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ITC242

Spring

Session Examination 2005


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FACULTY OF SCIENCE & AGRICULTURE

SCHOOL OF INFORMATION STUDIES

SPRING

SESSION EXAMINATION 2005

ITC242

Introduction to Data Communications


LECTURER:

Phil Roy



DAY & DATE:






TIME:


WRITING TIME:

Three (3) Hours



READING TI
ME:

Ten Minutes

MATERIALS SUPPLIED BY UNIVERSITY:



1 x 12pp Answer Booklet


General Purpose Answer Sheet

MATERIAL PERMITTED IN EXAMINATION:


Pens and Pencils, Calculator


2B pencil, eraser

NUMBER OF QUESTIONS:

Part A:

Forty (40) multiple choice quest
ions (1 mark each)


Part B:

Twenty Five (25) completion questions (1 mark each)


Part C:

Seven (7) short answer questions (5 marks each)

INSTRUCTIONS TO CANDIDATES:


1.

Enter your name, student number and signature at the bottom of this page.

2.

This is a closed

book examination, therefore no written material, reference books or notes will be permitted
into the examination room.

3.

ALL

questions should be attempted.

4.

Mark your answers to the multiple choice questions, Part A, on the general purpose answer sheet.

5.

Answ
ers
to Part B and Part C
are to be written in the examination answer booklets provided

6.

There are 100 marks in total.
Part A


40 marks, Part B


25 marks,

Part C


35 marks,

INSTRUCTIONS TO INVIGILATORS:

1.

QUESTION PAPER MUST BE COLLECTED


STUDENT NAME: …………
…………………………..STUDENT NO:…………………..


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STUDENT SIGNATURE:……………………………………………..


PART A: Multiple Choice Questions

(Each question is worth 1 mark each. Answer the questions on the general purpose
answer sheet provided).


1.

At which layer of the TCP/IP protocol suit
e would you find a chat program?


a.

Transport

b.

Presentation

c.

Application

d.

Session



2.

Digital lines attempt to offer what level of error
-
free transmission?


a.

99%

b.

90%

c.

80%

d.

70%



3.

Which term describes the process where data is packaged with necessary protocol
informat
ion as it passes through layers of the OSI reference model?


a.

Wrapping

b.

Encapsulation

c.

Encryption

d.

Protocolisation



4.

The sharing of a medium and its link by two or more devices is called




a.

Modulation

b.

Encoding

c.

Line discipline

d.

Multiplexing



5.

What component of
an unshielded twisted pair cable reduces it’s susceptibility to crosstalk?


a.

Outer conductor shielding

b.

A single inner conductor

c.

Twisted core conductor pairs

d.

Diameter of cable




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6.

The addition of unwanted electromagnetic energy onto a cable between transmitt
er and
receiver is:


a.

A
ttenuation

b.

N
oise

c.

A
mplitude

d.

S
pectrum



7.

A network style where the application and presentation logic resides on the client and the
data storage logic resides on a server is called:


a.

Client/Server

b.

Client Based

c.

Host Base

d.

Peer
-
to
-
Peer



8.

W
hen a bridge receives a packet that has a destination MAC address located on the same
segment from which it came, the packet is:


a.

Forwarded

b.

Blocked

c.

Repeated on all segments

d.

All of the above



9.

ISDN basic rate interface (BRI) multiplexes _______________ sep
arate data channels.


a.

One

b.

Two

c.

Three

d.

Four



10.

____________________ is a very powerful error detection technique and should be
considered for data transmission systems.


a.

Vertical redundancy check

b.

Cyclic redundancy checksum

c.

Simple parity

d.

Horizontal parity



11.

The

CSMA/CD network is described by which frame specification?


a.

IEEE 802.2

b.

IEEE 802.3

c.

IEEE 802.4

d.

IEEE 802.5



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12.

In a ____________________ subnet, a dedicated physical path is established to transmit the
data packets across the subnet.


a.

Circuit
-
switched

b.

Packet
-
s
witched

c.

Large

d.

Heavily loaded



13.

The length of a

IP
v4

address is:


a.

8 bits

b.

16 bits

c.

32 bits

d.

48 bits



14.


The concept that describes the merger of previously distinct telephony and information
technologies and markets is called:


a.

U
nification

b.

B
undling

c.

O
utsourcing

d.

M
erger

e.

C
onvergence



15.


The types of networks commonly used in businesses today include:


a.

