1.

NETWORKI
NGBASI
CS
1.
1COMPUTERNETWORK

A comput
er net
wor
k al
l
ows shar
ing of r
esour
ces and i
nfor
mat
ion among
i
nter
connect
ed dev
ices.I
nthe 1960s,t
he Adv
anced Resear
ch Pr
oject
sAgency
(
ARPA)st
art
ed f
undi
ng t
hedesi
gn oft
heAdv
anced Resear
ch Pr
oject
sAgency
Net
wor
k(ARPANET)f
ort
heUni
tedSt
atesDepar
tmentofDef
ense.I
twast
hef
ir
st
comput
ernet
wor
kint
hewor
ld.Dev
elopmentoft
henet
wor
kbegani
n1969,
basedon
desi
gnsdev
elopeddur
ingt
he1960s.

Comput
ernet
wor
kscanbeusedf
orav
ari
etyofpur
poses:

 Faci
l
itat
ing communi
cat
ions.Usi
ng a net
wor
k,peopl
e can communi
cat
e
ef
fi
cient
lyandeasi
l
yvi
aemai
l
,inst
antmessagi
ng,chatr
ooms,t
elephone,
v
ideot
elephonecal
l
s,andv
ideoconf
erenci
ng.

 Shar
inghar
dwar
e.I
nanet
wor
kedenv
ironment
,eachcomput
eronanet
wor
k
mayaccessandusehar
dwar
eresour
cesont
henet
wor
k,suchaspr
int
inga
documentonashar
ednet
wor
kpr
int
er.

 Shar
ingf
il
es,
dat
a,andi
nfor
mat
ion.I
nanet
wor
kenv
ironment
,aut
hor
izeduser
mayaccessdat
aandi
nfor
mat
ionst
oredonot
hercomput
ersont
henet
wor
k.
Thecapabi
l
ityofpr
ovi
dingaccesst
odat
aandi
nfor
mat
iononshar
edst
orage
dev
icesi
sani
mpor
tantf
eat
ureofmanynet
wor
ks.

 Shar
ing sof
twar
e.User
s connect
ed t
o a net
wor
k may r
un appl
i
cat
ion
pr
ogr
amsonr
emot
ecomput
ers.

 I
nfor
mat
ionpr
eser
vat
ion.

 Secur
it
y.

 Speedup.

1.
2NETWORKI
NG

Net
wor
kingi
sacommonsy
nony
mfordev
elopi
ngandmai
ntai
ningcont
act
sand
per
sonalconnect
ionswi
thav
ari
etyofpeopl
ewhomi
ghtbehel
pfult
oyouandy
our
car
eer
.

Net
wor
kingi
sthepr
act
iceofl
i
nki
ngt
woormor
ecomput
ingdev
icest
oget
herf
ort
he
pur
poseofshar
ingdat
a.Net
wor
ksar
ebui
l
twi
thami
xofcomput
erhar
dwar
eand
comput
ersof
twar
e.I
tisanespeci
all
yimpor
tantaspectofcar
eermanagementi
nthe
f
inanci
alser
vicesi
ndust
ry,
sincei
tishel
psy
oukeepabr
eastof
:

1.
3TYPESOFNETWORKS

 LocalAr
eaNet
wor
k

ALocalAr
eaNet
wor
k(LAN)i
sanet
wor
kthatconnect
scomput
ersanddev
icesi
na
l
i
mit
edgeogr
aphi
calar
easuchashome,
school
,comput
erl
abor
ator
y,of
fi
cebui
l
ding,
orcl
osel
yposi
ti
onedgr
oupofbui
l
dings.Eachcomput
erordev
iceont
henet
wor
kisa
node.Cur
rentwi
redLANsar
emostl
i
kel
ytobebasedonEt
her
nett
echnol
ogy
,
al
thoughnew st
andar
dsl
i
keI
TU-
TG.
hnal
sopr
ovi
deawayt
ocr
eat
eawi
redLAN
usi
ngexi
sti
nghomewi
res(
coaxi
alcabl
es,
phonel
i
nesandpowerl
i
nes)

 Per
sonalAr
eaNet
wor
k

A per
sonalar
eanet
wor
k(PAN)i
sacomput
ernet
wor
kusedf
orcommuni
cat
ion
among comput
erand di
ff
erenti
nfor
mat
ion t
echnol
ogi
caldev
ices cl
ose t
o one
per
son.Someexampl
esofdev
icest
hatar
eusedi
naPANar
eper
sonalcomput
ers,
pr
int
ers,f
axmachi
nes,t
elephones,PDAs,scanner
s,andev
env
ideogameconsol
es.
APANmayi
ncl
udewi
redandwi
rel
essdev
ices.Ther
eachofaPANt
ypi
cal
l
yext
ends
t
o10met
ers.Awi
redPANi
susual
l
yconst
ruct
edwi
thUSBandFi
rewi
reconnect
ions
whi
l
etechnol
ogi
essuchasBl
uet
oot
handi
nfr
aredcommuni
cat
iont
ypi
cal
l
yfor
ma
wi
rel
essPAN.

 HomeAr
eaNet
wor
k

Ahomear
eanet
wor
k(HAN)i
sar
esi
dent
ialLANwhi
chi
susedf
orcommuni
cat
ion
bet
weendi
git
aldev
icest
ypi
cal
l
ydepl
oyedi
nthehome,usual
l
yasmal
lnumberof
per
sonalcomput
ers and accessor
ies,such as pr
int
ers and mobi
l
e comput
ing
dev
ices.Ani
mpor
tantf
unct
ioni
stheshar
ingofI
nter
netaccess,of
tenabr
oadband
ser
vicet
hroughaCATV orDi
git
alSubscr
iberLi
ne(
DSL)pr
ovi
der
.Itcanal
sobe
r
efer
redt
oasanof
fi
cear
eanet
wor
k(OAN)
.

 Wi
deAr
eaNet
wor
k

Awi
dear
eanet
wor
k(WAN)i
sacomput
ernet
wor
kthatcov
ersal
argegeogr
aphi
c
ar
easuchasaci
ty,count
ry,orspansev
eni
nter
cont
inent
aldi
stances,usi
ng a
communi
cat
ionschannelt
hatcombi
nesmanyt
ypesofmedi
asuchast
elephone
l
i
nes,cabl
es,andai
rwav
es.AWANof
tenusest
ransmi
ssi
onf
aci
l
iti
espr
ovi
dedby
common car
ri
ers,such as t
elephone compani
es.WAN t
echnol
ogi
es gener
all
y
f
unct
ionatt
hel
owert
hreel
ayer
soft
heOSIr
efer
encemodel
:thephy
sicall
ayer
,the
dat
ali
nkl
ayer
,andt
henet
wor
klay
er.

 CampusNet
wor
k

Acampusnet
wor
kisacomput
ernet
wor
kmadeupofani
nter
connect
ionofl
ocal
ar
ea net
wor
ks (
LAN'
s) wi
thi
nal
i
mit
ed geogr
aphi
calar
ea.The net
wor
king
equi
pment
s(swi
tches,r
out
ers)andt
ransmi
ssi
onmedi
a(opt
icalf
iber
,copperpl
ant
,
Cat
5cabl
i
nget
c.)ar
eal
mostent
ir
elyowned(
byt
hecampust
enant/owner
:an
ent
erpr
ise,
uni
ver
sit
y,gov
ernmentet
c.)
.

I
nthecaseofauni
ver
sit
ycampus-
basedcampusnet
wor
k,t
henet
wor
kisl
i
kel
yto
l
i
nkav
ari
etyofcampusbui
l
dingsi
ncl
udi
ng;academi
cdepar
tment
s,t
heuni
ver
sit
y
l
i
brar
yandst
udentr
esi
dencehal
l
s.

 Met
ropol
it
anAr
eaNet
wor
k

AMet
ropol
i
tanar
eanet
wor
kisal
argecomput
ernet
wor
kthatusual
l
yspansaci
tyor
al
argecampus.

 Vi
rt
ualPr
ivat
eNet
wor
k

Av
irt
ualpr
ivat
enet
wor
k(VPN)i
sacomput
ernet
wor
kinwhi
chsomeoft
hel
i
nks
bet
weennodesar
ecar
ri
edbyopenconnect
ionsorv
irt
ualci
rcui
tsi
nsomel
arger
net
wor
k(e.
g.,
theI
nter
net
)inst
eadofbyphy
sicalwi
res.Thedat
ali
nkl
ayerpr
otocol
s
oft
hev
irt
ualnet
wor
kar
esai
dtobet
unnel
edt
hrought
hel
argernet
wor
kwhent
hisi
s
t
hecase.Onecommonappl
i
cat
ioni
ssecur
ecommuni
cat
ionst
hrought
hepubl
i
c
I
nter
net
,butaVPNneednothav
eexpl
i
citsecur
it
yfeat
ures,
suchasaut
hent
icat
ionor
cont
entencr
ypt
ion.VPNs,f
orexampl
e,can beused t
o separ
atet
het
raf
fi
cof
di
ff
erentusercommuni
ti
esov
eranunder
lyi
ngnet
wor
kwi
thst
rongsecur
it
yfeat
ures.

2.NETWORKTOPOLOGY

Net
wor
ktopol
ogyi
sthel
ayoutpat
ter
nofi
nter
connect
ionsoft
hev
ari
ousel
ement
s
(
li
nks,nodes,et
c.)ofacomput
ernet
wor
k.Net
wor
ktopol
ogi
esmaybephy
sicalor
l
ogi
cal
.Phy
sicalt
opol
ogymeanst
hephy
sicaldesi
gnofanet
wor
kincl
udi
ngt
he
dev
ices,l
ocat
ion and cabl
einst
all
ati
on.Logi
calt
opol
ogyr
efer
sto how dat
ais
act
ual
l
ytr
ansf
err
edi
nanet
wor
kasopposedt
oit
sphy
sical
desi
gn.

