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8/10/2019 GATE Computer Networks Book
1/12
8/10/2019 GATE Computer Networks Book
2/12
8/10/2019 GATE Computer Networks Book
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Syllabus Computer Networks
THE GATE ACADEMY PVT.LTD. H.O.: #74, KeshavaKrupa (third Floor), 30thCross, 10thMain, Jayanagar 4thBlock, Bangalore-11 080 65700750 i f @th t d C i ht d W b th t d
Syllabus for Computer Networks
ISO/OSI stack, LAN technologies (Ethernet, Token ring), Flow and error control techniques,
Routing algorithms, Congestion control, TCP/UDP and sockets, IP(v4), Application layer
protocols (ICMP, DNS, SMTP, POP, FTP, HTTP); Basic concepts of hubs, switches, gateways, and
routers.
Analysis of GATE Papers
(Computer Network)
Year
Percentage of marks
Overall Percentage
2013
7.00
6.513
2012 9.00
2011
3.00
2010 8.00
2009 3.33
2008
6.00
2007
9.33
2006
7.33
2005
6.00
2004
7.33
2003 5.33
8/10/2019 GATE Computer Networks Book
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Contents Computer Networks
THE GATE ACADEMY PVT.LTD. H.O.: #74, Keshava Krupa (third Floor), 30th
Cross, 10th
Main, Jayanagar 4th
Block, Bangalore-11
080 65700750 i f @th t C i ht d W b th t d Page i
C O N T E N T S
Chapters Page No
1 Introduction
1 32
CCoommppuutteerrNNeettwwoorrkk 11
GGooaallss//AAddvvaannttaaggeessooffNNeettwwoorrkkiinngg 1133
CCoommppoonneennttssooffNNeettwwoorrkk 33
CCrriitteerriiaaooffaaNNeettwwoorrkk 33
CCllaassssiiffiiccaattiioonnooffaaNNeettwwoorrkk 33
TTyyppeessooffNNeettwwoorrkkCCoonnnneeccttiioonn 44
NNeettwwoorrkkTTooppoollooggyy 4466
TTrraannssmmiissssiioonnMMooddeess 6677
DDaattaaaannddDDaattaaCCoommmmuunniiccaattiioonn 77
TThheeMMooddeell 772200
NNeettwwoorrkkssCCoonnnneeccttiinnggDDeevviicceess 22002244
AAssssiiggnnmmeenntt11 2255
2288
AAssssiiggnnmmeenntt22 2299
AAnnsswweerrKKeeyyss 3300
EExxppllaannaattiioonnss 33003322
2 Physical Layers (Data rate, Digital transmission)
33 47
IInnttrroodduuccttiioonn 3333
TTrraannssmmiissssiioonnIImmppaaiirrmmeenntt 33333344
DDiiggiittaallttrraannssmmiissssiioonn 33443388
TTrraannssmmiissssiioonnMMooddee 33883399
MMuullttiipplleexxiinngg 33994400
TTrraannssmmiissssiioonnMMeeddiiaa 44004411
AAssssiiggnnmmeenntt11 44224444
AAssssiiggnnmmeenntt22 44444455
AAnnsswweerrKKeeyyss 4466
EExxppllaannaattiioonnss 44664477
8/10/2019 GATE Computer Networks Book
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Contents Computer Networks
THE GATE ACADEMY PVT.LTD. H.O.: #74, Keshava Krupa (third Floor), 30th
Cross, 10th
Main, Jayanagar 4th
Block, Bangalore-11
080 65700750 i f @th t C i ht d W b th t d Page ii
3
Medium Access Sublayer (LAN Technologies: Ethernet, Token
Ring)
48 64
IInnttrroodduuccttiioonn 4488
MMuullttiipplleeAAcccceessssPPrroottooccoollss 44885522
EEtthheerrnneettCCaabblliinngg 5533
TThhee880022..33MMAACCssuubbllaayyeerrpprroottooccooll 5544
IIEEEEEEssttaannddaarrdd880022..44--TTookkeennBBuuss 55445555
IIEEEEEEssttaannddaarrdd880022..55--TTookkeennRRiinngg 55555588
AAssssiiggnnmmeenntt11 55996600
AAssssiiggnnmmeenntt22 66006611
AAnnsswweerrKKeeyyss 6622
EExxppllaannaattiioonnss 66226644
4 The Data Link Layer (Flow and error control techniques) 65 - 99
DDaattaalliinnkkLLaayyeerrDDeessiiggnnIIssssuueess 66556688
EErrrroorrDDeetteeccttiioonnaannddEErrrroorrCCoorrrreeccttiioonn 66997788
FFlloowwCCoonnttrroollaannddEErrrroorrCCoonnttrrooll 7788
9911
