Miscellaneous Topic In Computer networks QUIZ PYQ GATE CS

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Question 1

Which of the following transport layer protocols is used to support electronic mail?

  • SMTP

  • IP

  • TCP

  • UDP

Question 2

Consider the diagram shown below where a number of LANs are connected by (transparent) bridges. In order to avoid packets looping through circuits in the graph, the bridges organize themselves in a spanning tree. First, the root bridge is identified as the bridge with the least serial number. Next, the root sends out (one or more) data units to enable the setting up of the spanning tree of shortest paths from the root bridge to each bridge.
Each bridge identifies a port (the root port) through which it will forward frames to the root bridge. Port conflicts are always resolved in favour of the port with the lower index value. When there is a possibility of multiple bridges forwarding to the same LAN (but not through the root port), ties are broken as follows: bridges closest to the root get preference and between such bridges, the one with the lowest serial number is preferred.

cs200682


For the given connection of LANs by bridges, which one of the following choices represents the depth first traversal of the spanning tree of bridges?

  • B1, B5, B3, B4, B2

  • B1, B3, B5, B2, B4

  • B1, B5, B2, B3, B4

  • B1, B3, B4, B5, B2

Question 3

Consider a LAN with four nodes S1, S2, S3 and S4. Time is divided into fixed-size slots, and a node can begin its transmission only at the beginning of a slot. A collision is said to have occurred if more than one node transmit in the same slot. The probabilities of generation of a frame in a time slot by S1, S2, S3 and S4 are 0.1, 0.2, 0.3 and 0.4, respectively. The probability of sending a frame in the first slot without any collision by any of these four stations is _________.

  • 0.462

  • 0.711

  • 0.5

  • 0.652

Question 4

Which of the following statements is TRUE about CSMA/CD  

  • IEEE 802.11 wireless LAN runs CSMA/CD protocol

  • Ethernet is not based on CSMA/CD protocol

  • CSMA/CD is not suitable for a high propagation delay network like satellite network

  • There is no contention in a CSMA/CD network

Question 5

In an Ethernet local area network, which one of the following statements is TRUE ?

  • A station stops to sense the channel once it starts transmitting a frame.

  • The purpose of the jamming signal is to pad the frames that are smaller than the minimum frame size.

  • A station continues to transmit the packet even after the collision is detected.

  • The exponential backoff mechanism reduces the probability of collision on retransmissions

Question 6

Consider the data given in

above question

. Consider the correct spanning tree for the previous question. Let host H1 send out a broadcast ping packet. Which of the following options represents the correct forwarding table on B3?[2 marks] (A)

 Hosts Port
 H1, H2, H3, H4 3
 H5, H6, H9, H10 1
 H7, H8, H11, H12 2

(B)

 Hosts Port
 H1, H2 4
 H3, H4 3
 H5, H6 1
 H7, H8, H9, H10,H11,H12 2

(C)

 Hosts Port
H3, H4 3
H5, H6, H9, H10 1
 H1, H2 4
 H7, H8, H11, H12 2

(D)

 Hosts Port
 H1, H2, H3, H4 3
 H5, H7, H9, H10 1
 H7, H8, H11, H12 4

  • A

  • B

  • C

  • D

Question 7

In the diagram shown below L1 is an Ethernet LAN and L2 is a Token-Ring LAN. An IP packet originates from sender S and traverses to R, as shown. The link within each ISP, and across two ISPs, are all point to point optical links. The initial value of TTL is 32. The maximum possible value of TTL field when R receives the datagram is

GATECS2014Q25

  • 25

  • 24

  • 26

  • 28

Question 8

HTML(Hypertext Markup Language) has language elements which permit certain actions other than describing the structure of the web document. Which one of the following actions is NOT supported by pure HTML (without any server or client side scripting)pages?

  • Embed web objects from different sites into the same page

  • Refresh the page automatically after a specified interval

  • Automatically redirect to another page upon download

  • Display the client time as part of the page

Question 9

Consider different activities related to email: 

m1: Send an email from a mail client to a mail server
m2: Download an email from mailbox server to a mail client
m3: Checking email in a web browser

Which is the application level protocol used in each activity?

  • m1: HTTP m2: SMTP m3: POP

  • m1: SMTP m2: FTP m3: HTTP

  • m1: SMTP m2: POP m3: HTTP

  • m1: POP m2: SMTP m3: IMAP

Question 10

A layer-4 firewall (a device that can look at all protocol headers up to the transport layer) CANNOT
 

  • block entire HTTP traffic during 9:00PM and 5 :0OAM
     

  • block all ICMP traffic
     

  • stop incoming traffic from a specific IP address but allow outgoing traffic to the same IP address
     

  • block TCP traffic from a specific user on a multi-user system during 9:00PM and 5:00AM
     

There are 43 questions to complete.

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