Var
ioust
opol
ogi
es:
:

 Bust
opol
ogy

Manydev
icesconnectt
oasi
ngl
ecabl
e"backbone"
.Ift
hebackbonei
sbr
oken,t
he
ent
ir
esegmentf
ail
s.Bust
opol
ogi
esar
erel
ati
vel
yeasyt
oinst
allanddon'
trequi
re
muchcabl
i
ngcompar
edt
otheal
ter
nat
ives.

Fi
g:2.
1

 Ri
ngTopol
ogy

I
nar
ing net
wor
k,ev
erydev
icehasexact
lyt
wo nei
ghbour
sforcommuni
cat
ion
pur
poses.Al
lmessagest
rav
elt
hroughar
ingi
nthesamedi
rect
ion.Li
ket
hebus
t
opol
ogy
,af
ail
urei
nanycabl
eordev
icebr
eakst
hel
oopandwi
l
ltakedownt
he
ent
ir
esegment
.A di
sadv
ant
ageoft
her
ingi
sthati
fanydev
icei
saddedt
oor
r
emov
edf
rom t
her
ing,t
her
ingi
sbr
okenandt
hesegmentf
ail
sunt
ili
tis"
ref
orged"
(
bydwar
fi
sh gol
dsmi
ths?
) I
tisal
so consi
der
abl
ymor
eexpensi
vet
han ot
her
t
opol
ogi
es.

Fi
g:2.
2

 St
arTopol
ogy

Ast
arnet
wor
khasacent
ralconnect
ionpoi
nt-l
i
keahuborswi
tch.Whi
l
eitt
akes
mor
ecabl
e,t
hebenef
iti
sthati
facabl
efai
l
s,onl
yonenodewi
l
lbebr
oughtdown.

Al
ltr
aff
icemanat
esf
rom t
hehuboft
hest
ar.Thecent
ralsi
tei
sincont
rolofal
lthe
nodesat
tachedt
oit
.Thecent
ral
hubi
susual
l
yaf
ast
,sel
f-
cont
ainedcomput
erandi
s
r
esponsi
blef
orr
out
ingal
ltr
aff
ict
oot
hernodes.Themai
nadv
ant
agesofast
ar
net
wor
kist
hatonemal
funct
ioni
ngnodedoesnotaf
fectt
her
estoft
henet
wor
k.
Howev
ert
hist
ypeofnet
wor
kcanbepr
onet
obot
tl
eneckandf
ail
urepr
obl
emsatt
he
cent
ral
sit
e.
 Fi
g:2.
3

 Tr
eeTopol
ogy

Al
soknownast
he'
Hier
archi
calt
opol
ogy
',t
het
reet
opol
ogyi
sacombi
nat
ionofbus
andst
art
opol
ogi
es.Theyar
ever
ycommoni
nlar
gernet
wor
ks.At
ypi
calscenar
ioi
s:
af
il
eser
veri
sconnect
edt
oabackbonecabl
e(e.
g.coaxi
al)t
hatr
unst
hrought
he
bui
l
ding,
from whi
chswi
tchesar
econnect
ed,
branchi
ngoutt
owor
kst
ati
ons.
 Fi
g:2.
4

 Mesht
opol
ogy

I
nthet
opol
ogi
esshownabov
e,t
her
eisonl
yonepossi
blepat
hfr
om onenodet
o
anot
hernode.I
fanycabl
eint
hatpat
hisbr
oken,
thenodescannotcommuni
cat
e.

Mesht
opol
ogyusesl
otsofcabl
est
oconnectev
erynodewi
thev
eryot
hernode.I
tis
v
eryexpensi
vet
owi
reup,buti
fanycabl
efai
l
s,t
her
ear
emanyot
herway
sfort
wo
nodest
ocommuni
cat
e.SomeWANs,l
i
ket
heI
nter
net
,empl
oymeshr
out
ing.I
nfact
t
heI
nter
netwasdel
i
ber
atel
ydesi
gnedl
i
ket
hist
oal
l
owsi
test
ocommuni
cat
eev
en
dur
inganucl
earwar
.
 Fi
g:2.
5

 Hy
bri
dTopol
ogy

Hy
bri
dnet
wor
kist
hecombi
nat
ionofdi
ff
erentt
opol
ogi
essuchasst
ar,Ri
ng,Mesh,
Buset
c.Forexampl
e,i
fadepar
tmentusesaBusnet
wor
k,seconddepar
tmentuses
t
her
ingnet
wor
k,t
hir
ddepar
tmentusest
heMeshnet
wor
kandf
our
thdepar
tment
usest
hest
arnet
wor
k.Al
lthenet
wor
ksofdi
ff
erentt
ypes(
off
ourdepar
tment
s)can
beconnect
edt
oget
hert
hroughacent
ralhub(
int
hef
orm ofst
arnet
wor
k)asshown
i
nthef
igur
eabov
e.

Fi
g:2.
6
 3.BASI
CNETWORKI
NGDEVI
CES

Comput
ernet
wor
kingdev
icesar
euni
tst
hatmedi
atedat
ainacomput
ernet
wor
k.
Comput
ernet
wor
king dev
ices ar
e al
so cal
l
ed net
wor
k equi
pment
,Int
ermedi
ate
Sy
stems(
IS)orI
nter
Wor
kingUni
t(I
WU)
.Uni
tswhi
char
ethel
astr
ecei
verorgener
ate
dat
aar
ecal
l
edhost
sordat
ater
minal
equi
pment
.

 3.
1Rout
ers

Ar
out
eri
sacommuni
cat
iondev
icet
hati
sused t
o connectt
wo l
ogi
cal
l
yand
phy
sical
l
ydi
ff
erentnet
wor
ks,
twoLANs,
twoWANsandaLANwi
thWAN.Themai
n
f
unct
ionoft
her
out
eri
stosor
ti
ngandt
hedi
str
ibut
ionoft
hedat
apacket
stot
hei
r
dest
inat
ionsbasedont
hei
rIPaddr
esses.Rout
erspr
ovi
dest
heconnect
ivi
tybet
ween
t
heent
erpr
isebusi
nesses,I
SPsandi
nthei
nter
neti
nfr
ast
ruct
ure,r
out
eri
samai
n
dev
ice.Ci
scor
out
ersar
ewi
del
yusedi
nthewor
ld.Ev
eryr
out
erhasr
out
ingsof
twar
e,
whi
chi
sknownasI
OS. Rout
eroper
atesatt
henet
wor
klay
eroft
heOSImodel
.
Rout
erdoesnotbr
oadcastt
hedat
apacket
s.

Wehav
etwot
ypesofr
out
er:
1.Har
dwar
e
2.Sof
twar
e.–Thi
srout
eri
spr
ovi
dedbyRRASSERVI
CE.

Fi
g:3.
1

 3.
2Swi
tches
Li
ket
her
out
er,aswi
tchi
sani
ntel
l
igentdev
icet
hatmapst
heI
Paddr
esswi
tht
he
MACaddr
essoft
heLAN car
d.Unl
i
ket
hehubs,aswi
tchdoesnotbr
oadcastt
he
dat
atoal
lthecomput
ers,i
tsendst
hedat
apacket
sonl
ytot
hedest
inedcomput
er.
Swi
tchesar
eusedi
ntheLAN,MANandWAN.I
nanEt
her
netnet
wor
k,comput
ers
ar
edi
rect
lyconnect
edwi
tht
heswi
tchv
iat
wist
edpai
rcabl
es.I
nanet
wor
k,swi
tches
uset
het
hreemet
hodst
otr
ansmi
tthedat
ai.
e.st
oreandf
orwar
d,cutt
hroughand
f
ragmentf
ree.

Wehav
etwot
ypesofswi
tch.
1.Mangeabl
eSwi
tch:I
thasconsol
epor
tbyusi
ngt
hiswecanmanaget
hisswi
tch
accor
dingt
oourneed.
2.Non-
Mangeabl
eSwi
tch:I
thasnoconsol
epor
tweuset
hisswi
tchaswepur
chase
i
t.

Fi
g:3.
2

 3.
3Hubs

Thecent
ralconnect
ingdev
icei
nacomput
ernet
wor
kisknownasahub.Ther
ear
e
t
wot
ypesofahubi
.e.act
ivehubandpassi
vehub. Ev
erycomput
eri
sdi
rect
ly
connect
edwi
tht
hehub.Whendat
apacket
sar
ri
vesathub,i
tbr
oadcastt
hem t
oal
l
t
heLAN car
dsi
nanet
wor
kandt
hedest
inedr
eci
pientpi
ckst
hem andal
lot
her
comput
ersdi
scar
dthedat
apacket
s.Hubhasf
ive,
eight
,si
xteenandmor
epor
tsand
onepor
tisknownasupl
i
nkpor
t,whi
chi
susedt
oconnectwi
tht
henexthub.
 Fi
g:3.
3

 3.
4Modems

Amodem i
sacommuni
cat
iondev
icet
hati
susedt
opr
ovi
det
heconnect
ivi
tywi
tht
he
i
nter
net
.Modem wor
ksi
ntwoway
si.
e.Modul
ati
onandDemodul
ati
on.I
tconv
ert
s
t
hedi
git
aldat
aint
otheanal
ogueandanal
oguet
odi
git
al.

