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8/12/2019 Computer Networks 2marks
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SNS COLLEGE OF ENGINEERING, COIMBATORE 641107
DEPARTMENT OF MCA
2010-2011 III SEM – COMPUTER NETWORKS
TWO MARKS QUESTIONS AND ANSWERS
I-UNIT
1. W!" #$ %!"! &'(()*#&!"#'*+
Data communication is the exchange of data between two devices via some form
of transmission medium (wire cable). It is considered as local if the communicating
devices are in the same building and is considered remote if the devices are farther apart.
2. L#$" ')" " &!!&"#$"#&$ "' #('/ " &"#/*$$ ' %!"! &'(()*#&!"#'*
$$"(.
•
Deliver
• !ccurac
• Timeliness
. W!" #$ %3#/ !*% !&&)!&+
D3#/ The sstem must deliver data to the correct destination. Data must be received
b the intended device or user and onl b that device or user.
A&&)!& The sstem must deliver data accuratel. Data that have been altered in
transmission and left uncorrected are unusable.
4. W!" #$ "#(3#*$$+
The sstem must deliver data in a timel manner. Data delivered late are useless.
In the case of video" audio and voice data" timel deliver means delivering data as the
are produced" in the same order that the are produced" and without significant dela.
This #ind of deliver is called real-time transmission.
5. W!" ! " &'('**"$ ' %!"! &'(()*#&!"#'* $$"(+
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• $essage
• %ender
• &eceiver
• $edium
• 'rotocol
6. W!" %' ') (!* ($$!, $*% !*% &#/+
M$$! The message is the information to be communicated. It consists of text"
number" pictures" sound or video or an combination of these.
S*% The sender is the device that sends the data message. It can be a computer"
wor#station" telephone handset" video camera and so on.
R&#/ The receiver is the device that receives the message. It can be a computer"
wor#station" telephone handset" television and so on.
7. W!" #$ (!*" "!*$(#$$#'* (%#)(+
The transmission medium is the phsical path b which a message travels from
sender to receiver. It consists of twisted pair wire" coaxial cable" fiber-optic cable" laser or
radio waves.
8. W!" #$ '"'&'3+
! protocol is a set of rules that govern data communication. It represents an
agreement between the communicating devices. ithout a protocol" two devices ma be
connected but cannot be communicated.
9. W!" #$ ! *":';+
! networ# is a set of devices connected b media lin#s. ! node can be a computer"
printer" or an other device capable of sending andor receiving data generated b other
nodes on the networ#. The lin#s connecting the devices are often called communication
channels.
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10. W!" #$ %#$"#)"% '&$$#* !*% 3#$" #"$ !%/!*"!$+
In distributed processing" a tas# is divided among multiple computers.
!dvantages*
• %ecurit+ncapsulation
• Distributed databases
• ,aster problem solving
• %ecurit through redundanc
• ollaborative processing.
11. W!" ! " &#"#!$ ' *":';+
• 'erformance
• &eliabilit
• %ecurit
12. <': " '(!*& &!* (!$)%+
'erformance can be measured b
Transmit time* Transmit time is the amount of time reuired for a message to travel from
one device to another.
&esponse time* &esponse time is the elapsed time between an inuir and a response.
1. W!" ! " !&"'$ "!" #('/ " '(!*& ' *":';+
The performance of a networ# depends on a number of factors including
• Number of users
• Tpe of transmission medium
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• /ardware
• %oftware
14. <': " 3#!#3#" ' ! *":'; &!* (!$)%+
• ,reuenc of failure
• &ecover time of a networ# after failure
• atastrophe
15. W!" #$ *":'; $&)#"+
Networ# securit issues including protecting data from unauthori0ed accessand viruses.
16. L#$" $'( ' " !3#&!"#'*$ ' *":';+
• $ar#eting and sales
• ,inancial services
• $anufacturing
• +lectronic messaging
• Director services
• Information services
• +lectronic data interchange(+DI)
• Teleconferencing
• ellular telephone
• able television
17. D#* 3#*; !*% 3#* &'*#)!"#'*.
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L#*; ! lin# is the phsical communication pathwa that transfers data from one device
to another.
L#* &'*#)!"#'* 1ine configuration refers to the wa two or more communication
devices attach to a lin#.
18. W!" ! " '$$#3 3#* &'*#)!"#'*$+
'oint-to-point* It provides a dedicated lin# between two devices.
$ultipoint* ! multipoint line configuration is one on which more than two specific
devices share a single lin#. The capacit of the channel is shared either spatiall or
temporall.
19. W!" #$ (!*" "''3'+
The term topolog refers to the wa a networ# is laid out" either phsicall or
logicall. The topolog of a networ# is the geometric representation of the relationship of
all the lin#s and lin#ing devices.
20. W!" ! " "''3'#$ !/!#3!3+
• $esh topolog
• %tar topolog
• Tree topolog
• 2us topolog
• &ing topolog
21. W!" ! " ":' "$ ' 3!"#'*$#$ '$$#3 #* "''3'+
P-"'- In this" the devices share the lin# euall. +xamples* &ing and mesh
topolog.
P#(!-$&'*%! In this" one device controls traffic and the others must transmit
through it. +xamples* %tar and tree topolog.
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22. W!" #$ ($ "''3'+ S"!" #"$ !%/!*"!$ !*% %#$!%/!*"!$.
In mesh topolog" ever device has a dedicated point-to-point lin# to ever other
device.
A%/!*"!$
• +liminates traffic problems
• &obust
• 'rivac or securit
• +as fault identification and fault isolation.
D#$!%/!*"!$
• Installation and reconfiguration are difficult
• %heer bul# of the wiring can be greater than the available space can
accommodate.
• The hardware reuired to connect each lin# can be prohibitivel
expensive.
2. W!" #$ $"! "''3'+ S"!" #"$ !%/!*"!$.
In a star topolog" each device has a dedicated point-to-point lin# onl to acentral controller" usuall called a hub. The devices are not directl lin#ed to each other.
!dvantages*
• 1ess expensive
• +as to install and reconfigure
• !dditions" moves and deletions involve onl one connection between that
device and the hub.
• &obustness
• +as fault identification and fault isolation.
24. W!" #$ " "''3'+
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The tree topolog is a variation of a star. !s in a star" nodes in a tree are lin#ed to
a central hub that controls the traffic to the networ#. The central hub in the tree is an
active hub.
25. W!" #$ !&"#/ ) !*% !$$#/ )+
!ctive hub* !n active hub contains a repeater" which is a hardware device that
regenerates the received bit patterns before sending them out.
'assive hub* ! passive hub provides a simple phsical connection between the attached
devices.
26. W!" ! " !%/!*"!$ ' " "''3'+
The advantage is same as of star. In addition" it has two advantages*
• It allows more devices to be attached to a single central hub and can therefore
increase the distance a signal can travel between devices.
• It allows the networ# to isolate and prioriti0e communications from different
computers.
27. W!" #$ " )$ "''3'+
In bus topolog" one long cable acts as a bac#bone to lin# all the devices in
the networ#.
28. W!" ! " !%/!*"!$ !*% %#$!%/!*"!$ ' )$ "''3'+
A%/!*"!$
• +as installation
• Uses less cabling
D#$!%/!*"!$
• Difficult reconfiguration and fault isolation.
• !ddition of new device reuire modification or replacement of the
bac#bone.
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• ! fault or brea# in the bus cable stops all transmission.
• The damaged area reflects signals bac# in the direction of origin" creating
noise in both directions.
29. W!" #$ #* "''3'+
In a ring topolog" each device has a dedicated point-to-point line configuration
onl with the two devices on either side of it. ! signal is passed along the ring in one
direction from device to device until it reaches its destination.
