Computer Networking Fundamentals Practice Test Practice Tests

Question 1

Calculate the maximum data rate of a noiseless channel with a bandwidth of 3 kHz transmitting two signal levels. Use the Nyquist formula: $MaximumDataRate = 2 	imes Bandwidth 	imes log_2(Levels)$

Accepted Answer

6000 bits/second

Question 2

What is the Shannon-Hartley theorem used to calculate?

Accepted Answer

C. The maximum data rate of a noisy channel

Answer

A. The minimum bandwidth required for a signal

Answer

B. The signal-to-noise ratio of a channel

Answer

D. The propagation delay of a signal

Question 3

A channel has a bandwidth of 4 kHz and a signal-to-noise ratio (SNR) of 20 dB. Calculate the channel capacity using the Shannon-Hartley theorem: $C = B 	imes log_2(1 + SNR)$, where SNR is a ratio, not in dB. First convert SNR from dB to a ratio using $SNR_{ratio} = 10^{(SNR_{dB}/10)}$.

Accepted Answer

Approximately 26.63 kbps

Question 4

Which of the following is NOT a guided transmission medium?

Accepted Answer

D. Radio waves

Answer

A. Twisted pairs

Answer

B. Coaxial cables

Answer

C. Fiber optics

Question 5

Frequency Hopping Spread Spectrum (FHSS) is more resistant to narrowband interference than Direct Sequence Spread Spectrum (DSSS).

Accepted Answer

True

Answer

False

Question 6

Which of the following are advantages of fiber optic cables compared to copper cables? (Select all that apply)

Answer

A. Higher bandwidth

Answer

B. Lower attenuation

Answer

C. Immunity to electromagnetic interference

Answer

D. Lower cost

Question 7

Calculate the free space path loss in dB for a signal with a frequency of 2.4 GHz traveling a distance of 10 meters. Use the formula: $FSPL = 20log_{10}(d) + 20log_{10}(f) + 20log_{10}(\frac{4\pi}{c})$, where d is the distance in meters, f is the frequency in Hz, and c is the speed of light ($3 	imes 10^8$ m/s).

Accepted Answer

Approximately 60.08 dB

Question 8

A channel has a bit rate of 4 kbps and a propagation delay of 20 ms. For what range of frame sizes does Stop-and-Wait give an efficiency of at least 50%? Show your calculations using MathJax.

Accepted Answer

To achieve at least 50% efficiency with Stop-and-Wait, the transmission time must be at least equal to the propagation delay.  Let $L$ be the frame size in bits. The transmission time $T_t = \frac{L}{4000}$ seconds, and the propagation delay $T_p = 0.02$ seconds.  We need $T_t \geq T_p$, so $\frac{L}{4000} \geq 0.02$.  Therefore, $L \geq 4000 	imes 0.02 = 80$ bits. The frame size must be at least 80 bits.

Question 9

Consider a simplified stop-and-wait protocol where the sender sends a frame and waits for an ACK. Assume the probability of a frame being lost is $p$, and the probability of an ACK being lost is also $p$. What is the average number of transmissions required for a single frame to be successfully delivered and acknowledged? Use MathJax notation.

Accepted Answer

C. $\frac{1}{1-2p+p^2}$

Answer

A. $\frac{1}{1-p}$

Answer

B. $\frac{1}{1-p^2}$

Answer

D. $\frac{1}{p}$

Question 10

A 10 Mbps Ethernet link is being used to transmit data. The frame size is 1500 bytes. What is the maximum achievable throughput, taking into account the minimum interframe gap of 9.6 microseconds and the preamble of 8 bytes? Use MathJax notation.

Accepted Answer

B. Approximately 7.75 Mbps

Answer

A. Approximately 9.87 Mbps

Answer

C. Approximately 8.21 Mbps

Answer

D. Approximately 10 Mbps

Question 11

Which of the following are key considerations in the design of the Data Link Layer? Select all that apply.

Answer

Framing

Answer

Error Control

Answer

Flow Control

Answer

Addressing

Question 12

In CSMA/CD, after a collision, a station waits a random amount of time before retransmitting. The range from which the random time is chosen increases with each successive collision.

Accepted Answer

True

Answer

False

Question 13

Consider a slotted ALOHA network with $N$ stations. Each station attempts to transmit with probability $p$ in each slot. What is the probability that exactly one station succeeds in transmitting in a given slot? Express your answer using MathJax notation.

Accepted Answer

The probability that exactly one station succeeds is given by $P(	ext{1 success}) = Np(1-p)^{N-1}$.

Question 14

Consider a network employing distance vector routing. A node X has the following distance vector: D(X,A)=2, D(X,B)=5, D(X,C)=1. X receives updates from its neighbors A, B, and C with the following vectors:

*   From A: D(A,B)=4, D(A,C)=3
*   From B: D(B,A)=6, D(B,C)=2
*   From C: D(C,A)=1, D(C,B)=3

Calculate the new distance vector of X after applying the Bellman-Ford equation. Show your calculations for each destination.

Accepted Answer

D(X,A) = min(2, 1+1, 5+6, 1+1) = 2
D(X,B) = min(5, 2+4, 5+0, 1+3) = 4
D(X,C) = min(1, 2+3, 5+2, 1+0) = 1

Question 15

A router receives packets with different QoS requirements. Which packet scheduling algorithm prioritizes packets based on their class and ensures that higher priority packets are served before lower priority packets, but can lead to starvation?

Accepted Answer

A. Strict Priority Queueing

Answer

B. Weighted Fair Queueing

Answer

C. Round Robin

Answer

D. First-Come, First-Served

Question 16

Which of the following are key functions of the transport layer?

Answer

A. Providing reliable data transfer

Answer

B. Segmenting data for transmission

Answer

C. Routing packets across networks

Answer

D. Multiplexing and demultiplexing connections

Answer

E. Encrypting data for secure transmission

Question 17

In TCP, the receiver advertises its receive window to the sender, indicating the amount of free buffer space available. A zero window size indicates that the receiver cannot accept any more data at the moment.

Accepted Answer

True

Answer

False

Question 18

Consider a network where two autonomous systems (AS1 and AS2) are connected. AS1 has a policy to only accept traffic from AS2 if the destination is within AS1's address space. AS2 advertises a route to a prefix that is not within AS1's address space. Explain what will happen and why.

Accepted Answer

AS1 will reject the route advertisement from AS2 because it violates AS1's import policy. BGP routers in AS1 will not add the route to their routing table, and traffic destined for that prefix will not be routed through AS1.

Question 19

A network operator wants to implement differentiated services (DiffServ). They want to ensure that voice traffic receives preferential treatment over best-effort data traffic. Which DiffServ PHB (Per-Hop Behavior) would be most suitable for voice traffic?

Accepted Answer

B. Expedited Forwarding (EF)

Answer

A. Assured Forwarding (AF)

Answer

C. Best Effort (BE)

Answer

D. Class Selector (CS)

Question 20

Calculate the checksum for the following 16-bit words: 11001100 00000000, 10101010 11111111, 00001111 11110000. Show the steps.

Accepted Answer

1. Sum the words: 11001100 00000000 + 10101010 11111111 + 00001111 11110000 = 00111100 11101111 (with carry)
2. Add the carry: 00111100 11101111 + 1 = 00111100 11110000
3. Take the 1's complement: 11000011 00001111

Computer Networking Fundamentals Practice Test Practice Tests

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Computer Networking Fundamentals Practice Test

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