The document provides an overview of distributed systems, defining them as software systems where independent computers work together and appear as a single entity to users. It discusses the historical development of distributed systems, the advantages of their use, and organizational structures like middleware. Key goals include resource sharing, openness, transparency, scalability, and concurrency to enhance system efficiency and user interaction.

1. A
PRESENTATIONON
DISTRIBUTEDSYSTEMS

2. • What are the Distributed
Systems ???
1
• Why distributed systems
???
2
• Organization of
Distribution systems.
3
• Goals of Distributed
Systems…
4
Outlines:

3. HISTORY
• 1945~1985
− Computers were large and expensive.
− No way to connect them.
− All systems were Centralized Systems.
 Mid-1980s
− Powerful microprocessors.
− High Speed Computer Networks (LANs , WANs).

4. Then came the
DISTRIBUTED
SYSTEMS…
HISTORY (Contd.)

5. What are Distributed
Systems????

6. Distributed Systems ? ?
• A distributed system is a s/w system through which a
collection of independent computers appears to its users as a
single, coherent system.
• A distributed system is one in which components located at
networked computers communicate and coordinate their
actions only by passing messages.

7. Distributed Systems

8. EXAMPLES
• World Wide Web (WWW) is the biggest example
of distributed system.
• Others are
– The internet
– An intranet which is a portion of the internet managed
by an organization

9. WHY DISTRIBUTED
SYSTEMS ? ?
• Availability of powerful yet cheap
microprocessors (PCs, workstations),
• Continuing advances in communication
technology

10. ORGANIZATION OF D.S.:
A distributed system organized as middleware.
− The middleware layer extends over multiple machines, and
offers each application the same interface.

11. GOALS OF D.S. :
Resource Sharing.
Openness.
Transparency.
Scalability.
Concurrency.

12. RESOURCE SHARING:
• Makes easier for users to access remote resources and
to share resources with other users.
 Examples: printers, files, Web pages, etc.
• Easily interact with other open systems
• Conform to well-defined interfaces
• Achieve independence in heterogeneity wrt
 Hardware
 Platform
 Languages
• Support different app/user-specific policies
• ideally, provide only mechanisms

13. • Determined primarily the degree to which new
resource-sharing services can be added and be
made available for use by a variety of client
programs.
OPENNESS:

14. • It hides the fact that the processes and
resources are physically distributed across
multiple computers.
• Transparency is of various forms as follows:
TRANSPARENCY:

15. Forms of transparency

16. • Size scalability
- number of users and processes
• Geographical scalability
- maximum distance between nodes
• Administrative scalability
- number of administrative domains
SCALABILITY

17. • Several clients may attempt to access a shared
resource at the same time.
• Any object that represents a shared resource in a
distributed system must be responsible for
ensuring that operates correctly in a concurrent
environment.
CONCURRENCY