Computer Network Test - 1 - PDF Flipbook
Computer Network Test - 1
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GATE
CSE
Computer
Network
Test-01Solutions
COMPUTER NETWOK
1. 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 K−X 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?
a) {m, KB+(H(m))}
b) {m, KB−(H(m))}
c) {m, KA−(H(m))}
d) {m, KA+(H(m))}
Answer: (b)
Solution:
The concept of digital signature Message is digested: h(m) and
cryptographically protected with sender's private key to become
sign and sent along with the message
2. Suppose that everyone in a group of N people wants to
communicate secretly with the N-I others using symmetric key
cryptographic system. The communication between any two
persons should not be decodable by the others in the group. The
number of keys required in the system as a whole to satisfy the
confidentiality requirement is
a) 2N
b) N(N − 1)
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c) N(N − 1)/2
d) (N − 1)2
Answer: (c)
Solution:
1 1key 2
1 1 2
3-nodes 3
2
3 keys-> 1+2 3
4-nodes
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1+2+3=6 keys
N-nodes ⇒ 1 + 2 +… (n − 1) = n(n−1) keys
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3. A client process P needs to make a TCP connection to a server
process S. Consider the following situations; the server process
S executes a socket (), a bind () and a listen () system call in that
order, following which it is preempted. Subsequently, the client
process P executes a socket () system call followed by connect
() system call to connect to the server process S. The server
process has not executed any accept () system call. Which one
of the following events could take place?
a) Connect() system call returns successfully
b) Connect() system call blocks
c) Connect() system call returns an error
d) Connect() system call results in a core dump
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Answer: (c)
4. A super net has a first address of 205.16.32.0 and a superset
mask of 255.255.248.0. A router receives 4 packets with the
following destination addresses. Which packet belongs to this
superset?
a) 205.16.42.56
b) 205.17.32.76
c) 205.16.31.10
d) 205.16.39.44
Answer: (d)
Solution:
Destination address = 205.1 6.39.44
Super net mask = 255.255.248.0
First address = 205.16.32.0
5. Weights in the neural network by propagating weight changes.
a) Forward from source to sink
b) Backward from sink to source
c) Forward from source to hidden nodes
d) Backward from sink to hidden nodes
Answer: (b)
Solution
Back propagation algorithm is a learning technique that adjusts
weights in neural network by propagation weight change
backward from the sink to the source nodes.
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6. Consider two hosts X and Y, connected by a single direct link of
rate 106 bits/sec. The distance between the two hosts is 10,000
km and the propagation speed along the link is 2x 108 m/sec.
Host X send a file of 50,000 bytes as one large message to host
Y continuously. Let the transmission and propagation delays be
p milliseconds and q milliseconds, respectively. Then the values
of p and q are
a) P = 50 and q = 100
b) P = 50 and q = 50
c) P = 100 and q = 50
d) P = 400 and q = 50
Answer: (d)
Solution:
Given: B = 106 bps
Distance = 10000km
Tp= 2 × 108m/s
P = Tx = L = 50000 × 8 = 4 = 103 = 4000 = 400 m sec
B 100 × 104 10 103 10
Q = d = 50000 × 103 = 1 = 1 × 103 = 1000 = 50 m sec
v 2 × 108 20 20 103 20
7. In case of Bus/Tree topology signal balancing issue is
overcome by:
a) Strong Transmitter
b) Polling
c) Segmentation
d) Modulation
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Answer: (c)
Solution:
Network segmentation is the act or profession of spelling a
computer network into subnetworks, each being a network
segment, advantages of such spilling are primarily for boosting
performance and improving security. That reduces congestion,
improved security, containing network problems and controlling
network problems and controlling visitor access.
8. Is sometimes said to be object oriented, because the only way to
manipulate kernel objects is by invoking methods on their
handles.
a) Windows NT
b) Windows XP
c) Windows VISTA
d) Windows 95/98
Answer: (a)
Solution:
An object oriented operating system is an operating system that
uses methods of object-oriented programming.
Windows NT is sometimes said to objects is by involving
methods (API functions) on their handles. On the other hand, it
lacks some of the most basic properties of object oriented
systems such as inheritance and polymorphism.