HHiigghh--lleevveellDDaattaaLLiinnkkCCoonnttrrooll((HHDDLLCC))PPrroottooccooll 99119933
AAssssiiggnnmmeenntt11 99449955
AAssssiiggnnmmeenntt22 99559966
AAnnsswweerrKKeeyyss 9977
EExxppllaannaattiioonnss 99779999
5
Routing & Congestion Control 100 114
Routing 110000110011
Routing Algorithms: 110011110077
AAssssiiggnnmmeenntt11 110088111100
AAssssiiggnnmmeenntt22 111100111111
AAnnsswweerrKKeeyyss 111122
EExxppllaannaattiioonnss 111122111144
8/10/2019 GATE Computer Networks Book
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Contents Computer Networks
THE GATE ACADEMY PVT.LTD. H.O.: #74, Keshava Krupa (third Floor), 30th
Cross, 10th
Main, Jayanagar 4th
Block, Bangalore-11
080 65700750 i f @th t C i ht d W b th t d Page iii
6
TCP/IP, UDP And Sockets, IP(V4) 115 145
OOvveerrVViieewwooffTTCCPP//IIPP 111155
111177
NNeettwwoorrkkLLaayyeerr 111177112211
AAddddrreessssiinnggoonnIInntteerrnneett 112222112266
SSuubbnneettttiinngg 112277113311
OOtthheerrPPrroottooccoolliinntthheeNNeettwwoorrkkLLaayyeerr 113311113333
TTrraannssppoorrttLLaayyeerr 113333113377
AAssssiiggnnmmeenntt11 113388113399
AAssssiiggnnmmeenntt22 114400
114411 AAnnsswweerrKKeeyyss 114422
EExxppllaannaattiioonnss 114422114455
7
Application Layer 146 157
TThheeDDoommiiaannNNaammeeSSeerrvviiccee((DDNNSS)) 114466114477
FFiilleeTTrraannssffeerrPPrroottooccooll((FFTTPP)) 114488114499
TTrriivviiaallFFiilleeTTrraannssffeerrPPrroottooccooll((TTFFTTPP)) 114499
SSiimmpplleeMMaaiillTTrraannssffeerrPPrroottooccooll((SSMMTTPP)) 114499115500
UUnniiffoorrmmRReessoouurrcceeLLooccaattoorr((UURRLL)) 115500
MMuullttiippoosseeIInntteerrnneettMMaaiillEExxtteennssiioonnss((MMIIMMEE)) 115500
PPoossttOOffffiicceePPrroottooccooll((PPOOPP)) 115511
HHyyppeerrtteexxttTTrraannssffeerrPPrroottooccooll((HHTTTTPP)) 115511
AAssssiiggnnmmeenntt11 115522115533
AAssssiiggnnmmeenntt22 115544
AAnnsswweerrKKeeyyss 115555
EExxppllaannaattiioonnss 115555115577
8 Network Security 158 175
SSyymmmmeettrriicckkeeyyoorrPPrriivvaatteekkeeyyaallggoorriitthhmmss 115588116600
AAssyymmmmeettrriicckkeeyyAAllggoorriitthhmm((oorr))PPuubblliicckkeeyyAAllggoorriitthhmm 116600116611
DDiiggiittaallSSiiggnnaattuurreess 116611116622
FFiirreewwaallllss 116622
116688
8/10/2019 GATE Computer Networks Book
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Contents Computer Networks
THE GATE ACADEMY PVT.LTD. H.O.: #74, Keshava Krupa (third Floor), 30th
Cross, 10th
Main, Jayanagar 4th
Block, Bangalore-11
080 65700750 i f @th t C i ht d W b th t d Page iv
AAssssiiggnnmmeenntt11 116699117700
AAssssiiggnnmmeenntt22 117711
117722
AAnnsswweerrKKeeyyss 117733
EExxppllaannaattiioonnss 117733117755
9
Module Test 176 - 191
TTeessttQQuueessttiioonnss 117766118844
AAnnsswweerrKKeeyyss 118855
EE
xx
pp
llaa
nn
aa
ttiioo
nn
ss
11
88
55
11
99
11
Reference Books 192
8/10/2019 GATE Computer Networks Book
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Chapter 1 Computer Networks
THE GATE ACADEMY PVT.LTD. H.O.: #74, Keshava Krupa (third Floor), 30th
Cross, 10th
Main, Jayanagar 4th
Block, Bangalore-11
080 65700750 i f @th t C i ht d W b th t d P 1
CHAPTER 1
Introduction
Computer Network
A computer network is created when several computers
andterminal
device are connected
together by data communication system.
A network is basically a communication system for computers.
