Lec01 Network Architecture Models

8/9/2019 Lec01 Network Architecture Models

1/56

COMPUTER NETWORKS

INTRODUCTION

Shanika Ekanayake


2/56

Aim and objective of the lecture

Aim

To develop an understanding of the odern net!or"te#hnologies in #oon use toda$

Objective

To %e a%le to deonstrate an understanding of the iportan#eof #ouni#ation standards& in#luding an appre#iation of

proto#ol la$er odels and enhan#eents to those standards


3/56

Introdu#tion

'i and o%(e#tive of the le#ture Models of net!or" ar#hite#ture ISO ) ISO Model

The ISO ) ISO Model What is ISO ) ISO odel What is ISO ) ISO odel

Inforation e*#hange using the OSI odel ISO+OSI Seven ,a$ers

Ph$si#al ,a$er Data ,in" ,a$er Net!or" ,a$er Transport ,a$er

Session ,a$er Presentation ,a$er 'ppli#ation ,a$er

Introdu#tion to TCP-IP odel The TCP-IP Model TCP-IP Model

Suar$

Introduction to the Lecture Slide


4/56

Models of network architecture

Network

' #on#eptual frae!or" that des#ri%es ho! data andnet!or" inforation are #ouni#ated fro an appli#ationon one #oputer through net!or" edia to an appli#ationon other #oputers in ters of di.erent la$ers/

Net!or" ar#hite#ture is a design of a #ouni#ationsnet!or" and also "no!n as a Referen#e odel/

T!o t$pes of Referen#e odels &

Open Referen#e odels ) 'r#hite#ture is pu%li#all$availa%le 0e/g/ OSI odel 1

Closed Referen#e odels 0proprietar$ s$stes1 )

'r#hite#ture is un"no!n 0e/g/ I2M3s SN' 4 la$er odel1


5/56

ISO ) International Organi5ation for Standardi5ation/

OSI ) Open S$stes Inter#onne#tion/

ISO is esta%lished in 6784 and it is a ultinational %od$

dedi#ated to !orld!ide agreeent on internationalstandards/

ISO standard that #overs all aspe#ts of net!or"#ouni#ations is the OSI odel !hi#h introdu#ed in late

6749s/

Note ISO + organi5ation/ OSI + odel/

The ISO OSI Model


6/56

!hat is ISO OSI model""# De:nes data

#ouni#ation fun#tionsusing 4 la$ers !hi#h areorgani5ed in the se;uentialorder of events o##urringduring a #ouni#ationssession/

Top < la$ers + =o!appli#ations !ithin endstations #ouni#ate ea#hother and also !ith users/

2otto 8 la$ers + End toend data transission/

M$ths a%out ISO OSI odel& The OSI Model is not a

te#hnolog$/ The OSI Model is not a proto#ol/


7/56

Information e$chan%e usin% the OSI

model

Proto#ol Data Unit0PDU1 + Inforation delivered as a unit aongpeer entities of net!or"s #ontaining #ontrol inforation and user


8/56

!hy ISO OSI model""#

Advanta%es of ISO OSI model

Interopera%ilit$ %et!een devi#es fro variousvendors/

=igh aintaina%ilit$/

Cost redu#tion/

'ssists in proto#ol design& %e#ause proto#ols thatoperate at a spe#i:# la$er have de:ned

inforation and interfa#es/

'n edu#ational tool + ISO-OSI odel not (uste*plains the operation of the OSI proto#ols& ite*plains net!or"ing in general ters/

Prevents te#hnolog$ or #apa%ilit$ #hanges in one


9/56

,a$er 6 of the OSI odel/

Responsi%le for the oveent of individual %its froone node 0hop1 to the ne*t/

&hysicalLayer


10/56

&hysicalLayer 'ont"(o)*to*(o)+elivery


11/56

&hysicalLayer 'ont"

Ph$si#al la$er de:nes standards for DTE+DCEinterfa#e !/r/t/

Me#hani#al Spe#i:#ations

Ele#tri#al Spe#i:#ations >un#tional Spe#i:#ations

Pro#edural Spe#i:#ations


12/56

&hysicalLayer 'ont"

Mechanical Specifcations

Shape of the #onne#tor/

Nu%er of pins/

Diaeter of a pin/

Distan#e %et!een t!o pins Et#/


13/56

&hysicalLayer 'ont"

Electrical Specifcations

Use ?oltage levels/

E/g/@ A6B + ?A9B + 9 ?

