DOEACC Society 2007 DOEACC A Level A9-R3 Data Communication and Networks - Question Paper

D) none of the above
1.10 Light is confined within the core of a simple optical fiber by
A) refraction
B) total internal reflection at the outer edge of the cladding
C) total internal reflection at the core cladding boundary
D) reflection from the fiber's plastic coating
A9-R3 Page two of five January, 2007
2. every statement beneath is either actual or FALSE. select the most improper one
and ENTER in the “tear-off” sheet attached to the ques. paper, subsequent
instructions therein. (1 x 10)
2.1 Coaxial cable provides data rates over 10 Mbps and frequencies upto 400 MHz.
2.2 Synchronous transmission is known as start/stop transmission.
2.3 UTP Category three can be used in Fast Ethernet networks.
2.4 FDDI specifies protocol for network layer.
2.5 CRC fault detection technique is used in TCP.
2.6 Circuit switching is generally more efficient than packet switching for non-voice
communication.
2.7 The functional grouping and reference points of B-ISDN are the identical for regular ISDN.
2.8 QPSK uses the phase shift of multiple of 60 degree.
2.9 Data rate supported by LED is generally higher than semiconductor lasers in fiber optic
communication.
2.10 10Base5 and Thick Net are the identical term used for a kind of LAN implementation.
3. Match words and phrases in column X with the nearest related meaning/
word(s)/phrase(s) in column Y. Enter your selection in the “tear-off” ans sheet
attached to the ques. paper, subsequent instructions therein. (1 x 10)
X Y
3.1 Sharing of communication channel A. Modem
3.2 Virtual Terminal Protocol B. Multi drop line
3.3 Contention and collision are issues in C. Ring topology
3.4 Return to zero D. Quantization
3.5 Converts a series of binary voltage pulse into
analog signal by encoding the digital data onto a
carrier frequency
E. BNC
3.6 every router periodically shares its own knowledge
about the network with its immediate neighbor
routers
F. Distance vector routing
3.7 Every router has its own unique routing table G. Application layer
3.8 The message units exchanged ranging from two
protocol entities
H. Link state routing
3.9 Surface propagation is related with I. Bus topology
3.10 Router operates under the layer in OSI reference
model
J. Manchester coding
K. Transport layer
L. Network layer
M. Binary coding
N. Very Large Frequency
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4. every statement beneath has a blank space to fit 1 of the word(s) or phrase(s) in
the list beneath. Enter your option in the “tear-off” ans sheet attached to the
ques. paper, subsequent instructions therein. (1 x 10)
A. Twisted pair B. Presentation layer C. Packet Switching
D. Piggy backing E. Delay F. Data encapsulation
G. Application layer H. Star I. Circuit Switching
J. RJ 45 K. TCP L. Data link
M. Direct connection N. Full Duplex O. 32 Bytes
P. BNC
4.1 Digital signals can also be transmitted in ________ mode.
4.2 ________ circuits are improper circuits for transmission of voice and real-time data.
4.3 FTP, SMTP and Telnet are standard protocol for the ________.
4.4 The main disadvantage of satellite communication is its huge ________ in propagation.
4.5 ________ is a technique used to recover from occasional frame loss issue.
4.6 The LAP-B protocol is an example of the standard for the ________ layer of the OSI
reference model.
4.7 Due to less info capacity the coaxial cable has lower degree of attenuation at
high frequencies than ________ cable.
4.8 ________ switching technique is also known as store-and-forward.
4.9 Connections to the thin Ethernet cable are generally made using ________ connectors.
4.10 The minimum frame size in 802.3 LAN is ________.
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PART TWO
(Answer any 4 questions)
5.
a) On a transmission channel, 700 character messages is transmitted in synchronous and
asynchronous mode using ASCII seven bit code. For transmission purpose in synchronous
data stream, there are 2 synchronous characters and a single fault detection
character is added. In the case of asynchronous data transmission there is 1 begin bit,
one stop bit and a single fault detection character is added. compute the efficiency of
transmission in the above 2 kinds of transmission modes.
b) discuss 3 services that a data link protocol provides to sending and receiving devices
to help them coordinate and communicate.
(8+7)
6.
a) describe forwarding function. discuss its significance with the help of suitable example.
b) elaborate the various classes of addresses used in IPv4? List their ranges in dotted
decimal notation.
c) Why is frequency modulation superior to amplitude modulation?
d) discuss the functioning of cellular radio.
(6+3+3+3)
7.
a) What basic functions does a communication satellite perform? provide a good cause why
uplink and downlink frequencies are not identical. Why earth dish antennas are generally
parabolic in shape?
b) FSK is a good option for low speed modems. discuss why it is not suitable for high
speed modems?
c) What is distributed routing? Compare it with hierarchial routing.
(6+5+4)
8.
a) elaborate the 5 layers of the TCP/IP model? Briefly define the functionality of every
layer.
b) Briefly discuss ICMP. How is an ICMP message datagram constructed?
(10+5)
9.
a) What is the function of a null modem? Show the internal communications used within a
null modem and explains the significance of every connection.
b) What is the purpose of cladding in an optical fiber? explain its density with respect to
the core.
c) Mention any 3 requirements for reliable data transfer?
(8+4+3)
A9-R3 Page five of five January, 2007

Earning:   Approval pending.