Informatics Practices Class XII

Informatics Practices Class XII Chapter 1 Solutions.

Chapter 1 Back Exercise Solutions

COMPUTER NETWORKING

MULTIPLE CHOICE QUESTIONS

1. Which of the following topologies is a combination of more than one topologies?

a. Bus             b. Tree

c. Star             d. None of these

2. Which of the following is used for wireless communication?

a. Optical Fiber         b. UTP cable

c. Radio Waves       d. Coaxial Cable

3. Which of the following is not a transmission medium?

a. Telephone Network         b. Coaxial Cable

c. Modem                              d. Microwaves

4. IP addresses of two computers on a network:

a. Can be the same             b. Cannot be the same

c. Are not defined                d. Must match with a third computer

5. Bluetooth can be used for

a. Long distance communication b. Short distance communication

c. In mobile phones only                d. None of the above

6. Micro waves are

a. Uni directional    b. Omni directional

c. Guided media       d. Not used for communication.

7. Snooping is

a. A threat to data security                       b. Not a threat to data security

c. Good for laptops                           d. A topology

8. A repeater

a. Regenerates the received signal       b. Destroys the received signal

c. Can be used as a hub                            d. None of the above

9. Satellite links are generally used for

a. PANs         b. LANs

c. MANs         d. All of the above

10. A domain name maps to

a. A URL                    b. An IP address

c. A website               d. All of the above

ANSWER THE FOLLOWING QUESTIONS

1.    1. What is a computer network? What are its advantages?

Ans.    A computer network is a collection of interconnected computers and other

devices which are able to communicate with each other and share hardware

and software resources.

A few of these advantages are:

Resource Sharing

Cost saving

Collaborative user interaction

Time saving

Increased storage

2. What is meant be communication channels? Give two examples of guided media and two examples of unguided media.

Ans. A medium of data transmission over a computer network is called a channel or a transmission medium. Channels may be guided (wired) or unguided (wireless).

Guided Media are Twisted Pair Cable, Co-axial Cable, and Optical Fiber Cable.

Unguided Media are Radio Waves, Microwaves, Bluetooth.

3. Which communication channel(s) is/are suitable in each of the following situations:

a. Setting up a LAN

Wired, Guided, Twisted Pair Cable.

b. Transfer of data from a laptop to a mobile phone.

Wireless, Unguided, Bluetooth.

c. Transfer of data from one mobile phone to another.

Wireless, Unguided, Bluetooth.

d. Creating a remote control that can control multiple devices in a home.

Wireless, Unguided, Infra Red.

e. Very fast communication between two offices in two different countries.

Wireless, Unguided, Satellite links.

f. Communication in a hilly area

Wireless, Unguided, Radio Waves. .

g. Communication within a city and its vicinity where cost of cabling is too high.

Wireless, Unguided, Micro Waves

4. Why is a switch called an intelligent hub?

Ans.: A Switch is an intelligent device that connects several nodes to form a network

and redirects the received information only to the intended node(s). its work faster then the hub.

5. When is a repeater used in a computer network?

Ans.: When the data is transmitted over a network for long distances, the data

signal gets weak after certain distance. some device is required which can re-strengthen the data signal before it gets too weak. Repeater is such a device.

6. Diagramatically show how would you connect 6 PCs, 1 server, 1 printer, and 2

scanners in

a. Star topology        b. Bus topology

7. Two engineers in the same room have connected their Palm-tops using bluetooth for working on a Group presentation. Out of the following, what kind of Network have

they formed?

LAN, MAN, PAN, WAN

8. What is a MAC address? What is the difference between a MAC address and an IP

address?

Ans. : Each NIC has a universally unique address assigned to it by its manufacturer. This address is known as the MAC (Media Access Control) address of the card.

Difference between MAC Address and IP is that MAC addresses are 12-digit hexadecimal (or 48 bit) numbers. Example: MM-MM-MM-SS-SS-SS The first half (MM:MM:MM) of a MAC address contains the ID number of the adapter manufacturer. The second half (SS:SS:SS) of a MAC address represents the serial number assigned to the adapter (NIC) by its manufacturer.

An IP address is a group of four bytes (or 32 bits) each of which can be a number

from 0 to 255. A typical IP address looks like this: 59.177.134.72

9. Give some examples of domain names and URLs. How is a domain name different

from a URL?

Ans: http://www.cbse.nic.in/welcome.htm  is a URL and in this www.cbse.nic.in is a domain name. A domain name usually has more than one parts: top level domain name or primary domain name and sub-domain name(s). For example, in the domain name , in is the primary domain name; nic is the sub-domain of in; cbse is the sub-domain of nic. URL is the path through which we can open the website in a web browser.