Fi
g:3.
4

 3.
5LANCar
ds

LANcar
dsornet
wor
kadapt
ersar
ethebui
l
dingbl
ocksofacomput
ernet
wor
k.No
comput
ercancommuni
cat
ewi
thoutapr
oper
lyi
nst
all
edandconf
igur
edLANcar
d.
Ev
eryLANcar
dispr
ovi
dedwi
thauni
queI
Paddr
ess,
subnetmask,
gat
ewayandDNS
(
ifappl
i
cabl
e).AnUTP/
STPcabl
econnect
sacomput
erwi
tht
hehuborswi
tch.Bot
h
endsoft
hecabl
ehav
etheRJ-
45connect
orsonei
sinser
tedi
ntot
heLANcar
dand
onei
nthehub/
swi
tch.LANcar
dsar
einser
tedi
ntot
heexpansi
onsl
otsi
nsi
det
he
comput
er.Di
ff
erentLANcar
dssuppor
tdi
ff
erentspeedf
rom 10/
100t
o10/
1000.

Et
her
net=speed10mbps
FastEt
her
net=100mbps
Gi
gaEt
her
net=1000mbps
Fast
gigaEt
her
net=10000mbps

Fi
g:3.
5

 3.
6Net
wor
kRepeat
er

Ar
epeat
erconnect
stwosegment
sofy
ournet
wor
kcabl
e.I
tret
imesandr
egener
ates
t
hesi
gnal
stopr
operampl
i
tudesandsendst
hem t
otheot
hersegment
s.When
t
alki
ngabout
,et
her
nett
opol
ogy
,youar
epr
obabl
ytal
ki
ngaboutusi
ngahubasa
r
epeat
er.Repeat
ersr
equi
reasmal
lamountoft
imet
oregener
atet
hesi
gnal
.Thi
scan
causeapr
opagat
iondel
aywhi
chcanaf
fectnet
wor
kcommuni
cat
ionwhent
her
ear
e
sev
eralr
epeat
ersi
nar
ow.Manynet
wor
kar
chi
tect
uresl
i
mitt
henumberofr
epeat
ers
t
hatcanbeusedi
nar
ow.Repeat
erswor
konl
yatt
hephy
sicall
ayeroft
heOSI
net
wor
kmodel
.
 Fi
g:3.
6

 3.
7Br
idge

Abr
idger
eadst
heout
ermostsect
ionofdat
aont
hedat
apacket
,tot
ellwher
ethe
messagei
sgoi
ng.I
treducest
het
raf
fi
conot
hernet
wor
ksegment
s,si
ncei
tdoesnot
sendal
lpacket
s.Br
idgescanbepr
ogr
ammedt
orej
ectpacket
sfr
om par
ti
cul
ar
net
wor
ks.Br
idgi
ngoccur
satt
hedat
ali
nkl
ayeroft
heOSImodel
,whi
chmeanst
he
br
idgecannotr
eadI
Paddr
esses,butonl
ytheout
ermosthar
dwar
eaddr
essoft
he
packet
.Inourcaset
hebr
idgecanr
eadt
heet
her
netdat
awhi
chgi
vest
hehar
dwar
e
addr
essoft
hedest
inat
ionaddr
ess,
nott
heI
Paddr
ess.Br
idgesf
orwar
dal
lbr
oadcast
messages.
 Fi
g:3.
7

Thehar
dwar
eaddr
essi
sal
socal
l
edt
heMAC(
medi
aaccesscont
rol
)addr
ess

 3.
8Gat
eway

A gat
ewaycant
ransl
atei
nfor
mat
ionbet
weendi
ff
erentnet
wor
kdat
afor
mat
sor
net
wor
kar
chi
tect
ures.I
tcant
ransl
ateTCP/
IPt
oAppl
eTal
ksocomput
erssuppor
ti
ng
TCP/
IPcancommuni
cat
ewi
thAppl
ebr
andcomput
ers.Mostgat
eway
soper
ateat
t
heappl
i
cat
ionl
ayer
,butcanoper
ateatt
henet
wor
korsessi
onl
ayeroft
heOSI
model
.Gat
eway
swi
l
lst
artatt
hel
owerl
evelandst
ri
pinf
ormat
ionunt
ili
tget
stot
he
r
equi
redl
evelandr
epackaget
hei
nfor
mat
ionandwor
kit
swaybackt
owar
dthe
har
dwar
elay
eroft
heOSImodel
.Toconf
usei
ssues,
whent
alki
ngaboutar
out
ert
hat
i
susedt
oint
erf
acet
oanot
hernet
wor
k,t
hewor
dgat
ewayi
sof
tenused.Thi
sdoes
notmeant
her
out
ingmachi
nei
sagat
ewayasdef
inedher
e,al
thoughi
tcoul
dbe.

4.NETWORKMODELS

When deal
i
ng wi
th net
wor
king,y
ou mayheart
he t
erms "
net
wor
k model
"and
"
net
wor
klay
er"usedof
ten.Net
wor
kmodel
sdef
ineasetofnet
wor
klay
ersandhow
t
hey i
nter
act
.Ther
e ar
e sev
eraldi
ff
erentnet
wor
k model
s dependi
ng on what
or
gani
zat
ionorcompanyst
art
edt
hem.Themosti
mpor
tantt
woar
e:

TCP/
IP Model
:-Thi
smodeli
ssomet
imescal
l
edt
heDOD modelsi
ncei
twas
desi
gnedf
ort
hedepar
tmentofdef
ence.I
tisal
socal
l
edt
hei
nter
netmodelbecause
TCP/
IPi
sthepr
otocol
usedont
hei
nter
net
.

OSINet
wor
kModel
:-TheI
nter
nat
ionalSt
andar
dsOr
gani
zat
ion(
ISO)hasdef
ineda
st
andar
dcal
l
edt
heOpenSy
stemsI
nter
connect
ion(
OSI
)ref
erencemodel
.Thi
sisa
sev
enl
ayerar
chi
tect
urel
i
stedi
nthenextsect
ion.

Fi
g:4.
1

4.
1Lay
ersi
ntheTCP/
IPmodel

 Appl
icat
ion Lay
er(
process-
to-
process)
:Thi
sist
he scope wi
thi
n whi
ch
appl
i
cat
ionscr
eat
euserdat
aandcommuni
cat
ethi
sdat
atoot
herpr
ocesses
orappl
i
cat
ionsonanot
herort
hesamehost
.Thecommuni
cat
ionspar
tner
s
ar
eof
tencal
l
edpeer
s.Thi
siswher
ethe"
higherl
evel
"pr
otocol
ssuchas
SMTP,
FTP,
SSH,
HTTP,
etc.oper
ate.
  Tr
anspor
t Lay
er (
host
-t
o-host
): The Tr
anspor
t Lay
er const
it
utes t
he
net
wor
kingr
egi
mebet
weent
wonet
wor
khost
s,ei
theront
hel
ocalnet
wor
kor
onr
emot
enet
wor
kssepar
atedbyr
out
ers.

 I
nter
net Lay
er (
int
ernet
wor
king)
:The I
nter
net Lay
er has t
he t
ask of
exchangi
ng dat
agr
ams acr
oss net
wor
k boundar
ies.I
tist
her
efor
e al
so
r
efer
redt
oast
hel
ayert
hatest
abl
i
shesi
nter
net
wor
king,
indeed,
itdef
inesand
est
abl
i
shes t
he I
nter
net
.Thi
slay
erdef
ines t
he addr
essi
ng and r
out
ing
st
ruct
uresusedf
ort
heTCP/
IPpr
otocol
sui
te.

 Li
nkLay
er:Thi
slay
erdef
inest
henet
wor
kingmet
hodswi
tht
hescopeoft
he
l
ocalnet
wor
kli
nkonwhi
chhost
scommuni
cat
ewi
thouti
nter
veni
ngr
out
ers.
Thi
slay
erdescr
ibest
hepr
otocol
susedt
odescr
ibet
hel
ocal
net
wor
ktopol
ogy
andt
hei
nter
facesneededt
oaf
fectt
ransmi
ssi
onofI
nter
netLay
erdat
agr
ams
t
onext
-nei
ghborhost
s.

4.
2Lay
ersi
nOSIModel

TheOSI
,orOpenSy
stem I
nter
connect
ion,
modeldef
inesanet
wor
kingf
ramewor
kfor
i
mpl
ement
ingpr
otocol
sinsev
enl
ayer
s.Cont
roli
spassedf
rom onel
ayert
othenext
,
st
art
ingatt
heappl
i
cat
ionl
ayeri
nonest
ati
on,andpr
oceedi
ngt
othebot
tom l
ayer
,
ov
ert
hechannel
tot
henextst
ati
onandbackupt
hehi
erar
chy
.

 Appl
icat
ion(
Lay
er7)
:Thi
slay
ersuppor
tsappl
i
cat
ionandend-
userpr
ocesses.
Communi
cat
ionpar
tner
sar
eident
if
ied,qual
i
tyofser
vicei
sident
if
ied,user
aut
hent
icat
ionandpr
ivacyar
econsi
der
ed,
andanyconst
rai
ntsondat
asy
ntax
ar
eident
if
ied.

 Pr
esent
ati
on(
Lay
er6)
:Thi
slay
erpr
ovi
desi
ndependencef
rom di
ff
erencesi
n
dat
arepr
esent
ati
on (
e.g.
,encr
ypt
ion)by t
ransl
ati
ng f
rom appl
i
cat
ion t
o
net
wor
kfor
mat
,andv
icev
ersa.

