Definition of Distributed System
A distributed system is a network that consists of autonomous computers that are connected using a distribution middleware.
They help in sharing different resources and capabilities to provide users with a single and integrated coherent network.
Examples of Distributed Systems
1. Intranets
A single authority protected access – a firewall.
Services:
- Infrastructure services
- File service
- Name service
- Application services
2. Resource Sharing
Resource Sharing and the Web Hardware resources (reducen costs) Data resources (shared usage of information) Service resources search engines computer-supportedncooperative working Service vs. server.
Goals Of Distributed System
- Making resources accessible
- Distribution transparency
- Opennessn Scalability
- Security
- System design requirements
1. Making Resources Accessible
- Naming Access control
- Security
- Availability
- Performance
- Mutual exclusion of users
2. Transparency
Distribution in users viewpoint: a single unified system.
3. Concurrency
- Several simultaneous users.
- Integrity of data
- Mutual exclusion
- Synchronization
4. Openness
- Making the network easier to configure and modify.
- Openness facilitates
- Interoperability,
- Portability,
- Extensibility,
- Adaptivity
5. Security
Security is a big challenge in a distributed environment, especially when using public networks.
6. Scalability
Distributed systems should be scalable with respect to geography, administration or size.
7. Reliability
Compared to a single system, a distributed system should be highly capable of being secure, consistent and have a high capability of masking errors.