Download - Networks Lecture Notes
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Introduction 1-1
EECS 325/425
Michael Rabinovich
Introduction
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Introduction 1-2
Logistics Lecture time: Wed/Fri 9:00-10:15am !!ice hours: Wednesda"s 1:00-#:00$m or b"
a$$ointment %lin 50&' (rading:
)ome*or+s: #5,
.o be turned in on the due date FR class verdue home*or+ loses 10, o! value once $ast due and !urther 10,
ever" # hours %including *ee+ends etc2' )ome*or+ not acce$tedonce it3s over hours $assed due
4roects: #0, Midterm: #0,
Final: 65, .e7t: 8urose and Ross om$uter ;et*or+s: a to$-do*n
a$$roach2
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8e" =dvice: e Resource!ul>
?I learned ever"thing !rom the boo+2@ Atud" grou$s !!ice hours .=s
Whatever *or+s>
Introduction 1-3
Atud" grou$s:
8 to discuss home*or+/$roect 8 to e7$lain a home*or+ solution to each other as long as no one takes notes with them from
discussion!
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Introduction 1-4
Bnderstanding om$uter;et*or+s What ha$$ens *hen I clic+ on this lin+C
htt$://cnn2com
= number o! com$uters across the countr" are involved
)undreds o! +ilob"tes travel thousands o! miles )andled b" doDens o! rela" devices
= number o! $rotocols *or+ together: )..4 E;A BE4
.4 I4 (4 A4F =R4 thernet WiFi
= number o! com$anies get involved The course oecti"e# a $eak ehind the scene%
http://cnn.com/http://cnn.com/ -
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Introduction 1-5
ourse bectives
4rovide basic overvie* o! the net*or+ing area Internet $rotocol stac+ 4rotocol e7am$les at a$$lication trans$ort net*or+ and
lin+ la"ers Internet hierarch" addressing routing algorithms
4re$are !or in-de$th stud" in selected areas (ain initial e7$erience in creating net*or+
a$$lications (et e7$osure to lo*-level net*or+ $rogramming ;ot a vocational course>
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Introduction 1-6
.hese lecture notes are based heavil" on the slides $rovided b" theauthors o! the boo+2 =ll material $rovided b" the authors should beconsidered as belonging to their co$"right: G 199
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Introduction 1-7
What3s the Internet: an architecture vie*
millions o! connectedcom$uting devices: hosts 0nd hosts end s"stems
4s servers la$to$s smart$hones
running net*or+ a$$s
mail Web (ames 4#4 communication lin+s
!iber co$$er radio satellite
routers:!or*ard $ac+ets%chun+s o! data'
Internet:net*or+ o! net*or+s 4rotocols:)..4 it.orrent
A+"$e
mobile network
global ISP
regional ISPhomenetwork
institutional network
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Introduction 1-8
What3s a $rotocolC
human $rotocols: =t restaurant =t a doctor3s o!!ice Introductions
s$eci!ic msgs sent
s$eci!ic actions ta+en
*hen msgs receivedor other events
Ee!ine con"entions
What time is itC
7cuse me
JesC
#:00
time
?(ot .imeC@ 4rotocol
.han+s
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Introduction 1-9
What3s a net*or+$rotocolC
machines rather thanhumans
4rotocols:
Fde!ine !ormat K order o! msgs sentamong net*or+ entities9
Factions ta+en on msg recei$t9 otherevents
.4 connectionreuest
.4 connectionres$onse
!ileN
time
Web $age do*nload
(et headlines2html
=ll communication activit" in Internet governed b" $rotocols
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Whats the Internet: a service view
Infrastructure that providesservices to applications: Web, VoIP, email, games, e-
commerce, social nets,
provides programminginterface to apps hooks that allow apps to
connect to Internet
sen messages
receive messages
provies service options,analogo!s to postal service
mobile network
global ISP
regional ISPhomenetwork
institutional network
Intro!ction
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Introduction 1-11
= closer loo+ at net*or+ structure:
net*or+ edge:a$$lications andhosts
access net*or+s:*ired *irelesscommunication lin+s
net*or+ core: interconnected
routers net*or+ o!
net*or+s
mobile network
global ISP
regional ISPhomenetwork
institutional network
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Intro!ction
$ccess networks
Q: How to connect endsystems to edgerouter?
resiential access nets
instit!tional accessnetworks %school,compan&'
Wireless access networks
keep in mind: banwith %bits persecon' o( accessnetwork)
share or eicate)
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Intro!ction
$ccess net: igital s!bscriberline %+'
central office
ISP
telephone
network
DSLAM
.se existingtelephone line to central o/ce +$0 %+ $ccess0!ltiple1er' ata over + phone line goes to Internet voice over + phone line goes to telephone net 2re3!enc& ivision m!ltiple1ing:
16O +)D - 1 M)D !or do*nstream
#5 +)D - 16O +)D !or u$stream
0 +)D - +)D !or ordinar" tele$hone
4 *56 0bps !pstream transmission rate %t&picall& 4 " 0bps' 4 *7 0bps ownstream transmission rate %t&picall& 4 "# 0bps'
DSLmodem
splitter
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Eedicated Lin+s>
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Intro!ction
$ccess net: cablenetwork
cablemodem
splitter
cable headend
Channels
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ISP
cable modemtermination system
Shared access
frequency divisionmultiplexing: data,TV transmitted atdifferentfrequencies overshared cable network
92: h&bri ;ber coa1 as&mmetric: !p to 8#0bps ownstream
transmission rate, * 0bps !pstream
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Intro!ction
$ccess 1amples
$?@? .-Verse
VeriAon 2i=
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Intro!ction
$ccess net: homenetwork
to-from headend orcentral office
cable or DSL modem
router. firewall. "A!