 Sessi
on (
Lay
er 5)
: Thi
s l
ayer est
abl
i
shes,manages and t
ermi
nat
es
connect
ionsbet
weenappl
i
cat
ions.Thesessi
onl
ayerset
sup,coor
dinat
es,
and t
ermi
nat
es conv
ersat
ions,exchanges,and di
alogues bet
ween t
he
appl
i
cat
ionsateachend.I
tdeal
swi
thsessi
onandconnect
ioncoor
dinat
ion.
  Tr
anspor
t(Lay
er4)
:Thi
slay
erpr
ovi
dest
ranspar
entt
ransf
erofdat
abet
ween
endsy
stems,orhost
s,andi
sresponsi
blef
orend-
to-
ender
rorr
ecov
eryand
f
lowcont
rol
.Itensur
escompl
etedat
atr
ansf
er.

 Net
wor
k(Lay
er3)
:Thi
slay
erpr
ovi
desswi
tchi
ngandr
out
ingt
echnol
ogi
es,
cr
eat
ingl
ogi
calpat
hs,knownasv
irt
ualci
rcui
ts,f
ort
ransmi
tt
ingdat
afr
om
nodet
onode.

 Dat
aLi
nk(
Lay
er2)
:Att
hisl
ayer
,dat
apacket
sar
eencodedanddecodedi
nto
bi
ts.I
tfur
nishest
ransmi
ssi
on pr
otocolknowl
edgeand managementand
handl
eser
ror
sint
hephy
sicall
ayer
,fl
ow cont
rolandf
ramesy
nchr
oni
zat
ion.
Thedat
ali
nkl
ayeri
sdi
vi
dedi
ntot
wosubl
ayer
s:TheMedi
aAccessCont
rol
(
MAC)l
ayerandt
heLogi
cal
LinkCont
rol
(LLC)l
ayer
.

 Phy
sical(
Lay
er1)
:Thi
slay
erconv
eyst
hebi
tst
ream -el
ect
ri
cali
mpul
se,
li
ght
orr
adi
osi
gnal
--t
hrought
henet
wor
katt
heel
ect
ri
cal
andmechani
cal
lev
el..

TCP/
IPModelv
sOSIModel

Sr
.
TCP/
IPRef
erenceModel OSIRef
erenceModel
No.

1 Def
inedaf
tert
headv
entofI
nter
net
. Def
inedbef
oreadv
entofi
nter
net
.

Ser
vicei
nter
faceandpr
otocol
swer
enotSer
vicei
nter
faceandpr
otocol
sar
e
2
cl
ear
lydi
sti
ngui
shedbef
ore cl
ear
lydi
sti
ngui
shed

3 TCP/
IPsuppor
tsI
nter
networ
king I
nter
networ
kingnotsuppor
ted

4 Loosel
ylay
ered St
ri
ctl
ayer
ing

5 Pr
otocol
Dependantst
andar
d Pr
otocol
independentst
andar
d

6 Mor
eCr
edi
ble LessCr
edi
ble

TCPrel
iabl
ydeli
verspacket
s,I
Pdoesnot
7 Al
lpacket
sar
erel
i
abl
ydel
i
ver
ed
rel
i
abl
ydeli
verpacket
s
 5.
BASI
CNETWORKI
NGCABLES

Net
wor
kingCabl
esar
eusedt
oconnectonenet
wor
kdev
icet
oot
herort
oconnect
t
woormor
ecomput
erst
oshar
epr
int
er,
scanneret
c.Di
ff
erentt
ypesofnet
wor
k
cabl
es l
i
keCoaxi
alcabl
e,Opt
icalf
iber cabl
e,Twi
sted Pai
r cabl
es ar
e used
dependi
ng on t
he net
wor
k'st
opol
ogy ,
prot
ocol
and si
ze.The dev
ices can be
separ
atedbyaf
ewmet
ers(
e.g.v
iaEt
her
net
)ornear
lyunl
i
mit
eddi
stances(
e.g.v
ia
t
hei
nter
connect
ionsoft
heI
nter
net
).

Whi
l
ewi
rel
essmaybet
hewav
eoft
hef
utur
e,mostcomput
ernet
wor
ktodayst
il
l
ut
il
izecabl
est
otr
ansf
ersi
gnal
sfr
om onepoi
ntt
oanot
her

i
. Twi
stedPai
rCabl
e

i
i
. Opt
ical
FiberCabl
e

i
i
i. Coaxi
alCabl
e

Weuset
wot
ypesofcabl
einnet
wor
king:

1)St
rai
ghtCabl
e

Youusual
l
yusest
rai
ghtcabl
etoconnectdi
ff
erentt
ypeofdev
ices.Thi
sty
peofcabl
e
wi
l
lbeusedmostoft
het
imeandcanbeusedt
o:

1)Connectacomput
ert
oaswi
tch/
hub'
snor
mal
por
t.
2)Connectacomput
ert
oacabl
e/DSLmodem'
sLANpor
t.
3)Connectar
out
er'
sWANpor
ttoacabl
e/DSLmodem'
sLANpor
t.
4)Connectar
out
er'
sLANpor
ttoaswi
tch/
hub'
supl
i
nkpor
t.(
nor
mal
l
yusedf
or
expandi
ngnet
wor
k)
5)Connect2swi
tches/
hubswi
thoneoft
heswi
tch/
hubusi
nganupl
i
nkpor
tand
t
heot
heroneusi
ngnor
mal
por
t.

2)Cr
ossov
erCabl
e
Acr
ossov
ercabl
econnect
stwodev
icesoft
hesamet
ype,f
orexampl
eDTE-
DTE
orDCE-
DCE,
usual
l
yconnect
edasy
mmet
ri
cal
l
y(DTE-
DCE)
,byamodi
fi
edcabl
ecal
l
ed
acr
ossl
i
nk.Suchdi
sti
nct
ionofdev
iceswasi
ntr
oducedbyI
BM

Somet
imesy
ouwi
l
lusecr
ossov
ercabl
e,i
t'
susual
l
yusedt
oconnectsamet
ypeof
dev
ices.Acr
ossov
ercabl
ecanbeusedt
o:

1)Connect2comput
ersdi
rect
ly.
2)Connectar
out
er'
sLANpor
ttoaswi
tch/
hub'
snor
malpor
t(nor
mal
l
yusedf
or
expandi
ngnet
wor
k)
3)Connect2swi
tches/
hubsbyusi
ngnor
mal
por
tinbot
hswi
tches/
hubs.

Fi
g:5.
1

Col
ourcodi
ngofcabl
e:
St
rai
ght
:
1.or
angewhi
te 1.
orangewhi
te
2.or
ange 2.
orange
3.gr
eenwhi
te 3.
greenwhi
te
4.bl
ue 4.bl
ue
5.bl
uewhi
te 5.bl
uewhi
te
6.gr
een 6.gr
een
7.br
ownwhi
te 7.br
ownwhi
te
8.br
own 8.Br
own
Cr
osscabl
e:
1.or
angewhi
te 1.
greenwhi
te
2.or
ange 2.
green
3.gr
eenwhi
te 3.
orangewhi
te
4.bl
ue 4.bl
ue
5.bl
uewhi
te 5.bl
uewhi
te
6.gr
een 6.or
ange
7.br
ownwhi
te 7.br
ownwhi
te
8.br
own 8.Br
own

T-
568BSt
rai
ght
-Thr
oughEt
her
netCabl
e

Fi
g:5.
2

RJ-
45Cr
ossov
erEt
her
netCabl
e

Fi
g:5.
3

I
NSTALLI
NGCABLES
I
ntodaynet
wor
ks,UTP CABLESar
ecommonl
yusedt
oconnectcomput
ersi
na
net
wor
k.
Dependi
ngont
hecol
orcodi
ngs,wehav
edi
ff
erentcabl
esl
i
kest
rai
ghtcabl
e,cr
oss
cabl
eandr
oll
-ov
ercabl
e.
STRAI
GHTCABLE
Thecabl
eusedbet
weent
hePCandt
hehub/
swi
tchi
scal
l
edst
rai
ghtcabl
e.
St
rai
ghtcabl
ecanbeusedbet
ween
PC-SWI
TCH
PC-HUB
HUB(
UPLI
NKPORT)-HUB
CROSS-
OVERCABLE
Thecabl
eusedt
oconnectt
woPCsi
scal
l
edcr
oss-
overcabl
e.
Cr
osscabl
ecanbeusedbet
ween:
PC-PC
HUB-HUB
SWI
TCH-SWI
TCH
ROUTER-PC
ROLL-
OVERCABLE
Thecabl
eusedbet
weenahar
dwar
erout
erandaPCi
scal
l
edr
oll
-ov
ercabl
e.
I
nthi
scabl
e,t
hecol
orcodi
ngusedi
noneendi
srev
ersedi
ntheot
herend.
DATATRAVELONLYGREENORORANGEPAI
ROFCABLE.
 6.ADDRESSI
NGI
NCOMPUTERNETWORKI
NG