DTE and DCE should use sae ele#tri#al signallevels


14/56


15/56

&hysical Layer 'ont"

Procedural Specifcations

Pro#edure 0or steps1 of #ouni#ation %et!een DTE

and DCE/

E/g/@ DTE re;uests fro DCE to send data 0DTEa#tivates RTS pin1DCE sa$s OK 0DCE a#tivates CTS pin1


16/56

&hysical Layer 'ont"

Standard bodies o Physical Layer Specifcations

EI' ) Ele#troni# Industries 'llian#e/

ITU+T)International Tele#ouni#ation UnionTele#ouni#ation Standardi5ation Se#tor/

'NSI ) 'eri#an National Standards Institute /


17/56

+ataLinkLayer

,a$er of the OSI odel/ Responsi%le for oving fraes fro one node 0hop1

to the ne*t/


18/56

Data Link Layer Frame (E! Ethernet rame"

Ethernet frae is one of the ost !idel$ used fraeat the data lin" la$er/

+ataLinkLayer 'ont"


19/56

+ata Link Layer 'ont"

(o)*to*(o)+elivery


20/56

+ataLink Layer 'ont"

Data Link Layer Functionalities

Iportant fun#tionalities to guarantee thesu##essful transission of fraes fro one hop tothe ne*t/

>raing ) We have alread$ dis#ussed this/

Ph$si#al addressing/

>lo! #ontrol/

Error #ontrol/

'##ess #ontrol/


21/56

+ataLinkLayer 'ont"

Sub#layers

Contains t!o su%+la$ers


22/56


Physical $ddressin!

Ea#h devi#e is universall$uni;uel$ identi:ed %$ theph$si#al address 0M'C

address1/

8G %its long/

8G %its H 8G total addresses

HG6&848&74&469&


23/56

+ata Link Layer 'ont"Flow %ontrol

Spe#i:es ho! u#h data the Sender #an transit%efore re#eiving perission to #ontinue fro theRe#eiver/

The Re#eiver !ill %e for#ed to drop the pa#"ets

!hen the sender transits faster than theRe#eiver #an pro#ess the/

Solution@

Signal the Sender to slo! do!n to a ratea##epta%le to the Re#eiver/

This signal #an %e e*pli#it or ipli#it


24/56

+ata Link Layer 'ont"Flow %ontrol

Methods

Stop+and+WaitJo!#ontrol

Sliding!indo!Jo!#ontrol


25/56

+ata Link Layer 'ont"Error %ontrol

'llo!s the Re#eiver to tell the Sender a%out fraesdaaged or lost during transission& and #oordinatesthe re+transission of those fraes %$ the Sender/

Sin#e Jo! #ontrol provides the Re#eiverBsa#"no!ledgeent 0'CK1 of #orre#tl$+re#eivedfraes& it is #losel$ lin"ed to error #ontrol/

2asi# idea of error #ontrol

'CK ever$ #orre#tl$+re#eived frae and negativel$a#"no!ledge 0N'CK1 ea#h in#orre#tl$+re#eivedfrae/

Sender "eeps #opies of un+'CKed >raes to re+

transit if re;uired/


26/56

+ata Link Layer 'ont"&wo steps o Error %ontrol

Error Detection

Me#hanis of dete#ting errors in fraes&

Parit$ #he#" 0Odd parit$& Even parit$1 CRC ) #oon et#/

Error %orrection

'utoati# Repeat reuest 0'R1 is use to #orre#t errors/

'R retransits fraes in three #ases&

Daaged fraes ,ost fraes ,ost a#"no!ledgeents


27/56


$ccess %ontrol

When ore than a single #oputer is #onne#ted to the saelin"& !ho gets the turn to transit data and ho! to a#;uire thisturn/

The ost popular edia a##ess #ontrol e#hanis is CSM'-CDand it is ipleented in the Media '##ess Control su%+la$er ofthe Data ,in" ,a$er/


28/56

,etworkLayer

,a$er < of the OSI ode/

The net!or" la$er is responsi%le for the deliver$ ofindividual pa#"ets fro the sour#e host to thedestination host/


29/56

,etworkLayer

Source

to

+estination

+elivery


30/56

,etworkLayer'ont"

T!o a(or fun#tionalities&

'outin!