Local area networks, wide
-
area networks, and telephone networks

b.

Local area networks, telephone networks, and voice mail networks

c.

Wide area networks, voice mail networks
, and email networks

d.

Voice mail networks, email networks, and local area networks

e.

Television networks, voice networks, and data networks



16.


Which of the following is the most commonly used standard for computer communications?


a.

SLA

b.

TCP/IP

c.

ISO

d.

USD

e.

DLINK



17.


Which of the following does not represent a digital form of information?


a.

An MP3 player

b.

A Compact Disk containing music recordings

c.

A watch that displays date as DD:MM:YYYY

d.

The hour and minute hand on a clock

e.

A fax transmission

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18.


Which of the following rep
resents the most basic unit of digital information?


a.

Byte

b.

Nibble

c.

Pixel

d.

Bit

e.

Octet



19.


The time interval between when a user presses a key and when the result of that action
arrives at his or her workstation is called the:


a.

R
esponse time

b.

T
urn
-
around time

c.

T
hin
k time

d.

D
elay time

e.

T
ransmission time



20.


Which of the following is not a benefit of distributed data processing?


a.

Increased responsiveness to organizational needs

b.

Better correspondence to organizational patterns

c.

Greater user involvement and control

d.

Enhanced
centralization of data definitions

e.

Reduced systems incompatibility



21.


The development of a internationally distributed collection of multimedia files addressed
using universal resource locators led to the:


a.

Telnet package

b.

Email system

c.

World
-
wide
-
web

d.

FTP pa
ckage

e.

Domain resource locator



22.


Some of t
he problems of using IP numbers for addressing hosts in the Internet are resolved
using:


a.

T
he concept of domains and the use of domain names

b.

T
he use of Telnet applications

c.

T
he use of email servers

d.

S
plitting IP addr
esses into four octets

e.

U
sing fixed routing paths through the network



23.


The key features of the DNS database are


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a.

V
ariable
-
depth hierarchy for names, centralised databases, and name servers

b.

Resolvers, distributed databases, and address servers

c.

Central cont
rol of the database, resolvers, and distributed databases

d.

Domain name spaces, address servers, and variable
-
depth hierarchies

e.

Variable
-
depth hierarchy for names, distributed databases, and distribution
controlled by the database



24.


Which of the following i
s not a layer of the OSI model?


a.

Presentation layer

b.

Session layer

c.

TCP Layer

d.

Data link layer

e.

Physical layer



25.


Which of the following is not a layer of the TCP/IP model?


a.

Application layer

b.

Connection layer

c.

Transport layer

d.

Internet layer

e.

Network access layer



26.


A widely used extension to the RFC 822 framework that expands what can be sent via email
is called


a.

MIME

b.

ASCII

c.

VoIP

d.

SMTP

e.

IMAP



27.

SMTP is not concerned with the format or content of messages, except for two exceptions.
Which of the following is one of th
ese exceptions?


a.

SMTP standardizes the message character set as 7
-
bit ASCII

b.

SMTP standardizes the message length into multiples of the packet size

c.

SMTP checks for virus content

d.

SMTP adds binary attachments to the content, when present



28.


Which of the follo
wing is not a class of client/server processing?


a.

Host
-
based processing

b.

Server
-
based processing

c.

Client
-
based processing

d.

Access
-
based processing

e.

Cooperative processing

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29.


Which of the following describes class C networks?


a.

Many networks, each with a few hos
ts

b.

Medium number of networks, each with a medium number of hosts

c.

Few networks, each with many hosts

d.

A dedicated network, with a set number of hosts



30.


Which of the following LAN technologies has the highest capacity?


a.

Ethernet

b.

Fast Ethernet

c.

Wireless LAN

d.

Gi
gabit Ethernet



31.

Which
of the following is NOT one of the stated advantages of packet switching over circuit
switching?


a.

There is less network delay

b.

Line efficiency is greater

c.

Priorities can be used

d.

Ability to use multiple paths for increased reliability



32.


When using cellular networks:


a.

Single base station can serve multiple cells

b.

Adjacent cells must use the same frequencies

c.

Adjacent cells are assigned different frequencies

d.

Non
-
adjacent cells must be assigned different frequencies

e.

Non
-
adjacent cells can us
e any frequency



33.

Analogue signals differ from digital signals in that:


a.

Analogue signals are measured against time while digital signals are measured against
frequency

b.

Analogue signals are periodic, digital signals are not

c.