Ther
ear
etwoki
ndsofaddr
essesusedi
nnet
wor
ks:
1.
Phy
sical
addr
ess
2.Logi
cal
addr
ess
PHYSI
CALADDRESS
1.I
tisal
socal
l
edhar
dwar
eaddr
essorMACaddr
ess.
MACst
andsf
ormedi
aaccess
cont
rol
.
2.I
tispr
esenti
nthechi
pofaNI
Ccar
d.
3.I
tisuni
quef
orev
eryNI
Ccar
dandcannotbechanged.
4.I
tis48bi
ts.Outof48bi
ts,
24bi
tsofaddr
essi
sgi
venbyt
hemanuf
act
urerofNI
C
car
dandt
her
emai
ning24bi
tsofaddr
essi
sdef
inedasperi
nst
ruct
ionsgi
venby
I
EEE.
5.I
EEEst
andsf
orI
nst
it
uteofEl
ect
roni
csandEl
ect
ri
cal
Engi
neer
s.
LOGI
CALADDRESS
1.I
tisal
socal
l
edsof
twar
eaddr
ess.
2.I
tisgi
venbyt
heuserandcanbechangedany
time.
3.Sev
eral
schemesorpr
otocol
sar
eusedt
odef
inel
ogi
cal
addr
essi
nacomput
er.
4.Thesepr
otocol
sar
e:
TCP/
IP(
Transmi
ssi
onCont
rol
Prot
ocol
/I
nter
netPr
otocol
)
I
PX/
SPX(
Int
ernet
wor
kPacketExchange/
Sequent
ial
PacketExchange)
DLC(
Dat
aLi
nkCont
rol
)
Appl
eTal
k
PROTOCOL
Pr
otocol
isasetofr
uleswhi
chi
ncommuni
cat
ionbet
weencomput
ers.
TCP/
IP
1.I
thasbecomei
ndust
ry-
standar
d
2.I
twasdev
elopedbyDOD(
Depar
tmentofDef
ence)ofUSA.
3.I
tisusedbot
hinI
nter
net(
publ
i
cnet
wor
k)andI
ntr
anet(
pri
vat
enet
wor
k).
4.I
tisof32bi
ts.
5.Cur
rent
lyusedv
ersi
oni
sIPv
4.
6.I
Pv6i
sal
soav
ail
abl
e.
7.I
thasf
ourf
iel
dsoroct
ets.
8.Eachoct
eti
sof8bi
ts.
9.I
tcanber
epr
esent
edbyw.
x.y
.z
10.Mi
nimum v
alueofoct
eti
s0andmaxi
mum i
s255
11.Eachoct
etorf
iel
dcanhav
edeci
mal
val
uesr
angi
ngf
rom 0t
o255.
12.Accor
ding t
othev
alueofw orf
ir
stf
iel
d,wehav
efi
vecl
assesofTCP/
IP
Addr
esses.
Thef
ir
stt
hreecl
assesar
eonl
yusedf
orcomput
eraddr
essi
ngi
nanet
wor
k.
I
PADDRESSI
NG
I
P(I
NTERNETPROTOCOL)i
s32bi
t.I
tisdi
vi
dedi
n4oct
eteachoct
etcont
ain8bi
t.I
t
i
snumer
icali
dent
if
icat
ionofcomput
eronnet
wor
k.I
tisdi
vi
dedi
ntot
wopar
tsonei
s
net
wor
kandsecondi
shost
.Weusepr
ivat
eipaddr
essi
nLANwhi
chi
spr
ovi
dedby
I
ANA(
INTERNETASSI
GNI
NG NUMBRI
NG AUTHOURTI
Y).Themi
nimum v
alue(
per
oct
et)i
s0andt
hemaxi
mum v
aluei
s255.I
Paddr
essar
edi
vi
dedi
nfi
vecl
asses.
1.Net
wor
kID:
itr
epr
esentt
heno.ofonbi
tthati
s(1)
.
2.HostI
D:i
trepr
esentt
heno.ofof
fbi
tthati
s(0)
.
Cl
ass Range Net
wor
k HostI
D SubnetMask Tot
alI
P Val
i
dIP
I
D
A 1-
127 8 24 255.
0.0.
0 16777216 16777214
B 128-
191 16 16 255.
255.
0.0 65536 65534
C 192-
223 24 8 255.
255.
255.
0 256 254
D 224-
239 I
tisr
eser
vedf
ormul
ti
cast
.
E 240-
255 I
tisr
eser
vedf
orr
esear
ch/
sci
ent
if
icuse.

NOTE:
Weuseonl
yfi
rstt
hreecl
asswhi
chi
spr
ovi
debyI
ANAi
nLAN.
I
PAddr
essesar
edi
vi
dedi
ntot
wopar
ts:
1.Pr
ivat
eIPaddr
ess
2.Publ
i
c(l
i
ve)I
Paddr
ess.
RangeofPr
ivat
eIPAddr
ess:

Cl
assA10.
0.0.
0to10.
255.
255.
255
Cl
assB172.
16.
0.0t
o172.
31.
255.
255
Cl
assC192.
168.
0.0t
o192.
168.
255.
255
RangeofPubl
icI
PAddr
ess:
1.
0.0.
0to9.
255.
255.
255
11.
0.0.
0to126.
255.
255.
255
128.
0.0.
0to172.
15.
255.
255
172.
32.
0.0t
o192.
167.
255.
255
192.
169.
0.0t
o223.
255.
255.
255
Andanot
herr
angei
scal
l
edAPI
PA(
Aut
omat
icpr
ivat
eint
ernetpr
otocolAddr
essi
ng)
r
angei
s169.
254.
0.0t
o169.
254.
255.
255.
Wecanassi
gnt
heI
Paddr
essbyusi
ngt
womet
hods:
(
1)St
ati
cal
l
yormanual
l
y
(
2)Dy
nami
cal
l
y(byusi
ngDHCPser
ver
-dy
nami
chostconf
igur
ati
onpr
otocol
)

Buti
ncaseofy
ourcomput
erhasnoI
Paddr
esst
henI
Paddr
essi
sassi
gnedt
othe
comput
erf
rom API
PARange,butcommuni
cat
ioni
snotpossi
blewhencomput
er
hasI
Paddr
essf
rom API
PA.127.
0.0.
1ist
hel
oopbackaddr
essi
tisusedf
orsel
f-
communi
cat
ionandf
ort
roubl
eshoot
ingpur
pose.
SubnetMask:SubnetMaski
sal
so32bi
taddr
ess,whi
cht
ellushowmanybi
tsar
e
usedf
ornet
wor
kandhowmanybi
tsar
eusedf
orhostaddr
ess.
I
nsubnetmasknet
wor
kbi
tsar
eal
way
s1andhostbi
tsar
eal
way
s0.
I
PAddr
essi
nval
idorr
eser
veI
PAddr
ess:
Whenwear
egoi
ngt
oassi
gnI
PAddr
esst
oourcomput
eri
nter
facet
henwehav
eto
f
oll
owsomer
ules:
Rul
es:-
1.Al
lHostbi
tscannotbe0(
10.
0.0.
0),
becausei
trepr
esentnet
wor
kaddr
esswhi
chi
s
r
eser
vedf
orr
out
er.
2.Al
lHostbi
tcannotbe1(
10.
255.
255.
255.
),becausei
tisbr
oadcastaddr
essoft
hat
net
wor
k(10t
h)net
wor
k.
3.Al
lbi
tscannotbe0(
0.0.
0.0)
,becauset
hisaddr
essi
sreser
vedf
ordef
aul
trout
ing.
Def
aul
trout
ingi
susedi
ncaseofst
ubn/
w(meansournet
wor
khasnoexi
tpoi
nt)
.
4.Al
lbi
tscannotbe1(
255.
255.
255.
255)
,becausei
treser
vedf
orBr
oadcast
ing

C:
\>I
PCONFI
G(t
hiscommandi
susef
orI
Pcheck)
.
C:
\>I
PCONFIG/ALL(Thi
scmdisshowal
ldet
ailofy
ouri
nter
face.
).
Pi
ng–PacketI
nter
netGr
oper
Thi
scommand i
susedt
o checkt
heconnect
ivi
tywi
thot
hercomput
er.Pi
ng i
s
per
for
medwi
thi
nnet
wor
korout
sidet
henet
wor
k.I
nthi
spr
ocessf
ourpacket
sar
e
sendt
odest
inat
ionaddr
essandf
ourpacket
srecei
vedf
rom t
hedest
inat
ionaddr
ess.
I
CMP(
Int
ernetcont
rol
massagepr
otocol
)isusedf
ort
hispr
ocess.