Independent lo#al net!or"s are inter#onne#ted !ith ea#hother& therefore need a e#hanis to route the pa#"ets

fro one net!or" to another/

Lo!ical addressin!

To route a pa#"et %e$ond the %oundar$ of a lo#alnet!or"0 i/e/ to a di.erent lo#al net!or"1 ph$si#al address

alone is not enough/

Net!or" la$er eplo$s address t$pe #all logi#aladdresses to #ouni#ate aong net!or"s+IP addresses/

The logi#al addresses are in#luded in the net!or" la$er

header/


31/56

Trans)ort Layer


The transport la$er is responsi%le for the deliver$ of aessage fro one pro#ess to another/


32/56

Trans)ort Layer 'ont"

Process to Process Deliery


33/56

Trans)ort Layer'ont"

Transport la$er eplo$s several iportant fun#tionalities&

Servi#e+point addressing

Segentation and reasse%l$

Conne#tion #ontrol

>lo! #ontrol

Error #ontrol


34/56


Serice#point $ddressin! Process(Port addressin!"

To transfer a essage fro a sour#e pro#ess 0i/e/ the sour#eappli#ation1 to a destination pro#ess 0i/e/ the destinationappli#ation1 HL need a e#hanis to uni;uel$ identif$ ea#hpro#ess/

'ssigned a uni;ue nu%er !hi#h is #oonl$ "no!n as the portnu%er/

Port nu%er is a 6 %it integer nu%er and #an range fro 9 toile Transfer Proto#ol 0>TP1


35/56


Se!mentation and 'eassembly

The data passed to the transport la$er fro the la$er a%ove0i/e/ session la$er1 is too large to transfer at on#e/

Therefore& transport la$er %rea"s the data into sall #hun"s"no!n as segents %efore passing to the net!or" la$er/

't the re#eiver& the segents need to %e reasse%led to getthe full essage %efore passing to the upper la$er 0i/e/

session la$er1 at the re#eiver/


36/56


To ea#h segent a transport la$er header is added/


37/56

Trans)ort Layer 'ont"Transport la$er #an operate in t!o odes&

%onnection oriented

>irst a #onne#tion is esta%lished %et!een the sour#e andthe destination pro#esses/

'll segents are transported using this #onne#tion/

On#e the transport of segents is #oplete& the#onne#tion is terinated/

uarantees the deliver$ of segents/ To fa#ilitate this ode& transport la$er uses Transport

Control Proto#ol 0TCP1/

%onnectionless

Ea#h segent is treated as a single pa#"et and delivered tothe destination pro#ess !ithout an$ #onne#tions/

No guarantee on the deliver$ of the segents/ To fa#ilitate this ode& transport la$er uses User Datagra

Proto#ol 0UDP1/


38/56


Sae as the Data ,in" ,a$er& the Transport ,a$er also e;uipsJo! #ontrol and error #ontrol of segents/

The a(or di.eren#e in the t!o la$ers !/r/t Jo! and error

#ontrol is that&

Data ,in" ,a$er is #on#erned a%out the hop+to+hop Jo! anderror #ontrol %et!een t!o ad(a#ent hops/

Transport ,a$er is #on#erned a%out the end+to+end Jo! anderror #ontrol %et!een the sour#e and the destination 0!hi#h #an%e several hops apart fro ea#h other1/


39/56

SessionLayer

,a$er of the OSI odel/


40/56

SessionLayer'ont"Session ,a$er perfors t!o a(or fun#tionalities&

Dialo! %ontrol

'llo!s the t!o #ouni#ating pro#esses to enter into adialog 0i/e/ a t!o !a$ #ouni#ation1/