0. W!" ! " !%/!*"!$ ' #* "''3'+
• +as to install and reconfigure.
• !dding or deleting a device reuires moving onl two connections.
• +as fault isolation
• %ignal will be circulating at all times.
1. S"!" %#$!%/!*"!$ ' #* "''3'.
•
Unidirectional traffic
• ! brea# in the ring can disable the entire networ#.
2. W!" #$ "!*$(#$$#'* ('% !*% #"$ "$+
The transmission mode is used to define the direction of signal flow between
two lin#ed devices.
T$*
• %implex
• /alf-duplex
• ,ull-duplex.
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. W!" ! " &!"'#$ ' *":';$+
• 1ocal area networ#
• $etropolitan area networ#
• ide area networ#.
4. D#* '"'&'3.
! protocol is a set of rules that govern data communication. ! protocol defines
what is communicated" how it is communicated" and when it is communicated. The #e
elements of a protocol are
• %ntax
• %emantics
• Timing
5. W!" #$ $*"!=, $(!*"#&$ !*% "#(#*+
S*"!= %ntax refers to the structure or format of the data" meaning the order in which
the are presented.
S(!*"#&$ %emantics refers to the meaning of each section of bits.
T#(#* Timing refers to two characteristics*
• hen data should be sent
• /ow fast the can be sent.
6. W!" #$ $"!*%!% !*% 3#$" #"$ &!"'#$.
! standard provides model for development that ma#es it possible to wor#regardless of the individual manufacturer.
ategories*
• De facto (b fact)
• De 3ure (b law)
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7. W!" #$ D !&"' $"!*%!%$+
It is developed into two classes*
• 'roprietar standards
• Nonproprietar standards
8. W!" ! '#"! !*% *'*'#"! $"!*%!%$+
P'#"! $"!*%!%$ These standards are those originall invented b a commercial
organi0ation as a basis for the operation of its procedure. The are called closed standards
because the close off communications between sstems produced b different vendors.
N'*'#"! $"!*%!%$ These standards are those originall developed b groups or
committees that have passed them into the public domain. The are called open standards because the open communications between different sstems.
9. W' %/3'% $"!*%!%$+
%tandards are developed b cooperation among
• %tandards creation committees
•
,orums
• &egulator agencies
40. W!" ! " $"!*%!%$ #*/'3/% #* $"!*%!%$ &!"#'* &'((#""$+
• I%4 (International %tandards 4rgani0ation)
• ITU-T (International Telecommunications Union-Telecommunication
standards sector)
• !N%I (!merican National %tandards Institute)
• I+++ (Institute of +lectrical and +lectronics +ngineers)
• +I! (+lectronic Industries !ssociation)
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• Telcordia
41. W!" #$ ISO+
The I%4 is an organi0ation dedicated to worldwide agreement on international
standards in a variet of fields.
42. D#* ITU-T.
ITU-T is an international standards organi0ation related to the United Nations that
develops standards for telecommunications. Two popular standards developed b ITU-T
are
• 5 series
• 6 series
4. D#* ANSI.
!N%I" a nonprofit organi0ation" is the U.%. voting representative to both the I%4
and the ITU-T.
44. D#* IEEE.
The I+++ is the largest national professional group involved in developing
standards for computing" communication" electrical engineering and electronics.
45. D#* EIA.
+I! is an association of electronics manufacturers in the United %tates. It is
responsible for developing the +I!-787-D and +I!-98: standards.
46. W!" #$ "3&'%#!+
Telcordia provides research and development resources for the advancement of
telecommunications technolog.
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;<. L#$" $'( #('"!*" ')($.
• ,rame rela forum
• !T$ ,orum and !T$ consortium
• I+T,(Internet +ngineering Tas# ,orce) and
I%4(Internet %ociet
;=.W!" #$ R)3!"' A*&+
,(,ederal communication ommission) is one of the regulator agenc.
R$'*$##3#"$
• To review rate and service-charge applications made b telegraph and
telephone providers
• To review the technical specifications of communications hardware
• To establish reasonable common carrier rates of return
• To doivide and allocate radio frenuencies
• To assign carrier freuencies for radio and television broadcasts
;>.W!" #$ (*!" '* $$"(+
! open sstem is a model that allows an two different sstems to communicate regardless
of their underling architecture
9:. W!" #$ OSI ('%3+
The open sstem Interconnection model is a laered framewor# for the design of
networ# sstems that allows for communication across all tpes of computer sstems.
The purpose of 4%I model is to open communication between different sstems withoutreuiring changes to the underling hardware and software.
9?.I$ OSI ('%3 #$ ! '"'&'3+ E=3!#*.
The 4%I models not a protocol" It is a model for understanding and designing a networ#
architecture that is flexible" robust and interoperable.
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97. L#$" ')" " 3!$ ' OSI ('%3+
The model is built of seven ordered laers
• 'hsical laer (laer ?)
• Datalin# laer (laer 7)
• Networ# laer (laer 8)
• Transport laer (laer ;)
• %ession laer (laer 9)
• 'resentation laer (laer @)
• !pplication laer (laer <)
98. W!" #$ (!*" #*"!&+
+ach interface defines what information and services a laer must provide for the
laer above it. ell-defined interfaces and laer functions provide modularit to a networ#.
9;. <': " 3!$ ' OSI ('%3 #$ '/#%%+
The phsical" data lin# and networ# laer are the networ# support laers.The deal
with the phsical aspects of moving data from one device to another.
The %ession" presentation application laer are user support laers. The allow
interoperabilit among unrelated software sstems.
99. W!" #$ $#&!3 3!+
The phsical laer coordinates the functions reuired to transmit a bit stream over a
phsical medium.
It deals with the mechanical and electrical specifications of the interface and
transmission medium.
It also defines the procedures and functions that phsical devices and interfaces have to
perform for transmission to occur.
9@. S"!" " &!!&"#$"#&$ ' $#&!3 3!+
• 'hsical characteristics of interfaces and media.
• &epresentation of bits(:s and ?s)
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The networ# laer is responsible for the source-to-destination deliver of a pac#et
possibl across multiple networ#s. hereas the data lin# laer oversees the deliver of the
pac#et between two sstems on the same networ#" the networ# laer ensures that each pac#et
gets from its point of origin to its final destination.
@:. W!" ! " $'*$##3#"#$ ' *":'; 3!+
• 1ogical addressing
• &outing
@?. W!" #$ (!*" "!*$'" 3!+
The transport laer is responsible for source-to-destination deliver of the entire
message. hereas the networ# laer oversees end-to-end deliver of individual pac#ets" it does
not recogni0e an relationship between those pac#ets.
@7. S"!" $'( ' " $'*$##3#"#$ ' "!*$'" 3!.
• %ervice-point addressing
• %egmentation and reassembl
• onnection control
• ,low control
• +rror control
@8. W!" #$ (!*" $$$#'* 3!+
The session laer is the networ# dialog controller. It establishes" maintains" and
snchroni0es the interaction between communicating sstems.
@;. S"!" " $'*$##3#"#$ ' $$$#'* 3!.
• Dialog control
• %nchroni0ation
@9. W!" #$ $*"!"#'* 3! !*% 3#$" #"$ $'*$##3#"#$.
The presentation laer is concerned with sntax and semantics of the information
exchanged between two sstems.
R$'*$##3#"#$
• Translation
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• +ncrption
• ompression
@@. W!" #$ !3#&!"#'* 3!+
The application laer enables the user" whether human or software to access the
networ#. It provides user interfaces and support for services such as electronic mail" remote fileaccess and transfer" shared database management and other tpes of distributed information
services.
