Computer networks

Question 1

What is a computer network?

Answer 1

A computer network is a group of computers connected together using network cables. The computers are interlinked to exchange data.

Question 2

4 Types of computer networks:

Answer 2

Local Area Network (LAN)
Wide Area Network (WAN)
Metropolitan Area Network (MAN)
Personal Area Network (PAN)

Question 3

What is LAN?

Answer 3

Local Area Network is a type of network that spans over small geographical areas and is used for communication usually within an office premise or home.
LAN’s can be either wired or wireless.

Question 4

Characteristics of LANs:

Answer 4

-LAN’s enable the sharing of resources such as files or hardware devices that may be needed by multiple users.
Is limited in size, typically spanning a few hundred meters, and no more than a mile.
-Is fast, with speeds from 10 Mbps to 10 Gbps.
Requires little wiring, typically a single cable connecting to each device.
-Nodes in a LAN are linked together with a certain topology. These topologies include:
Bus
Ring
Star
-Requires little wiring, typically a single cable connecting to each device.
-Has lower cost compared to MAN’s or WAN’s.

Question 5

What is WAN?

Answer 5

A Wide Area Network is a type of network that covers a large geographic area such as country, continent or even whole of the world.

Question 6

Characteristics of WANs:

Answer 6

• A WAN is two or more LANs connected together. The LANs can be many miles apart.
• To cover great distances, WANs may transmit data over leased high -speed phone lines or wireless links such as satellites.
• Multiple LANs can be connected together using devices such as bridges, routers, or gateways, which enable them to share data.
• The world’s most popular WAN is the Internet.

Question 7

What is MAN?

Answer 7

A metropolitan area network (MAN) is a large computer network that usually spans a city or a large campus.

Question 8

Characteristics of MANs:

Answer 8

-A MAN is optimized for a larger geographical area than a LAN, ranging from several blocks of buildings to entire cities.
-A MAN might be owned and operated by a single organization, but it usually will be used by many individuals and organizations.
-A MAN often acts as a high speed network to allow sharing of regional resources.
-A MAN typically covers an area of between 5 and 50 km diameter.

Question 9

What is PAN?

Answer 9

A PAN is a network that is used for communicating among computers and computer devices (including telephones) in close proximity of around a few meters within a room.

Question 10

Characteristics of PANs:

Answer 10

-It can be used for communicating between the devices themselves, or for connecting to a larger network such as the internet.
-The devices may or may not belong to the person in question. The reach of a PAN is typically a few meters.
PAN’s can be wired or wireless.

Question 11

Advantages of Computer Networks:

Answer 11

• Sharing devices such as printers saves money.
• Files can easily be shared between users.
• Network users can communicate by email and instant messenger.
• Security is good - users cannot see other users’ files unlike on stand-alone machines.
• Data is easy to backup as all the data is stored on the file server.

Question 12

Disadvantages of Computer Networks:

Answer 12

• Purchasing the network cabling and file servers can be expensive.
• Managing a large network is complicated, requires training and a network manager usually needs to be employed.
• If the file server breaks down the files on the file server become inaccessible. Email might still work if it is on a separate server. The computers can still be used but are isolated.
• Viruses can spread to other computers throughout a computer network.
• There is a danger of hacking, particularly with wide area networks. Security procedures are needed to prevent such abuse, e.g. a firewall.

Question 13

What is a File Server?

Answer 13

It is a computer attached to a network responsible for shared access of all the documents. It is responsible for the central storage and management of data files so that other computers on the same network can access the files.

Question 14

What is an application server?

Answer 14

An application server is a type of server designed to install, operate and host applications and associated services for end users, IT services and organizations.

Question 15

What is a Proxy server?

Answer 15

A proxy server is a computer that offers a computer network service to allow clients to make indirect network connections to other network services.

Question 16

What is a Print Server?

Answer 16

A network print server is a dedicated server that connects a printer to a network.

Question 17

Network Devices:

Answer 17

Modems
Network Hubs
Switches
Bridges
Routers
HTTP Proxy servers 
Network Interface Cards (NIC)

Question 18

What is a modem?

Answer 18

A modem is a network device that both modulates and demodulates analog carrier signals for encoding and decoding digital information for processing.
It allows computers to communicate over telephone wires or cables.

Question 19

What is a network hub?

Answer 19

It is a common connection point for devices in a network.
Hubs are commonly used to connect segments of a LAN.
A 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.

Question 20

What is a switch?

Answer 20

It is a device that filters and forwards packets between LAN segments.
A switch determines the source and destination device of each packet and forwards data only to the specific device.

Question 21

What is a bridge?

Answer 21

A network bridge is software or hardware that connects two or more networks so that they can communicate.

Question 22

What is a router?

Answer 22

Routers are small physical devices that join multiple networks together.
They forward data packets between computer networks.

Question 23

What are HTTP proxy servers?

Answer 23

It is a server that sits between a client application, such as a Web browser, and a real server. It intercepts all requests to the real server to see if it can fulfill the requests itself. If not, it forwards the request to the real server.

Question 24

What is NIC?

Answer 24

Any computer that is to be connected to a network needs to have a network interface card (NIC). Most modern computers have these devices built into the motherboard, but in some computers you have to add an extra expansion card (small circuit board).

Question 25

Homework:

Answer 25

Conduct a research work on Network Topologies.

Make printouts of the diagrams alongside with their characteristics.