Client/Server Architecture
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
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
Advent of Client/Server Technology Improved information access Increased productivity Quick reponse to changing market place Rapid application development
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
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 & business+database logic on server)
Client-Server Models Distributed Presentation Remote Presentation Distributed Logic Remote Data Distributed Data
Client-Server Models 1 2 3 4 5 Client Server Network D D D D D BL BL EUD D BL BL BL EUD EUD EUD EUD EUD 1 2 3 4 5 Client
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
Three-Tier Architecture
From Two-Tier to N-Tier