Analogue signals are continuous
while digital signals remain at one constant level and
then move to another constant level

d.

Analogue signals operate a higher frequencies than digital signals

e.

Digital signals operate at higher frequencies than analogue signals



34.

Which of the following is NO
T one of the ways that frequency spectrum can be divided
among active users?


a.

frequency division multiple access

b.

time division multiple access

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c.

code division multiple access

d.

cell division multiple access



35.

The bandwidth of a signal is


a.

The width of the spec
trum

b.

The average of the frequencies

c.

The maximum amplitude of the signal

d.

The minimum amplitude in the signal



36.

A carrier wave is modulated with 4 amplitudes and 4 phase changes. How many bits can be
represented with each signal change?


a.

1

b.

2

c.

3

d.

4

e.

5



37.

Multiple
xing technique where multiple users use distinct time slots such that the transmitted
bits are shared by all users is called:


a.

Frequency division multiplexing

b.

Time division multiplexing

c.

Separate channel multiplexing

d.

Common channel multiplexing

e.

Separate fre
quency multiplexing



38.

______ is the message output after encryption occurs:


a.

Plaintext

b.

Ciphertext

c.

Key

d.

Encryption algorithm



39.

Fault management deals with:


a.

Facilities needed to evaluate the behaviour of managed objects and the effectiveness of
communication

b.

Aspects essential to operate OSI network management correctly and to protect managed
objects

c.

Facilities that enable charges to be established for the use of managed objects

d.

Facilities that exercise control over, identify, collect data from, and provide da
ta to
managed objects

e.

Facilities that enable the detection, isolation, and correction of abnormal operation of
the OSI environment


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40.

Which type of satellites orbit at an altitude of approximately 35,000 km, remain above the
same spot on the earth’s surface

but suffer from significant propagation delay?


a.

Low Earth Orbit (LEO) satellites

b.

Medium Earth Orbit (MEO) satellites

c.

Geostationary Earth Orbit (GEO) satellites

d.

None of the above

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PART B: Completion Questions

F
rom the provided words

s
elect the most appro
priate word
/s that complete

each
s
tatement.

Note: Not all words provided are used.

(Each question is worth 1 mark. Answer the questions in the Answer booklet provided.)


impulse

Router

fast

SAN

IEEE 802.11a

bluetooth

Reliability

protocol

VoIP

message tra
nsfer agent

asymmetric

Degradation

high speed

SMTP

frame check sequence

gigabit

Bridge

intranet

TCP

management agent

symmetric

Synchronous

hub

WAP

IEEE 802.11g

availability

frame

transport

DHCP

SNMP

token ring

Parity

w
hite

PDU

IDS

Physical

Extranet

a
ttenuation

UDP

SIP




1)

Thermal noise is uniformly distributed across the frequency spectrum and hence is often
referred to as ____
white
______ noise.


2)

A ___
protocol
_____ is a set of semantic and syntactic rules that describe how to transmit
data, especiall
y across a network.


3)

A ____
PDU
_______ is a

segment of data generated by a specific layer in a protocol stack;
usually consists of a blo
ck of data from a higher layer

encapsulated by the next lower layer
with a header and trailer.

It is passed to the corres
ponding layer on another device across a
network.


4)

Layer 4 of the OSI reference model is the _____
transport
_____ layer. It provides reliable
transfer of data between end points.


5)

_____
SIP
_____ is an application level control protocol for setting up, modify
ing and
terminating real time sessions between participants over an IP data network.


6)

Internet telephony is also commonly referred to as _____
VoIP
_____.


7)

__
SMTP
____ is the standard protocol for transferring mail between hosts in the TCP/IP
protocol suite.


8)

___
Intranet
___ is the term used to refer to the implementation of internet technologies
within a corporate organisation.


9)

An ___
extranet
___ makes use of TCP/IP protocols and applications to provide access to
corporate resources to other companies, custo
mers and suppliers located outside the
corporate network.


10)

A layer 4 protocol that is part of the TCP/IP protocol architecture, ____
UDP
____ is a
connectionless unreliable protocol.


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11)

A _____
SAN
____ is a separate network used to handle storage needs.


12)

A ____
router
___ operates at layer 3 of the OSI reference model and is involved with path
selection through a network.


13)

The ___
Gigabit
___ Ethernet 802.3 specification includes physical layer alternatives:
1000Base
-
LX, 1000Base
-
SX, 1000Base
-
CX and 1000BaseT.


