Lower Layers : SYBCS : Computer Networks 1 : PYQ

 1 mark

Q. If a composite signal is composed of five sine waves of frequencies 100, 300, 500, 700 & 900 Hz. What is the bandwidth of the signal?

Answer: The bandwidth of a signal is defined as the difference between the highest and the lowest frequencies present in the signal. In this case, the highest frequency is 900 Hz and the lowest frequency is 100 Hz. Therefore, the bandwidth of the signal is 900 - 100 = 800 Hz.

Q. A telephone network is an example of a circuit switched network. State True/False.

Answer: True. A telephone network is an example of a circuit-switched network, where a dedicated communication path is established between two endpoints for the duration of the call.

--Q.  List the three types of MAC protocol.

Answer: The three types of MAC (Medium Access Control) protocols are:

Contention-based MAC protocol

Reservation-based MAC protocol

Hybrid MAC protocol

Q. What is the responsibility of Physical Layer ?

Answer: The physical layer is responsible for transmitting raw data bits over a communication channel. It defines the characteristics of the physical medium, such as the physical and electrical properties of the transmission medium, the type of modulation to be used, the encoding of data, and the synchronization of data transmission.

Q. What is bandwidth?

Answer: Bandwidth refers to the maximum amount of data that can be transmitted over a network connection in a given amount of time. It is usually measured in bits per second (bps), kilobits per second (kbps), or megabits per second (Mbps). Bandwidth is an important factor in determining the speed and performance of a network connection.

Q. What is congestion?

Answer: Congestion refers to the situation where the network becomes overloaded with too much traffic, which can cause delays, dropped packets, and other problems. Congestion can occur when there are more users trying to use a network than it can handle, or when there are network bottlenecks or other issues that limit the flow of data.

Q. Define Jitter.

Answer: Jitter refers to the variation in the delay of packets as they are transmitted over a network. It can cause problems with real-time applications like video streaming and voice over IP (VoIP), where a consistent delay is required to maintain a smooth and uninterrupted stream.

Q. Define Latency.

Answer: Latency refers to the amount of time it takes for a packet of data to travel from one point on a network to another. It is usually measured in milliseconds (ms), and can be affected by factors like distance, network congestion, and the quality of the network infrastructure.

Q.  What is acknowledgment policy of data link layer for congestion control?

Answer: The acknowledgment policy of the data link layer for congestion control involves the use of techniques like flow control and error control to ensure that packets are transmitted reliably and efficiently over the network. This helps to prevent congestion by limiting the amount of data that can be transmitted at any given time, and by detecting and correcting errors that can lead to packet loss or other problems.

Q. Describe the functions performed by data link layer.

Answer: The data link layer is responsible for managing the physical connection between devices on a network, and for ensuring the reliable transmission of data over that connection. Its functions include framing, which involves dividing data into packets and adding header and trailer information to each packet; error detection and correction, which involves detecting and correcting errors that may occur during transmission; flow control, which involves regulating the flow of data between devices to prevent congestion; and access control, which involves managing the sharing of the network bandwidth among multiple devices.

Q. List data representation forms or types.

Answer: Some common data representation forms or types include:

1.Binary (base 2)

2.Decimal (base 10)

3.Hexadecimal (base 16)

4.ASCII (American Standard Code for Information Interchange)

5.Unicode

6.Floating point

7.BCD (Binary-Coded Decimal)

Q.  List the cables used with Ethernet LAN.

Answer: Some of the cables used with Ethernet LAN include:

1. Twisted pair cables (such as Cat5, Cat5e, Cat6, and Cat7)

2.Coaxial cables (such as RG-6 and RG-58)

3.Fiber optic cables (such as single-mode and multi-mode fiber)

Q. If the bandwidth of the channel is 10 kbps, how long does it take to transmit a frame of 100000 bits ?

Answer: To calculate the time it takes to transmit a frame of 100000 bits over a channel with a bandwidth of 10 kbps, we can use the formula:

Time = Number of bits ÷ Bandwidth

Plugging in the values, we get:

Time = 100000 bits ÷ 10000 bits/s = 10 seconds

Therefore, it would take 10 seconds to transmit a frame of 100000 bits over a channel with a bandwidth of 10 kbps.

4 mark

Q. Calculate the total delay for a frame of size 5 million bits which is sent on a link with 10 routers, each having queuing time 2 µs and a processing time of 1 µs. The length of the link is 2000 km and speed of light is 2 × 108 m/s in the link. The link has bandwidth 5 mbps.

