610.Web Architecture

8/7/2019 610.Web Architecture

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Introduction to theIntroduction to theWebWeb


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PrerequisitesPrerequisites

Basic computer skillsBasic computer skills

Experience using the World Wide WebExperience using the World Wide Web

Experience developing object-orientedExperience developing object-orientedsoftwaresoftware


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Learning ObjectivesLearning Objectives

Overview of Web and InternetOverview of Web and Internet

technologiestechnologies

Review of existing Web programmingReview of existing Web programmingtechnologiestechnologies


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AgendaAgenda

Internet TechnologiesInternet Technologies

Programming Languages and ParadigmsProgramming Languages and Paradigms

Programming the WebProgramming the Web


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The World Wide WebThe World Wide Web A way to access and share informationA way to access and share information

Technical papers, marketing materials, recipes,Technical papers, marketing materials, recipes,......

A huge network of computers: the InternetA huge network of computers: the Internet Graphical, not just textualGraphical, not just textual Information is linked to other informationInformation is linked to other information

Application development platformApplication development platform Shop from homeShop from home Provide self-help applications for customersProvide self-help applications for customers

and partnersand partners


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WWW ArchitectureWWW Architecture

Web Server

PC/Mac/Unix

+ BrowserClient

Server

Request:

http://www.msn.com/default.asp

Response:

Network TCP/IP


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WWW ArchitectureWWW Architecture Client/Server, Request/Response architectureClient/Server, Request/Response architecture

You request a Web pageYou request a Web page e.g.e.g. http://www.msn.com/default.asphttp://www.msn.com/default.asp

HTTP requestHTTP request

The Web server responds with data in the form of a WebThe Web server responds with data in the form of a Web

pagepage HTTP responseHTTP response

Web page is expressed as HTMLWeb page is expressed as HTML

Pages are identified as a Uniform Resource Locator (URL)Pages are identified as a Uniform Resource Locator (URL) Protocol:Protocol: httphttp

Web server:Web server: www.msn.comwww.msn.com

Web page:Web page: default.aspdefault.asp

Can also provide parameters:Can also provide parameters: ?name=Leon?name=Leon


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Web StandardsWeb Standards Internet Engineering Task Force (IETF)Internet Engineering Task Force (IETF)

http://www.ietf.org/http://www.ietf.org/ Founded 1986Founded 1986

Request For Comments (RFC) atRequest For Comments (RFC) at

http://www.ietf.org/rfc.htmlhttp://www.ietf.org/rfc.html

World Wide Web Consortium (W3C)World Wide Web Consortium (W3C)

http://www.w3.orghttp://www.w3.org Founded 1994 by Tim Berners-LeeFounded 1994 by Tim Berners-Lee

Publishes technical reports andPublishes technical reports and

recommendationsrecommendations


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Web Design PrinciplesWeb Design Principles Interoperability:Interoperability: Web languages andWeb languages and

protocols must be compatible with oneprotocols must be compatible with one

another independent of hardware andanother independent of hardware and

software.software. Evolution:Evolution: The Web must be able toThe Web must be able to

accommodate future technologies.accommodate future technologies.

Encourages simplicity, modularity andEncourages simplicity, modularity andextensibility.extensibility.

Decentralization:Decentralization: Facilitates scalabilityFacilitates scalability

and robustness.and robustness.


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Hypertext Markup Language (HTML)Hypertext Markup Language (HTML) The markup language used to representThe markup language used to represent

Web pages for viewing by peopleWeb pages for viewing by people Designed to display data, not store/transfer dataDesigned to display data, not store/transfer data

Rendered and viewed in a Web browserRendered and viewed in a Web browser Can containCan contain linkslinks to images, documents,to images, documents,

and other pagesand other pages Not extensibleNot extensible Derived from Standard Generalized MarkupDerived from Standard Generalized Markup

Language (SGML)Language (SGML) HTML 3.2, 4.01, XHTML 1.0HTML 3.2, 4.01, XHTML 1.0


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HTML FormsHTML Forms Enables you to create interactiveEnables you to create interactive

user interface elementsuser interface elements ButtonsButtons

Text boxesText boxes

Drop down listsDrop down lists

Check boxesCheck boxes

User fills out the form and submits itUser fills out the form and submits it Form data is sent to the Web server viaForm data is sent to the Web server via

HTTP when the form is submittedHTTP when the form is submitted


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Hypertext Transport Protocol (HTTP)Hypertext Transport Protocol (HTTP) The top-level protocol used to request andThe top-level protocol used to request and

return datareturn data E.g. HTML pages, GIFs, JPEGs, Microsoft WordE.g. HTML pages, GIFs, JPEGs, Microsoft Word

documents, Adobe PDF documents, etc.documents, Adobe PDF documents, etc.