14)

___
_
Bluetooth
____ is an always on, low power, short range wireless standard using the
2.4Ghz band for a wide range of devices.


15)

___
WAP
____ is a universal open standard developed to provide mobile users of wireless
phones access to telephony and information se
rvices including the Internet and the Web.


16)

A decrease in magnitude of current, voltage or power of a signal in transmission between
points is known as ___
attenuation
___.


17)

The term ___
asymmetric
__ is used in ADSL because more capacity is provided
downstrea
m, from the carrier to the customer, than upstream from the customer to the
carrier.


18)


In __
synchronous
___ TDM sources get a pre
-
assigned fixed proportion of time slots.


19)

___
SNMP
___ is an application level protocol that is part of the TCP/IP protocol suite
. It is a
collection of specifications for network management that include the protocol itself, the
definition of a database, and associated concepts.


20)

___
A
vailability
___ is the percentage of time that a particular function or application is
available for
users.


21)

A ___
frame
___ is a group of bits that includes data plus one or more addresses and other
protocol control information. It generally refers to a Link Layer protocol data unit.


22)

A __
token ring
___ network does not have collisions because access to the

medium is
controlled.


23)

The ___
physical
___ layer of the OSI reference model and TCP/IP protocol architecture is
concerned with electrical, mechanical and timing aspects.


24)

A ___
parity
___ bit is appended to an array of binary digits for use in error detectio
n.


25)

An __
IDS
___ usually works with a firewall or router to detect that a security breach was
attempted and inform a network administrator.


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PART C: Short Answer Questions

(Each question is worth 5 marks. Answer the questions in the Answer booklet provid
ed.
Use diagrams where appropriate to enhance your answers.)


1. Explain how local area networks differ from wide area networks.


Answer:

Local area networks are typically limited to a single premise where all interconnections are
implemented by and owned
by the business. In contrast, wide area networks typically involve
multiple premises and the interconnections must rely on access to public right
-
of
-
ways and
services provided by regulated common carriers.


2. List and describe the three primary methods fo
r replicating databases.


Answer:

1)

Real
-
time replication involves synchronizing all data immediately, as in transaction
systems.

2)

Non
-
real
-
time replication involves backups in batches, at fairly frequent intervals.

3)

Deferred replication involves bulk transf
er of changes at infrequent intervals.



3. Provide the full name for each of the following acronyms

PDU


TCP


UDP

SMTP

SNMP


Answer:

PDU

Protocol Data Unit

TCP

Transmission Control Protocol

UDP
User Datagram Protocol

SMTP
Simple Mail Transport Protoco
l

SNMP
Simple Network Management Protocol



4.
Describe one (1) of the following Wide Area Network technologies:



ISDN



X.25



ATM



FDDI



SONET


Answer: See Reading 2.


5.
Complete the following table describing IEEE 802.11 wireless LAN c
haracteristics
.



Freque
ncy

Maximum Data Rate

IEEE 802.11a



IEEE 802.11b



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IEEE 802.11g




Answer


Frequency

Maximum Data Rate

IEEE 802.11a

5Ghz

54Mbps

IEEE 802.11b

2.4Ghz

11Mbps

IEEE 802.11g

2.4Ghz

54Mbps



6.

Show all working and any assumptions for the following.

Give
n a resolution of 320 pixels x
240 pixels, 1 byte of colour information per pixel and a transmission rate of 30 frames per
second
:


a.

C
alculate the bandwidth necessary for this signal
.


b.
A 512MB flash drive after formatting has an actual capacity of 498
MB

(498,000,000 Bytes)
.
What length of transmission could be stored on
the

512MB flash drive?


c. In a
ddition to the 1 byte of colour,
sixteen levels of intensity are to be added for each pixel.
What length of transmission could now be stored on the 512M
B flash drive?


Answer:

a.

320 x 240 x 8bits x 30fps =
18.4 Mbps

b.

498
MB / (18.4Mbps / 8) = 2
1
6
.5

secs = 3min
3
6
.5

secs

c.

16 levels of intensity require an additional 4 bits per pixel.

498MB / (320 x 240 x 8 x 4 x 30fps)/8 = 498MB/9.2 = 54.13 secs



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7.
Descri
be the three types of modulation shown as (a), (b) and (c) in the following diagram.


© W. Stallings, Business Data Communications, 5
th

Edition, 2005.



Answer:

Answer removed


similar question in Assignment 2.