@<. W!" ! " $/#&$ '/#%% !3#&!"#'* 3!+
• Networ# virtual terminal
• ,ile transfer" access and management (,T!$)
• $ail services
• Director services
@=. L#$" ')" "$ ' "!*$(#$$#'* (%#!.
• Auided media
• Unguided media
@>. W!" #$ (!*" )#%% (%#!+
Auided media" which are those that provide a conduit from one device to another. It
includes
• Twisted-pair cable
• oaxial cable
• ,iber-optic cable
<:. W!" #$ (!*" ":#$"%-!# &!3+
Twisted-pair cable use metallic conductors that accept and transport signals in the form
of electrical current. It includes
• Unshielded twisted-pair (UT') cable
• %hielded twisted-pair (%T') cable.
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The twisted pair consists of two conductors each surrounded b an insulating material.
<?. W!" #$ )*$#3%% ":#$"%-!# &!3+
! twisted pair consists of two conductors" each with its own colored plastic
insulation. The plastic insulation is color-banded for identification.
olors are used both to identif the specific conductors in a cable and to indicatewhich wires belong in pairs and how the relate to other pairs in a larger bundle.
<7. W!" #$ (!*" $#3%% ":#$"%-!# >STP? &!3+
%hielded twisted pair cable has a metal foil or braided-mesh covering that encases
each pair of insulated conductors. The metal casing prevents the penetration of electromagnetic
noise. It also can eliminate a phenomenon called crosstal#" which is the undesired effect of one
circuit on another circuit.
<8. W!" #$ &'!=#!3 &!3+
oaxial cable carries signals of higher freuenc ranges than twisted-pair cable" in
part because the two media are constructed uite differentl.
Instead of having two wires" coax has a central core conductor of solid or stranded
wire enclosing in an insulating sheath" which is in turn" encased in an outer conductor of metal
foil" braid" or a combination of the two.
<;. W!" ! " /!#')$ &'!=#!3 &!3 $"!*%!%$+
Different coaxial cable design are categori0ed b their radio government (&A)
ratings. +ach &A number denotes a uniue set of phsical specifications" including the wiregauge of the inner conductor" the thic#ness and tpe of the inner insulator" the construction of the
shield" and the si0e and tpe of the outer casing.
S"!*%!%$
• &A-=(used in thic# +thernet)
• &A->(used in thic# +thernet)
• &A-??(used in thic# +thernet)
• &A-9=(used in thin +thernet)
• &A-9>(used for T5)
<9. W!" ! %#*" &'!=#!3 &!3 &'**&"'$+
The commonl used connectors are
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T-C'**&"'$ It allows a secondar cable to branch off from a main line.
T(#*!"'$ Terminators are reuired for bus topologies where one main cable acts as a
bac#bone with branches to several devices but does not itself terminate in a device.
<@. W!" #$ (!*" '"#&!3 #+
4ptical fiber is made of glass or plastic and transmits signals in the form of light. It
includes
• Nature of light
&efraction
ritical angle
&eflection
• 'ropagation
$ulti mode
%ingle mode
• ,iber si0es
• able connection
1ight sources for optical cable
<<. D#* !&"#'*.
1ight travels in a straight line as long as it is moving through a single uniform
substance. If a ra of light traveling through one substance suddenl enters another substance" its
speed changes abruptl" causing the ra to change direction. This change is called refraction.
78. W!" #$ (!*" !*3 ' #*&#%*& !*% !*3 ' !&"#'*+
The angles made b the beam of light in relation to the vertical axis are called I" for
incident and &" for refracted.
If the beam travels from a denser medium into a less dense medium" the value of I is
smaller than the value of &.
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hen light travels into more dense medium" the angle of incidence is greater than angle
of refraction and when light travels into a less dense medium" the angle of incidence is less than
the angle of refraction.
<>. D#* &#"#&!3 !*3.
!t some point in the process" the change in the incident angle results in a refracted angle
of >: degrees" with the refracted beam ling along the hori0ontal. The incident angle at this point
is #nown as critical angle.
=:. D#* R3&"#'*.
hen the angle of incidence becomes greater than the critical angle" reflection occurs.
/ere" the angle of incidence is alwas eual to the angle of reflection.
=?. W!" ! " /!#')$ '!!"#'* ('%$ !/!#3!3+
•$ultimode
%tep-index fiber
Araded-index fiber
• %ingle mode
=7. W!" #$ $#*3-('% !*% ()3"#-('%+
%ingle mode* %ingle mode uses step-index fiber and a highl focused source of light that
limits became to a small range of angles" all close to the hori0ontal.
$ultimode* It is named as multi-mode because multiple beams from a light source move
through the core in different paths.
=8. D#*"#!" $"-#*%= # !*% !%%-#*%= #.
%tep-Index fiber Araded-Index fiber
?. The densit of the core remains
constant from the center to the edges.
Densit is highest at the center of the core and
decreases graduall to its lowest at the edge.
7. %ome beams stri#e the interface of the
core and cladding at an angle smallerthan the critical angle.
2eams at angles move through a series of
constantl changing densities.
=;. S"!" " !%/!*"!$ !*% %#$!%/!*"!$ ' '"#&!3 #.
A%/!*"!$
• Noise resistance
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• 1ess signal attenuation
• /igher bandwidth
D#$!%/!*"!$
• ost
• Installationmaintenance
• ,ragilit.
=9. S"!" !')" )*)#%% (%#!.
Unguided media also #nown as wireless communication. It includes"
(?) &adio freuenc allocation
'ropagation of &adio waves.
• %urface propagation
• Tropospheric propagation
• Ionospheric propagation
• 1ine-of-sight propagation
'ropagation of specific signals
• 5er low freuenc(51,)
• 1ow freuenc(1,)
• $iddle freuenc($,)
• 5er high freuenc(5/,)
• Ultrahigh freuenc(U/,)
•
%uperhigh freuenc(%/,)
• +xtremel high freuenc(+/,)
(7). Terrestrial microwave.
&epeaters
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!ntennas
• 'arabolic dish antenna
• /orn antenna
(8) %atellite communication
Aeosnchronous satellites
,reuenc 2ands for satellite communication
(;) ellular telephon
ellular bands
Transmission
&eceiving
/andoff
Digital
=@. W!" #$ ('%(+
$odem stands for modulatordemodulator. ! modulator converts a digital signal intoan analog signal. ! demodulator converts an analog signal into digital signal.
87. <': " "!*$(#$$#'* !" &!* (*"#'*%+
2andwidth* +ver line has an upper limit and lower limit on the freuencies of the signals
it can carr. This limited range is called the bandwidth.
M'%( $%
!%B(!mplitude shift #eing) manipulates freuenc.
,%B(,reuenc %hift Being) manipulates freuenc.
'%B('hase %hift Being) manipulates phase.
C!$(Cuadrature !mplitude $odulation) manipulates both phase and
amplitude.
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88. W!" ! " %#*" ('%( $"!*%!%$+
2ell modems
ITU-T $odem standards
Intelligent modems.
89. W!" %'$ )3'!%#* (!*+
Transmission of data from the subscriber to the Internet provider (uploading) follows
these steps*
• Digital data are modulated b the modem at site !.
• !nalog data are sent from the modem to the switching station at site ! on the local
loop.
• !t the switching station" data are converted to digital using '$('ulse codemodulation).
• Digital data travel through the digital networ# of the telephone compan and are
received b the Internet provider computer.
90. W!" %'$ %':*3'!%#* (!*+
Transmission of data from the Internet provider to the modem at site !(downloading
follows these steps*
• Digital data are sent b the computer of the Internet provider through thedigital telephone networ#.