This dialog #an %e either half duple* or full duple*/ Therefore& session la$er is a dialog #ontroller/ Coon session+la$er servi#es in appli#ation

environents use reote pro#edure #alls 0RPCs1/

Synchroni)ation

Session la$er adds #he#"points in %et!een the long datastrea passed %$ the la$er a%ove 0i/e/ presentationla$er1/

These #he#"points adds an additional level of veri:#ationof the re#eived data for the re#eiver/

It allo!s inforation of di.erent streas& perhaps

originating fro di.erent sour#es& to %e properl$#o%ined or s$n#hroni5ed/


41/56

&resentationLayer

,a$er of the OSI odel/


42/56

&resentationLayer'ont"There are three a(or fun#tions perfored %$ the Presentation

,a$er&

&ranslation Sender and Re#eiver a$ %e using t!o di.erent

forats to represent data 0e/g/ 'SCII vs/ UNICODE1/ Translation is the pro#ess of #onverting data&

>ro sender+dependent forat to a #oonforat at the sender/

>ro #oon forat to the re#eiver+dependentforat at the re#eiver/

Encryption To prevent unauthori5ed people fro vie!ing the

data/

%ompression To redu#e the nu%er of %its to %e transitted/ Iportant !hen sending ultiedia #ontent su#h as

audio and video/


43/56


A))lication Layer


44/56

A))licationLayercont"

'ppli#ation la$er is user interfa#e to the net!or"/

Provides an$ useful appli#ations to fa#ilitate our da$+to+da$ tas"s&

Eail servi#es/ >ile transferring/ Reote terinal/ et#/


45/56

E*ample Scenario+ %onnection to a website ia a ,i#fconnection

(-"Ph$si#al la$er + Wi+>i #ard of the #oputer !hi#h transitsdata using the IEEE G9/66n standard/

(."Data lin" la$er + Conne#ting to a router via D=CP/

(/"Net!or" la$er + D=CP provides an IP address to the s$ste/

(0"Transport la$er + On#e the #oputer o%tains an IP address& it#an #onne#t to the Internet via the TCP proto#ol/

(1"Session la$er + The s$ste a$ then esta%lish a Net!or"2asi# Input-Output S$ste0Net2IOS1 session/

(2"Presentation la$er+ If a se#ure #onne#tion is esta%lishedonne#tion a$ involve an SS, #onne#tion/

>inall$& (3"'ppli#ation la$er + Consists of the =TTP #onne#tionto the !e%site/


46/56

,etworks fits to ISO-OSI layered

architecture

Mo%ileNet!or"

G9/66 !irelessNet!or"

'TM Net!or"

>rae Rela$Net!or"


47/56

The T'&-I& Model TCP-IP 0 Transission Control Proto#ol-Internet Proto#ol1 is a

proto#ol !hi#h developed using the Departent of Defense0DoD1 referen#e odel to de:ne a large #olle#tion of proto#olsthat allo! #oputers to #ouni#ate/

It has a 8 la$er ar#hite#ture/

TCP- IP de:nes ea#h of these proto#ols inside do#uent #alledRe;uests >or Coents 0R>Cs1/

2$ ipleenting the re;uired proto#ols in TCP-IP R>Cs& a#oputer #an %e relativel$ #on:dent that it #an #ouni#ate

!ith other #oputers that also ipleent TCP-IP/

The TCP-IP proto#ol suite !as developed %efore the OSI odel!as pu%lished/ 's a result& it does not use the OSI odel as areferen#e/

It is iportant to %e failiar !ith the OSI odel& though&%e#ause OSI is used to #opare the TCP-IP Suite !ith other


48/56

T'&-I&Model


49/56

Summary


50/56

Summaryof the ISO OSI Layers


51/56

,ames used for +ata at each layer


52/56

Addresses used at different layers


53/56

'onnectionsused at different layers


54/56

&rotocolsused at each layer


55/56

OSILayersin O)erations


56/56

Thank .ou

Lec01 Network Architecture Models

Documents

Transcript of Lec01 Network Architecture Models