ch2-transport layer.pptx

8/9/2019 ch2-transport layer.pptx

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Transport LayerK.Venkata Ramana,Associate Professor,

Dept of CSE,RVRJCCE,

Guntur.


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The Big Picture

At!ou"! t!e protoco suite is cae#$TCP%&P,$ t!ere are more mem'ers of

t!is famiy t!an (ust TCP an# &P. )i"ure 'eo* s!o*s an o+er+ie* of

t!ese protocos.


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The Big Picture


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The Big Picture

o+in" from ri"!t to eft, t!e ri"!tmost -+eappications are usin" &P+.

T!e ne/t si/ appications use &P+0.

T!e eftmost appication, tcp#ump,communicates #irecty *it! t!e #ataink usin"eit!er t!e 1SD packet -ter 21P)3 or t!e#ataink pro+i#er interface 2DLP&3.

T!e #as!e# ine 'eneat! t!e nine appicationson t!e ri"!t are AP&, *!ic! is normay socketsor 4T&. T!e interface to eit!er 1P) or DLP& #oesnot use sockets or 4T&.


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The Big Picture

T!e trace route pro"ram uses t*o sockets5one for &P an# anot!er for &CP

Description of eac! of t!e protoco 'o/es int!is -"ure.

&P+0 5&nternet Protoco +ersion 0. &P+0,*!ic! *e often #enote as (ust &P, !as 'een

t!e *ork!orse protoco of t!e &P suite sincet!e eary 6789s. &t uses :;


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The Big Picture

TCP5 Transmission Contro Protoco.

TCP is a connectionotice t!at TCP can use eit!er &P+0 or &P+.


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The Big Picture

=DP5 =ser Data"ram Protoco.

=DP is a connectioness protoco, an#

=DP sockets are an e/ampe of#ata"ram sockets.

T!ere is no "uarantee t!at =DP

#ata"rams e+er reac! t!eir inten#e##estination.

As *it! TCP, =DP can use eit!er &P+0 or&P+.


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The Big Picture

&GP5 &nternet Group ana"ementProtoco. &GP is use# *it! muticastin",*!ic! is optiona *it! &P+0.

ARP 5A##ress Resoution Protoco. ARPmaps an &P+0 a##ress into a !ar#*area##ress 2suc! as an Et!ernet a##ress3.

ARP is normay use# on 'roa#castnet*orks suc! as Et!ernet, token rin",an# )DD&, an# is not nee#e# on point


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The Big Picture

RARP5 Re+erse A##ress ResoutionProtoco. RARP maps a !ar#*are

a##ress into an &P+0 a##ress. &t issometimes use# *!en a #iskess no#eis 'ootin".

&CP+ 5&nternet Contro essa"eProtoco +ersion . &CP+ com'inest!e functionaity of &CP+0, &GP, an#ARP.


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The Big Picture

1P) 5 1SD packet -ter. T!is interfacepro+i#es access to t!e #ataink ayer. &t

is normay foun# on 1erkeey


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Packet e/c!an"e for TCPconnection


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SCTP AssociationEsta'is!ment an# Termination


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Packet e/c!an"e for SCTP Association


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SCTP ?PT&?>S

SCTP uses parameters an# c!unks tofaciitate optiona features.

>e* features are #e-ne# 'y a##in" eit!erof t!ese t*o items, an# ao*in" normaSCTP processin" rues to report unkno*nparameters an# unkno*n c!unks.

T!e upper t*o 'its of 'ot! t!e parameterspace an# t!e c!unk space #ictate *!atan SCTP recei+er s!ou# #o *it! anunkno*n parameter or c!unk


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SCTP ?PT&?>S

Currenty, t*o e/tensions for SCTP areun#er #e+eopment5

6. Dynamic a##ress e/tension 5 *!ic! ao*scooperatin" SCTP en#points to #ynamicay

a## an# remo+e &P a##resses from an

e/istin" association.

;. Partia reia'iity e/tension 5@!en a messa"e'ecomes too o# to sen# 2accor#in" to t!eappications #irection3, t!e messa"e *i 'e

skippe# an# t!us no on"er sent to t!e peer.

T!is means t!at not a #ata is assure#.


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Port >um'ers

@!en a cient *ants to contact a ser+er,t!e cient must i#entify t!e ser+er *it!*!ic! it *ants to communicate.

TCP, =DP, an# SCTP #e-ne a "roup of*e


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Port >um'ers

Cients normay use ep!emera ports,t!at is, s!ort


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Port num'ers


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Port >um'ers

T!e port num'ers are #i+i#e# into t!ree ran"es56. T!e *eA re"isters an#ists t!e uses of t!ese ports as a con+enience to t!ecommunity. @!en possi'e, t!e same port is assi"ne#to a "i+en ser+ice for 'ot! TCP an# =DP.

:. T!e #ynamic or pri+ate ports5076B; t!rou"! BB:B.T!e &A>A says not!in" a'out t!ese ports. T!ese are*!at *e ca ep!emera ports.


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Port >um'ers =ni/ systems !a+e t!e concept of a

reser+e# port, *!ic! is any port ess t!an69;0. T!ese ports can ony 'e assi"ne#to a socket 'y an appropriatey pri+ie"e#process.

