CBSE Class 12 Computer Science Computer Networks Worksheet Set A

Question. The number of bits transmitted per second is called _________.
a. Bit rate
b. Baud rate
c. Data rate
d. Transfer rate
Answer. A

Question. The messages sent over a network is divided into small pieces called _________.
a. Units
b. Chunks
c. Packets
d. Bits
Answer. C

Question. A _______________ is established in circuit switching before actual communication.
a. Switch
b. Link
c. Protocol
d. Hub
Answer. B

Question. The ____________ is the difference between upper and lower frequencies of a communication medium.
a. Bandwidth
b. Data rate
c. Latency
d. communication speed
Answer. A

Question. The unit of Bandwidth is?
a. Khz
b. Hz
c. Watt
d. KW
Answer. B

Question. For every device connected to a network, there will be a unique ______________.
a. Name
b. ID
c. IP Address
d. IC
Answer. C

Question. Which one of the following devices will you suggest for connecting all the computers within each block of a building?
a. Switch/Hub
b. Modem
c. Telephone
d. Repeateri
Answer. A

Question. What is the name of the browser developed and released by Google?
a) Chrome
b) Googly
c) Heetson
d) Titanium
Answer. A

Question. Which of the following is a Web Browser?
a) MS-office
b) Notepad
c) Firefox
d) Word 2007
Answer. C

Question. The other name for communication medium is:
a. Channel
b. Source
c. Hub
d. Switch
Answer. A

Question. In your school there is a library, and you can use the internet to do research, this library will most likely be a WAN network?
a. True
b. False
Answer. A

Question. Types of Networks are Categories by their Geographical Area cover?
a. True
b. False
Answer. A

Question. Metropolitan Area Network Normally Require an Internet connection?
a. True
b. False
Answer. A

Question. Who invented the WWW in 1989?
Answer. Tim Berners-Lee

Question. Special software’s that is used to view webpages are ____________
Answer. Web browsers

Question. ________ are used to store webpages, so whenever a request, it will serve the request.
Answer. Web servers

Question. ____________ are programs /computers used to store information’s in the form of webpages.
Answer. Web servers

Question. Name any two common web browsers.
Answer. Google Chrome, Mozilla Firefox

Question. Internet can be used to get reservation of trains and air planes through _______ service.
Answer. E-reservation

Question. ___________ helps to create and maintain social relationship over web.
Answer. Social networking websites

Question. Give examples for Wired media and Wireless media.
Answer. Wired media: Optical Fiber cable Wireless media: Microwaves, Radio waves

Question. Name the device which connects multiple nodes to form a network. It redirects the received information only to the intended node(s).
Answer. Switch

Question. Web pages that are linked to each other via __________
Answer. hyperlinks

Question. Define modulation?
Answer. Modulation is a process of changing the characteristics of the carrier wave by super imposing the message signal on a high frequency signal.

Question. What is IP?
Answer. IP is a connectionless protocol responsible for providing addresses of each computer and performing routing.

Question. What do you mean by amplitude?
Answer. The amplitude of a wave is its maximum disturbance from its undisturbed position.

Question. What is demodulation? 
Answer. Demodulation is the reverse process of modulation where data is extracted from the received signal. 

Question. Define frequency?
Answer. The frequency of a wave is the number of waves produced by a source per second.

Short Answer

Question. What is modulation process?
Answer. A carrier wave by itself does not carry much information. To include a message, another wave, a message signal, that carries the data to be transmitted needs to be imposed on top of the carrier signal, this process is known as modulation. Modulation alters the shape of a carrier wave to encode the speech or data information that is to be carried. The main function of the carrier wave is to carry the audio and video signal from the transmitter to the receiver.

Question. What do you understand by collision in wireless network?
Answer. A network collision occurs when two or more devices attempt to transmit data over a network at the same time. For example, if two computers on an Ethernet network send data at the same moment, the data will "collide" and not finish transmitting.

Question. How full duplex is different from half duplex?
Answer. In full duplex mode, the signal is sent in both directions at the same time. In simplex mode, only one device can transmit the signal whereas in half duplex mode, both devices can transmit the signal, but one at a time.

Question. What is error detection?
Answer. Error detection refers to the techniques used to detect noise or other impairments introduced into data while it is transmitted from source to destination. Error detection ensures reliable delivery of data across vulnerable networks.

Question. Distinguish between routing and routing table?
Answer. Routing is the process of efficiently selecting a path in a network along which the data packets will travel to their destination where as a routing table is a table maintained by routers that maintains routing information based on which router determines the best path to reach to a network.