Just as the telephone system allows two people to talk, networks allow computers tocommunicate. Figure 1.1 illustrate a simple computer network where computer A and B can
communicate and share resources through computer C.
Fig. 1.1 Computer A and B can access files on C and
can use the printer connected to C.
Goals / Advantages of Networking
(1)
Program and file sharing
Software resources can also be used more effectively over a network. With stand-alone
computers (i.e. not connected to network), the software used on the computer must bepresent on each computers hard disk. It is also difficult and time consuming to install and
A B
C
8/10/2019 GATE Computer Networks Book
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Chapter 1 Computer Networks
THE GATE ACADEMY PVT.LTD. H.O.: #74, Keshava Krupa (third Floor), 30th
Cross, 10th
Main, Jayanagar 4th
Block, Bangalore-11
080 65700750 i f @th t C i ht d W b th t d P 2
configure the software individually on every computer. With a network one can centrally
install and configure the software, which can be accessed at the entire connected
computer.
(2)
Network Resource sharing
Network resources include printers, plotters, Fax modems, scanners, floppy disks, CD-ROMS and storage devices (i.e. Hard disks) which can be shared by terminals connected to
network. For example the sharing of a resource such as a storage device.
(3) Database sharing
A database program is an ideal application for a network. A network feature called recordlocking lets multiple users simultaneously access a file without corrupting the data.
Record locking insures that no two users edit the same record at the same time.
(4)
Economical Expansion of the PC Base
Networks provide an economical way to expand the number of computers in an
organization.
(5) Ability to use network softwareA class of software called Groupware is designed specifically for networks. It lets users
interact and coordinate their activities.
Note: Not all software will use a network even if one is installed. You should check thesoftware documentation to see what features, if any, the software provides in a network
environment.
(6) Ability to use electronic mail
Electronic mail lets users easily communicate with one another Messages are dropped inmailboxes for the recipients to read at a convenient time.
(7) Creation of workgroupsGroups are important in networks. They can consist of users who work in a department or
who are assigned to special project. With Netware, one can assign users to groups and
then give each group access to special directories and resources not accessible by otherusers. This saves the trouble of assigning access to each individual user.
(8) Centralized ManagementBecause Netware users dedicated servers can be grouped in one location, along with the
shared resource attached to them, for easier management.
Hardware upgrades, software backups, system maintenance and system protection aremuch easier to handle when these devices are in one location.
(9) Security
A network provides more secure environment for a companys important information.
Security starts with the login procedure to ensure that a user accesses the network usinghis or her own account. This account is tailored (i.e. made according to the user
requirements) to give the user access only to authorized areas of the server and the
network. Login restrictions can force a user a log in at one specific station and only during
specific time frame or period.
