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Introduction 1-1
Introduccin a las
Redes deComputadoras
Introduccin
Nota acerca de las transparencias del curso:
Estas transparencias estn basadas en el sitio web que acompaa el libro, y
han sido modificadas por los docentes del curso.
All material copyright 1!"#$1#
%.& 'urose and '.(. )oss, All )ights )eser*ed
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Introduction 1-3
Aspectos administrativos:
Aprobacin
%aboratorio
na tarea introductoria)
*res +bligatorios (entrega obligatoria)Grupos de tres estudiantes)
&onitoreos cada semana con un docente en grupos
reducidos (, o - grupos a la ve".
De/ensa en m01uina con el mismo docente.
(reglamento completo de aprobacin en el EVA)2arcial
*erico (da puntos para el e3amen.
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Introduction 1-4
Recursos
&oodle
eva./ing.edu.u4 5ibliogra/a
Computer Networking: A Top Down Approach)6t' edition. #im 7urose) 7eit' Ross) Addison89esle4) #ul4 -;. IS5;;?.
@t' edition. #im 7urose) 7eit' Ross) Addison89esle4) &arc' ->. IS5;>.
t' edition. #im 7urose) 7eit' Ross) Addison89esle4) &arc' -,-. IS5
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C'apter ,: Introduction
+ur goal: get /eel and
terminolog4
more dept') detail
later in course approac':
use Internet ase3ample
+vervieB: B'atFs t'e Internet
B'atFs a protocol
netBorH edge 'osts) access net)
p'4sical media
netBorH core: pacHetJcircuit
sBitc'ing) Internet structure
per/ormance: loss) dela4)
t'roug'put
securit4
protocol la4ers) service models
'istor4 +ntroduction 1"
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C'apter ,: roadmap
,., 9'at is t'e Internet
,.-
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9'atFs t'e Internet: nuts and bolts vieB
millions o/ connectedcomputing devices:
'osts K end s4stems
running netBorH appsome netBorH
Institutional netBorH
&obile netBorH
Global IS2
Regional IS2
router
2C
server
Birelesslaptop
cellular'and'eld
BiredlinHs
accesspoints
communication linHs
/iber) copper)
radio) satellite
transmission rateK bandBidt'
routers:/orBard pacHets
(c'unHs o/ data
+ntroduction 1"-
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+t'er Internet appliances
+nternet phones
+ntroduction 1"
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Internet Si"e
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9'atFs t'e Internet: nuts and bolts vieB
protocols control sending)receiving o/ msgs e.g.) *C2) I2) **2) SH4pe)
Et'ernet
Internet: netBorH o/netBorHs loosel4 'ierarc'ical
public Internet versus private
intranet
Internet standards R!C: Re1uest /or comments
IE*!: Internet Engineering
*asH !orce
ome netBorH
Institutional netBorH
&obile netBorH
Global IS2
Regional IS2
+ntroduction 1"1$
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9'atFs t'e Internet: a service vieB
communication in/rastructureenables distributed
applications:
9eb) $oI2) email) games)
e8commerce) /ile s'aring
communication services
provided to apps:
reliable data deliver4 /rom
source to destination
best e//ort (unreliable
data deliver4
+ntroduction 1"11
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9'atFs a protocol
'uman protocols: B'atFs t'e time
I 'ave a 1uestion
introductions
L speci/ic msgs sent
L speci/ic actions taHen
B'en msgs received)
or ot'er events
netBorH protocols: mac'ines rat'er t'an
'umans
all communication
activit4 in Internetgoverned b4 protocols
protocols de/ine /ormat) order
o/ msgs sent and received
among netBorH entities)and actions taHen on msg
transmission) receipt
+ntroduction 1"1#
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9'atFs a protocol
a 'uman protocol and a computer netBorH protocol:
M:+t'er 'uman protocols
/i
/i
0ot the
time
#:$$
234 connectionresponse
0ethttp:55www.awl.com56urose"ross
7file8time
+ntroduction 1"19
234 connectionrequest
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C'apter ,: roadmap
,.,9'at is t'e Internet
,.-
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A closer looH at netBorH structure:
netBorH edge:applications and
'osts access netBorHs)
p'4sical media:Bired) Bireless
communication linHs
netBorH core: interconnected
routers
netBorH o/ netBorHs
+ntroduction 1"1
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*'e netBorH edge:
end s4stems ('osts: run application programs
e.g. 9eb) email
at edge o/ netBorH
clientJserver
peer8peer
clientJserver model client 'ost re1uests) receives
service /rom alBa4s8on server
e.g. 9eb broBserJserver email
clientJserver
peer8peer model: minimal (or no use o/ dedicated
servers
e.g. SH4pe) 5it*orrent
+ntroduction 1"1!
