81. Which one of the following socket API functions converts an unconnected active TCP socket into a passive socket.
a. connect
b. bind
c. listen
d. accept
Answer: (c).listen

82. Packets of the same session may be routed through different paths in
a. TCP, but not UDP
b. TCP and UDP
c. UDP, but not TCP
d. Neither TCP, nor UDP
Answer: (b).TCP and UDP

83. The maximum window size for data transmission using the selective reject protocol with n-bit frame sequence numbers is:
a. 2^n
b. 2^(n-1)
c. 2^n – 1
d. 2^(n-2)
Answer: (b).2^(n-1)

84. Which of the following functionalities must be implemented by a transport protocol over and above the network protocol ?
a. Recovery from packet losses
b. Detection of duplicate packets
c. Packet delivery in the correct order
d. End to end connectivity
Answer: (d).End to end connectivity

85. Which of the following is not true about User Datagram Protocol in transport layer?
a. Works well in unidirectional communication, suitable for broadcast information
b. It does three way handshake before sending datagrams
c. It provides datagrams, suitable for modeling other protocols such as in IP tunneling or Remote Procedure Call and the Network File System
d. The lack of retransmission delays makes it suitable for real-time applications
Answer: (b).It does three way handshake before sending datagrams

86. Suppose two hosts use a TCP connection to transfer a large file. Which of the following statements is/are False with respect to the TCP connection?

1. If the sequence number of a segment is m, then the sequence
number of the subsequent segment is always m+1.
2. If the estimated round trip time at any given point of time
is t sec, the value of the retransmission timeout is always
set to greater than or equal to t sec.
3. The size of the advertised window never changes during the
course of the TCP connection.
4. The number of unacknowledged bytes at the sender is always
less than or equal to the advertised window
a. 3 only
b. 1 and 3 only
c. 1 and 4 only
d. 2 and 4 only
Answer: (b).1 and 3 only

87. A link has a transmission speed of 10^6 bits/sec. It uses data packets of size 1000 bytes each. Assume that the acknowledgment has negligible transmission delay, and that its propagation delay is the same as the data propagation delay. Also assume that the processing delays at nodes are negligible. The efficiency of the stop-and-wait protocol in this setup is exactly 25%. The value of the one-way propagation delay (in milliseconds) is ___________.
a. 4
b. 8
c. 12
d. 16
Answer: (c).12

88. Identify the correct order in which a server process must invoke the function calls accept, bind, listen, and recv according to UNIX socket API.
a. listen, accept, bind recv
b. bind, listen, accept, recv
c. bind, accept, listen, recv
d. accept, listen, bind, recv
Answer: (b).bind, listen, accept, recv

89. Assume that the bandwidth for a TCP connection is 1048560 bits/sec. Let α be the value of RTT in milliseconds (rounded off to the nearest integer) after which the TCP window scale option is needed. Let β be the maximum possible window size with window scale option. Then the values of α and β are
a. 63 milliseconds 65535 × 21^4
b. 63 milliseconds 65535 × 2^16
c. 500 milliseconds 65535 × 2^14
d. 500 milliseconds 65535 × 2^16
Answer: (c).500 milliseconds 65535 × 2^14

90. Consider the following statements.

I. TCP connections are full duplex.
II. TCP has no option for selective acknowledgment
III. TCP connections are message streams.
a. Only I is correct
b. Only I and II are correct
c. Only II and III are correct
d. All of I, II and III are correct
Answer: (a).Only I is correct