(10) Access to more than one operating system
Netware provides connections for many different operating systems, including DOS, OS/2,UNIX, and Apple Talk. Users of these systems can access files on the Netware server.
8/10/2019 GATE Computer Networks Book
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Chapter 1 Computer Networks
THE GATE ACADEMY PVT.LTD. H.O.: #74, Keshava Krupa (third Floor), 30th
Cross, 10th
Main, Jayanagar 4th
Block, Bangalore-11
080 65700750 i f @th t C i ht d W b th t d P 3
(11) Enhancement of the corporate structure
Networks can change the structure of an organization and the way it is managed. Users
who work in a specific department and for a specific manager no longer need to be in thesame physical area. Their offices can be located in areas where their expertise is most
needed. The network ties them to their department managers and systems. Thisarrangement is useful for special project in which individuals from different departments,
such as research, production and marketing, need to work closely with each other.
Components of Network
Computer networks have the following fundamental components:1. Server
2. Workstations
3.
Network Interface Cards4. Cabling system
5. Shared Resources and Peripherals.
Criteria of a Network
A network must able to meet a certain number of criteria. The most important of these are
follows
(i) Performance:performance can be measured in many ways, including transmit time andresponse time. The performance of a network depends upon these following factors:
(i)
Number of users
(ii) Types of transmission medium(iii)
Capacity of connected hardware
(iv)
Efficiency of the software
(ii) Reliability: In addition to accuracy of delivery. Network reliability is measured by thefrequency of failure, the time it takes for a link to recover from a failure.
(iii)Security: Network security issues include protecting data from the unauthorized access.
Classification of network
It contains two or more computer along with a transmission path to share information and
resource of communication system. By the networking we can make interconnection of two ormore network device
Depending upon the graphical area, we can divide the computer network in 3 parts.
(i) LAN (Local Area Network)
(ii) MAN (Metropolitan Area Network)(iii)
WAN (Wide Area Network)
(i)
LAN:It spans over a diameter of 2 km, typically data transfer rate for LAN is 10-100 Mbps,
it is used by a signal organization. It propagates high transmission over unexpensivemedia. Example co-axial cable, twisted pair cable.
(ii) MAN:
It spans over 10 100km diameter. Data rate for MAN is 10 Mbps. Some special
equipments are required for transmission.
(iii) WAN:It spans across the country or nation. Data transfer rate for WAN is 1.5 mbps. It isused by multiple organizations
8/10/2019 GATE Computer Networks Book
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Chapter 1 Computer Networks
THE GATE ACADEMY PVT.LTD. H.O.: #74, Keshava Krupa (third Floor), 30th
Cross, 10th
Main, Jayanagar 4th
Block, Bangalore-11
080 65700750 i f @th t C i ht d W b th t d P 4
Types of Network Connection
In a network two or more device are connected together through link. Link is a path forcommunication that transfer data from one device to another.
There are two possible type of connection.(i)
Point to point
(ii)
Multi-point
(i)
Point to point: In this case one device is connected to another device.
Fig 1.2 Point to Point connection
(ii) Multi-point: Here two or more device are connected to each other. In a multipoint
connection the capacity of the channel is shared either spatially or temporarily.
Fig 1.3 Multi-point connection
Network Topology
There are two types of topology1.
Physical topology
2. Logical topology
1. Physical topology:
Physical topology represent the physical structure of computer
network. It tells how different computers are connected across its communication
path. There are six basic topology possible.(i) Mess (ii) Star (iii)Ring (iv)Hybrid
(v) Bus (vi) Cellular
(i) Mess Topology:In mesh topology every device has a dedicated point to point link to
every other device. A fully connected mesh network has n(n 1)/2 physical channelto link n device. To accommodate that many links, every device on the network must
have (n-1) input/output ports.
Advantages
(i) Eliminate traffic problems(ii)
A mesh topology is robust
(iii)
It is more secure and private(iv) Fault identification and fault isolation is easy
Work station
Work station
Main
frame
Work station
Work station Work stationLink
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