Request/Response protocolRequest/Response protocol

Methods:Methods: GETGET,, POSTPOST,, HEADHEAD, ,

HTTP 1.0: simpleHTTP 1.0: simple HTTP 1.1: more complexHTTP 1.1: more complex


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GET /default.asp HTTP/1.0

Accept: image/gif, image/x-bitmap, image/jpeg, */*Accept-Language: en

User-Agent: Mozilla/1.22 (compatible; MSIE 2.0; Windows 95)

Connection: Keep-Alive

If-Modified-Since: Sunday, 17-Apr-96 04:32:58 GMT


HTTP RequestHTTP Request

Method File HTTP version Headers

Data none for GET

Blank line


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HTTP/1.0 200 OKDate: Sun, 21 Apr 1996 02:20:42 GMT

Server: Microsoft-Internet-Information-Server/5.0

Connection: keep-alive

Content-Type: text/html

Last-Modified: Thu, 18 Apr 1996 17:39:05 GMT

Content-Length: 2543

Some data... blah, blah, blah


HTTP ResponseHTTP Response

HTTP version Status code Reason phrase Headers

Data


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HTTP Server Status CodesHTTP Server Status Codes

CodeCode DescriptionDescription

200200 OKOK

201201

CreatedCreated

301301 Moved PermanentlyMoved Permanently

302302 Moved TemporarilyMoved Temporarily

400400 Bad Request notBad Request notunderstoodunderstood

401401 UnauthorizedUnauthorized

403403 Forbidden not authorizedForbidden not authorized

404404 Not FoundNot Found

500500 Internal Server ErrorInternal Server Error


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HTTPHTTP HTTP is a stateless protocolHTTP is a stateless protocol

Each HTTP request is independent ofEach HTTP request is independent of

previous and subsequent requestsprevious and subsequent requests

HTTP 1.1 introducedHTTP 1.1 introduced keep-alivekeep-alive forfor

efficiencyefficiency

Statelessness has a big impact on howStatelessness has a big impact on how

scalable applications are designedscalable applications are designed


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CookiesCookies A mechanism to store a small amount ofA mechanism to store a small amount of

information (up to 4KB) on the clientinformation (up to 4KB) on the client

A cookie is associated with a specific webA cookie is associated with a specific web

sitesite

Cookie is sent in HTTP headerCookie is sent in HTTP header

Cookie is sent with each HTTP requestCookie is sent with each HTTP request

Can last for only one session (until browserCan last for only one session (until browser

is closed) or can persist across sessionsis closed) or can persist across sessions

Can expire some time in the futureCan expire some time in the future


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URIs, URLs and URNsURIs, URLs and URNs Uniform Resource Identifier (URI = URL or URN)Uniform Resource Identifier (URI = URL or URN)

Generic term for all textual names/addressesGeneric term for all textual names/addresses

Uniform Resource Locator (URL)Uniform Resource Locator (URL)

The set of URI schemes that have explicit instructions onThe set of URI schemes that have explicit instructions onhow to access the resource over the Internet,how to access the resource over the Internet,e.g.e.g. httphttp,, ftpftp,, gophergopher

Uniform Resource Name (URN)Uniform Resource Name (URN)1) A URI that has an institutional commitment to1) A URI that has an institutional commitment to

availability, etc.availability, etc.

2) A particular scheme intended to identify resources2) A particular scheme intended to identify resources

e.g.e.g.urn:schemas:httpmail:subjecturn:schemas:httpmail:subject


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Internet TechnologiesInternet TechnologiesMultipurpose Internet Mail Extensions (MIME)Multipurpose Internet Mail Extensions (MIME) Defines types of data/documentsDefines types of data/documents

text/plaintext/plain

text/htmltext/html

image/gifimage/gif

image/jpegimage/jpeg

audio/x-pn-realaudioaudio/x-pn-realaudio

audio/x-ms-wmaaudio/x-ms-wma video/x-ms-asfvideo/x-ms-asf

application/octet-streamapplication/octet-stream


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MIMEMIME Specifies character sets, e.g. ASCIISpecifies character sets, e.g. ASCII