A t!e &A>A *e


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Port >um'ers T!ese cients ca t!e i'rary function

rres+port to create a TCP socket an#assi"n an unuse# port in t!e ran"eB6:69;: to t!e socket.

T!is function normay tries to 'in#port 69;:, an# if t!at fais, it tries to'in# 69;;, an# so on, unti it eit!er

succee#s or fais on port B6:.


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Socket Pair

T!e socket pair for a TCP connection is t!e foure/t, a cient starts on t!e !ost *it! &Pa##ress ;9.68.66;.;67 an#e/ecutes an acti+e open to t!e ser+ers

&P a##ress of 6;.69.:;.;B0. T!e ep!emera port c!osen 'y t!e

cient TCP is 6B99 .

T!is is s!o*n in )i"ure 'eo*.


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TCP port num'ers an#concurrent Ser+ers


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@!en t!e ser+er recei+es an# acceptst!e cients connection, it forks a copyof itsef, ettin" t!e c!i# !an#e t!e

cient, as s!o*n in )i"ure ;.6:.

?n t!e muti!ome# ser+er, t!e ocaa##ress is -e# in for t!e connecte#

socket 26;.69.:;.;B03 once t!econnection is esta'is!e#.


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?n t!e ser+er, t!e t*o connections are #istinct5t!e socket pair for t!e -rst connection #iIersfrom t!e socket pair for t!e secon# connection

'ecause t!e cients TCP c!ooses an unuse#port for t!e secon# connection 26B963.

TCP cannot #emutipe/ incomin" se"ments 'yookin" at (ust t!e #estination port num'er.

TCP must ook at a four eements in t!e socketpair to #etermine *!ic! en#point recei+es anarri+in" se"ment.


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&n )i"ure ;.60, *e !a+e t!ree sockets *it!t!e same oca port 2;63.

&f a se"ment arri+es from ;9.68.66;.;67

port 6B99 #estine# for 6;.69.:;.;B0 port;6, it is #ei+ere# to t!e -rst c!i#.

&f a se"ment arri+es from ;9.68.66;.;67port 6B96 #estine# for 6;.69.:;.;B0 port

;6, it is #ei+ere# to t!e secon# c!i#. A ot!er TCP se"ments #estine# for port

;6 are #ei+ere# to t!e ori"ina ser+er *it!

t!e istenin" socket.


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1uIer Sies an# Limitations

Limits t!at aIect t!e sie of &P #ata"rams5

a/imum sie5

?f an &P+0 #ata"ram is B,B:B 'ytes, incu#in" t!e

&P+0 !ea#er. T!is is 'ecause of t!e 6


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a/imum transmission unit 2T=3

&P+ !as a (um'o payoa# option, *!ic! e/ten#s t!epayoa# en"t! -e# to :; 'its, 'ut t!is option issupporte# ony on #atainks *it! a ma/imum

transmission unit 2T=3 t!at e/cee#s B,B:B. any net*orks !a+e an T= *!ic! can 'e #ictate# 'y

t!e !ar#*are. )or e/ampe, t!e Et!ernet T= is 6,B99'ytes.

?t!er #atainks, suc! as point


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inimum ink T= an# minimum


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Pat! T= T!e smaest T= in t!e pat! 'et*een

t*o !osts is cae# t!e pat! T=.

To#ay, t!e Et!ernet T= of 6,B99 'ytesis often t!e pat! T=.

T!e pat! T= nee# not 'e t!e same in'ot! #irections 'et*een any t*o !osts'ecause routin" in t!e &nternet is oftenasymmetric.


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)ra"mentation5 @!en an &P #ata"ram is to 'e sent out an

interface, if t!e sie of t!e #ata"ram e/cee#s t!eink T=, fra"mentation is performe# 'y 'ot! &P+0an# &P+.

T!e fra"ments are not normay reassem'e# untit!ey reac! t!e -na #estination.

&P+0 !osts an# routers perform fra"mentation on

#ata"rams.

1ut *it! &P+, ony !osts perform fra"mentationon #ata"rams t!at t!ey "enerate &P+ routers #onot fra"ment #ata"rams t!at t!ey are for*ar#in".


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Dont fra"ment5 MDont fra"ment$ 2D)3 'it in t!e &P+0 !ea#er

speci-es t!at t!is #ata"ram must not 'efra"mente#, eit!er 'y t!e sen#in" !ost or 'y anyrouter.

A router t!at recei+es an &P+0 #ata"ram *it! t!eD) 'it set *!ose sie e/cee#s t!e out"oin" inksT= "enerates an &CP+0 $#estinationunreac!a'e, fra"mentation nee#e# 'ut D) 'it

set$ error messa"e . Since &P+ routers #o not perform fra"mentation,

t!ere is an impie# D) 'it *it! e+ery &P+#ata"ram.


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TCP ?=TP=T


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=DP ?=TP=T


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SCTP ?=TP=T


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Stan#ar# &nternet ser+ices


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Protoco usa"e 'y common &nternetAppications

ch2-transport layer.pptx

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