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Access netBorHs and p'4sical media
M: oB to connect ends4stems to edge router
residential access nets
institutional access
netBorHs (sc'ool)compan4
mobile access netBorHs
7eep in mind:
bandBidt' (bits per
second o/ access
netBorH
s'ared or dedicated+ntroduction 1"1-
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telephone
network Internet
home
dial-up
modem
ISP
modem
(e.g., AO!
home
P"
central
o##ice
uses e3isting telep'on4 in/rastructure
'ome directl48connected to central o//ice
up to @7bps direct access to router (o/ten less
canFt sur/) p'one at same time: not alBa4s on
Dial8up &odem
+ntroduction 1"1
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Residential access: cable modems
uses cable *$ in/rastructure) rat'er t'an
telep'one in/rastructure
!C: '4brid /iber coa3
as4mmetric: up to =&bps doBnstream) -&bps upstream
netBorHo/ cable) /iber attac'es 'omes to IS2
router
'omes s'are access to router unliHe DS%) B'ic' 'as dedicated access
+ntroduction 1"#$
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Residential access: cable modems
;iagram: http:55www.cabledatacomnews.com5cmic5diagram.html +ntroduction 1"#1
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home
cable headend
cable distribution
networ6
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home
cable headend
cable distribution
networ6
ser*er
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Cable
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home
cable headend
cable distribution
networ6
3hannels
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1 # 9 ! -
!D& (more s'ortl4:
+ntroduction 1"#
Cable
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O0
O
central o##iceopticalplitter
O0
O0
optical
#ier
optical#ier
Internet
!iber to t'e ome
optical linHs /rom central o//ice to t'e 'ome
tBo competing optical tec'nologies: 2assive +ptical netBorH (2+
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, &bps
, &bps
, &bps
, Gbps
server
Et'ernet
sBitc'
institutional
routerto institutionFs
IS2
Et'ernet Internet access
t4picall4 used in companies) universities) etc , &bps) ,&bps) ,Gbps) ,Gbps Et'ernet
toda4) end s4stems t4picall4 connect into Et'ernet
sBitc'
+ntroduction 1"#-
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9ireless access netBorHs
s'ared Bireless access netBorHconnects end s4stem to router via base station aHa access point
Bireless %A
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ome netBorHs
*4pical 'ome netBorH components: DS% or cable modem
routerJ/ireBallJ
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2'4sical &edia
bit:propagates betBeen
transmitterJrcvr pairs
p'4sical linH:B'at lies
betBeen transmitter Q
receiver
guided media: signals propagate in solid
media: copper) /iber) coa3
unguided media: signals propagate /reel4) e.g.)
radio
*Bisted 2air (*2 tBo insulated copper
Bires Categor4 =: traditional
p'one Bires) , &bps
Et'ernet Categor4 @:
,&bps Et'ernet
+ntroduction 1"9$
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2'4sical &edia: coa3) /iber
Coa3ial cable: tBo concentric copper
conductors
bidirectional
baseband: single c'annel on cable legac4 Et'ernet
broadband: multiple c'annels on
cable !C
!iber optic cable: glass /iber carr4ing lig'tpulses) eac' pulse a bit
'ig'8speed operation:
'ig'8speed point8to8pointtransmission (e.g.) ,Fs8
,Fs Gpbs
loB error rate: repeaters
spaced /ar apart immune
to electromagnetic noise
+ntroduction 1"91
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2'4sical media: radio
signal carried inelectromagnetic
spectrum
no p'4sical Bire
bidirectionalpropagation environment
e//ects: re/lection
obstruction b4 obects inter/erence
Radio linH t4pes: terrestrial microBave
e.g. up to 6@ &bps c'annels
%A
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C'apter ,: roadmap
,.,9'at is t'e Internet
,.-
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*'e
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Circuit SBitc'ing: !D& and *D&
&;
frequency
time
2;
frequency
time
users
EBample:
+ntroduction 1"9-
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2acHet SBitc'ing: Statistical &ultiple3ing
se1uence o/ A Q 5 pacHets 'as no /i3ed timing pattern bandBidt' s'ared on demand: statistical multiple3ing.
