Computer Network Test - 4 - PDF Flipbook

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GATE
CSE

Computer
Network

Test-04Solutions

COMPUTER NETWOK

1. Choose the best matching between Group I and Group II.

Group-I Group-II

P: Data link layer 1. Ensures reliable transport of data

over a physical point to point link

Q: Network layer 2. Encodes/decodes data for physical

Transition

R: Transport layer 3. Allows end -to-end communication

between two processes

4. Routes data from one network node

to the next

a) P-1 Q-4 R-3

b) P-2, Q-4, R-1

c) P-2, Q-3, R-1

d) P-1,Q-3,R-2

Answer: (a)

Solution:

Data link: layer offers reliability on link: to link: basis, whereas

transport layers offer the same on end to end basis. Network

layer is responsible for routing

2. In an IPv4 datagram, the M bit is 0, the value of HLEN is 10, the

value of total length is 400 and the fragment offset value is 300.

The position of the datagram, the sequence numbers of the first

and the last bytes of the payload, respectively are

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a) Last fragment, 2400 and 2789
b) First fragment, 2400 and 2759
c) Last fragment, 2400 and 2759
d) Middle fragment, 300 and 689
Answer: (c)
Solution:
For last fragment always M = 0. If HLEN is 10 then header
length is 40 bytes (We use scale factor of 4 in HLEN).Therefore
total data in fragment is 400 - 40 = 360 bytes. Since offset is
300, total bytes ahead of this fragment is 8x300 = 2400 bytes
(we use scale factor of 8 in offset). Therefore it is last fragment,
starting byte is 2400 and ending byte is 2759
(Actually 2400 + 360 = 2760 bytes but byte number starts with
zero, so it is from 2400 to 2759)
3. Identify the i incorrect statement:
a) The ATM adaptation layer is not service dependent,
b) Logical connections in ATM are referred to as virtual channel

connections.
c) ATM is a streamlined protocol with minimal error and flow

control capabilities.
d) ATM is also known as cell relay.
Answer: (a)

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Solution:
The adaption layer defines how to segment at and reassemble
higher level packets into ATM cells, and how to handle various
transmission aspects in the ATM layer
The main services provided by AAL (ATM adaption layer) are:
• Segmentation and reassembly
• Handling of transmission errors
• Handling of lost and miss inserted cell conditions
• Timing and flow control
4. Two computers C1 and C2 are configured as follows. C1 has IP
address 203.197.2.53 and netmask 255.255.128.0. C2 has IP
address 203.197.75.201 and netmask 255.255.192.0 which one
of the following statements is true?
a) C1 and C2 both assume they are on the same network
b) C2 assumes C1 is on same network, but C1 assumes C2 is on

a different network
c) C1 assumes C2 is on same network, but C2 assumes C1 is on

a different network
d) C1 and C2 both assume they are on different networks
Answer: (c)
Solution:
Both netmask one subnet mask In C1 (255.255.128.0) 7 bits are
borrowed from Network,
therefore 27 networks are aggregated i.e., 128 Networks.

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C1 was 203.197.2.53, If we consider this as starting network
then last Network in this super net is 203.197.130. So C1
assumes C2 (203.197.75.201) is within C1, C2 has netmask
255.255.192.0, 6 bits are borrowed from network, there 26 = 64
Networks are aggregated, could be form 203.197.75, ……,
203.197.139 ……...
Therefore C1 assumes C2 is on the same network, but C2
assumes C1 is on a different network.
5. ARP (Address Resolution Protocol) is a
a) TCPIIP protocol used to dynamically bind a high-level IP

address to a low level physical hardware address
b) TCPIIP high level protocols for transferring files from one

machine to another
c) protocol used to monitor computers
d) protocol that handles error and control messages
Answer: (a)
6. The DNS maps the IP address to
a) A binary address as strings
b) A n alphanumeric address
c) A hierarchy of domain names
d) A hexadecimal address
Answer: (c)
Solution:
The domain name system maps the IP addresses to a hierarchy
of domain names.

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7. 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.
a) B1, B5, B3, B4, B2
b) B1, B2, B5, B2, B4
c) B1, B5, B3, B3, B4
d) B1, B3, B4, B5, B2
Answer: (c)
Solution:
In spanning tree, every bridge lies in the tree, but no cycles (or
loops) are formed. Hence answer is B1, B5, B2, B3, B4.

