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111. A serial transmission Ti uses 8 information bits, 2 start bits, 1 stop bit and 1 parity bit for each character. A synchronous transmission T2 uses 3 eight bit sync characters followed by 30 eight bit information characters. If the bit rate is 1200 bits/second in both cases, what are the transfer rates of Ti and T2?
a. 100 characters/sec, 153 characters/sec
b. 80 characters/sec, 136 characters/sec
c. 100 characters/sec, 136 characters/sec
d. 80 characters/sec, 153 characters/sec
Answer: (c).100 characters/sec, 136 characters/sec

112. In a sliding window ARQ scheme, the transmitter's window size is N and the receiver's window size is M. The minimum number of distinct sequence numbers required to ensure correct operation of the ARQ scheme is
a. min (M, N)
b. max (M, N)
c. M + N
d. MN
Answer: (c).M + N

113. Which one of the following protocols is NOT used to resolve one form of address to another one?
a. DNS
b. ARP
c. DHCP
d. RARP
Answer: (c).DHCP

114. Identify the correct sequence in which the following packets are transmitted on the network by a host when a browser requests a webpage from a remote server, assuming that the host has just been restarted.
a. HTTP GET request, DNS query, TCP SYN
b. DNS query, HTTP GET request, TCP SYN
c. DNS query, TCP SYN, HTTP GET request
d. TCP SYN, DNS query, HTTP GET request
Answer: (c).DNS query, TCP SYN, HTTP GET request

115. A firewall is to be configured to allow hosts in a private network to freely open TCP connections and send packets on open connections. However, it will only allow external hosts to send packets on existing open TCP connections or connections that are being opened (by internal hosts) but not allow them to open TCP connections to hosts in the private network. To achieve this the minimum capability of the firewall should be that of
a. A combinational circuit
b. A finite automaton
c. A pushdown automaton with one stack
d. A pushdown automaton with two stacks
Answer: (d).A pushdown automaton with two stacks

116. Which protocol will be used to automate the IP configuration mechanism which includes IP address, subnet mask, default gateway, and DNS information?
a. SMTP
b. DHCP
c. ARP
d. TCP/IP
Answer: (b).DHCP

117. In Go–back 3 flow control protocol every 6th packet is lost. If we have to send 11 packets. How many transmissions will be needed ?
a. 10
b. 17
c. 12
d. 9
Answer: (b).17

118. What will be the total minimum bandwidth of the channel required for 7 channels of 400 kHz bandwidth multiplexed together with each guard band of 20 kHz?
a. 2800 khz
b. 2600 khz
c. 3600 khz
d. 2920 khz
Answer: (d).2920 khz

119. Which of the following is false:
a. Digital signature is used to verify that a message is authentic
b. Digital certificate is issued by a third party
c. Digital certificate ensures integrity of the message
d. Digital signature ensures non-repudiation
Answer: (c).Digital certificate ensures integrity of the message

120. The subnet mask for a particular network is 255.255.31.0. Which of the following pairs of IP addresses could belong to this network?
a. 172.57.88.62 and 172.56.87.233
b. 10.35.28.2 and 10.35.29.4
c. 191.203.31.87 and 191.234.31.88
d. 128.8.129.43 and 128.8.161.55
Answer: (d).128.8.129.43 and 128.8.161.55