• !t the switching station" digital data are converted to analog using '$.
• !nalog data are sent from the switching station at site ! to the modem on the
local loop.
• !nalog data are demodulated b the modem at site !.
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UNIT-2
?. hat are the tpes of errors
• %ingle-bit error
• 2urst error
7. hat is meant b single-bit error and burst error
S#*3-#" ' The term single bit error means that onl one bit of a given data unit such as a
bte" character" data unit or pac#et is changed from : to ?.
B)$" ' The term burst error means that two or more bits in the data unit have changed from
? to : or from : to ?. (ie) multiple bits are changed.
8. hat is redundanc
+rror detection uses the concept of redundanc" which means adding extra bits for detecting
errors at the destination. Instead of repeating the entire data stream" a shorter group of bits ma beappended to the end of each unit. This techniue is called redundanc because the extra bits are redundant
to information" the are discarded as soon as the accurac of the transmission has been determined.
;. hat are tpes of redundanc chec#s available
• 5erticals redundanc chec#(5&) #nown as parit chec#
• 1ongitudinal redundanc chec#(1&)
• clical redundanc chec#(&)
• hec#sum
9. +xplain parit chec#
In verticals redundanc chec#" a parit bit is added to ever data unit so that the total number of
?s becomes even. %ome sstem ma also use odd-parit chec# where the number of ?s should be odd.
5& can detect all single bit errors. It can detect burst errors onl if the total number of errors in
each data unit odd.
@. hat is 1&
In longitudinal redundanc chec#" a bloc# of bits is organi0ed in a table and divided into rows
and a redundant row of bits is added to the whole bloc#.
<. hat is &
& is based on binar division. In &" instead of adding bits together to achieve a desired
parit" a seuence of redundant bits called & or the & remainder is appended to end of data unit son
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that the resulting data unit becomes exactl divisible b a second" predetermined binar number. !t its
destination" the incoming data unit is divided b the same number.
& includes (?) & generator (7) & chec#er (8) 'olnomials.
=. hat is the role of remainder in &
If there is no remainder" the data unit assumed to be intact and is therefore accepted. If there is a
remainder" it indicates that the data unit has been damaged in transit and therefore must be re3ected.
>. hat are the ualities of the valid &
• It much have exactl one less bit than the divisor.
• !ppending it to the end of the data string must ma#e the resulting bit seuence exactl divisible
b the divisor.
?:. hat are the properties of a polnomial
•
It should not be divisible b x.
• It should be divisible b (xE?).
??. %tate the performance of &.
& is a ver effective error detection method.
• & can detect all burst errors that affect an odd number of bits.
• & can detect all burst errors of length less than or eual to the degree of the
polnomial.
• & can detect with a ver high probabilit burst errors of length greater than the degree
of the polnomial.
?7. hat is meant b chec#sum
hec#sum if the field used for error detection. It is formed b adding bit streams using ?s
complement arithmetic and then complementing the result.
?8. hat does the sender do in chec#sum
• The unit is divided into # sections" each of n bits.
• !ll sections are added together using ?s complement to get the sum.
• The sum is complemented and becomes the chec#sum.
• The chec#sum is sent with the data.
?;. hat does the receiver do in chec#sum
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• The unit is divided into # sections" each of n bits.
• !ll sections are added together using ?s complement to get the sum.
• The sum is complemented.
• If the result is 0ero" the data are accepted" otherwise the are re3ected.
?9. /ow the error correction can be handled
+rror correction can be handled in two was.
• In one" when an error is discovered" the receiver can have the sender retransmit the entire
data unit.
•
In the other" a receiver can use an error correcting code" which automaticall correctscertain errors.
?@. hat is hamming code
/amming code is a method that adds redundant bits to a data unit to detect and correct bit errors.
The hamming code can be applied to data units of an length and uses the relationship between data and
redundanc bits. In the hamming code" for a data unit of m bits" use the formula 7rFGmErE? to determine
r" the number of redundant bits needed.
?<. Define flow control.
,low control refers to a set of procedures used to restrict the amount of data the sender can send before waiting for ac#nowledgement. Incoming data must be chec#ed and processed before the can be
used. The rate of such process is slower than the rate of transmission. ,or this reason" each receiving
device has a bloc# of memor called the buffer" reserved for storing incoming data until the are
processed. If the buffer begins to fill up" the receiver must be able to tell the sender to halt transmission
until it is once again able to receive.
?=. hat are the categories of flow control
• %top-and-wait method
•
%liding window
?>. Define stop-and-wait method.
In the stop-and-wait method of flow control" the sender sends one frame and waits for an
ac#nowledgement before sending the next frames. The process of sending and waiting repeats until the
sender transmits an end of transmission frame.
7:. hat are the advantages and disadvantages of stop-and-wait method
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A%/!*"! simplicit (+ach frame is chec#ing and ac#nowledged before the next frame is sent.)
D#$!%/!*"! Inefficienc (%top-and-wait is slow).
7?. hat is sliding window method
In the sliding window method of flow control" several frames can be in transit at a time. The
sliding window refers to imaginar boxes at both the sender and the receiver.
77. hat does the sender window do
The sliding window of the sender shrin#s from the left when frames of data are sent. The sliding
window of the sender expands to the right when ac#nowledgements are received.
78. hat does the receiver window do
The sliding window of the receiver shrin#s from the left when frames of data are received. The
sliding window of the receiver expands to the right when ac#nowledgments are sent.
7;. hat is meant b the term error control
+rror control refers primaril to methods of error detection and retransmission. +rror control in
the data lin# laer is based on automatic repeat reuest (!&C)" which means retransmission of data in
three cases* damaged frame" lost frame" and lost ac#nowledgment.
79. hat are the categories of error control
(?) %top-and-wait !&C
(7) %liding window !&C
Ao-bac#-n
%elective re3ect
7@. hat are the features of basic flow control mechanism in stop-and-wait
• The sending device #eeps a cop of the last frames transmitted until it receives an
ac#nowledgment for that frames.
• ,or identification purposes" both data frames and !B frames are numbered alternatel : and ?.
• If an error is discovered in a data frame" indicating that it has been corrupted in transit" a N!B
frame is returned.
• The sending device is euipped with a timer.
7<. hat are the features of basic flow control mechanism in sliding window
• The sending device #eeps copies of all transmitted frames until the have been ac#nowledged.
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• In addition to !B frames" the receiver has the option of returning a N!B frame if the data have
been received damaged.
• 1i#e stop-and-wait !&C" the sending device in sliding window !&C is euipped with a timer to
enable it to handle lost ac#nowledgments. N-? frames ma be sent before an ac#nowledgment
much be received.
7=. Difference between go-bac#-in !&C and selective re3ect !&C.
G'-!&;-* ARQ S3&"#/ @&" ARQ
If one frame is lost or damaged" all frames
sent since the last frame ac#nowledged are
transmitted.
In selective re3ect !&C" onl the specific
damaged or lost frame is retransmitted.
Duplicate frames are discarded Duplicate frames are not discarded.
&etransmission begins with the last
ac#nowledged frame even if subseuent
frames have arrived correctl.
4nl the unac#nowledged frame is
retransmitted.
1ess performance 2etter performance
+as to implement /ard to implement
7>. hat are all the bit oriented protocols available
• %nchronous data lin# control (%D1)
• /igh-level data lin# control (/D1)
• 1in# access procedures (1!')
• 1ocal area networ#s (1!N)
8:. hat is /D1
/D1 is a bit-oriented data lin# protocol designed to support both half-duplex and full-duplex
communication over point-to-point and multipoint lin#s. %stems using /D1 can be characteri0ed b
their" tpes" their configuration" and their response modes.