Supports multi-part messagesSupports multi-part messages

Originally designed for email, but alsoOriginally designed for email, but alsoused in other places, such as HTTPused in other places, such as HTTP


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BrowsersBrowsers Client-side applicationClient-side application

Requests HTML from Web server andRequests HTML from Web server and

renders itrenders it

Popular browsers:Popular browsers: NetscapeNetscape

Internet ExplorerInternet Explorer

OperaOpera othersothers

Also known as a User AgentAlso known as a User Agent


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Clients & ServersClients & Servers Client and Server computers both have:Client and Server computers both have:

CPUCPU

MemoryMemory

I/OI/O DisksDisks

NetworkNetwork

BusBus

Multi-tasking operating systemMulti-tasking operating system

ApplicationsApplications


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Clients & ServersClients & Servers ClientsClients

Generally supports a single userGenerally supports a single user

Optimized for responsiveness to userOptimized for responsiveness to user

User interface, graphicsUser interface, graphics

ServersServers Supports multiple usersSupports multiple users

Optimized for throughputOptimized for throughput

More: CPUs (SMP), memory, disks (SANs), I/OMore: CPUs (SMP), memory, disks (SANs), I/O

Provide services (e.g. Web, file, print, database,Provide services (e.g. Web, file, print, database,

e-mail, fax, transaction, telnet, directory)e-mail, fax, transaction, telnet, directory)


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Proxy Servers & FirewallsProxy Servers & Firewalls Proxy ServerProxy Server

A server that sits between a client (running aA server that sits between a client (running abrowser) and the Internetbrowser) and the Internet

Improves performance by caching commonlyImproves performance by caching commonlyused Web pagesused Web pages

Can filter requests to prevent users fromCan filter requests to prevent users fromaccessing certain Web sitesaccessing certain Web sites

FirewallFirewall A server that sits between a network and theA server that sits between a network and theInternet to prevent unauthorized access to theInternet to prevent unauthorized access to thenetwork from the Internetnetwork from the Internet


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NetworksNetworks Network = an interconnected collection ofNetwork = an interconnected collection of

independent computersindependent computers

Why have networks?Why have networks?

Resource sharingResource sharing ReliabilityReliability

Cost savingsCost savings

CommunicationCommunication

Web technologies add:Web technologies add: New business models: e-commerce, advertisingNew business models: e-commerce, advertising

EntertainmentEntertainment

Applications without a client-side installApplications without a client-side install


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NetworksNetworks Network scopeNetwork scope

internet: a collection of connected networksinternet: a collection of connected networks

Internet: a specific world-wide network based on TCP/IP,Internet: a specific world-wide network based on TCP/IP,

used to connect companies, universities, governments,used to connect companies, universities, governments,organizations and individuals. Originated as ARPANET,organizations and individuals. Originated as ARPANET,

funded by the US DoD.funded by the US DoD.

intranet: a network based on Internet technologies thatintranet: a network based on Internet technologies that

is internal to a company or organizationis internal to a company or organization

extranet: a network based on Internet technologies thatextranet: a network based on Internet technologies thatconnects one company or organization to anotherconnects one company or organization to another


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NetworksNetworks Network technology is largely determinedNetwork technology is largely determined

by scale:by scale: Local Area Network (LAN): Span up to a fewLocal Area Network (LAN): Span up to a few

kilometers. Bus vs. ring topologieskilometers. Bus vs. ring topologies Wide Area Networks (WAN): Can span aWide Area Networks (WAN): Can span a

country or continent. WANs use routers ascountry or continent. WANs use routers as

intermediate nodes to connect transmissionintermediate nodes to connect transmission

lineslines


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NetworksNetworks Network technologyNetwork technology

BroadcastingBroadcasting Packets of data are sent from one machine andPackets of data are sent from one machine and

received by all computers on the networkreceived by all computers on the network Multicast: packets are received by a subset of theMulticast: packets are received by a subset of the

machines on a networkmachines on a network

Point-to-pointPoint-to-point Packets have to be routed from one machine toPackets have to be routed from one machine to

another; there many be many pathsanother; there many be many paths In general, geographically localized networksIn general, geographically localized networks

use broadcasting, while disperse networks useuse broadcasting, while disperse networks usepoint-to-pointpoint-to-point


