1. Distributed Systems Architecture

2. Distributed systems architecture • Advantages • Resource Sharing • Openness • Concurrency • Scalability • Fault Tolerance • Disadvantages • Complexity • Security • Manageability • Unpredictability

3. Distributed systems architecture • Client-Server • Distributed Objects

4. Client-Server architecture • Two-tier Architectures: server(s)/client(s) • Thin-Client model: Applications and ‘heavy work’ resides on server(s). Client(s) serve as interface for the server(s) • Fat-Client model: Most of the programming logic resides on the client(s) side. Server(s) handles data. • Applet model: intermediate model

5. Client-Server architecture (cont.) • Three-tier Architectures: presentation / processing / data management • Example: Internet Banking Application • Presentation: Web browser (+ web server) • Processing: Server side applications • Data management: RDBMS

6. Distributed objects architecture • Objects that provide interfaces to a set of services that they provide. • Objects can communicate with other objects to generate requests / provide services • Object broker => middleware

7. Distributed objects architecture • Advantages: • No need to decide on ‘locations’ for services, each object can work on any place • Very open system architectures • Flexible and scalable • System can be reconfigured dynamically • Disadvantages: • Systems are very difficult to design

8. P2P architecture • De-centralized systems • Computations can be carried on by any node • Service oriented system architectures

9. Suggested readings • 12.3.1 CORBA