CN Data Link Layer

Question 41

Data transmitted on a link uses the following 2D parity scheme for error detection: Each sequence of 28 bits is arranged in a 4×7 matrix (rows r₀ through r₃, and columns d₇ through d₁) and is padded with a column d₀ and row r₄ of parity bits computed using the Even parity scheme. Each bit of column d₀ (respectively, row r₄) gives the parity of the corresponding row (respectively, column). These 40 bits are transmitted over the data link.

The table shows data received by a receiver and has n corrupted bits. What is the mini­mum possible value of n?

• 1
• 2
• 3
• 4

Question 42

Suppose that the one-way propagation delay for a 100 Mbps Ethernet having 48-bit jamming signal is 1.04 micro-seconds. The minimum frame size in bits is:

• 112
• 160
• 208
• 256

Question 43

Which of the following statement is False about the efficiency of the given channel?

• If we want to send big packets on the channel, then Stop and Wait is good choice.
• If length of packet increases, efficiency of channel also increases.
• Distance between sender and receiver is directly proportional to efficiency of channel.
• Efficient might be less if capacity of channel is high.

Question 44

Consider a simple communication system where multiple nodes are connected by a shared broadcast medium (like Ethernet or wireless). The nodes in the system use the following carrier-sense the medium access protocol. A node that receives a packet to transmit will carrier-sense the medium for 5 units of time. If the node does not detect any other transmission in this duration, it starts transmitting its packet in the next time unit. If the node detects another transmission, it waits until this other transmission finishes, and then begins to carrier-sense for 5 time units again. Once they start to transmit, nodes do not perform any collision detection and continue transmission even if a collision occurs. All transmissions last for 20 units of time. Assume that the transmission signal travels at the speed of 10 meters per unit time in the medium. Assume that the system has two nodes P and Q, located at a distance d meters from each other. P starts transmitting a packet at time t = 0 after successfully completing its carrier-sense phase. Node Q has a packet to transmit at time t = 0 and begins to carrier-sense the medium. The maximum distance d (in meters, rounded to the closest integer) that allows Q to successfully avoid a collision between its proposed transmission and P’s on going transmission is _______ . Note -This was Numerical Type question.

• 50
• 150
• 20
• 60

Question 45

Which of the following devices takes data sent from one network device and forwards it to the destination node based on MAC address ?

• Hub
• Modem
• Switch
• Gateway

Question 46

The number of bits used for addressing in Gigabit Ethernet is __________.

• 32 bit
• 48 bit
• 64 bit
• 128 bit

Question 47

Suppose we want to download text documents at the rate of 100 pages per second. Assume that a page consists of an average of 24 lines with 80 characters in each line. What is the required bit rate of the channel?

• 192 kbps
• 512 kbps
• 1.248 Mbps
• 1.536 Mbps

Question 48

If a file consisting of 50,000 characters takes 40 seconds to send, then the data rate is __________.

• 1 kbps
• 1.25 kbps
• 2 kbps
• 10 kbps

Question 49

Match the following Layers and Protocols for a user browsing with SSL :

• (1)
• (2)
• (3)
• (4)

Question 50

The maximum size of the data that the application layer can pass on to the TCP layer below is __________. (A) 2¹⁶ bytes (B) 2¹⁶ bytes + TCP header length (C) 2¹⁶ bytes - TCP header length (D) 2¹⁵ byte.

• (1), (2) and (4)
• (2) and (4)
• (2), (3) and (4)
• All option are correct.