8?. hat are the station tpes available in /D1
/D1 differentiates between three tpes of stations*
• 'rimar station
• %econdar station
• ombined station
87. %tate the function of primar and secondar station.
The primar station sends commands to the secondar station. In other words" the primar station
sends commands and secondar station sends responses.
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88. Describe about combined station.
! combined station sends both commands and responses. ! combined station is one of a set of
connected peer devices programmed to behave either as a primar or as a secondar depending on the
nature and direction of the transmission.
8;. %tate configuration and its tpes in /D1.
The word configuration refers to the relationship of hardware devices on a lin#. The
configurations are of three tpes*
• Unbalanced configuration
• %mmetrical configuration
• 2alanced configuration
89. Define unbalanced configuration.
!n unbalanced configuration (also #nown as masterslave configuration) is one in which onedevice is primar and the others are secondar. Unbalanced configuration can be point-to-point if onl
two devices are involved. The can be multipoint with one primar controlling several secondaries.
8@. Define smmetrical configuration.
! smmetrical configuration is one in which each phsical station on a lin# consists of two
logical stations" one a primar and the other a secondar. %mmetrical configuration behaves li#e an
unbalanced configuration except that control of the lin# can shift between the two stations.
8<. hat is balanced configuration
! balanced configuration is one in which each phsical station in a point-to-point topolog are ofthe combined tpe. The stations are lin#ed b a single line that can be controlled b either station.
8=. hat are the modes of communication in /D1
/D1 supports three modes of communication between stations.
• Normal response mode (N&$)
• !snchronous response mode (!&$)
• !snchronous balanced mode (!2$)
8>. hat is N&$
Normal response mode refers to the standard primar-secondar relationship. In this mode" a
secondar device must have permission from the primar device transmission of one or more frames
containing data.
;:. hat is !&$
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In asnchronous response mode" a secondar ma initiate a transmission without permission from
the primar whenever the channel is idle. !ll transmission from a secondar must still be made to
primar for rela to final destination.
;?. hat is !2$
In asnchronous balanced mode" all stations are eual and therefore onl combined stations
connected in point-to-point are used. +ither combined station ma initiate transmission with the othercombined station without permission.
;7. hat are the tpes of frames available in /D1
/D1 defines three tpes of frames.
• Information frames (I-frames)
• %upervisor frames (%-frames)
• Unnumbered frames (U-frames)
;8. hat are the functions of various frames
• I-frames are to transport user data and control information relating to user data.
• %-frames are used onl to transport control information" primaril data lin# laer flow and error
controls.
• U-frames are reserved for sstem management. Information carried b u-frames intended for
managing the lin# itself.
;;. hat are the fields does the frame in /D1 holds
+ach frame in /D1 ma contain up to@ fields.
• ! beginning flag field
• !ddress field
• ontrol field
• Information field
• ,rame chec# seuence (,%) fields
• +nding flag field.
;9. hat is meant b bit stuffing
2it stuffing is the process of adding one extra : whenever there are five consecutive ?s in the data
so that the receiver does not mista#e the data for a flag.
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;@. hat is ', bit
The control fields of all three tpes of frames contain a bit called pollfinal (',) bit. !n I-frame
contains two 8-bit flow and error control seuences" called N(%) and N(&). N(%) specifies the number of
the frame being sent and N(&) is the ac#nowledgement field and it indicates the number of the frame
expected in return in a two-wa exchange.
;<. Define piggbac#ing
'iggbac#ing means combining data to be sent and ac#nowledgement of the frames received in
one single frame.
;=. hat are the tpes of %-frame
• &eceive read frame (&&)
• &eceive not read (&N&)
• &e3ect (&+H)
• %elective-re3ect (%&+H)
;>. hat are the categories of U-frame
The U-frame commands and response can be divided into five basic functional categories.
• $ode setting
• Unnumbered-exchange
• Disconnection
• Initiali0ation
• $iscellaneous
9:. hat are the tpes of lin# access procedures (1!')
• 1in# access procedure" balanced (1!'2)
• 1in# access procedure for D channel (1!'D)
• 1ind access procedure for modems (1!'$)
9?. Define 1!N.
! local area networ# is usuall privatel owned and lin#s the devices in a single office" building"
or campus. 1!Ns are designed to allow resources to be shared between personal computers or
wor#stations.
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1!Ns are distinguished from other tpes of networ#s b their transmission media and topolog.
The will use onl one tpe of transmission medium. The most common 1!N topologies are bus" ring
and star.
97. Define +thernet.
I+++ =:7.8 supports a 1!N standard called +thernet. It defines two categories* 2aseband and
2roadband.
98. Difference between baseband and broadband.
BASEBAND BROADBAND
2aseband specifies digital signal 2roadband specifies analog signal
The standards of baseband are ?:2ase9(thic#
+thernet)"?:2ase7(thin +thernet)" ?:2ase-
T(Twisted-pair +thernet)" ?2ase9(%tar1!N)
and ?::2ase-T
?:2road8@ is the standard
9;. hat does the number and letter in standard means
The first number (?:" ? or ?::) indicates the data rate in $bps. The last number or letter (9" 7" ?
or T) indicated cable length or the tpe of cable. +xample* ?:2ase;" ?2ase9
99. hat is a collision
henever multiple users have unregulated access to a single line" there is a danger of signals into
unusable noise" are called collisions. !s traffic increases on a multiple-access lin#" collision also
increases.
9@. hat is %$!!
The access mechanism used in an +thernet is called carrier sense multiple access with collision
detection (%$!D). %$!D is the result of an evolution from multiple access ($!) to carrier
sense multiple access (%$!) and finall to carrier sense multiple access with collision detection.
9<. /ow the frame in I+++ =:7.8 will be
I+++ =:7.8 specifies one tpe of frame containing seven fields*
• 'reamble
• %tart frame delimiter (%,D)
• Destination address (D!)
• %ource address (%!)
• 1engthtpe of 'DU
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• =:7.7 frame
• &
9=. hat is I+++ =:7.9
I+++ =:7.9 is also #nown as to#en ring. To#en ring allows each station to send one frame per
turn. The mechanism that coordinates this rotation is called to#en passing. ! to#en is a simple placeholder frame that is passed form station to station around the ring.
9>. hat are the tpes of frames in to#en ring protocol
(?) Datacommand frame
• %tart delimiter (%D)
• !ccess control (!)
• ,rame control (,)
• Destination address (D!)
• %ource address (%!)
• =:7.7 'DU frame
• &
• +nd delimiter (+D)
• ,rame status (,%)
(7) To#en frame
(8) !bort frame
@:. hat is ,DDI
,iber distributed data interface (,DDI) is a local area networ# protocol. It supports data rates of
?:: $bps and provides a high speed alternative to +thernet and to#en ring.
@?. hat are the two tpes of data frames in ,DDI
• S*&'*')$ It refers to information that is real time. It is #nown as %-frames.
• A$*&'*')$ It refers to information that is not real. It is #nown as !-frames.
@7. hat are the tpes of time registers in ,DDI
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• %nchronous !llocation (%!)
• Target To#en &otation Time (TT&T)
• !bsolute $aximum Time (!$T)
@8. hat is %!" TT&T J !$T
• S*&'*')$ A33'&!"#'* >SA? The %! register indicates that the length of time allowed each
station for sending snchronous data.
• T!" T';* R'"!"#'* T#( >TTRT? The TT&T register indicates the average time reuired
for a to#en to circulate around the ring exactl once.
• A$'3)" M!=#()( T#( >AMT? The !$T register holds a value eual to twice the TT&T.