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NetworksNetworks

Application

Layer

Presentation

Layer

Session

Layer

Transport

Layer

NetworkLayer

Data Link

Layer

Physical

Layer

InternetLayer

Application

LayerTelnet FTP SMTP DNS RIP SNMP HTTP

IP

Host-to-Host

Transport

Layer

TCP UDP

Token

RingEthernet ATM

Frame

Relay

Network

Interface

Layer

OSI Model

Layers

TCP/IP

Protocol

Architecture

Layers

TCP/IP

Protocol Suite

ARPICMPIGMP


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Network Protocol StackNetwork Protocol Stack

HTTP

TCP

IP

Ethernet

HTTP

TCP

IP

Ethernet


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Networks - Internet LayerNetworks - Internet Layer Internet Protocol (IP)Internet Protocol (IP)

Responsible for getting packets fromResponsible for getting packets from

source to destination across multiple hopssource to destination across multiple hops

Not reliableNot reliable

IP address: 32 bit value usually written inIP address: 32 bit value usually written in

dotted decimal notation as four 8-bitdotted decimal notation as four 8-bit

numbersnumbers(0 to 255); e.g. 130.50.12.4(0 to 255); e.g. 130.50.12.4


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Networks - Transport LayerNetworks - Transport Layer Provides efficient, reliable andProvides efficient, reliable and

cost-effective servicecost-effective service Uses the Sockets programming modelUses the Sockets programming model

Ports identify applicationPorts identify application Well-known ports identify standard servicesWell-known ports identify standard services

(e.g. HTTP uses port 80, SMTP uses port 25)(e.g. HTTP uses port 80, SMTP uses port 25)

Transmission Control Protocol (TCP)Transmission Control Protocol (TCP)

Provides reliable, connection-oriented byteProvides reliable, connection-oriented bytestreamstream

UDPUDP Connectionless, unreliableConnectionless, unreliable


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Networks - Application LayerNetworks - Application Layer Telnet: Remote sessionsTelnet: Remote sessions

File Transfer Protocol (FTP)File Transfer Protocol (FTP)

Network News Transfer Protocol (NNTP)Network News Transfer Protocol (NNTP) Simple Network Management ProtocolSimple Network Management Protocol

(SNMP)(SNMP)

Simple Mail Transfer Protocol (SMTP)Simple Mail Transfer Protocol (SMTP)

Post Office Protocol (POP3)Post Office Protocol (POP3)

Interactive Mail Access Protocol (IMAP)Interactive Mail Access Protocol (IMAP)


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Networks -Networks - Domain Name System (DNS)Domain Name System (DNS) Provides user-friendly domain names,Provides user-friendly domain names,

e.g.e.g. www.msn.comwww.msn.com Hierarchical name space with limited rootHierarchical name space with limited root

namesnames

DNS servers map domain names toDNS servers map domain names toIP addressesIP addresses

.com .net .gov

.edu

.org .mil .in


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Extensible Markup Language (XML)Extensible Markup Language (XML) Represents hierarchical dataRepresents hierarchical data

A meta-language: a language for definingA meta-language: a language for defining

other languagesother languages

ExtensibleExtensible

Useful for data exchange andUseful for data exchange and

transformationtransformation

Simplified version of SGMLSimplified version of SGML


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AgendaAgenda


Programming Languages andProgramming Languages and

ParadigmsParadigms


.NET Overview.NET Overview


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Programming LanguagesProgramming Languages

Machine codeMachine code

Assembly languageAssembly language

High-level languagesHigh-level languages Fortran, LISP, CobolFortran, LISP, Cobol

C, Pascal, Basic, SmalltalkC, Pascal, Basic, Smalltalk

C++, EiffelC++, Eiffel

Java, C#Java, C# Scripting languagesScripting languages

Shell scripts, Perl, TCL, Python, JavaScript,Shell scripts, Perl, TCL, Python, JavaScript,

VBScriptVBScript


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Programming ParadigmsProgramming Paradigms

Unstructured programmingUnstructured programming

Structured programmingStructured programming

Object-oriented programmingObject-oriented programming Component-based programmingComponent-based programming

Event-based programmingEvent-based programming


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Structured ProgrammingStructured Programming SequenceSequence

ConditionalConditional if then elseif then else

switchswitch LoopingLooping

for i from 1 to nfor i from 1 to n

do whiledo while

do untildo until FunctionsFunctions

ExceptionsExceptions


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Object-Oriented ProgrammingObject-Oriented Programming Objects have data and behaviorObjects have data and behavior

