Architecture

Layers

Application, services
Middleware
Operating sytsem              |
Computer and network hardware | Platform

Platform

Fundamental communications and resource management services

Middleware

In order to support heterogeneous computers and networks while offering a single-system view, distributed sytems are often organized by means of layer of software-that is, logically placed between a higher-level layer consisting of users and applications, and a layer underneath consisteing of opearting sytsems and basic communication facilities.

applications - middleware - operating systems

Advantages

Disadvantages

Applications

Distributed applications, services

Distributed Operating System

Tightly-coupled operating sytem fro multi-processorts and homogeneours multi-computers

Network Operating System

Loosely-coupled operating sytem for heterogeneous mukti-computers. It connects differnt independent computers that each have their own operating sytem so that useres can easily use the services available on each computer.

Middleware is an additional layer atop of NOS implemnenting general-purpose services.

Client-server Architectures

Multitiered Architectures

Peer-to-peer systems

A client or server may be physically split up into logically equivalent parts, but each part is operating on its own share of the complete dataset.

Remote Procedure Call

Distributed-Object Architecture

Design Requirements