@;. hat are the timers available in ,DDI
• T';* R'"!"#'* T#( >TRT? The T&T runs continuousl and measures the actual time ta#en
b the to#en to complete a ccle.
• T';* <'3%#* T#( >T<T? It shows how much time remains for sending asnchronous
frames once the snchronous frames have been sent.
@9. hat are the tpes of frames available in ,DDI
The ,DDI standard divides transmission functions into four protocols
• 'hsical $edium Dependent ('$D)
• 'hsical ('/K)
• $edia !ccess ontrol ($!)
• 1ogical 1in# ontrol (11)
@@. hat are the frame fields in ,DDI
• %tart Delimiter (%D)
• ,rame ontrol (,)
•
!ddresses
• Data
• &
• +nd Delimiter (+D)
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• ,rame %tatus (,%)
@<. hat are the three tpes of notes in ,DDI
• Dual !ttachment %tation (D!%)
• %ingle !ttachment %tation (%!%)
• Dual !ttachment oncentration (D!)
@=. hat is meant b bridges
2ridges operate in both the phsical and data lin# laers of 4%I model. 2ridges can divide a large
networ# into smaller segments. It can also rela frames between two originall separate 1!N. 2ridges
contain logic that allows them to #eep the traffic for each segment separate. It also provides securit
through the partitioning of traffic.
@>. hat are the tpes of 2ridges
• %imple 2ridge
• $ultiport 2ridge
• Transparent 2ridge
<:. hat are the issues to be considered in connecting a bridge to different 1!N
• ,rame format
• 'aload si0e
• Date rate
• !ddress bit order
• !c#nowledgment
• ollision
• 'riorit
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UNIT L III
T4 $!&B%
?. hat is an internetwor#
hen two or more are connected" the become an internetwor#" or internet. Individual
networ#s devices such as routers and gatewas.
7. hat is switching and list its tpes
! switched networ# consists of a series of inter lin#ed nodes. called switches.
%witches are hardware or software devices capable of creating temporar connections between
two or more devices lin#ed to the switch but not to each other.
Tpes*
• ircuit switching
• 'ac#et switching
• $essage switching
8. hat is circuit switching
ircuit switching creates a direct phsical connection between two devices such as phones or
computers. It transmits onl analog signals. 5oice communication is onl possible.
It includes an one of the two technologies*
• %pace-division switches
• Time-division switches
;. hat are disadvantages of circuit switching
• 1ess suited for data and non voice transmission.
• Data rate
• Inflexible
• onsiders all transmissions as eual.
9. hat is pac#et switching
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In a pac#et switched networ#" data are transmitted in discrete units of potentiall variable
length bloc#s called pac#ets. 1onger transmissions are bro#en into multiplepac#ets.+ach pac#et
contains not onl but also a header with control information(such as and source and destination
addresses).
@. hat are the pac#et switching approaches
• Datagram approach
• 5irtual circuit approach
i.switched virtual circuit
ii. 'ermanent virtual circuit
<. +xplain datagram approach.
In datagram approach" each pac#et is treated independentl from all others. 'ac#ets are
#nown as datagrams.ommunication is achieved through multiplexing (Time divisionmultiplexing and freuenc division multiplexing) and demultiplexing.
=. +xplain virtual circuit approach.
In virtual circuit approach" the relationship between all pac#ets belonging to a message or
session is preserved. ! single route is chosen between sender and receiver at the beginning of the
session. hen the data are sent" all pac#ets of the transmission travel one after another along that
route.
>. hat is %5 and '5
S:#"&% /#")!3 &#&)#"
It is comparable to dial-up lines in circuit switching. In this method" 5irtual circuit is
created whenever it is needed and exists onl for the duration of the specific exchange.
P(!**" /#")!3 &#&)#"
These are comparable to leased lines in circuit switching. In this method" the same virtual
circuit is provided between two users on a continuous basis. The circuit is dedicated to the
specific users. No one else can use it.
?:. Difference between circuit switching and virtual switching.
C#&)#" $:#"&#* #")!3 $:#"&#*
It creates a path between two points.
The phsical path is created b
setting the switches for the durationof the dial or leased line
It creates a route between two points.
This means each switch creates an entr in its routing
table for the duration of the session or duration of theleased line
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The lin#s that made here arededicated. The cannot be used b
other connection
The lin#s that ma#e a route can be shared b otherconnections
11.W!" #$ ($$! $:#"&#*+
$essage switching is #nown as store and forward switching.In this mechanism" a nodereceives a message" stores it until the appropriate route is free" then sends it along. There is no
direct lin# between the sender and receiver of a transmission. In message switching" the
messages are stored and relaed from secondar storage (dis#)" while in pac#et switching the
pac#ets are stored and forwarded from primar storage(&!$).
?7. hat are the protocols available in networ# laer
!t the networ# laer" T'I' supports the internetwor# protocol (I').I' in turn contains four
supporting protocols* !'&" &!&'" I$' and IA$'.
?8. Describe about I'.
I' is the transmission mechanism used b the T'I' protocols. It is an unreliable and
connectionless datagram protocol a best-effort deliver service. The term best-effort means that
I' provides no error chec#ing or trac#ing. I' transports data in pac#ets called datagramMs" each
of which is transported separatel.
?;. /ow will be the addressing in I'
+ach internet address consists of four btes (87 bits) defining three fields*
class tpe" net id" host id.
?9. hat is net id and host id
N" #%
This is assigned b internetwor# information center. It identifies the devices to-which a
device is attached.
<'$" #%
This is assigned b networ# administrator. It identifies the specific device on that
networ#.
?@. hat are tpes of classes available
C3!$$ A The use onl one bte to identif class tpe and net id" The remaining three btes
available for host id. The possible networ# addresses are ?.:.:.: to ?7<.:.:.:.
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C3!$$ B The use two btes to identif net id and two btes for host id. The possible
networ# addresses are ?7=.:.:.: to ?>?.799.:.:.
C3!$$ C The use two btes to identif net id and one bte for host id.The possible networ#
address is ?>7.:.:.: to 778.779.799.:.
C3!$$ D
lass D is reserved for multicasting. $ulticasting allows copies of a datagram to be passed
to select group of hosts rather to an individual host.It is similar to broadcasting" but where
broadcasting reuires that a pac#et be passed to all possible destinations" multicasting allows
transmission to a selected subset. The address are 77;.:.:.: to 7;:.:.:.:.
C3!$$ E
lass + addresses are reserved for future use. The possible address areFG7;:.:.:.
?<. hat is sub netting
In I' addressing one portion of the address indicates a networ# (net id)and the other portion
indicates the host on the networ#(host id).
In man cases" these two levels of hierarch are not enough.
4ne solution to this problem is subnetting" the further division of a networ#s called
subnetwor#s.
?= .what are the levels of hierarch in sub netting
• Net-id* This is the first level which defines the site.
• %ubnet id* this is the second level. It defines the phsical subnetwor#.
• /osted* This is the third level.It defines the connection of the host to the subnetwor#
?>./ow will be the routing of I' datagram
The routing of an I' datagram involves three steps*
• Deliver to the site
• Deliver to the subnetwor#
• Deliver to the host
7:. Define mas#ing.
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$as#ing is the process that extracts the address of the phsical networ# from an I' address.
$as#ing can be done whether we have sub netting or not. If there is no sub netting" mas#ing
+xtracts the networ# address from an I' address. If there is sub netting" mas#ing extracts the
subnetwor# address from an I' address.
7?. hat are tpes of mas#ing
• 2oundar level mas#ing
• Nonboundar level mas#ing
77 .hat are the rules to be followed in boundar level mas#ing
• The btes in the I' address that correspond to 799 in the mas# will be repeated in
the subetwor# address.