Data: members, fields, variables, slots, propertiesData: members, fields, variables, slots, properties

Behavior: methods, functions, proceduresBehavior: methods, functions, procedures

Using objects is easyUsing objects is easy First instantiate the type of object desiredFirst instantiate the type of object desired

Then call its methods and get/set its propertiesThen call its methods and get/set its properties

Designing new types of objects can be hardDesigning new types of objects can be hard Design goals often conflict: simplicity,Design goals often conflict: simplicity,

functionality, reuse, performancefunctionality, reuse, performance


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Object-Oriented ProgrammingObject-Oriented Programming Key object-oriented conceptsKey object-oriented concepts

IdentityIdentity EncapsulationEncapsulation

Data + behaviorData + behavior Information hiding (abstraction)Information hiding (abstraction)

Classes vs. instancesClasses vs. instances PolymorphismPolymorphism

InterfacesInterfaces Delegation, aggregationDelegation, aggregation InheritanceInheritance PatternsPatterns


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Component-Based ProgrammingComponent-Based Programming ComponentsComponents

Independent modules of reuse and deploymentIndependent modules of reuse and deployment

Coarser-grained than objectsCoarser-grained than objects

(objects are language-level constructs)(objects are language-level constructs) Includes multiple classesIncludes multiple classes

Often language-independentOften language-independent

In the general case, the component writerIn the general case, the component writerand the component user dont know eachand the component user dont know each

other, dont work for the same company,other, dont work for the same company,

and dont use the same languageand dont use the same language


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Component-Based ProgrammingComponent-Based Programming Component Object Model (COM)Component Object Model (COM) Initial Microsoft standard for componentsInitial Microsoft standard for components

Specifies a protocol for instantiating and usingSpecifies a protocol for instantiating and using

components in-process, across processes orcomponents in-process, across processes or

across machine boundariesacross machine boundaries

Basis for ActiveX, OLE, and many otherBasis for ActiveX, OLE, and many other

technologiestechnologies

Can be created in Visual Basic, C++, .NET, Can be created in Visual Basic, C++, .NET,

Java BeansJava BeansJava standard for componentsJava standard for components

Not language-independentNot language-independent


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Event-Based ProgrammingEvent-Based Programming When something of interest occurs, an event isWhen something of interest occurs, an event is

raised and application-specific code is executedraised and application-specific code is executed Events provide a way for you to hook in yourEvents provide a way for you to hook in your

own code into the operation of another systemown code into the operation of another system

Event = callbackEvent = callback User interfaces are all about eventsUser interfaces are all about events

onClickonClick,, onMouseOveronMouseOver,, onMouseMoveonMouseMove

Events can also be based upon time orEvents can also be based upon time orinteractions with the network, operatinginteractions with the network, operatingsystem, other applications, etc.system, other applications, etc.


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AgendaAgenda


Programming Languages and ParadigmsProgramming Languages and Paradigms

Programming the WebProgramming the Web .NET Overview.NET Overview


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Client-Side CodeClient-Side Code What is client-side code?What is client-side code?

Software that is downloaded from Web serverSoftware that is downloaded from Web serverto browser and then executes on the clientto browser and then executes on the client

Why client-side code?Why client-side code? Better scalability: less work done on serverBetter scalability: less work done on server Better performance/user experienceBetter performance/user experience Create UI constructs not inherent in HTMLCreate UI constructs not inherent in HTML

Drop-down and pull-out menusDrop-down and pull-out menusTabbed dialogsTabbed dialogs

Cool effects, e.g. animationCool effects, e.g. animation Data validationData validation


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Client-Side TechnologiesClient-Side Technologies DHTML/JavaScriptDHTML/JavaScript

COMCOM ActiveX controlsActiveX controls

COM componentsCOM components

Remote Data Services (RDS)Remote Data Services (RDS)

JavaJava

Plug-insPlug-ins HelpersHelpers

Remote ScriptingRemote Scripting


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Dynamic HTML (DHTML)Dynamic HTML (DHTML) Script that is embedded within an HTMLScript that is embedded within an HTML

pagepage

Usually written in JavaScript (ECMAScript,Usually written in JavaScript (ECMAScript,

JScript) for portabilityJScript) for portability Internet Explorer also supports VBScript andInternet Explorer also supports VBScript and

other scripting languagesother scripting languages

Each HTML element becomes an objectEach HTML element becomes an object

that has associated events (e.g.that has associated events (e.g. onClickonClick))