I
CMP
I
nter
netCont
rol
Messagi
ngPr
otocol
isusedbypi
ngandt
racer
out
eut
il
it
ies.
Pi
ng(
PacketI
nter
netGr
oper
)enabl
esy
out
oval
i
dat
ethatanI
Paddr
essexi
stsand
canaccept
r
equest
s.Thef
oll
owi
ngt
ransmi
ssi
onsar
eusedbyt
hePi
ngut
il
it
y:
 Pi
ngsendsanechor
equestpackett
orecei
vet
heechor
esponse.
 Rout
erssendDest
inat
ionUnr
eachabl
emessageswhent
heycan’
treacht
he
dest
inat
ion
net
wor
kandt
heyar
efor
cedt
odr
opt
hepacket
.Ther
out
ert
hatdr
opst
he
packetsends
t
heI
CMPDUmessage.
C:
\>pi
ng(I
Pofdestinat
ion)fore.
g10.0.
0.1
C:
\>pi
ng(I
Pofdestinat
ion)–t( f
orcont
inue)
.
Pr
essct
rl
+ctostopping.
1.Replyf
rom Desti
nation:
Replyf
rom 10.1.1.
1:bytes=32t
ime<1msTTL=255
Replyf
rom 10.1.1.
1:bytes=32t
ime<1msTTL=255
Replyf
rom 10.1.1.
1:bytes=32t
ime<1msTTL=255
Replyf
rom 10.1.1.
1:bytes=32t
ime<1msTTL=255
Pi
ngstatisti
csfor10.0.
0.1:
Packet
s:Sent=4, Received=4,Lost=0( 0%loss),
Approxi
mat eroundtri
pt i
mesinmill
i-
seconds:
1.Minimum =0ms, Maximum =0ms, Aver
age=0ms
This message appear when dest inat
ion computer pr
oper
ly conf
igur
ed and
connect
edwi
thsamenet
wor
kipaddr
ess.
2.Requestt
imeout(
R.T.
O):
-Thi
smessageappearwhenDest
inat
ioncomput
erhas
somepr
obl
em .
Foreg:I
Paddr
essdoesnotexi
t,net
wor
kcabl
eunpl
ugged,
comput
er
shut
down,
int
erconnect
ionf
ir
ewal
lenabl
e.
3.Dest
inat
ionhostunr
eachabl
e:-Thi
smassageappearwhenourcomput
erdesi
re
t
ocommuni
cat
ewi
thanot
hern/
wbutourcomput
erhasnogat
ewayI
Paddr
ess.
4.Repl
yfr
om gat
ewaybutDest
inat
ionhostunr
eachabl
e:-
Thi
smassageappear
whencomput
erdesi
ret
ocommuni
cat
ewi
thanot
hernet
wor
kcomput
erbutour
r
out
erhasnor
out
einf
ormat
ioni
nit
srout
ingt
abl
eforDest
inat
ionn/
w.
5.Har
dwar
eer
ror
:-Thi
smassageappear
swhendur
ingcommuni
cat
ionournet
wor
k
goesunpl
ugged.
6.Negot
iat
ingI
PSecur
it
y:-Thi
smassageappear
swhenourcomput
erhasI
P-Sec
ser
viceenabl
edwi
thsecur
ecommuni
cat
ionr
ulenegot
iat
ion.

7.SOFTWARE

7.
1SI
MULATOR

Anet
wor
ksi
mul
atori
sapi
eceofsof
twar
eorhar
dwar
ethatpr
edi
ctst
hebehav
iorof
anet
wor
k,wi
thoutanact
ual
net
wor
kbei
ngpr
esent
.

Net
wor
ksi
mul
ator
sser
veav
ari
etyofneeds.Compar
ed t
othe costand t
ime
i
nvol
vedi
nset
ti
ngupanent
ir
etestbedcont
aini
ngmul
ti
plenet
wor
kedcomput
ers,
r
out
ersanddat
ali
nks,net
wor
ksi
mul
ator
sar
erel
ati
vel
yfastandi
nexpensi
ve.They
al
l
owengi
neer
stot
estscenar
iost
hatmi
ghtbepar
ti
cul
arl
ydi
ff
icul
torexpensi
vet
o
emul
ateusi
ngr
eal
har
dwar
e-f
ori
nst
ance,
simul
ati
ngt
heef
fect
sofasuddenbur
sti
n
t
raf
fi
coraDoSat
tackonanet
wor
kser
vice.

Thesi
mul
atort
hatwehav
eusedt
ocr
eat
easi
mul
ati
onoft
henet
wor
kdesi
gnoft
he
Pr
ojecti
sCI
SCOPACKETTRACER.
 SS:
7.1

8.PROJECT DESCRI
PTI
ON

Lay
outoft
hepr
oposedNet
wor
k
Wehav
edesi
gnedanet
wor
kScenar
ioi
nwhi
chwehav
eusedt
heconcept
sof
r
out
ers,swi
tches,ser
ver
s,Rout
ing,Redi
str
ibut
ion,wehav
egi
vendet
ailst
udyof
abov
etopi
cs.
..
.

 8.
1Rout
ing

Rout
ingi
sthepr
ocessofsel
ect
ingpat
hsi
nanet
wor
kal
ongwhi
cht
osend
net
wor
ktr
aff
ic.Rout
ingi
sper
for
medf
ormanyki
ndsofnet
wor
ks,i
ncl
udi
ng
t
het
elephonenet
wor
k(Ci
rcui
tswi
tchi
ng),
elect
roni
cdat
anet
wor
ks(
suchas
t
heI
nter
net
),andt
ranspor
tat
ionnet
wor
ks.Thi
sar
ti
clei
sconcer
nedpr
imar
il
y
wi
thr
out
ingi
nel
ect
roni
cdat
anet
wor
ksusi
ngpacketswi
tchi
ngt
echnol
ogy
.

I
n packetswi
tchi
ng net
wor
ks,r
out
ing di
rect
spacketf
orwar
ding,t
he t
ransi
tof
l
ogi
cal
l
yaddr
essed packet
sfr
om t
hei
rsour
cet
owar
dthei
rul
ti
mat
edest
inat
ion
t
hrough i
nter
medi
atenodes, t
ypi
cal
l
y har
dwar
e dev
ices
cal
l
edr
out
ers,
bri
dges,
gat
eway
s,f
ir
ewal
l
s, orswi
tches. Gener
al-
pur
posecomput
erscanal
sof
orwar
dpacket
sandper
for
mrout
ing,t
hought
heyar
e
notspeci
ali
zedhar
dwar
eandmaysuf
ferf
rom l
i
mit
edper
for
mance.Ther
out
ing
pr
ocessusual
l
ydi
rect
sfor
war
dingont
hebasi
sofr
out
ingt
abl
eswhi
chmai
ntai
na
r
ecor
doft
her
out
est
ovar
iousnet
wor
kdest
inat
ions.Thus,const
ruct
ingr
out
ing
t
abl
es,whi
char
ehel
dint
her
out
er'
smemor
y,i
sver
yimpor
tantf
oref
fi
cientr
out
ing.
Mostr
out
ing al
gor
it
hms use onl
y one net
wor
k pat
h ata t
ime,butmul
ti
pat
h
r
out
ingt
echni
quesenabl
etheuseofmul
ti
pleal
ter
nat
ivepat
hs.

Dy
nami
cRout
ing

Dy
nami
crout
ingper
for
mst
hesamef
unct
ionasst
ati
crout
ingexcepti
tismor
e
r
obust
.St
ati
crout
ingal
l
owsr
out
ingt
abl
esi
nspeci
fi
crout
erst
obesetupi
nast
ati
c
mannersonet
wor
krout
esf
orpacket
sar
eset
.Ifar
out
eront
her
out
egoesdownt
he
dest
inat
ionmaybecomeunr
eachabl
e.Dy
nami
crout
ing al
l
owsr
out
ing t
abl
esi
n
r
out
erst
ochangeast
hepossi
bler
out
eschange.Ther
ear
esev
eral
prot
ocol
susedt
o
suppor
tdy
nami
crout
ingi
ncl
udi
ngRI
PandOSPF.

DYNAMI
CROUTI
NG
 Dy
nami
cRout
ing

Rout
edandRout
ing
Prot
ocol
s

Rout
ed Rout
ing

I
nteri
orGateway Ext
eri
orGateway
I
P I
P Appl
e
Pr
otocols Pr
otocol
s

Di
st-
V Li
nk-
S Hy
bri
d

RI
Pv1,
2 OSPF

Nov
ellRI
P I
GRP NLSP EI
GRP BGPv
4

RTMP I
S-I
S

Fi
g:8.
1.1

Rout
edpr
otocol
s:

TCP/
IP,I
PX-
SPXar
epr
otocol
swhi
char
eusedi
naLocalAr
eaNet
wor
k(LAN)so
comput
erscancommuni
cat
ebet
weenwi
theachot
herandwi
thot
hercomput
erson
t
heI
nter
net
.Chancesar
ethati
nyourLAN y
ouar
emostpr
obabl
yrunni
ngTCP/
IP.
Thi
spr
otocoli
swhatwecal
la "
rout
ed"pr
otocol
.The t
erm "
rout
ed"r
efer
sto
somet
hingwhi
chcanbepassedonf
rom onepl
ace(
net
wor
k)t
oanot
her
.Int
he
exampl
eofTCP/
IP,t
hisi
swheny
ouconst
ructadat
apacketandsendi
tacr
osst
o
anot
hercomput
eront
heI
nter
net

Rout
ingpr
otocol
s:

Rout
ingpr
otocol
swer
ecr
eat
edf
orr
out
ers.Thesepr
otocol
shav
ebeendesi
gnedt
o
al
l
owt
heexchangeofr
out
ingt
abl
es,
orknownnet
wor
ks,
bet
weenr
out
ers.Ther
ear
e
al
otofdi
ff
erentr
out
ingpr
otocol
s,eachonedesi
gnedf
orspeci
fi
cnet
wor
ksi
zes,
soI
am notgoi
ngt
obeabl
etoment
ionandanal
yset
hem al
l
,butIwi
l
lfocusont
hemost
popul
ar.

Dy
nami
cRout
ingPr
otocol
s

Ther
ear
e3t
ypesofDy
nami
crout
ingpr
otocol
s,t
hesedi
ff
ermai
nlyi
nthewayt
hat
t
heydi
scov
erandmakecal
cul
ati
onsaboutr
out
es(
cli
ckt
osel
ect
):

1)Di
stanceVect
or

2)Li
nkSt
ate

3)Hy
bri
d

 Di
stanceVect
orr
out
erscomput
ethebestpat
hfr
om i
nfor
mat
ionpassedt
o
t
hem f
rom nei
ghbor
s

 Li
nkSt
ater
out
erseachhav
eacopyoft
heent
ir
enet
wor
kmap

 Li
nkSt
ater
out
erscomput
ebestr
out
esf
rom t
hisl
ocal
map
 Fi
g:8.
1.2
DI
STANCEVECTORROUTI
NGPROTOCOLS

Di
stanceVect
orr
out
ing pr
otocol
susef
requentbr
oadcast
s(255.
255.
255.
255 or
FF:
FF:
FF:
FF)oft
hei
rent
ir
erout
ingt
abl
eev
ery30sec.onal
lthei
rint
erf
acesi
nor
der
t
o communi
cat
ewi
tht
hei
rnei
ghbour
s.Thebi
ggert
her
out
ingt
abl
es,t
hemor
e
br
oadcast
s.Thi
smet
hodol
ogyl
i
mit
ssi
gni
fi
cant
lyt
hesi
zeofnet
wor
konwhi
ch
Di
stanceVect
orcanbeused.

