 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.
-> Only suitable for small networks.

Switch - device in a computer network that connects other devices together.
-> Multiple data cables are plugged into a switch to enable communication between different networked devices.

Question 20

There are three types of “nets” in an organizational network, what are they?

Answer 20

Intranet - private network, owned by a large company.
-> Only authenticated users of the organization can access the database system, directory and can distribute documents and workflow.

Extranet - private network designed to allow business partners and vendors to communicate in a virtual space.

Internet - largest network in the world.

Question 21

What are the things that you could install to protect your network?

Answer 21

Firewall - system designed to prevent unauthorised access to or from a private network.

• Monitors and controls the incoming and outgoing network traffic based on pre-setting rules.
• Performs actions such as blocking or filtering traffic before entering a private network.
• Eg. A company may limit the size of an attachment file from an incoming email. If the size is greater than the set rules, the email will bounce back to the sender.
• Can be hardware or software-based or both; should be placed at the first line of defense of any network.

IDS - also known as an intrusion detection system; software or hardware that analyses all network traffics.

• All devices connected to the network are being monitored by the system.
• Detects and alerts a system administrator to stop the suspicious attack.
• Alert goes to central system, log will be used to investigate whether a malicious activity was going on or it was a false alarm.
• Should be placed after the firewall.

Virtual Private Network (VPN) - secures connection over the internet between the employee’s computer and the company’s network.

• The user has access to the remote network after validation of credentials.
• Safer than using public network.