Script provides code to respond to browserScript provides code to respond to browser

eventsevents


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DHTMLDHTML The DHTML Document Object Model (DOM)The DHTML Document Object Model (DOM)

window

history document location screen

all location children selectionforms body links

text buttonradio textarea select

password

file

checkbox submit

reset

option

navigator framesevent


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Server-Side CodeServer-Side Code

What is server-side code?What is server-side code? Software that runs on the server, not the clientSoftware that runs on the server, not the client

Receives input fromReceives input from URL parametersURL parameters HTML form dataHTML form data

CookiesCookies

HTTP headersHTTP headers

Can access server-side databases, e-mailCan access server-side databases, e-mailservers, files, mainframes, etc.servers, files, mainframes, etc.

Dynamically builds a custom HTML responseDynamically builds a custom HTML response

for a clientfor a client


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Server-Side CodeServer-Side Code

Why server-side code?Why server-side code? AccessibilityAccessibility

You can reach the Internet from any browser, anyYou can reach the Internet from any browser, anydevice, any time, anywheredevice, any time, anywhere

ManageabilityManageability Does not require distribution of application codeDoes not require distribution of application code Easy to change codeEasy to change code

SecuritySecurity

Source code is not exposedSource code is not exposed Once user is authenticated, can only allow certainOnce user is authenticated, can only allow certain

actionsactions

ScalabilityScalability Web-based 3-tier architecture can scale outWeb-based 3-tier architecture can scale out


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Server-Side TechnologiesServer-Side Technologies

Common Gateway Interface (CGI)Common Gateway Interface (CGI)

Internet Server API (ISAPI)Internet Server API (ISAPI)

Netscape Server API (NSAPI)Netscape Server API (NSAPI)

Active Server Pages (ASP)Active Server Pages (ASP)

Java Server Pages (JSP)Java Server Pages (JSP)

Personal Home Page (PHP)Personal Home Page (PHP)

Cold Fusion (CFM)Cold Fusion (CFM)

ASP.NETASP.NET


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Active Server Pages (ASP)Active Server Pages (ASP)

Technology to easily create server-sideTechnology to easily create server-side

applicationsapplications

ASP pages are written in a scriptingASP pages are written in a scripting

language, usually VBScript or JScriptlanguage, usually VBScript or JScript An ASP page contains a sequence of staticAn ASP page contains a sequence of static

HTML interspersed with server-side codeHTML interspersed with server-side code

ASP script commonly accesses andASP script commonly accesses andupdates data in a databaseupdates data in a database


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ASPASP

HTTP request(form data, HTTP

header data)

HTTP responseHTML, XML

ASP page

(static HTML,server-side logic)


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ArchitecturesArchitectures

N TierN Tier

Application ServersApplication Servers

MiddlewareMiddlewareIntranetsIntranets


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What to Know AboutWhat to Know About

ArchitecturesArchitectures Evolution of ArchitecturesEvolution of Architectures Evolution of COMEvolution of COM

DefinitionsDefinitions ASPASP

MiddlewareMiddleware

Database transparencyDatabase transparency

ADOADO


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Client/ServerClient/Server

Client/ServerClient/Server evolvesevolves along the line of PCalong the line of PC

computing and Microsoftcomputing and Microsoft

PC moved from complement to substitutePC moved from complement to substitute

for Host systemsfor Host systems 80s PCs were personal80s PCs were personal

90s PCs were departmental90s PCs were departmental

00s PCs are enterprise wide platforms00s PCs are enterprise wide platforms


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Key Problems ofKey Problems of

Client/ServerClient/Server ScalabilityScalability ManageabilityManageability

ComplexityComplexity Ease of UseEase of Use

Application DevelopmentApplication Development


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Network ArchitecturesNetwork Architectures

Host-based networksHost-based networks: the host computer: the host computer

performs virtually all of the workperforms virtually all of the work

Client-based networksClient-based networks: the client computer: the client computer

performs virtually all of the workperforms virtually all of the work Client-server networksClient-server networks: the work is shared: the work is shared

between the hosts and clientsbetween the hosts and clients


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Host-Based ArchitecturesHost-Based Architectures


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Host-Based ArchitecturesHost-Based Architectures

ScalabilityScalability Pros provide large scale accessPros provide large scale access Cons expensive, lumpy, slowCons expensive, lumpy, slow

Centralized ManagementCentralized Management ComplexityComplexity

Poor user interfacePoor user interface Application backlog low level tools,Application backlog low level tools,

specialized knowledgespecialized knowledge


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Client-Based ArchitecturesClient-Based Architectures

Evolution of standalone PC to fill gaps inEvolution of standalone PC to fill gaps in

departmental computing needsdepartmental computing needs


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Serveracts as a remote disk drive. Client does all the processing.

