1. Chapter 2: System models
2.1 introduction
2.2 Physical models
2.3 Architectural models
2.4 Fundamental models

2. Fundamental Models Interaction model – performance and time.
Failure model – processes and communication.
Security model - processes and communication.

3. Introduction : Problems & threats
The three different models
Difficulties of D.S.
widely varying models,
wide range of system environments,
internal problems
external threats

4. Physical models Three generation of Distributed System:
Early distributed systems
Internet-scale distributed systems
Contemporary distributed systems
Distributed systems of systems

6. Architectural models
Approaches like: client-server,peer-to- peer,distributed objects, distributed components, and distributed event based systems.

7. Architectural elements
Communication entities
Communication paradigms
(figure 2.2)

8. Architectural elements

9. Classifying processes
Server processes
Client processes
Peer processes - Symmetrical manner
Goal – identifies the roles and responsibility
Specify the placement of the processes.

10. Architectural style based on there role
Client-server
peer-to-peer

11. Client-server

12. peer-to-peer

13. Dynamic systems Built as: moving code from one process of another.
discover available services of others.

14. placement Mapping of services to multiple servers Caching Mobile code
Mobile agents

15. Architectural pattern
Software architecture – structure of software, services, requests. Layering
Services layers

16. Architectural pattern
Tiered Architecture

17. Architectural pattern
Thin Clients

18. Architectural pattern
Other commonly occurring patterns
The proxy pattern
The use of brokerage

19. Middleware Solution.

20. Fundamental models
Interaction model
Failure model
Security model

21. Interaction model Factors Affecting the interaction processes in D.S.
Performance of communication channels
Computer clock & time events
-synchronous D.S.
-asynchronous D.S.

22. Interaction model
Event ordering

23. Failure model Omission failures Process Omission failures
Communication Omission failures
Arbitrary failure
Timing failure

24. Timing failures

25. Security model
Protection object
Securing process