RI
PV1:

Rout
ing I
nfor
mat
ion Pr
otocol(
RIP)i
sat
rueDi
stance-
Vect
orr
out
ing pr
otocol
.It
sends t
he compl
ete r
out
ing t
abl
e out t
o al
l act
ive i
nter
faces ev
ery 30
seconds.RI
Ponl
yuseshopcountt
odet
ermi
net
hebestwayt
oar
emot
enet
wor
k,
buti
thasamaxi
mum al
l
owabl
ehopcountof15,meani
ngt
hat16i
sdeemed
unr
eachabl
e.RI
Pwor
kswel
linsmal
lnet
wor
ks,buti
tisi
nef
fi
cientonl
argenet
wor
ks
wi
thsl
owWANl
i
nksoronnet
wor
kswi
thl
argenumberofr
out
ersi
nst
all
ed.

RI
Pcomesi
ntwodi
ff
erentv
ersi
ons.RI
Pver
sion1usesonl
ycl
assf
ulr
out
ing,whi
ch
meanst
hatal
ldev
icesi
nthenet
wor
kmustuset
hesamesubnetmask.Thi
sis
becauseRI
Pver
sion1doesnoti
ncl
udet
hesubnetmaskwheni
tsendsupdat
es.RI
P
v
1usesbr
oadcast
s(255.
255.
255.
255)
.

RI
Pver
sion2does,howev
er,andt
hisi
swhatwecal
lcl
assl
essr
out
ing(
checkt
he
Subnet
ti
ngsect
ionf
ormor
edet
ail
s).RI
Pv2usesmul
ti
cast
s(224.
0.0.
9)t
oupdat
eit
s
r
out
ingt
abl
es.

COMMANDS:
-

Conf
igur
eRIP:
Usethef
oll
owingcommandtoenabl
eRI
PonRout
erA:
Rout
erA(
confi
g)#r
outerr
ip

Configur
et heroutert
oreceiv
eandsendonl
yRI
PVer
sion2packet
susi
ngt
he
fol
l
owi ngcommand:
RouterA(confi
g-r
outer)
#versi
on2

Usethefol
l
owi
ngcommandst
ospeci
fyt
henet
wor
ksdi
rect
lyconnect
edt
othe
rout
er:
Rout
erA(
conf
ig-
rout
er)
#net
wor
k192.
168.
11.
0
Rout
erA(
conf
ig-
rout
er)
#net
wor
k192.
168.
22.
0

I
nter
iorGat
ewayPr
otocol-I
GRP

I
nter
ior Gat
eway Rout
ing Pr
otocol (
IGRP)i
s a Ci
sco pr
opr
iet
aryDi
stance-
Vect
orr
out
ingpr
otocol
.Thi
smeanst
hatal
lyourr
out
ersmustbeCi
scor
out
ersi
n
or
dert
ouseI
GRPi
nyournet
wor
k,keepi
nmi
ndt
hatWi
ndows2000nowsuppor
tsi
t
aswel
lbecauset
heyhav
eboughtal
i
cencef
rom Ci
scot
ouset
hepr
otocol

Ci
scocr
eat
edt
hisr
out
ingpr
otocol
toov
ercomet
hepr
obl
emsassoci
atedwi
thRI
P.

I
GRPhasamaxi
mum hopcountof255wi
thadef
aul
tof100.Thi
sishel
pfuli
nlar
ger
net
wor
ksandsol
vest
hepr
obl
em oft
her
ebei
ngonl
y15hopsmaxi
mum possi
blei
n
aRI
Pnet
wor
k.I
GRPal
sousesadi
ff
erentmet
ri
cfr
om RI
P.I
GRPusesbandwi
dthand
del
ayoft
hel
i
nebydef
aul
tasa met
ri
cfordet
ermi
ning t
he bestr
out
eto an
i
nter
net
wor
k.Thi
siscal
l
ed a composi
temet
ri
c.Rel
i
abi
l
ity
,load and Maxi
mum
Tr
ansmi
ssi
onUni
t(MTU)canal
sobeused,
alt
hought
heyar
enotusedbydef
aul
t.

COMMANDS:
-

Rout
erA#conf
igur
eter
minal

Ent
erconf
igur
ati
oncommands,
oneperl
i
ne.Endwi
thCnt
l/z

Rout
erA#(
conf
ig)
#rout
eri
grpASno.

Rout
erA#(
conf
ig-
rout
er)
#net
wor
kipaddr
ess

Rout
erA#(
conf
ig-
rout
er)
#exi
t

Li
nkSt
ateRout
ingPr
otocol
s:

Li
nk St
atepr
otocol
s, unl
i
keDi
stance Vect
orbr
oadcast
s, use mul
ti
cast
. Li
nk
St
ater
out
ingpr
otocol
sdonotv
iew net
wor
ksi
nter
msofadj
acentr
out
ersandhop
count
s,butt
heybui
l
dacompr
ehensi
vev
iew oft
heov
eral
lnet
wor
kwhi
chf
ull
y
descr
ibest
heal
lpossi
bler
out
esal
ongwi
tht
hei
rcost
s.Usi
ngt
heSPF(
Shor
testPat
h
Fi
rst
)al
gor
it
hm,t
her
out
ercr
eat
esa"
topol
ogi
caldat
abase"whi
chi
sahi
erar
chy
r
efl
ect
ingt
henet
wor
krout
ersi
tknowsabout
.Itt
henput
sit
'ssel
font
het
opoft
his
hi
erar
chy
,andhasacompl
etepi
ctur
efr
om i
t'
sownper
spect
ive.

Li
nkSt
atepr
otocol
sincompar
isont
oDi
stanceVect
orpr
otocol
shav
e:

 Bi
gmemor
yrequi
rement
s

 Shor
testpat
hcomput
ati
onsr
equi
remanyCPUci
rcl
es

 I
fnet
wor
kisst
abl
eli
tt
lebandwi
dthi
sused;
reactqui
ckl
ytot
opol
ogychanges

 Announcement
scannotbe“
fi
lt
ered”
.Al
lit
emsi
nthedat
abasemustbesent
t
onei
ghbor
s

 Al
lnei
ghbor
smustbet
rust
ed

 Aut
hent
icat
ionmechani
smscanbeusedt
oav
oidundesi
redadj
acenci
es

 Nospl
i
thor
izont
echni
quesar
epossi
ble

OpenShor
testPat
hFi
rst(
OSPF)Rout
ingPr
otocol
:-

OpenShor
testPat
hFi
rst(
OSPF)i
sar
out
ingpr
otocoldev
elopedf
orI
nter
netPr
otocol
(
IP)net
wor
ksbyt
hei
nter
iorgat
ewaypr
otocol(
IGP)wor
kinggr
oupoft
heI
nter
net
Engi
neer
ingTaskFor
ce(
IETF)
.Thewor
kinggr
oupwasf
ormedi
n1988t
odesi
gnan
I
GPbasedont
heshor
testpat
hfi
rst(
SPF)al
gor
it
hm f
orusei
ntheI
nter
net
.Si
mil
art
o
t
heI
nter
iorGat
ewayRout
ingPr
otocol(
IGRP)
,OSPFwascr
eat
edbecausei
nthemi
d-
1980s,
theRout
ingI
nfor
mat
ionPr
otocol
(RI
P)wasi
ncr
easi
ngl
yunabl
etoser
vel
arge,
het
erogeneousi
nter
net
wor
ks.

OSPFi
sacl
assl
essr
out
ingpr
otocol
,whi
chmeanst
hati
nit
supdat
es,
iti
ncl
udest
he
subnetofeachr
out
eitknowsabout
,thus,enabl
i
ngv
ari
abl
e-l
engt
hsubnetmasks.
Wi
thv
ari
abl
e-l
engt
hsubnetmasks,anI
Pnet
wor
kcanbebr
okeni
ntomanysubnet
s
of v
ari
ous si
zes.Thi
s pr
ovi
des net
wor
k admi
nist
rat
ors wi
th ext
ra net
wor
k-
conf
igur
ati
on f
lexi
bil
i
ty.These updat
es ar
e mul
ti
cast
s atspeci
fi
c addr
esses
(
224.
0.0.
5and224.
0.0.
6).

OSPFhast
wopr
imar
ychar
act
eri
sti
cs:

 1)Thepr
otocol
isopen(
non-
propr
iet
ary
),whi
chmeanst
hati
tsspeci
fi
cat
ioni
s
i
nthepubl
i
cdomai
n.TheOSPFspeci
fi
cat
ioni
spubl
i
shedasRequestFor
Comment
s(RFC)1247.
 2)Thesecond pr
inci
palchar
act
eri
sti
cist
hatOSPFi
sbased on t
heSPF
al
gor
it
hm,
whi
chsomet
imesi
sref
err
edt
oast
heDi
j
kst
raal
gor
it
hm,
namedf
or
t
heper
soncr
edi
tedwi
thi
tscr
eat
ion.