Searches slow down the network, each query

has the server pass the entire database over the



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ScalabilityScalability Pros cheap & easy to add a station up to limitsPros cheap & easy to add a station up to limits Cons severely limited by bandwidth/architectureCons severely limited by bandwidth/architecture Cons changes to application must be made onCons changes to application must be made on

server and all clientsserver and all clients

Decentralized ManagementDecentralized Management ComplexityComplexity

Graphical user interfaceGraphical user interface

Off the shelf applications high level toolsOff the shelf applications high level tools Custom apps difficult to developCustom apps difficult to develop


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Improved Scalability less data trafficAn SQL request is generated in the clientand transmitted to the server. The DBMSsearches locally and returns only matching

records greatly reducing data traffic.

Two Tier Client/ServerTwo Tier Client/Server

COM C t Obj tCOM C t Obj t


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COM - Component ObjectCOM - Component Object

ModelModel

Rapid development & lower costs by using readyRapid development & lower costs by using readymade building blocksmade building blocks

Components called like subroutinesComponents called like subroutines

Two tier system - components downloaded to theTwo tier system - components downloaded to theclient to execute, uses lots of bandwidth bogsclient to execute, uses lots of bandwidth bogsdown WANs and enterprise networksdown WANs and enterprise networks


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Three Tier Client/ServerThree Tier Client/Server

Application serverApplication server stores & executes components for clients stores & executes components for clients Easier management - centralizing application logicEasier management - centralizing application logic Reduces network trafficReduces network traffic Optimizes network processing - Lower load on client. Can use thinOptimizes network processing - Lower load on client. Can use thin

clients, NCs, older PCs,clients, NCs, older PCs,

Three Tier ObjectThree Tier Object


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CORBA Common ObjectCORBA Common Object

Request BrokerRequest Broker

ArchitectureArchitecture

DCOM (MS) DistributedDCOM (MS) Distributed

Component Object ModelComponent Object Model

Allows components to beAllows components to be

executed remotely withexecuted remotely with

results sent back to clientresults sent back to client

Three Tier ObjectThree Tier Object

ModelsModels


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API ApplicationAPI Application

Programming Interface andProgramming Interface and

three tier architecture bringsthree tier architecture brings

the power of layering logicthe power of layering logic layering logic - change a layerlayering logic - change a layer

without changing the otherswithout changing the others

Application logic - (ex. TaxApplication logic - (ex. Tax

software)software)

Three Tier Client/ServerThree Tier Client/Server


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Web Mail as 3 Tier SystemWeb Mail as 3 Tier System

Systems Management & Performance:Systems Management & Performance:


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Systems Management & Performance:Systems Management & Performance:Web Sites & MS WindowsWeb Sites & MS Windows

DNADNA

Front End stateless load balancing, cloned systemsFront End stateless load balancing, cloned systems

Back End stateful, partitioningBack End stateful, partitioning


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N-Tier ArchitectureN-Tier Architecture

.

Web Server or

Application Server

HTML pages Applets and components

Programming scripts

HTML pages Applets and components

Programming scripts

WelcomeProductsandSupport

1. Web Client 2. Web Server

Computer with

Web browser

HTTP server engine HTML forms processing

State management

Executable program calls

Server-side scripting

HTTP server engine HTML forms processing

State management

Executable program calls

Server-side scripting

HTTP Web Server

3. Server Programs

Executable program

Database access Business logic

Server-side component

calls

Executable program

Database access Business logic

Server-side component

calls

4. Database Server

DBMS system

Database storage Database transactions

Stored procedures

DBMS system

Database storage Database transactions

Stored procedures

Database Server

with DBMS

Client Server

ServerServer


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What is a Web Application?What is a Web Application?

