Three Tier Architecture

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Three Tier Architecture
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Two-Tier Applications

• 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
  etc)
• user interface and business processing tend to
  get mixed together.
• with much similar processing on many client
  machines extending existing applications and
  implementing new ones becomes more complex.

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Three-Tiered Applications

• 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

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Client 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.

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Middle tier

• 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.

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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-tier application, the middle-tier and
  data source tier are combined.)

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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.

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Three - Tier Network
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Advantages of Three-tier architecture

• removes a huge processing burden from client
  machines.
• 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.

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Using an Internet Server
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Client Side Connection
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Middle Tier