8. MMS (multimedia messaging service) uses ------ types of
messages to perform messaging transactions
a) 4
b) 6
c) 8
d) 10
Answer: (a)
Solution:
Multimedia message service (MMS) is a store- and –forward
method of transmitting graphics, video clips, audio file s and

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short text messages over wireless network using the WAP
protocol
9. Which type of Bridge would be used to connect an Ethernet
Segment with a token ring segment?
a) Transparent Bridge
b) Source-Route Bridge
c) Translation Bridge
d) None of these
Answer: (c)
Solution:
Source routing is a communications protocol in which the
sending station is wired of all the bridges in the network and
predetermines the complete route to the destination station
before transmitting Token ring uses this method
Transparent bridges are devices which connects more than one
network segments with other bridge to make all routing
decisions
Translating bridge is a type of bridge that interconnects two
different types of LAN protocols, such as Ethernet and token
ring.
10. X.25 protocol consists of:
a) physical and Frame levels
b) Frame and packet revers
c) Physical, Frame and Packet levels
d) None of the above

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Answer: (c)
Solution:
X.25 is an ITU-T standard protocol for packet switched wide
area network (WAN) communication, An X.25 WAN consists
of packet switching exchange (PSE) nodes as the networking
hardware, and leased lines, plain old telephonic is physical
links
X.25 protocol consists of physical frame and packet levels
11. Baseband is
a) transmission of signals without modulation
b) a signal all of whose energy is contained within a finite

frequency range
c) simultaneous transmission of data to a number of stations
d) all of these
Answer: (a)
12. What is the maximum size of data that the application layer can
pass on to the TCP layer below?
a) Any size
b) 216 bytes - size of TCP header
c) 216 bytes
d) 1500 bytes
Answer: (a)

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Solution:
Application layer can forward any size of the data to transport
layer, but Transport layer should ensure that each segment
should be of 64 KB.
13. The TRAP is one of the interrupts available in INTEL 8085.
Which one of the following statements is true of TRAP?
a) it is level triggered
b) it is negative edge triggered
c) it is +ve edge triggered
d) it is both +ve and -ve edges triggered
Answer: (d)
Solution:
Interrupt is a mechanism by which an I/O or an instruction can
suspend the normal execution of processor and get itself
serviced, the are 6 pins available in 8085 for interrupt that are
TRAP, RST 7.5, RST ‘TRAP’ is both positive and negative
edge triggered.
14. Auto dialling allows
a) to dial a phone numbers by typing them on the keyboard
b) both (c) and (b)
c) none of these
d) a personal computer to answer in-coming calls without

human assistance
Answer: (a)

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15. A network 198 78.41.0 is a
a) Class A network
b) Class B network
c) Class C network
d) Class D network
Answer: (c)
Solution:
The range of class 'C' network is 192.0.0 0 to 223.255.255.0.
Since, 198.78.41.0 lies this network, hence it is a class 'C'
network.

16. Coaxial cables are categorized by Radio Government rating are
adapted for specialized functions. Category RG-59 with
impedance 75Ω used for
a) Cable TV
b) Ethernet
c) Thin Ethernet
d) Thick Ethernet
Answer: (a)
Solution:
RG- 59 is a specific type of coaxial cable, often used for low
power videos and RF signal connections the cable has a
characteristic impedance of 75 ohms and a capacitance of round
20 pF/ft

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17. Overlaying
a) requires use of a loader
b) allows larger programs, but requires more effort
c) is most used on large computers
d) is transparent to the user
Answer: (d)

18. TDM is______:
a) A primary/secondary type protocol
b) A peer/peer protocol
c) A Non-priority peer/peer protocol
d) A priority type protocol
Answer: (c)
Solution:
Time-division multiplexing (TDM) is a method of transmitting
and receiving independent signals over a common signal path
by means of synchronized switches at each of the transmission
line so that each signal appears on the line only a fraction of
time in an alternating pattern
TDM is non-priority peer/protocol Token bus/token ring are
known as priority peer to peer protocol

19. Match the following with respect to HTML tags and usage.
List-l
A. CITE
B. EM
C. VAR

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D. SAMP
List-ll
1. italic presentation
2. Represents output from programs
3. Represents to another source
4. Argument to a program
Code:

A BC D
a) 3 1 4 2
b) 2 3 1 4
c) 4 2 3 1
d) 1 3 4 1
Answer: (a)
Solution:
The tag defines the title of a work Note a person’s
name if not the title of a work
The tag is phrase tag; it renders as emphasized text
tag marks txt that has stress emphasis which traditionally
means that the text is displayed in italics by the browser
The HTML tah is used to format text in a document it
can include a variable in a mathematical expression
The HTML (SAMP> element is an element intended to identify
sample output from a computer program.