IISActive Server Pages

Script Logic

COM

HTTP Clients

ServicesTransaction server

Message Queuing

Commerce

Databases and Directories


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Architecture TiersArchitecture Tiers

Business LogicBusiness Logic COM - Component Object ModelCOM - Component Object Model

Service accessibilityService accessibility

Visual Basic, C++, JavaVisual Basic, C++, Java

, Cobol, Pascal, Cobol, Pascal Used from Active Server PagesUsed from Active Server Pages

COM components provide:COM components provide: Encapsulation of internal detailsEncapsulation of internal details

Modularity for code reuseModularity for code reuse

Intellectual Property SecurityIntellectual Property Security


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N Tier Intranet -N Tier Intranet -

ScalabilityScalability

Application Server

Farm

Web Server

Mainframe Legacy Application

Corporate Data Stores

Active

Server

Application

Distributed COM

Distributed Components

Users(running web browser)

HTTP


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N Tier ArchitectureN Tier Architecture

PresentationPresentation Business logicBusiness logic Data servicesData services

WebWebBrowserBrowser

OthersOthers

Int

ernetInforma

tio

InternetInfo

rma

tio

Se

rver\L

DAPS

er

Se

rver\LDAPS

er

MTSMTS

DCOMDCOM

SQL ServerSQL Server

DirectoryDirectory

MicrosoftMicrosoftExchangeExchange

MSMQMSMQ

Com

pone

nts

Com

pone

nts

HTTPHTTP

LDAPLDAP

Architecture Of AArchitecture Of A


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IISIIS

Architecture Of AArchitecture Of A

Commerce SiteCommerce Site

Commerce Server SuppliedCommerce Server Supplied

ComponentsComponentsHTMLHTML .ASP.ASP DataData

SQL,SQL,

Oracle,Oracle,

(ODBC(ODBC

complicompli

ant)ant)

Tha
Tha

Cop Cop

Tha
Tha

Cop Cop{.{.


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.ASP.ASP

Get Access through ODBC DSNGet Access through ODBC DSN

Select Appropriate Data with SQL QuerySelect Appropriate Data with SQL Query

Step through the data and display on your pageStep through the data and display on your page

Commerce: AccessingCommerce: Accessing

The DataThe Data Data is accessed using ADO and any ODBC compliant database canData is accessed using ADO and any ODBC compliant database can

be easily usedbe easily used


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MiddlewareMiddleware

Conversion layer, sits between client andConversion layer, sits between client and

databasedatabase

Database transparencyDatabase transparency - middleware translates- middleware translates

DB using OLE DB (API)DB using OLE DB (API) Data access logic (ADO, OLE DB)Data access logic (ADO, OLE DB)

application written independent of source of databaseapplication written independent of source of database

integrate data from incompatible sourcesintegrate data from incompatible sources

Allows multi-vendor solutionsAllows multi-vendor solutions

fi f


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Benefits ofBenefits of

Client-Server ArchitecturesClient-Server Architectures ScalabilityScalability ManageableManageable

Cost Effective - PC hardware is more thanCost Effective - PC hardware is more than

1000 times cheaper than mainframe1000 times cheaper than mainframe

hardware for the same computing power.hardware for the same computing power.

Complexity easy on user, tough on ITComplexity easy on user, tough on IT


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IntranetsIntranets

In-house web site not accessible by publicIn-house web site not accessible by public

Gives benefits of three tier modelGives benefits of three tier model Low bandwidth requirementsLow bandwidth requirements

Thin clientThin client Lower management cost /deployment costLower management cost /deployment cost

ScalabilityScalability

Reduces complexity - cross platformReduces complexity - cross platform

interoperability, standard interfaceinteroperability, standard interface Emerging tools and standards HTML notEmerging tools and standards HTML not

suited to applications, DHTML, XML, Biztalksuited to applications, DHTML, XML, Biztalk


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Elements of the IntranetElements of the Intranet

Client - Browser Client - Browser navigation, interpretation of HTML from server, lightnavigation, interpretation of HTML from server, light

processingprocessing dynamic HTML - does processing on client Webdynamic HTML - does processing on client Web

pages function more like regular software, betterpages function more like regular software, bettercontrol of interfacecontrol of interface

Server -Server - serves up HTML to client via HTTP, lower bandwidthserves up HTML to client via HTTP, lower bandwidth

needed between server and clientneeded between server and client Active Server Pages (.asp), script languageActive Server Pages (.asp), script language

embedded in HTML pages that generates HTMLembedded in HTML pages that generates HTMLoutput from remote procedure call on serveroutput from remote procedure call on server

610.Web Architecture

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