10. What is domain name resolution?

Ans: Domain Name Resolution is the process of getting the corresponding IP address from a domain name.

11. Define Network security? What kind of attacks can be made on data and computer

networks?

Ans: The term Network Security refers to all activities undertaken to protect a computer network from attacks to its security. This covers protection of computers in the premises and data on the network from both internal and external attacks.

Attacks on network security are as follows:

1. Denial of service attacks:

2. Intrusion Problems:

3. Snooping

4. Eavesdropping

12. List some methods which are used for network security.

Ans:

Some methods used for network security are:

1.    Login Password.

2.    Firewall.

3.    Anti Virus Software.

4.    File Permissions.

13. Differentiate (with examples wherever possible) between :

a. LAN and MAN                  b. MAN and WAN

c. Hub and Switch               d. Guided and Unguided media

Ans:

LAN and MAN:

A LAN (local area network) is a group of computers and network devices connected together, usually within the same building. By definition, the connections must be high speed and relatively inexpensive (e.g., token ring orEthernet).

A MAN (metropolitan area network) is a larger network that usually spans several buildings in the same city or town.

MAN and WAN

A WAN (wide area network), in comparison to a MAN, is not restricted to a geographical location, although it might be confined within the bounds of a state or country. A WAN connects several LANs, and may be limited to an enterprise (a corporation or an organization) or accessible to the public. The technology is high speed and relatively expensive. The Internet is an example of a worldwide public WAN.

A MAN (metropolitan area network) is a larger network that usually spans several buildings in the same city or town.

Hub and Switch:

A Switch is an intelligent device that connects several nodes to form a network

and redirects the received information only to the intended node(s). its work faster then the hub.

A Hub is an electronic device that connects several nodes to form a network and

redirects the received information to all the connected nodes in broadcast mode.

Guided and Unguided media

Guided media is also know as wired media. A number of various types of cables are used to transfer data over computer networks. These are Twisted Pair Cable, Co-axial Cable, and Optical Fiber Cable.

Unguided media is also know as wireless Media. Electromagnetic waves are used for wireless communication over computer networks. Frequencies of waves are measured in Hertz (Hz). These categories are (in increasing order of frequencies): radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and Gamma rays.

14. Write one advantage of star topology over bus topology and one advantage of bus topology over star topology.

Characteristics of Star topology:

It is more efficient topology as compared to bus topology.

It is easy to install

It is easy to diagnose the fault in Star topology.

It is easy to expand depending on the specifications of central hub/switch

Characteristics of Bus topology:

It is easy to install.

It requires less cable length and hence it is cost effective.

15. Ishika Industries has set up its new production unit and sales office at Ranchi. The

company compound has 4 buildings as shown in the diagram below:

Distances between these buildings are as follows:

Administrative Office to Factory A             150 m

Factory A to Factory B                                 50 m

Factory B to Sales Office                            100m

Sales Office to Administrative office        200m

Administrative Office to Factory B             125 m

Number of Computers in each of the buildings is follows:

Administrative Office           15

Factory A                               25

Factory B                               18

Sales Office                          15

1. Suggest a cable layout of connections between the buildings so that each building is directly connected to Administrative Office.

Star Topology.

2. Suggest the most suitable place (i.e. building) to house the server of this production unit with a suitable reason.

Administrative Office because it is directly connected to all other building.

3. Suggest the placement of the following devices with justification:

(i) Repeater

(ii) Hub/Switch

Administrative Office to Factory A             150 m             Switch

Factory A to Factory B                                 50 m               Switch

Factory B to Sales Office                            100m              Switch

Sales Office to Administrative office        200m              Repeater

Administrative Office to Factory B             125 m             Switch

4. The Administrative office of this unit is to be linked with the head office situated in

Patiala (Punjab). What will be the most economical way to do this? Justify your

answer.

WAN we can connect administrative office to head office using internet. Reasons are internet is cheaper and also the distance between the 2 offices is more.

LAB EXERCISES

TEAM BASED TIME BOUND EXERCISES

1.    Find the IP addresses of at least five computers in your school.

Command to find the IP address of a computer is ipconfig. To run this command open cmd (Command Prompt) and the type ipconfig there you will find the ip address of a machine.

2. Find the MAC addresses of at least 2 computers in your lab. Then verify their

manufacturer's name on the net.

Command to find the MAC address of a computer is ipconfig /all. To run this command open CMD and type ipconfig /all. In the output you will find the option called Physical Address this is called MAC Address.

3. Find the layout of LAN in your school's labs. If you think some modifications can be done in the layout, note these down in your notebook.

In our school we are using Star topology.

4. Find the name of Internet Service Provider of your school.

iBerry.

5.    Find the IP address of your school's web site.

To find the ip address of a website open whois.net website and type the website name, here you will get all the details of that website.

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