wired Ethernet /$00 Mbps1
wireless accesspoint /(' Mbps1
wirelessde2ices
often combinedin single bo3
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Intro!ction
>nterprise access networks%>thernet'
t&picall& !se in companies, !niversities, etc
"# 0bps, "##0bps, "Cbps, "#Cbps transmission rates
toa&, en s&stems t&picall& connect into >thernet switch
Ethernetswitch
institutional mail.web ser2ers
institutional router
institutional link toISP /Internet1
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Intro!ction
Wireless access networks
share wirelessaccess network connects en s&stem to ro!ter via base station aka access point
wireless LAs: within b!iling %"## (t'
E#*5""bFg %Wi2i': "", 670bps transmission rate
wie-area wireless access provie b& telco %cell!lar'
operator, "#s km between " an "# 0bps 8C, 7C: ?>
to Internet
to Internet
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Introduction 1-19
.he ;et*or+ ore
mesh o! interconnectedrouters
the!undamentaluestion:ho* is datatrans!erred through netC circuit s*itching:
dedicated circuit $ercall: tele$hone net
$ac+et-s*itching:datasent thru net indiscrete ?chun+s@
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Introduction 1-20
;et*or+ ore: ircuit A*itching
nd-end resourcesreserved !or ?call@
lin+ band*idth s*itch
ca$acit" dedicated resources:
no sharing circuit-li+e
%guaranteed'$er!ormance call setu$ reuired
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Introduction 1-21
;et*or+ ore: ircuit A*itching
net*or+ resources%e2g2 band*idth'divided into ?slices@
slices allocated to calls resource slice idlei! not
used b" o*ning call %nosharing'
dividing lin+ band*idthinto ?slices@ !reuenc" division time division
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Introduction 1-22
ircuit A*itching: FEM and .EM
!DM
fre4uenc5
time
6DM
fre4uenc5
time
' usersE3ample7
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Introduction 1-23
;et*or+ ore: 4ac+et A*itching
each end-end data streamdivided into $ac+ets
$ac+ets !rom di!!erentusers sharenet*or+
resources each $ac+et uses !ull lin+
band*idth resources used as needed
resource contention: aggregate resource
demand can e7ceedavailable ca$acit"
congestion: $ac+etsueue *ait !or lin+ use
store and !or*ard:$ac+ets move one ho$
at a time ;ode receives com$lete
$ac+et be!ore !or*arding
and*idth division into ?slices@
Eedicated allocation
Resource reservation
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Introduction 1-24
4ac+et A*itching: Atatistical Multi$le7ing
Aeuence o! = K $ac+ets does not have !i7ed $atternshared on demand statistical multi$le&ing2
.EM: each host gets same slot in revolving .EM !rame2
=
10 Mb/sthernet
125 Mb/s
E
statistical multi$le&ing
ueue o! $ac+ets*aiting !or out$utlin+
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Introduction 1-25
4ac+et s*itching versus circuit s*itching
1 Mb/s lin+ each user:
100 8b/s *hen ?active@ active 10, o! time
circuit-s*itching: 10 users
$ac+et s*itching: *ith 65 users
$robabilit" N 10 activeless than 2000
4ac+et s*itching allo*s more users to use net*or+>
; users
1 Mb$s lin+
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Introduction 1-26
4ac+et s*itching versus circuit s*itching
(reat !or burst" data resource sharing
sim$ler no call setu$ 7cessive congestion:$ac+et dela" and loss
$rotocols needed !or reliable data trans!ercongestion control
;o guaranteed $er!ormance P: )o* to $rovide circuit-li+e behaviorC
band*idth guarantees needed !or audio/video a$$s
Is $ac+et s*itching a ?slam dun+ *innerC@
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Introduction 1-27
4ac+et-s*itching: datagram and virtualcircuit net*or+s
(oal:move $ac+ets through routers !rom source todestination
datagram net*or+: destination address in $ac+et determines ne7t ho$
4ath ma" change !rom one datagram to another Routers !orget about a datagram a!ter !or*arding to ne7t
ho$
virtual circuit net*or+: each $ac+et carries tag %virtual circuit IE' tag
determines ne7t ho$ !i7ed $ath determined at call setu$ time remains the same
thru call routers maintain$er-call state
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Introduction 1-28
;et*or+ .a7onom"
.elecommunicationnet*or+s
ircuit-s*itchednet*or+s
FEM .EM
4ac+et-s*itchednet*or+s
;et*or+s
*ith Qs
Eatagram
;et*or+sEM