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9. After the update in the previous question, the link N1 – N2 goes
down. N2 will reflect this change immediately in its distance
vector as cost, 00. After the NEXT ROUND of update, what
will be the cost to N1 in the distance vector of N3?
a) 3
b) 9
c) 10
d) ∞
Answer: (c)
Solution:
If poison we use in applied there N2 says it is always ∞ .But in
question there asked what its value at N3 is. So alternative
router is N3 → N4 → N5 → N1, so its value is 2 + 4 + 3 + 1=10
1 N1
3
N5 N2
It is down
∞4 6 So N2à N1 is
N4 2 N3
Please note, in question they asked “NEXT ROUND” of update,
means ′∞′at N2 will be received by N5 but not by N3, hence N3
still assume N3 → N4 → N5 → N2 is will alternative route no
N1.
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10. In a mobile communication system, a geographic region is
divided into cells. For each frequency set, there is a buffer wide
where that frequency is not used"
a) one-cell
b) two-cells
c) three-cells
d) four-cells
Answer: (b)
Solution:
For each frequency set, thus is a buffer 2 cells wide in which
that frequency is not used.
11. Which of the following is the difference between a multiplexer
and a statistical multiplexer?
a) Statistical multiplexers need buffers while multiplexers do
not need buffers
b) Multiplexer use X.25 protocol, while statistical multiplexers
use the Alpha protocol
c) Multiplexers often waste the output link capacity while
statistical multiplexers oppose its use
d) Multiplexers use Time Division Multiplexing (TDM) while
statistical multiplexers uses Frequency Division Multiplexing
Answer: (a)
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12. If we get both local and remote echoes, every character we type
will appear on the screen
a) once
b) twice
c) three times
d) none of these
Answer: (b)
13. The station to hub distance in which it is 2000 meters.
a) 100 Base -TX
b) 100 Base -FX
c) 100 Base -T4
d) 100 Base -T1
Answer: (b)
Solution:
In the 100BASE-TX distance between the station and the hub
(or switch) should be less than 100 meters.
The 100BASE-FX design uses two optimal fibers, one to carry
frames from the hub to the station .the encoding 4B/5B and
signaling is NRZ-1 the distance between the station and the hub
(or swath) should be less than 2000 meters.
14. What is the function of a translating bridge?
a) Connect similar remote LANs
b) Connect similar local LANs
c) Connect different types of LANs
d) Translate the network addresses into a layer 2 address
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Answer: (c)
Solution:
Transition Bridge is a type of bridge that interconnects two
different types of LAN protocols, such as Ethernet and token
ring translating bridges are generally very complicated devices.
15. The spacing between character pairs is called:
a) kerning
b) x-height
c) inter cap
d) serif
Answer: (a)
Solution:
In topography kerning(less commonly mortising is the process
of adjusting the spacing between characters in a proposal font,
usually to achieve a visually pleasing result.
The x-height or corpus size refers to the distance between the
base line and the baseline and the mean line of lower-case letters
in a type face.
16. In which Routing Method do all the routers have a common
database?
a) Distance vector
b) Link state
c) Link vector
d) Dijkstra method
Answer: (b)
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Solution:
The linked list necessary database requires more memory than a
distance vector requires.
Link state, the complex algorithm requires more CPU time than
a distance vector protocol requires.
The flooding of link state packets adversely affects available
bandwidth, particularly in unstable internetworks.
A distance Vector routing protocol requires that a router
inform its Neighbours of topology changes periodically
compared to link state protocols,
Which require a router to inform all the nodes in a network of
topology changes, distance vector routing protocols have less
computational complexity and message overhead?