Long Answer

Question. What are the types of modulation techniques?
Answer. Modulation is a technique in which some characteristics of a carrier signal is varied in accordance with a message signal. The two major techniques of modulation:
1. Amplitude modulation: The amplitude of a wave is its maximum disturbance from its undisturbed position. It is measured in the form of the height of the wave. In amplitude modulation the strength of the carrier signal i.e., the amplitude is varied as per the changes in the amplitude of the modulating signal. It is the technique in which the amplitude of the carrier signal is varied in line with the variations in the intensity of the modulating signal, i.e., the message and the resultant signal is the modulated signal. The overall amplitude or envelope of the carrier is modulated to carry the actual message.
2. Frequency modulation: The frequency of a wave is the number of waves produced by a source, per second. It is measured as the number of waves that pass a certain point in one second. In frequency modulation the frequency of the carrier signal is varied as per the changes in the amplitude of the modulating signal. With the frequency modulation, the frequency of the carrier wave is shifted proportionally to the intensity of the modulating signal. The frequency modulated wave is shifted continuously.

Question. What is CSMA/CA and how it works?
Answer. Carrier-sense multiple access with collision avoidance (CSMA/CA) in computer networking, is a network multiple access method in which carrier sensing is used, but nodes attempt to avoid collisions by beginning transmission only after the channel is sensed to be "idle". The basic working principle of CSMA/CA is:
1. Node ready to transmit or talk.
2. Listen for other nodes, if any transmission is taking place. One of the two possibilities are:
a. Busy: A transmission is taking place, we have to perform following steps:
- Increase back off or wait time.
- Sleep as per binary exponential back off (BEB).
- Wake up and go to step 1.
b. Free: No transmission is taking place, we have to perform the following steps:
- Send message.
- Verify it proper transmission has taken place using one of the following two methods:
- Acknowledgement method.
- Request to send or clear to send method.

Question. What are the advantages and disadvantages of single and two dimensional parity checking techniques?
Answer. Advantages of Single dimensional parity checking are:
1. It is a simple mechanism which is easy to implements.
2. It is an inexpensive technique for detecting the errors in data transmission. Disadvantages of single Dimensional parity checking are:
1. It can detect only single bit errors which occur rarely.
2. In the data transmitted two bits get interchanged, then even though the data gets affected, but the parity bit will remain correct. Advantages of two dimensional parity checking are: 1. It is more efficient than single dimensional parity technique.
2. It can detect multiple bit errors also, which sometimes single dimensional parity checking technique cannot.
Disadvantages of two dimensional parity checking are:
1. It cannot detect compensating multiple bit errors.
2. This technique cannot detect 4 or more bit errors in some cases.

Question. Explain checksum?
Answer. Checksum refers to a sum of some bits calculated from digital data that is used to ensure the data integrity at the receiver’s end. The checksum is calculated as per as a specific scheme and is used for error checking in computer networks. The checksum error detection scheme works as:
At the sender mode, before transmission:
1. The data being transmitted is divided into equal sized k number of segments where each segment contains m number of bits.
2. The divided k segments are added using 1’s complement arithmetic and extra bits are added back to the sum.
3. The final sum’s complement is calculated, this is the checksum.
4. Now all the data segments is sent along with the checksum.
At the receiver mode, after transmission:
5. Step 2 is repeated at the receiver’s end i.e., all the data segments are added using 1’s complement arithmetic to get the new sum.
6. This calculated new sum is added with the received checksum and then complemented.
- If the result is all 0 the transmission is successful that means there is no error-accept the data.
- If the result is not all 0 then the transmission is with error – reject the data.

Question. Explain TCP?
Answer. The TCP suite is the current de facto standard for both local and wide area networking. TCP is used as the primary or sole communication protocol on nearly all new computer networks. TCP ensures reliable communication and uses ports to deliver packets. It is a connection oriented protocol. TCP also fragments and reassembles messages, using a sequencing function to ensure that packets are reassembled in the correct order. In TCP a connection must be built using a handshake process before information is sent or received. A handshake process means establishing a direct connection between sender and receiver with the start signal, acknowledgement signals etc. TCP is a connection-oriented protocol, which means a connection is established and maintained until the application programs at each end have finished exchanging messages. It determines how to break application data into packets that networks can deliver, sends packets to and accepts packets from the network layer, manages flow control, and—because it is meant to provide error-free data transmission—handles retransmission of dropped or garbled packets as well as acknowledgement of all packets that arrive.