01.theosi tcp ipmodel

8/12/2019 01.Theosi Tcp Ipmodel

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The OSI Model


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Topics

What are Protocols ?Why we need Protocols and Standards

The OSI Reference Model The Seven Layers of the ModelResponsibilities of Each Layer

The Application Layer The Presentation Layer The Session Layer The Transport Layer The etwor! Layer The "ata Lin! Layer

The Physical Layer


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What are Protocols ?

Let#s loo! at what happen$

Oh %y&od' whatdid he say

?

(h)n*bi+t

th,n*n-y .an*n/i c0i *1

n2a ?

They do not 3nderstand eachother beca3se they are 3sin*

di4erent lan*3a*es5


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What are Protocols ? 6cont7

ow' Let#s loo! at what happensne8t$

They can 3nderstand each otherbeca3se they are 3sin* the sa%e

lan*3a*e5


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So in order for two people to spea! toeach other' the 9rst thin* they sho3ldto a*ree on is the lan*3a*e' orprotocols' to 3se5:o%%3nication between hosts on the

networ! is the sa%e5 When hosts be*inco%%3nicatin* with each other' they9rst %3st a*ree on what protocols to

3se5


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I e5ico I e5ico


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A *ro3p of protocol is called a protocol s3iteor a protocol stac!5

When co%bined with other protocols' the

protocol *ro3p that res3lt is called aprotocol suite 5 T:P;IP' for e8a%ple' is aprotocol s3ite5


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Why We eed Protocols and

StandardsR3les < or protocols and standards < arei%portant to ens3re co%patibility betweendi4erent !inds of thin*s

=owever' before a protocol is accepted

and widely i%ple%ented' it has to passri*oro3s testin*5 So a standard fra%ewor!is 3sed to help desi*n' co%pare' test' andeval3ate protocols5


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The Seven Layers of the OSI

Model The *oal of the OSI %odel is to brea! downthe tas! of data co%%3nication intosi%ple steps5 These steps are calledlayers5

The OSI %odel is %ade 3p of sevendistinct layers5 Each layer has certainresponsibilities5


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The Seven Layers of the OSI

Model


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IP Header 1IP Header 1IP Header 1

IP Header 1IP Header 1Frame Header IIP Header 1Frame Header I IP Header 1Frame Header I IP Header1

IP Header 1

Ie5icoIe5icoIe5icoIe5icoIe5ico

Ie5ico Ie5ico Ie5ico Ie5icoIe5ico Ie5ico

Ie5ico Ie5ico Ie5ico Ie5ico Ie5icoIe5icoIe5ico Ie5ico Ie5ico Ie5ico Ie5icoIe5ico Ie5ico




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The Application Layer

Let#s loo! at what is happenin*$

You are surfng on theInternet You type an address o a

Website

The Website is deliveredto you

Webro!ser

Web "erver

Internet E8plorer5ln!


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The Application Layer

The Application layer is the top layerof the OSI %odel5

The p3rpose of the Application layeris to %ana*e co%%3nicationsbetween applications5

Webro!ser

Web "erver

Internet E8plorer5ln!


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The Application LayerE8a%ple of the Application layer$

>ile transferElectronic %ail

Ter%inal accessWord processin*Web rowser


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The Presentation Layer



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The Presentation Layer

The Presentation layer is the layerbelow the Application layer andabove the Session layer5

The Presentation ensures that theinformation that the applicationlayer of one system sends out isreadable by the application layer of

another system.


