Transport Layer

Question 31

Generally TCP is reliable and UDP is not reliable. DNS which has to be reliable uses UDP because

• UDP is slower
• DNS servers has to keep connections
• DNS requests are generally very small and fit well within UDP segments
• None of these

Question 32

Station A uses 32 byte packets to transmit messages to Station B using a sliding window protocol. The round trip time delay between A and B is 40 ms and the bottleneck bandwidth on the path A and B is 64 kbps. What is the optimal window size that A should use?

• 5
• 10
• 40
• 80

Question 33

Suppose there are n stations in a slotted LAN. Each station attempts to transmit with a probability P in each time slot. The probability that only one station transmits in a given slot is _______.

• nP(1 – P)^{n – 1}
• nP
• P(1 – P)^{n – 1}
• n^P(1 – P)^{n – 1}

Question 34

What is the maximum size of data that the application layer can pass on to the TCP layer below?

• Any size
• 2¹⁶ bytes - size of TCP header
• 2¹⁶ bytes
• 1500

Question 35

An ACK number of 1000 in TCP always means that

• 999 bytes have been successfully received
• 1000 bytes have been successfully received
• 1001 bytes have been successfully received
• None of the above

Question 36

Consider the following statements : A. High speed Ethernet works on optic fiber. B. A point to point protocol over Ethernet is a network protocol for encapsulating PPP frames inside Ethernet frames. C. High speed Ethernet does not work on optic fiber. D. A point to point protocol over Ethernet is a network protocol for encapsulating Ethernet frames inside PPP frames. Which of the following is correct ?

• A and B are true; C and D are false.
• A and B are false; C and D are true.
• A, B, C and D are true.
• A, B, C and D are false.

Question 37

Suppose you are browsing the world wide web using a web browser and trying to access the web servers. What is the underlying protocol and port number that are being used?

• UDP, 80

• TCP, 80

• TCP, 25

• UDP, 25

Question 38

If link transmits 4000 frames per second and each slot has 8 bits, the transmission rate of circuit of this TDM is ______.

• 64 Kbps
• 32 Mbps
• 32 Kbps
• 64 MbpS

Question 39

Which algorithm is used to shape the bursty traffic into a fixed rate traffic by averaging the data rate?

• solid bucket algorithm
• spanning tree algorithm
• hocken helm algorithm
• leaky bucket algorithm

Question 40

The protocol data unit for the transport layer in the internet stack is

• segment
• message
• datagram
• frame