Mumbai University > Computer Engineering > Sem 8 > Parallel and Distributed Systems

Marks: 10M

Difficulty: Medium

1] Architectural models: This model describes responsibilities distributed between system components and how these components are places.

They are broadly classified as:

a) Client server model : In this model, the system is structured as a set of processes called servers, that offer services to the users, called clients. It is based on simple request/reply protocol implemented with send/receive primitives or RPC

b) Peer to peer model : In this all processes play similar role without distinction client and servers. This is most general and flexible model. It distributes resources widely. The problem lies in its high complexity in planing objects retrieving them and maintaining replies.

2] Interaction models : This model handles process execution, message delivery, clock drifts and other time related issues. In synchronous distributed system, these a notion of global physical time only such systems can be used for handling time applications. It is possible to use time in order to detect failures. the only problem is that it is difficult and costly to implement syndromes distributed systems.

Mainly distributed systems are asynchronous they have no bounds on execution time, transmission delays and drift rates between local clocks, as then is no global clock, reasoning can be only in terms of logical time.

3] Fault models : Failures can occur in both processes and communication channels, the reason can be software/hardware or both faults. Fault models are needed in order to build systems with predictable behavior in case of faults. such systems will function according to the predictable only as long as the real faults behave as defined by the "fault model".