17. An IP packet has arrived with the first 8 bits as 0100 0010.
Which of the following is correct?
a) The number of hops this packet can travel is 2.
b) The total number of bytes in header is 16 bytes
c) The upper layer protocol is ICMP
d) The receiver rejects the packet
Answer: (d)
Solution:
As the HLEN is of 4 bit but (0000 to 0.100) is treated as don’t
care condition. Receiver accepts when HLEN (0101 to 111i)
i.e., 20 – 60 byte. But here header length given 16 byte so
receiver will reject the packet
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18. Which of the following has the smallest default maximum
physical receive packet size?
a) ARC net
b) Ethernet
c) Token Ring [4 Mbps]
d) Token Ring [16 Mbps]
Answer: (b)
19. Which of the following is a wrong example of network layer?
a) X.25 level – 2 – ISO
b) Source Routing and Domain naming – Usenet
c) X.25 Packet Level Protocol (PLP) – ISO
d) Internet Protocol (IP) – ARPANET
Answer: (a)
20. The TCP sliding window
a) can be used to control the flow of information
b) always occurs when the field value is 0
c) always occurs when the field value is 1
d) occurs horizontally
Answer: (a)
Solution:
TCP sliding window can be used to control the flow of
information. A sliding window is a feature of packet-based data
transmission protocols, by placing limits on the number of
packets that can be transmitted or received at any given time, a
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sliding window protocol allows an unlimited number of packets
to be communicated using fixed-size sequence numbers.
21. Frequency shift keying is used mostly in
a) Radio transmission
b) Telegraphy
c) Tele phone
d) None of the above
Answer: (b)
Solution:
Frequency shift keying is used mostly in telegraphy.
FSK is a frequency modulation scheme in which digital
information is transmitted through discreet frequency changes of
a carrier signal.
22. E-Chou pal refers to
a) Calling meeting of Sarpanches electronically.
b) Conducting Panchayat meeting using latest electronic
gadgets.
c) Providing window of information to villagers and farmers in
NIC network.
d) None of the above
Answer: (c)
Solution:
E-choupal which is an initiative by ITC is to empower the
farmer as with expect knowledge is order to enhance the
competitiveness in the global market
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23. Which of the following file transfer protocols use these TCP and
establishes two virtual circuits between the local and remote
server?
a) FTP
b) TFTP
c) TELNET
d) NFS
Answer: (a)
Solution:
The file transfer protocol is a started network protocol used to
transfer computer files between a client and server model
architecture and uses separated control and data connections
between the client and the data
24. ALOHA
a) use for channel allocation problem
b) is use of data transfer
c) is buffering
d) all of these
Answer: (a)
25. A station in a network in a network forward incoming packets
by placing them on its shortest output queue. What routing
algorithm is being used?
a) Hot potato routing
b) Flooding
c) Static routing
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d) Delta routing
Answer: (a)
Solution:
In commercial network routing between autonomous system
which are interconnected in multiple locations, hot potato
routing is the practice of passing as quickly as possible, thus
using their network for wide area transit.
26. Existent is:
a) network layer
b) transport layer
c) presentation layer
d) application layer
Answer: (a)
Solution:
When there is one small network based on broadcast philosping,
this layer is either absent or has very minimal functionally.
27. Which statement is false?
a) PING is a TCP/IP application that sends datagrams once every
second in the hope of an echo response from the machine
being PINGED
b) If the machine is connected and running a TCP/IP protocol
stack, it should respond to the PING datagram with a
datagram of its own
c) If PING encounters an error condition, an ICMP message is
not returned
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d) PING display the time of the return response in milliseconds
or one of several error messages
Answer: (c)
Solution:
The PING command is a command prompt command used to test
the ability of the source computer to reach a specified destination
computer.
If PING encounters an error condition, an ICMP message is
returned.
28. Which of the following techniques is used for allocating
capacity on a satellite channel using fixed-assignment FDM?
a) Amplitude modulation
b) Frequency-division multiple access
c) Frequency modulation
d) Frequency-shift keying
Answer: (b)
29. The ATM cell is:
a) 48 bytes’ long
b) 53 bytes’ long
c) 64 bytes’ long
d) 69 bytes’ long
Answer: (b)
Solution:
Shortest job first CPU scheduling is advantageous.
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Because of its simplicity and because it minimizes the average
amount of time each process has to wait until its execution is
complete.
So, as per shortest job first
J3 = 3, J4 = 5, J2 = 6, J1 = 9
30. 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?
a) UDP, 80
b) TCP, 80
c) TCP, 25
d) UDP, 25
Answer: (b)
Solution:
The underlying protocol for browsing web server is TCP. HTTP
uses TCP is its underlying transport layer protocol and is used to
access the web server.
The HTTP runs at 8080 i.e., 80 port address.
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