COMMANDS:
-

Rout
er#conf
igt
ermi
nal

Rout
er(
conf
ig)
#rout
erospfpr
ocess-
id

Rout
er(
conf
ig-
rout
er)
#net
wor
knet
wor
k-numbermaskar
eaar
ea-
id

Exampl
e:

Rout
er(
conf
ig-
rout
er)
#net
wor
k10.
1.23.
00.
0.0.
255ar
ea0
Var
iousRout
ingPr
otocol
EI
GRP:
-

EnhancedI
nter
iorGat
ewayRout
ingPr
otocol
(EI
GRP)i
sanot
herCi
scopr
opr
iet
ary
,
hy
bri
d(hasf
eat
ureofDi
stanceVect
orandLi
nkSt
atepr
otocol
s),i
nter
iorgat
eway
pr
otocol(
IGP)used byr
out
erst
o exchange r
out
ing i
nfor
mat
ion.EI
GRPuses a
composi
te met
ri
c composed ofBandwi
dth,Del
ay,Rel
i
abi
l
ity
,and Loadi
ng t
o
det
ermi
net
hebestpat
hbet
weent
wol
ocat
ions.

EI
GRPcanr
out
eIP,I
PXandAppl
etal
k.Al
ongwi
thI
S-I
S,i
tisoneoft
hef
ew mul
ti
-
pr
otocol
rout
ingpr
otocol
s.

TheDi
ff
usi
ng Updat
e Al
gor
it
hm (
DUAL) i
s t
he hear
t ofEI
GRP. I
n
essence,
DUALal
way
skeepsabackupr
out
einmi
nd,
incaset
hepr
imar
yrout
egoes
down.DUALal
sol
i
mit
showmanyr
out
ersar
eaf
fect
edwhenachangeoccur
stot
he
net
wor
k.

Ther
eisnomaxi
mum al
l
owabl
enumberofhops.I
naEI
GRPnet
wor
k,eachr
out
er
mul
ti
-cast
s"hel
l
o"packst
odi
scov
eri
tsadj
acentnei
ghbor
.Thi
sadj
acencydat
abase
i
sshar
edwi
thot
herr
out
ert
obui
l
dat
opol
ogydat
abase.Fr
om t
het
opol
ogydat
abase
t
hebestr
out
e(Successor
)andt
hesecondbestr
out
e(Feasi
bleSuccessor
)isf
ound.

EI
GRPi
scl
assl
ess,meani
ngi
tdoesi
ncl
udet
hesubnetmaski
nrout
ingupdat
es.
Howev
er,bydef
aul
t'aut
o-summar
y'i
senabl
e.Youmustdi
sabl
eify
ouwantsubnet
i
nfor
mat
ionf
rom ot
hermaj
ornet
wor
ks.

TheEI
GRPmet
ri
cisacanbeacompl
excal
cul
ati
on,butbydef
aul
titonl
yuses
bandwi
dthanddel
ayt
odet
ermi
net
hebestpat
h.

COMMANDS:
-

Rout
er#conf
igt
ermi
nal

Rout
er(
conf
ig)
#rout
erei
grpAS

Rout
er(
conf
ig-
rout
er)
#net
wor
kX.
X.X.
X
  Ser
ver
s

Aser
veri
spr
imar
il
yapr
ogr
am t
hatr
unsonamachi
ne,pr
ovi
dingapar
ti
cul
arand
speci
fi
cser
vicet
oot
hermachi
nesconnect
edt
othemachi
neonwhi
chi
tisf
ound.

Nowaday
s,ser
verf
unct
ional
i
tyhasbecomesor
ich,compl
exandv
ari
edi
nnat
ure
t
hatt
her
ear
ewhol
ever
ypower
fulcomput
ersdedi
cat
edt
obei
ngexcl
usi
vel
yser
ver
s.
Thi
shasl
edmanynon-
techni
calpeopl
etodenot
eser
ver
sasbei
ngmachi
nest
hat
r
unser
vices.

Anet
wor
kser
veri
sacomput
erdesi
gnedt
opr
ocessr
equest
sanddel
i
verdat
ato
ot
her(
cli
ent
)comput
ersov
eral
ocalnet
wor
kort
heI
nter
net
. Net
wor
kser
ver
s
t
ypi
cal
l
yar
econf
igur
edwi
thaddi
ti
onalpr
ocessi
ng,memor
yandst
oragecapaci
tyt
o
handl
ethel
oadofser
vici
ngcl
i
ent
s.

DHCPSERVER

DHCP (
Dynami
cHostConf
igur
ati
onPr
otocol
)isapr
otocolt
hatal
l
owsacent
ral
comput
ert
oaut
omat
ical
l
yassi
gnt
heTCP/
IP net
wor
kconf
igur
ati
ont
oindi
vi
dual
wor
k-st
ati
onsonapr
ivat
enet
wor
k.Wi
thDHCPenabl
edi
tsuf
fi
cest
oenabl
ethe
"
Obt
ainanI
P addr
essaut
omat
ical
l
y"i
ntheTCP/
IP conf
igur
ati
onont
hepr
ivat
e
net
wor
k.TheDHCPSer
vert
hent
akesov
ert
her
esponsi
bil
i
tyofassi
gni
ngt
heTCP/
IP
par
amet
ers,
signi
fi
cant
lyl
ower
ingt
het
askofnet
wor
kmai
ntenance

Fi
g:8.
5.1

HowDoesDHCPWor
k?

Atboott
imet
hecomput
erhasnonet
wor
kpar
amet
ersassi
gnedt
oit
.Thef
oll
owi
ng
l
i
stpr
ovi
desanov
erv
iewoft
het
ypi
cal
net
wor
kpar
amet
ers:
 I
Paddr
essandnet
wor
kmask

Def
aul
trout
e/gat
ewayñanI
Paddr
esswhi
chwi
l
lbeusedf
orf
orwar
dingpacket
s
whosedest
inat
ionsar
ebey
ondl
ocal
net
wor
k

DNSser
ver
sforr
esol
vi
ngI
nter
netnames(
e.g.i
nter
net
.com)t
oIPaddr
esses

Wor
kst
ati
onpar
amet
ers,
e.g.
,domai
nnameorwor
kgr
oup/
wor
kst
ati
onname

St
ati
crout
es

I
Pfor
war
dingset
ti
ng

MTUsi
ze

Ot
herset
ti
ngs(
acompl
etel
i
stcanbef
oundi
ntheDHCPRFCs)

 St
ati
cconf
igur
ati
on.

Wi
th st
ati
c conf
igur
ati
on,t
he cl
i
ent comput
er uses pr
e-conf
igur
ed net
wor
k
par
amet
ers.Thedi
sadv
ant
agesoft
hisappr
oachi
ncl
udet
hepossi
bil
i
tyofI
Paddr
ess
conf
li
ctsandt
headmi
nist
rat
ivei
ssuespossi
blewhenmanual
l
yconf
igur
ingmany
i
nter
nal
cli
ent
s.
  DHCPconf
igur
ati
on(
aut
omat
ic)
.

Wi
thaut
omat
icconf
igur
ati
on,
thecomput
erobt
ainsi
tsnet
wor
kpar
amet
ersf
rom t
he
DHCPSer
ver
.Thi
swayt
heI
Paddr
essesar
eaut
omat
ical
l
ymanagedandaccor
dingl
y
addr
essconf
li
ctsar
eav
oided.I
fmanualandaut
omat
icnet
wor
kconf
igur
ati
onsar
e
usedt
oget
her
,theadmi
nist
rat
ormustensur
ethatt
heDHCPSer
verwon’
tassi
gnI
P
addr
essesusedbymanual
l
y-conf
igur
edcomput
ers

Howt
oconf
igur
etheDHCPser
ver

Oncey
ouhav
econsi
der
edt
hei
mpl
i
cat
ionsofDHCPi
nyournet
wor
k,y
ouar
eready
t
ogetst
art
edwi
tht
hesi
mpl
econf
igur
ati
on.

Fi
g:8.
5.2

Forasmal
lnet
wor
k,t
heconf
igur
ati
onoft
heDHCPSer
veri
snotv
erychal
l
engi
ngand
t
heI
nJoyDHCPSer
verPl
ugi
nisdel
i
ber
atel
ydesi
gnedt
obeext
remel
ysi
mpl
e.I
nfact
,
i
ntheI
nJoyFi
rewal
l
ô,y
oucani
mmedi
atel
yenabl
etheDHCPSer
verandhav
eit
oper
ati
onal
inl
esst
hanami
nut
e.Her
eishow.

DNSSERVER

TheDomai
nNameSy
stem (
DNS)i
sast
andar
dtechnol
ogyf
ormanagi
ngt
henames
ofWebsi
tesandot
herI
nter
netdomai
ns.DNSt
echnol
ogyal
l
owsy
out
oty
penames
i
ntoy
ourWeb br
owserl
i
kecompnet
wor
king.
about
.com and y
ourcomput
ert
o
aut
omat
ical
l
yfi
ndt
hataddr
essont
heI
nter
net
.A keyel
ementoft
heDNSi
sa
wor
ldwi
decol
l
ect
ionofDNSser
ver
s.What
,then,
isaDNSser
ver
?

Answer
:ADNSser
veri
sanycomput
err
egi
ster
edt
ojoi
ntheDomai
nNameSy
stem.
ADNSser
verr
unsspeci
al-
pur
posenet
wor
kingsof
twar
e,f
eat
uresapubl
i
cIPaddr
ess,
andcont
ainsadat
abaseofnet
wor
knamesandaddr
essesf
orot
herI
nter
nethost
s.