Answer: 

Assuming that the frame is transmitted using store-and-forward switching:

First, we can calculate the transmission delay:

Transmission delay = Size of the frame ÷ Bandwidth

Transmission delay = 5,000,000 bits ÷ 5,000,000 bits/s = 1 second

Next, we can calculate the propagation delay:

Propagation delay = Distance ÷ Speed of light

Propagation delay = 2,000,000 meters ÷ 2 × 10^8 meters/s = 0.01 seconds

Then, we can calculate the queuing delay for each router:

Queuing delay = Queuing time + Processing time

Queuing delay = 2 µs + 1 µs = 3 µs

Finally, we can calculate the total delay:

Total delay = Transmission delay + Propagation delay + (Number of routers x Queuing delay)

Total delay = 1 second + 0.01 seconds + (10 routers x 3 µs) = 0.031 seconds or 31 milliseconds

Therefore, the total delay for the frame would be approximately 31 milliseconds.

-Q. State the difference between LAN and WAN.

Answer: 

Point	LAN (Local Area Network)	WAN (Wide Area Network)
Definition	A network of devices that are located in the same geographic area, such as an office, building, or campus..	A network of devices that are spread over a large geographic area, such as a city, country, or even multiple countries.
Ownership	Typically owned and managed by a single organization, such as a company, school, or government agency.	May be owned and managed by multiple organizations or service providers.
Speed	High-speed connectivity with data transfer rates of up to 10 Gbps.	Lower data transfer rates due to the longer distance and multiple network components.
Cost	Lower cost due to the smaller network size and fewer network components.	Higher cost due to the larger network size and more network components.
Example	Home or small office networks, school or university networks, corporate networks.	The internet, wide-area corporate networks, telecommunications networks.

Q.  Explain the Data link protocols for noiseless channel.

Answer: Data link protocols for noiseless channels typically focus on ensuring the reliable transmission of data over the channel, while minimizing the overhead and delay introduced by the protocol itself. One common protocol for noiseless channels is the High-Level Data Link Control (HDLC) protocol, which uses a sliding window mechanism to manage flow control and error detection and correction. Other protocols for noiseless channels include Point-to-Point Protocol (PPP) and Serial Line Internet Protocol (SLIP).

Q.  Give the difference between WLAN and Bluetooth.

Answer:

Point	WLAN (Wireless Local Area Network)	Bluetooth
Range	Covers a larger area, typically several hundred feet or more.	Covers a smaller area, typically up to 30 feet.
Speed	High-speed connectivity with data transfer rates of up to 10 Gbps.	Lower data transfer rates, typically up to 1 Mbps.
Interference	Can be subject to interference from other wireless networks or electronic devices.	Uses frequency hopping to avoid interference from other wireless devices.
Power	Requires more power to operate due to the larger range and higher data transfer rates.	Uses less power, making it ideal for low-power devices such as headphones and smartwatches..
Use Case	Typically used to provide wireless connectivity in a larger area, such as a home or office building.	Often used to connect devices that are in close proximity, such as headphones, speakers, and smartwatches.

Q. What is Taxonomy for Media Access Protocol?

Answer: The Taxonomy for Media Access Protocol (T-MAP) is a framework for classifying different media access protocols used in communication networks. It categorizes media access protocols based on several factors, including the type of network topology used, the type of medium used for transmission (e.g., wired or wireless), and the access method used to manage the sharing of the medium among multiple devices (e.g., contention-based or reservation-based).

Q. Which are the methods of framing.

Answer: The methods of framing refer to the different ways in which data can be divided into frames for transmission over a network. Some common methods of framing include:

1. Byte-oriented framing: divides data into fixed-size frames based on the number of bytes in each frame.

2. Bit-oriented framing: divides data into variable-size frames based on the presence of specific bit patterns in the data stream.

3. Character-oriented framing: divides data into frames based on the presence of specific character patterns in the data stream.

Q.Write note on Circuit Switching.

Answer: Circuit switching is a networking technique in which a dedicated communication path is established between two devices for the duration of the communication session. This path is reserved exclusively for the use of the two devices, and is not shared with any other devices on the network. Circuit switching was widely used in traditional telephone networks, but has been largely replaced by packet switching in modern communication networks. One advantage of circuit switching is that it provides a predictable and reliable connection with guaranteed bandwidth and low latency.

Q. What is framing ? Explain any two framing methods with example

Asnwer: Framing refers to how information is presented or communicated to influence how people perceive or understand an issue or topic. The way information is framed can impact how people respond, think, and act.

Here are two examples of framing methods:

Gain-Framing: This framing method emphasizes the benefits or positive outcomes of a particular action or behavior. The goal is to encourage people to take action by highlighting the potential gains. For instance, a campaign to encourage people to quit smoking may use gain-framing by emphasizing the health benefits of quitting smoking such as better lung function, reduced risk of lung cancer, and improved overall health.

Loss-Framing: This framing method highlights the negative consequences or losses that may occur if a particular action or behavior is not taken. The goal is to motivate people to take action by emphasizing what they stand to lose if they don't act. For instance, an ad campaign for a health insurance company may use loss-framing by emphasizing the potential financial losses a person may face if they don't have adequate health insurance coverage, such as high medical bills or bankruptcy due to medical expenses.