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3-Tier Client/Server

Architecture

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Background

Demand enterprise-class applications

Partitioning of applications

2-Tier, 3-Tier, N-Tier

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What are these Tiers ?

Physical partitioning of applications

terminal(tier1), minicomputer(tier2),mainframes(tier3)

Logical partitioning of applications 2-tier

client(tier 1) :a big chunk of application

server(tier 2) : DBMS

3-tier client(tier1) : GUI

application server(tier2) : all chunk of businessapplications

server(tier3) : DBMS

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GUI

SQL, File Server, HTTP protocol

Tier 1Tier 2

Database(or

Other Resource

Managers)

A 2-Tier Client-Server Application Architecture

Tier 3

RPCs, Conversations, Queues,

Publish-and-Subscribe,

Broadcasts, Object invocations

GUI

Tier 2Tier 1

Application Database(orOther Resource

Managers)

A 3-Tier Client-Server Application Architecture

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Why 3-Tier Architecture ?

Reasons

Meets the requirements of large-scale internetand intranet client/server applications

Is easier to manage and deploy on the network most of code runs on the servers, especially

technologies like Java applets

Minimizes network interchanges by creatingabstract levels of service

Provides better security

by not exposing the database schema to the client

by enabling more fine-grained authorization on theserver

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Three Tiers

The key to using Remote Data Service technology lies inunderstanding the three-tiered client/server model. This approachseparates the various components of a client/server system intothree "tiers":

Client Tier

Middle Tier

Data source Tier

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3-tier architecture

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Arch(cont..)

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Client tier

A local computer on which either a Web browser displays aWeb page that can display and manipulate data from aremote data source, or (in non-Web-based applications) astand-alone compiled front-end application.

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Middle tier

A Server computer that hosts components which encapsulate anorganization's business rules. Middle-tier components can eitherbe Active Server Page scripts executed on Internet InformationServer, or (in non-Web-based applications) compiled executables.

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Data source tier

A computer hosting a database management system (DBMS),such as a Microsoft SQL Server database. (In a two-tierapplication, the middle-tier and data source tier are combined.)

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Advantages

Removes a huge processing burden from client machines.

Can be used to consolidate enterprise-wide business rules asapplication servers process business rules in a single place foruse by multiple applications. When rules change, only a change to

the application server is required.

Any knowledge of the database server may be hidden from theclient. Database queries may be presented to client in alternativeforms.

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2-Tier

Architecture

3-Tier

ArchitectureCosttoDevelopandMaintain

Application Complexity and Length of Application Life

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Conclusion

It has become a safe bet to implement your

applications using a 3-tier client/server

Architecture

It supports

- security

- reusability

- step-wise, add-on, and customized integration- etc

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