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20. An example of a layer that is absent in broadcast networks is:
a) physical layer
b) presentation layer
c) network layer
d) application layer
Answer: (c)
Solution:
The TCP/IP model network layer does not say much what
occurs here except to point out that the host has to connect to the
network using some protocol so it can send IP packets to the
network

21. Consider a TCP client and a TCP sever running on two different
machines. After completing data transfer, the TCP client calls
close to terminate the connection and a FIN segment is sent to
the TCP server. Server-side TCP responds by sending an ACK,
which is received by the client-side TCP. As per the TCP
connection state diagram (RFC 793), in which state does the
client-side TCP connection wait for the FIN from the server-side
TCP?
a) LAST-ACK
b) TIME_WAIT
c) FIN-WAIT-1
d) FIN-WAIT_2
Answer: (d)

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Solution:

22. Which of the following are Data Link Layer standard?
1. Ethernet
2. HSSI
3. Frame Relay
4. 10-Base T
5. Token Ring
a) 1, 2, 3
b) 1, 3, 5
c) 1, 3, 4, 5
d) 1, 2, 3, 4, 5
Answer: (c)

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Solution:
Ethernet supports both physical and data link layer on the OSI
model the high-speed serial interface (HSSI-operate at the
physical layer on OSI model Ethernet uses 10- base-T
Frame relay is a standardized wide area network technology that
specifies the physical and data link layer of digital
telecommunications channels using a packets methodology
Token ring is a data link technology for local area networks
(LANs) it operates at layer 2 of the OSI model.
23. At any given time, Parallel Virtual Machine (PVM) has
____send buffer and ____ receive buffer.
a) one-one
b) one-two
c) two-two
d) two-one
Answer: (b)
Solution:
Parallel virtual machine (PVM) is a software tool for parallel
networking of computers it is designed to allow a network of
heterogeneous Unix and/or windows machines to be used as
single distributed parallel processor
24. Bulletin board system
a) is a public access message system
b) is a modem capable of accepting commands
c) converts analog signals to digital signals

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d) converts digital signals to analog signals
Answer: (a)
25. Terminal emulation allows

a) a dumb terminal to pretend that it is a personal computer
b) a personal computer to pretend that it is computer terminal
c) a dumb terminal to produce a local echo
d) both (a) and (c)
Answer: (b)
26. The process of modifying IP address information in IP packet
headers while in transit across a traffic routing device is called
a) Port address translation (PAT)
b) Network address translation (NAT)
c) Address mapping
d) Port mapping
Answer: (b)
Solution:
Network address translator is used to convert private IP into
public IP and for vice versa.
27. Which of the following is not a valid multicast MAC address?
a) 01: 00: 5E: 00: 00: 00
b) 01: 00: 5E: 00: 00: FF
c) 01: 00: 5E: 00: FF: FF
d) 01: 00: 5E: FF: FF: FF
Answer: (d)

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Solution:
Multicast MAC Address range of 01-00-5E-00-00-00 to 01-00-
5E-7F-FF-FF i.e. all lower bit should be 1.
28. Which type of links is used for a connection between two DTE
devices?
a) X.21
b) Frame Relay
c) ATM
d) Modem
Answer: (d)
Solution:
Data terminal equipment (DTM) is an end instrument that
converts user information into signal or reconverts received
signals.
Two different types of devices are assumed on each end of the
interconnecting cable for a case of simply adding DTE to the
topology (e.g., to a hub, DEC), which also brings a less trivial
case of interconnection of devices of the same type: DTE-DTM
or DCE-DCE.
Such cases need cross-over cables, such as for the Ethernet or
null modem for RS- 232.
Usually, the DTE device is the terminal (or a computer
emulating a terminal), and the DCE is a modem or other carrier-
owned device.

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29. In which layer of network architecture, the secured socket layer
(SSL) is used?
a) physical layer
b) session layer
c) application layer
d) presentation layer
Answer: (d)
Solution:
Secured socket layer is defined as ‘operating over some reliable
transport layer’ which places it as application layer protocol in
the TCP/IP reference model and as presentation layer protocol
in the OSI model.

30. Satellite Switched Time-Division Multiple Access (SS/TDMN)
is
a) method of determining which device has access to the
transmission medium at any time
b) a medium access control technique for multiple access
transmission media
c) a form of TDMA in which act switching is used to
dynamically change the channel assignments
d) all of these
Answer: (c)

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