Client/Server Architecture

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Client/Server Architecture
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Advent of Client/Server Technology

• In systems centralised around mainframe, a no. of
  dumb terminals used to be connected to a powerful
  server, which performed all the processing
• It became increasingly difficult to keep up pace
  with changing scenarios (business rules,
  technologies etc.) as modifying these systems was
  a time consuming activity and besides affected
  all the users

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Advent of Client/Server Technology

• With the advent of PCs, the processing could be
  distributed between client and server, which
  accrued several benefits
• A powerful Graphical User Interface (GUI) could
  be provided to the user instead of Character
  based interface, which was user-friendly
• The processing could be distributed between
  client and server, thus taking some load off the
  server

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Advent of Client/Server Technology

• Improved information access
• Increased productivity
• Quick reponse to changing market place
• Rapid application development

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The Tiers

• Applications can be logically distributed into
  several layers, each of which is known as a Tier
• Windows DNA refers to these tiers as -
• User Services
• Business Services
• Data Services

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Two-Tier Architecture

• In a Two-Tier Architecture the applications are
  mostly divided into a user-services tier and a
  data-services tier
• The application logic resides either in the user
  interface or on the server, producing two models
  
• Fat Client (UserInterface Business Logic on
  client database logic on the server)
• Fat Server (User Interface logic on client
  businessdatabase logic on server)

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Client-Server Models

• Distributed Presentation
• Remote Presentation
• Distributed Logic
• Remote Data
• Distributed Data

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Client-Server Models
Server
D
D
D
D
D
BL
BL
BL
Network
EUD
D
BL
BL
BL
EUD
EUD
EUD
EUD
EUD
1
3
2
4
5
Client
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Three-Tier Architecture

• In a three tier architecture the business
  services are assigned a separate tier called
  middle tier and is handled by middleware like MTS
  and IIS

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Three-Tier Architecture

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From Two-Tier to N-Tier