• The btes in the I' address that correspond to : in the mas# will change to : in
the subnetwor# address.
78. hat are the rules to be followed in nonboundar level mas#ing
• The btes in the I' address that correspond to 799 in the mas# will be repeated in
the subnetwor# address.
• The btes in the I' address that correspond to : in the mas# will change to : in the
subnetwor# address.
• ,or other btes" use the bit-wise !ND operator.
7;. hat is !&'
The address resolution protocol associates an I' address with the phsical address. I, the
NI on particular machine fails" the phsical address changes. The I' address" on the hand" have
universal 3urisdiction cannot be changed. !&' is used to find the phsical address of the node
when its internet address is #nown.
79. hat is &!&'
The reverse address resolution (&!&') allows a host to discover its internet address when it
#nown onl to its phsical address. The host wishing to retrieve its internet address broadcasts an
&!&' uer pac#et that contains its phsical address to ever host on its phsical networ#.
! server on the networ# recogni0es the &!&' pac#et the hostMs internet address.
7@ .hat is I$'
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The internet group message protocol (I$') has been designed to help a multicast touter the
hosts in a 1!N that are members of a multicast group.
It also handles both control and error messages" but its sole function is to respect problems" not
correct them. &esponsibities for correction lies with the sender.
7<. hat is IA$'
The internet group message protocol (IA$') has been designed to help a multicast router
identif the hosts in a 1!N that are members of a multicast group. It is a companion to the I'
protocol
7= hat is router
&outer is an internetwor#ing device operating at the first three 4%I laers router is attached
to two or more networ#s and forwards pac#ets from one networ# to another.The process
performed b the router is #nown as routing.
7>. hat are the routing concepts available
• 1east-cost routing
• Non adaptive and adaptive routing
8:. hat is 1east-cost routing
1east-cost routing*
The least-cost routing is based on efficienc* which of the available
pathwas is the cheapest or shorest.hen shortest means the pathwa reuiring the smallestnumber of relas" it is called hop-count routing"in which ever lin# is considered to be of eual
length and given the value one.
8?. hat is nonadaptive and adaptive routing
N'*!%!"#/ ')"#*
In nonadaptive routing" the routing decisions are not made based on the
condition or topolog of the networ#s.
A%!!"#/ ')"#*
In adaptive routing" the router ma select a new route for each pac#et in
response to changes in condition and topolog of the networ#s.
87. hat is routing algorithm
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The algorithm used b a router to determine the optimum path for a pac#et is #nown as
routing algorithm. The following are the routing algorithms
• Distance vector routing
• 1in# state routing
88. hat is distance vector routing
In distance vector routing" each router periodicall shares its #nowledge about the entire networ#
with its neighbors. The three #es to understand how this algorithm wor#s are as follows*
• Bnowledge about the whole networ#
• &outing onl to neighbors
• Information sharing at regular intervals
8;./ow the information will be shared in distance vector routing
! router sends its #nowledge to its neighbors. The neighbors add this #nowledge to their
own #nowledge and send the whole table to their own neighbors. In this wa" the first router gets
its own information bac# plus new information about its neighborMs other neighbors. In distance
vector routing" the cost is based on hop count
89. hat is routing table
! table containing information a router needs to route pac#ets. The information mainclude the networ# address the cost" the address of the next hop" and so on.
Networ# ID ost Next hop
---------------------- ----------------------------- ---------------------------------
The networ# ID is the final destination of the pac#et. The cost is the number of hops a pac#et
must ma#e to get there. The next router is the router to which a pac#et must be delivered on its
wa to a particular destination.
8@. hat is lin# state routing
In lin# state routing" each router shares its #nowledge of its neighborhood with everother router in the internetwor#. It has
• Bnowledge about the neighborhood
• To all routers
• Information sharing when there is a change
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8<. hat are factors to be considered when cost is applied to pac#et
• ost is applied onl b routers and not b an other stations on a networ#
• ost is applied as a pac#et leaves the router rather than as its enters.
8=. hat is mean b flooding
,looding means that a router sends its information to all of its neighbors. +ach neighbor
sends the pac#et to all of its neighbors" and so on. +ver router that receives the pac#et sends
copies to all of its neighbors. ,inall" ever router receives a cop of the same information.
8>. hat is 1in# %tate 'ac#et (1%')
hen a router floods the networ# with information about its neighborhood" it is said to
be advertising. The basis of this advertising is a %hort pac#et called a lin# state pac#et. !n 1%'
contains four fieldsO
!dvertiser Networ# ost Neighbor ----------------- ------------------- ----------------- --------------
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UNIT ITRANS PORT LAER
?. W!" #$ )*&"#'* ' "!*$'" 3!+
The protocol in the transport laer ta#es care in the deliver of data from
one application program on one device to an application program on another
device. The act as a lin# between the upper laer protocols and the services
provided b the lower laer.
2. W!" ! " %)"#$ ' " "!*$'" 3!+
The services provided b the transport laer
+nd-to- end deliver
!ddressing &eliable
deliver ,lowcontrol $ultiplexing
. W!" #$ " %#*& ":* *":'; 3! %3#/ !*% " "!*$'"
3! %3#/+
N":'; 3! %3#/ T!*$'" 3! %3#/
The networ# laer is responsible for
the the source-to-destination
deliver of pac#et
The transport laer is responsible for
source-to-destination deliver of the
entire message.
4. W!" ! " ') !$&"$ 3!"% "' " 3#!3 %3#/ ' %!"!+
The four aspects are"
+rror control %euence
control 1oss control
Duplication control
5. W!" #$ (!*" $(*"+
!t the sending and receiving end of the transmission" T' divides long
transmissions into smaller data units and pac#ages each into a frame called a segment.
6. W!" #$ (!*" $(*"!"#'*+
hen the si0e of the data unit received from the upper laer is too long for the
networ# laer datagram or data lin# laer frame to handle" the transport protocol
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divides it into smaller usable bloc#s. The dividing process is called segmentation.
<. W!" #$ (!*" C'*&!"*!"#'*+
The si0e of the data unit belonging to single sessions are so small that several
can fit together into a single datagram or frame" the transport protocol combines them into a
single data unit. The combining process is called concatenation.
8. W!" ! " "$ ' ()3"#3=#*+
The tpes of multiplexing are"
Upward multiplexing
Downward multiplexing
9. W!" ! " ":' '$$#3 "!*$'" $/#&$+
Two basic tpes of transport services are"
onnection service
onnectionless services
10. T "!*$'" 3! &!"$ " &'**&"#'* ":* $')& !*% %$"#*!"#'*. W!"
! " " /*"$ #*/'3/% #* " &'**&"#'*+
,or securit" the transport laer ma create a connection between the two
end ports. ! connection is a single logical path between the source and destination that
is associated with all pac#ets in a message. reating a connection involves three
steps*
•
onnection establishment• Data transfer J onnection release.
11. W!" #$ (!*" &'*$"#'*+
ongestion in a networ# occurs if user sends data into the networ# at a rate
greater than that allowed b networ# resources.
12. W " &'*$"#'* '&&)$ #* *":';+
ongestion occurs because the switches in a networ# have a limited buffer
si0e to store arrived pac#ets.
?8. W!" #$ (!*" )!3#" ' $/#&+
The ualit of service defines a set of attributes related to the performance of
the connection. ,or each connection" the user can reuest a particular attribute each service
class is associated with a set of attributes.