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The Presentation LayerActions of the Presentation layer$

>or%at of data"ata str3ct3re"ata conversion

"ata co%pression"ata encryptionE8a%ples of the Presentation layer$

PI:T < This is pict3re for%at 3sed by Macintosh

MI"I < The M3sical Instr3%ent "i*ital Interface is 3sed fordi*iti@ed %3sic5 MPE& < The Movin* Pict3re E8perts &ro3p#s standard for theco%pression and codin* of %otion video for :"s 5

RT> < Rich Te8t >or%at is a 9le for%at that lets yo3 e8chan*ete8t 9les between di4erent word processors' even in di4erent


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The Session Layer



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The Session Layer

The Session is below thePresentation layer5

The Session layer establishes'%ana*es' and ter%inates sessionsbetween two co%%3nicatin* hosts5


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The session layerActions of the Session layer$Sessions

"ialo*:onversations

"ata e8chan*e

E8a%ples of the Session layer$#et!or$ File "ystem %#F"& < "eveloped by S3n

Microsyste%s and 3sed with T:P;IP and ni8wor!station to allow transparent access to re%otereso3rces5'ppleTal$ "ession Protocol %'"P& < client;server%echanis%' which both establishes and %aintains sessions

between AppleTal! client and server %achines5


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The Transport Layer

The Transport layer is below the Sessionlayer5

The Transport layer can *3arantee thatpac!ets are received5


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The Transport Layer The Transport layers se*%ents and reasse%blesdata into a data strea%


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The Transport Layer

The pri%ary f3nction of the Transport layeris to ens3re that the data pac!ets it

receives fro% the Session layer arrivereliably5 The Transport layer does this by 3sin* twotypes of trans%issions$ connectionless

and connection oriented 5

The Transport layer also has the Bob of%ana*in* the speed of co%%3nicationbetween devices5 This is !nown as (o!


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The Transport Layer:onnectionless trans%issions6cont7

ser "ata*ra% Protocol 6 "P7 is ane8a%ple of connectionless protocol

Applications that 3se "P to send theirdata infor%ation is " S' T>TPC5


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The Transport Layer:onnectionless trans%issions6cont7

Trans%ission :ontrol Protocol 6T:P7 is ane8a%ple of connectionDoriented protocol

Applications that 3se T:P to send theirdata infor%ation is " S' >TP' =TTP' SMTP'C


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The Transport Layer

the threeDway handsha!eIn connectionDoriented trans%ission' boththe sender and receiver have to Boin to thesession5 The receiver %3st !now that thesender is sendin* pac!ets in order toanswer 6ac!nowled*%ent7

So' the sender %3st 9rst establish aconnectionDoriented session with thereceiver' which is called a call set3p' orthree)!ay handsha$e


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The Transport Layerthe threeDway handsha!e6cont7

Let#s loo! at what happens$In the three)!ay handsha$e process' when=ost A 6sender7 want to establish a session

with =ost 6receiver7' it 9rst send to thereceiver a synchroni*e se*%ent5

=ost 6receiver7 after e8a%ine thesynchroni@e pac!et fro% =ost A' if a*ree' it

will send ac!nowled*e%ent synchroni@ese*%ent to =ost A5

Synchroni@e 6:an I tal! to yo3 ?7

Ac! 6 es7' Synchroni@e 6 :an I tal! to yo3 ?7

=ost A after receives the synchroni@ese*%ent fro% =ost ' it will send an

ac!nowled*e%ent se*%ent to =ost toac!nowled*e to connection5

Ac! 6 es7

+onnection ,stablished

-ata Trans er%send segments&


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The Transport layer

>low :ontrolOnce data transfer is in pro*ress'con*estion can occ3r for two reasons5


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The Transport layer

>low :ontrol 6cont7>irst' the sendin* device %i*ht be able to*enerate traFc faster than the networ! cantransfer it5


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The Transport layer

>low :ontrol 6cont7 The second reason is that %3ltiple devicesneed to send data to the sa%e destination5


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The Transport layer

>low :ontrol 6cont7When data*ra% arrive too G3ic!ly for adevice to process' it te%porarily stores the%in %e%ory5


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The Transport layer

>low :ontrol 6cont7If the data*ra%s are part of a s%all b3rst' thisb34erin* solves the proble%5


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The Transport layer

>low :ontrol 6cont7=owever' if the traFc contin3es at this rate'the device event3ally e8ha3sts its %e%oryand %3st discard additional data*ra%s thatarrive5