*D&: eac' 'ost gets same slot in revolving *D& /rame.
A
5
C, &bJs
Et'ernet
,.@ &bJs
D E
statisticalmultiple3ing
1ueue o/ pacHetsBaiting /or output
linH
+ntroduction 1"$
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2acHet8sBitc'ing: store8and8/orBard
taHes %JR seconds totransmit (pus' out
pacHet o/ % bits on to linHat R bps
store and /orBard: entirepacHet must arrive atrouter be/ore it can be
transmitted on ne3t linH dela4 K =%JR (assuming
"ero propagation dela4
E3ample:
% K ;.@ &bits
R K ,.@ &bps transmission dela4 K ,@
sec
R R R%
more on dela4 s'ortl4 L
+ntroduction 1"1
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2acHet sBitc'ing versus circuit sBitc'ing
E3ample:
, &bJs linH
eac' user: , HbJs B'en active
active ,T o/ time
circuit8sBitc'ing: , users
pacHet sBitc'ing: Bit' =@ users) probabilit4 U
, active at same time is
less t'an .6
2acHet sBitc'ing alloBs more users to use netBorH
6:5aran 8 pacHet8
sBitc'ing in militar4 nets ,>;:AR2Anet conceived
b4 Advanced Researc'
2roects Agenc4
,>>:/irst AR2Anet node
operational
,>;-:
AR2Anet public demonstration
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Internet istor4
,>;:A%+Anet satellitenetBorH in aBaii
,>;6:Cer/ and 7a'n 8arc'itecture /or interconnectingnetBorHs
,>;:Et'ernet at Pero3 2ARC late;Fs:proprietar4
arc'itectures: DECnet) S:AR2Anet 'as - nodes
Cer/ and 7a'nFs internetBorHingprinciples: minimalism) autonom4 8
no internal c'anges
re1uired to interconnectnetBorHs
best e//ort service model stateless routers decentrali"ed control
de/ine toda4Fs Internetarc'itecture
,>;-8,>?: InternetBorHing) neB and proprietar4 nets
+ntroduction 1"$
Internet istor4
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Internet istor4
,>?=:deplo4ment o/
*C2JI2
,>?-:smtp e8mail
protocol de/ined ,>?=:D?@:/tp protocolde/ined
,>??:*C2 congestion
control
neB national netBorHs:
Csnet) 5I*net)
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Internet istor4
earl4 ,>>Fs:AR2Anet
decommissioned
,>>,:@ earl4 ,>>s:9eb
'4perte3t Z5us' ,>6@) Fs[
*&%) **2: 5erners8%ee
,>>6: &osaic) later >Fs: commerciali"ationo/t'e 9eb
late ,>>Fs \ -Fs: more Hiller apps: instant
messaging) 2-2 /ile s'aring
netBorH securit4 to /ore/ront
est. @ million 'ost) ,
millionW users
bacHbone linHs running at
Gbps
,>>) -Fs: commerciali"ation) t'e 9eb) neB apps
+ntroduction 1"#
Internet istor4
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Internet istor4
-,: O;@ million 'osts
voice) video over I2
2-2 applications: 5it*orrent
(/ile s'aring SH4pe ($oI2)22%ive (video
more applications: You*ube)
gaming) *Bitter
Bireless) mobilit4
+ntroduction 1"9
Introduction: Summar4
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Introduction: Summar4
Covered a ton o/ material Internet overvieB
B'atFs a protocol
netBorH edge) core) accessnetBorH pacHet8sBitc'ing versus
circuit8sBitc'ing Internet structure
per/ormance: loss) dela4)
t'roug'put la4ering) service models securit4
'i
You noB 'ave: conte3t) overvieB)
/eel o/ netBorHing
more dept') detail to/olloB