14. W!" ! " ":' &!"'#$ ' Q'S !""#)"$+
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The two main categories are
User 4riented
Networ# 4riented
15. L#$" ')" " )$ 3!"% !""#)"$+
User related attributes are
%& L %ustainable ell &ate
'& L 'ea# ell &ate
$&- $inimum ell &ate
5DT L ell 5ariation Dela Tolerance
16. W!" ! " *":';$ 3!"% !""#)"$+
The networ# related attributes are"
ell loss ratio (1&)
ell transfer dela (TD)
ell dela variation
(D5) ell error ratio
(+&)
17. W!" #$ " %#*& ":* $/#& '#*" !%%$$, 3'#&!3 !%%$$ !*%
$#&!3 !%%$$+
S/#& '#*" !%%$$#* L'#&!3 !%%$$#* P$#&!3 !%%$$#*
The transport laer header
includes a tpe of address
called a service point
address or port address"
which ma#es a data deliver
from a specific process on
one computer to a specific
process on another
computer.
If a pac#et passes the
networ# boundar we need
another addressing to
differentiate the source and
destination sstems. The
networ# laer adds a
header" which indicate the
logical address of the sender
and receiver.
If the frames are to be
distributed to different
sstems on the networ#" the
data lin# laer adds the
header" which defines the
source machineMs address
and the destination
machineMs address.
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UNIT-5
?. What is domain name system?
Domain name sstem (DN%) is a client server application that identifies each host
on the Internet with a uniue user-friendl name.
DN% is a T'PI' application service that converts user-friendl names to I' address.
7. 1ist out the various sections of domain name space
In the internet" domain name space is divided into different sections*
-FAeneric domains
-Fountr domains
-FInverse domains
8. Describe about generic domains
The generic domains define registered hosts according to their generic behavior.
+ach node in the tree defines a domain. hich is an index to the domain name space database It
allows three-character labels.
;. 1ist some of the generic domain labels with description
1abel Description
om ommercial organi0ation
+ddo +ducational Institutions
Aov Aovernment Institutions
Int International organi0ations.
$il $ilitar groups
Net Networ# support centers
4rg Nonprofit organi0ations
!rts ultural organi0ations
,irm 2usinesses or firms
Info Information service providers
No personal nomenclatures
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9. Describe about countr domains
The countr domain section follows the same format as the generic domain but
uses two-character countr abbreviations in pave of the three character organi0ational
abbreviation at the first level.
%econd-level labels can be organi0ational or the can be more specific national designations.
@. rite about inverse domain
The inverse domain is used to map an address to a name.
<. at is %$T'
The T'I' protocol that supports electronic mail on the Internet is called simple
mail Transfer protocol (%$T').
It is a sstem for sending messages to other computer users based on e-mail address.
%$T' provides for mail exchange between users on the same or different computers and
supports.
-Fsending a single message to one or move recipients.
-Fsending messages that include text" voice" video or graphics.
-Fsending messages to users on networ#s outside the Internet.
=.hat are the components of %$T'
The %$T' client and server is divided into two components.
-FU$ !*" >UA)* the U! prepares the message creates the envelope" and puts the
message in the envelope.
-F The $T! transfers the mail across the Internet.
>. rite about addressing sstem in %$T'
The addressing sstem used b %$T' consists of two parts*
-FL'&!3 !"* The local parts define the name of a special file" called the user mailbox" where
all of the mail received for a user is stored for retrieval b the user agent.
-FD'(!#* *!(* The second part of the address is the domain name. !n organi0ation usuall
selects one or more hosts to receive and send e-mailO the are sometimes called mail exchangers.
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?:. Define $I$+
$ultipurpose Internet mail +xtension ($I$+) is a supplementar protocol that
allows the transfer of multimedia messages.
??. hat is post office protocol
'ost office 'rotocol is a protocol used b mail server in con3unction with %$T' to
receive and hold mail for hosts.
It is a client-server protocol that is used between a user wor# station and a mail server.
?7. hat is file transfer protecting
,ile transfer protocol (,T') is the standard mechanism provided batchPI' for
coping a file from one host to another.
,T'differs from other clientMs server applications in that it establishes two connections between
the hosts.ont connections is used for data transfer. The other for control information.
?8. hat are the components available in ,T'
In ,T'" the client has three components*
-Fthe user interface.
-Fclient control process.
-Fclient data transfer process.
The server has two components*
-Fserver control process.
-Fserver data transfer process.
?;. hat is /TT'
The /pertext transfer protocol is a protocol uses mainl to access data on the orld ide eb.
The protocol transfers data in the form of plain text" hpertext" audio" and video and so on.
It is called as hpertext transfer protocol because its efficienc allows its use in a hpertextenvironment where there are rapid 3umps from one document to another.
?9. rite about the functions of /TT'
/TT' functions li#e a combination of ,T' and %$T'.
It is similar to ,T' because it transfers files and uses the services of T'.
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/TT' is li#e %$T' because the data transferred between the client and server loo#
li#e %$T' $essages.
?@. %tate the Difference 2etween /TT' and %$T'*
/TT' %$T'
The messages are sent from the clientto the %erver and from the %erver
from the lient.
The /TT' messages are read and
interpreted b onl /TT' server and
/TT' client.
/TT' messages are delivered
immediatel.
The messages are sent from the client tothe server.
The %$T' messages can be read b
humans.
%$T' messages are stored and
forwarded.
?<. hat is U&1
The Uniform &esource 1ocator (U&1) is a standard for specifing an #ind of
information on the Internet. The U&1 defines four things*
- M"'%* The method is the protocol used to retrieve the document.
-F'$" &'()"* /ost is the computer where he information is located.
-FP'" 'ort is potional.if port is included" it should be inserted between the host and the pathand it should be separated from the host b a colon.
-FP!" 'ath is the pathname of the file where the information is located.
$ethod * /ost * 'ort 'ath
?=. at is orld ide eb
The orld ide eb is the repositor of information spread all over the
world and lin#ed together. The www has a uniue combination of flexibilit portabilit and user-
friendl features that dist anguish it from other services provided b the Internet.
?>. hat is meant b /pertext and hpermedia
/pertext and hpermedia are documents lin#ed to one another through the
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concept of pointers./pertext documents contain onl text" whereas hpermedia documents
cand contain pictures" graphics and sound.
7:. Describe about 2rowser !rchitecture
+ach browser usuall consists of three parts*
-FC'*"'33* The controller receives input from the #eboard or the mouse.
-FC3#*" P'!($* The controller uses the client programs to access the document. The client
program can be one of the methods such as /TT'" ,T' or T+1N+T.
-FI*""$* The controller uses interpreter to displa the document on the screen. The
interpreter can be /T$1 or 3ava" depending on the tpe of document.
7?. 1ist out the categories of web pages
-F%tatic documents.
-FDnamic documents.
-F!ctive documents.
77. rite about static document
%tatic document are fixed content documents that are created are stored in a server.
(+gg)/T$1. /T$1 is a language used to create static web pages.
The webpage contains" head" which contains title of the page" bod" which includes text and tags"
which provide structure to a document" format text" insert" figures" lin# different documentstogether etc.
78. hat is dnamic document
The dnamic document is created b a server onl at a browser reuest. hen reuest arrives"
the web server runs an application program that creates the dnamic document. (+gg) AI.AI
is a standard for creation Jhandling dnamic web documents.
7;. hat are the steps to be followed b a server when it handles dnamic document
! server that handles dnamic documents follows these steps*
-F The server examines the U&1 to find if it defines a dnamic document.
-FIf the U&1 defines a dnamic document" the server executes the program.
-FThe server sends the output of the program to the client.
79. hat is active document
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!n active document is a cop of the program retrieved b the client and run at the
client site.
(+gg) 3ava.
Hava is a combination of high-level programming language. ! run time environment
and a class librar that allows programmer to write an active document and a browser to run it.
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