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The Transport layer

>low :ontrol 6cont7Instead of losin* the data' the transportf3nction can iss3e a Hnot ready indicator tothe sender5


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The Transport layer

>low :ontrol 6cont7 This acts li!e a stop si*n and si*nal thesender to discontin3e sendin* se*%ent traFcto the receiver5


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The Transport layer

>low :ontrol 6cont7After the receivin* device has processed s3Fcientse*%ents to free space in its b34er' the receiversends a Hready transport H indicator < which is li!e

a *o si*nal5


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The Transport layer

>low :ontrol 6cont7When they receives this indicator' the senderscan res3%e se*%ent trans%ission5


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The Transport LayerAc!nowled*e%ent

The transport layer provide a reliable servicere*ardless of the G3ality of the 3nderlyin*networ!


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The Transport LayerAc!nowled*e%ent 6cont7

The sender also start a ti%er when it senta pac!et5If the ti%er e8pires before an ac!nowled*e%ent isreceived' it retrans%its the pac!et5


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The Transport LayerWindowin* 6cont7

The G3antity of data se*%ents 6%eas3red inbytes7 that the trans%ittin* %achine isallowed to send witho3t receivin* anac!nowled*%ent for the% is called awindow 5the si@e of the window controls how %3chinfor%ation is transferred fro% one end to theother

You and I !ill use !indo! si*e o 1 .I agree


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10 21342121

15 2132121

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E E

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The etwor! Layer

Let#s loo! at what ishappenin*$

15 2132121 is innet!or$

attached to , 2"o


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The etwor! Layer

The etwor! layer' which is belowthe Transport layer5

It is responsible for ro3tin* thepac!et based on its lo*ical address5

10 21342121

15 2132121

16262621

E E

EQ


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The etwor! LayerActions that the etwor! layer have todeal $ 68 l 7 with$

Pac!etsRo3te' ro3tin* table' ro3tin* protocolLo*ical address>ra*%entation

E8a%ples of the etwor! layerprotocols$

Internet Protocol 6IP7


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10 21342121

15 2132121

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The "ata Lin! Layer

Let#s loo! at what is happenin*$ eah' host 5 5 5 islocated in networ!

attached to S 53t the networ!attached to S is a

>ra%e Relay networ!So I have to reDencaps3late this pac!et

into >ra%e Relay fra%e5

So

This pac!et isdestined for5 5 5 that is in

networ! attachedto %y E interface5

And %y E is anEthernetinterface5

So


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The "ata Lin! Layer

The "ata Lin! layer is below the etwor!layer5

The "ata Lin! layer is concerned withphysical addressin*5

7'+ address66)63)5 )6 ),F)68

The "ata Lin! layer provides the physicaltrans%ission of the data5


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The "ata Lin! Layer The "ata Lin! layer is %ade 3p of Q s3blayers$

The Lo*ical Lin! :ontrol 6LL:7 s3blayer5 The Media Access :ontrol 6MA:7 s3blayer


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The "ata Lin! LayerLo*ical Lin! :ontrol 6LL:7 s3blayer

Lo*ical Lin! :ontrol 6LL:7 s3blayer isresponsible for identifyin* etwor! layer

protocols and then encaps3latin* intofra%e If the etwor! layer *ive %e anIP pac!et' I will encaps3late itinto a fra%e li!e this

3t if the etwor! layer *ive %ean IP pac!et' I will encaps3late

it into fra%e li!e


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The "ata Lin! LayerMedia Access :ontrol 6MA:7 s3blayer

Media Access :ontrol 6MA:7 s3blayerde9nes how pac!ets are placed on the%edia5

If the networ! interface card6 I:7 has RUV port and

connected to crossover cable5I will transfer fra%e on pin Qand receive fra%e on pin N

3t if the networ!interface card 6 I:7 has

: port' I will transferfra%e in another way5


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The physical layer

>or E8a%ple$TP' STP' coa8ial' >iber cable

RUV ' RU connector" X' " Q connector

baseQ' base ' baseT' baseT8


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The end

01.theosi tcp ipmodel

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