Three Tier Architecture
• Tend to push a lot of processing onto the
client (fat client)
• This can cause several problems
– clients may require a lot of resources(memory,disc
– user interface and business processing tend to get
– with much similar processing on many client
machines extending existing applications and
implementing new ones becomes more complex.
The key to using Remote Data Service technology lies in
understanding the three-tiered client/server model. This
approach separates the various components of a
client/server system into three "tiers":
• Client Tier
• Middle Tier
• Data source Tier
A local computer on which either a Web browser displays a
Web page that can display and manipulate data from a
remote data source, or (in non-Web-based applications)
a stand-alone compiled front-end application.
A Server computer that hosts components which
encapsulate an organization's business rules.
Middle-tier components can either be Active
Server Page scripts executed on Internet
Information Server, or (in non-Web-based
applications) compiled executables.
Data source tier
A computer hosting a database management
system (DBMS), such as a Microsoft SQL
Server database. (In a two-tier application,
the middle-tier and data source tier are
Tiers can be on Same machine
These tiers don't necessarily correspond to physical
locations on the network.
For example, all three tiers may exist on only two
machines. One machine could be a Windows 95
computer running Internet Explorer 4.0 as its browser.
The second machine could be a Windows NT Server
computer running both Internet Information Server and
Microsoft SQL Server.
Designing applications this way gives you greater flexibility
when deploying processes and data on the network for
maximum performance and ease of maintenance.
Three - Tier Network
Advantages of Three-tier
• removes a huge processing burden from client
• can be used to consolidate enterprise-wide
business rules as application servers process
business rules in a single place for use 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 the client. database queries may
be presented to client in alternative forms.
Using an Internet Server
Client Side Connection