CN |Gate-2016| Previous Year Questions| Set-5

Set-15 GATE-2006 CN

CN |Gate-2016| Computer Networks

1. Which one of the following protocols is NOT used to resolve one form of address to another one? [GATE – 2016]

a. DNS
b. ARP

Answer : c)

2. Which of the following is/are example(s) of stateful application layer protocols? [GATE – 2016]

(i) HTTP
(ii) FTP
(iii) TCP
(iv) POP3

a. (i) and (ii) only
b. (ii) and (iii) only
c. (iv) only
d. (ii) and (iv) only

Answer : d)
CN |Gate-2016|

3. Consider that B wants to send a message m that is digitally signed to A. Let the pair of private and public keys for A and B be denoted by Kx and Kx+ for x = A,B, respectively. Let Kx(m)  represent the operation of encrypting m with a key Kx and H(m) represent the message digest. Which one of the following indicates the CORRECT way of sending the message m along with the digital signature to A? [GATE – 2016]

a. {m, KB+ (H (m) ) }
b. {m, KB (H (m) ) }
c. {m, KA (H (m) ) }
d. {m, KA+  (m) }

Answer : b)

4. An IP datagram of size 1000 bytes arrives at a router. The router has to forward this packet on a link whose MTU (maximum transmission unit) is 100 bytes. Assume that the size of the IP header is 20 bytes.

The number of fragments that the IP datagram will be divided into for transmission is _________. [GATE – 2016]

a. 13
b. 14
c. 15
d. 16

Answer : a)

5. For a host machine that uses the token bucket algorithm for congestion control, the token bucket has a capacity of 1 megabyte and the maximum output rate is 20 megabytes per second. Tokens arrive at a rate to sustain output at a rate of 10 megabytes per second. The token bucket is currently full and the machine needs to send 12 megabytes of data. The minimum time required to transmit the data is seconds _________. [GATE – 2016]

a. 1.1 sec
b. 1.2 sec
c. 1.3 sec
d. 1.4 sec

Answer : a)

6. A sender uses the Stop-and-Wait ARQ protocol for reliable transmission of frames. Frames are of size 1000 bytes and the transmission rate at the sender is 80 Kbps (1Kbps = 1000 bits/second). Size of an acknowledgement is 100 bytes and the transmission rate at the receiver is 8 Kbps. The one-way propagation delay is 100 milliseconds.

Assuming no frame is lost, the sender throughput is _________ bytes/second. [GATE – 2016]

a. 2500
b. 2501
c. 2502
d. 2503

Answer : a)

7. Anarkali digitally signs a message and sends it to Salim. Verification of the signature by Salim requires : [GATE – 2016]

a. Anarkali’s public key.
b. Salim’s public key.
c. Anarkali’s private key.
d. Salim’s private key.

Answer : a)

8. In an Ethernet local area network, which one of the following statements is TRUE? [GATE – 2016]

a. A station stops to sense the channel once it starts transmitting a frame.
b. A station continues to transmit the packet even after the collision is detected.
c. The exponential backoff mechanism reduces the probability of collision on retransmissions.
d. The purpose of the jamming signal is to pad the frames that are smaller than the minimum frame size.

Answer : c)
CN |Gate-2016|

9. 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. [GATE – 2016]

a. HTTP GET request, DNS query, TCP SYN
b. DNS query, TCP SYN, HTTP GET request
c. TCP SYN, DNS query, HTTP GET request
d. DNS query, HTTP GET request, TCP SYN

Answer : b)

10. A network has a data transmission bandwidth of 20 × 106 bits per second. It uses CSMA/CD in the MAC layer. The maximum signal propagation time from one node to another node is 40 microseconds. The minimum size of a frame in the network is _________ bytes. [GATE – 2016]

a. 200
b. 201
c. 202
d. 203

Answer : a)

11. For the IEEE 802.11 MAC protocol for wireless communication, which of the following statements is/are TRUE? [GATE – 2016]

I. At least three non-overlapping channels are available for transmissions.
II. The RTS-CTS mechanism is used for collision detection.
III. Unicast frames are ACKed.

a. ll I, II, and III
b. I and III only
c. II and III only
d. II only

Answer : b)


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