1. Chapter 1 Characterization of Distributed Systems
From Coulouris, Dollimore, Kindberg and Blair Distributed Systems: Concepts and Design

2. Distributed System
A number of networked computers communicate and coordinate actions only by passing massages
Computing
Networking
Storage
More power to execute jobs that cannot be done in a single machine, achieving pervasive computing

3. Selected applications on distributed systems
Finance and commerce
eCommerce e.g. Amazon and eBay, PayPal, online banking and trading
The information society
Web information and search engines, ebooks, Wikipedia; social networking: Facebook and MySpace.
Creative industries and entertainment
online gaming, music and film in the home, user-generated content, e.g. YouTube, Flickr
Healthcare
health informatics, on online patient records, monitoring patients
Education
e-learning, virtual learning environments; distance learning
Transport and logistics
GPS in route finding systems, map services: Google Maps, Google Earth
Science
The Grid as an enabling technology for collaboration between scientists
Environmental management
sensor technology to monitor earthquakes, floods or tsunamis

4. Characteristics of Distributed System
Concurrency
Concurrent execution of jobs
No global clock
Coordinate actions
Synchronization
Independent failure
Hardware/software failure
Protection, recovery and availability

5. Trends of Distributed System
Pervasive networking and modern Internet
Distributed computing as a utility
Mobile and ubiquitous computing
Distributed multimedia systems

6. Pervasive networking and modern Internet
intranet
ISP
desktop computer:
backbone
satellite link
server: ☎
network link:

7. Distributed computing as a utility

8. Mobile and ubiquitous computing

9. Distributed multimedia systems

10. Resource allocation in a physical infrastructure
Resource sharing
Resource allocation in a physical infrastructure
Computing, networking and storage resources
Efficiency, scalability and reliability/availability
Distributed system’s perspective
Sharing a service, e.g., web search engine
Read, write and delete operations on files
An interface that provides and manages these operations
Remote invocation through communication

11. Challenges of Distributed System
Heterogeneity
Openness
Security
Scalability
Failure handling
Concurrency
Transparency
Quality of Service

12. Programming languages Implementation by different developers
Heterogeneity
Networks
Computer hardware
Operating systems
Programming languages
Implementation by different developers

13. Interoperability Portability Extensibility Flexibility
Openness
Interoperability
Implementation from different manufacturer can work
together relying on standard rules
Portability
Application from one distributed system can be
executed on another system that implements the same
service
Extensibility
Easy to add/remove new features and functions
Flexibility
Separating policy from mechanism

14. Confidentiality Integrity Availability
Security
Confidentiality
Against disclosure to unauthorized ones
Integrity
Against alteration or corruptions of the shared
resources
Availability
Against interference with the means to access the
shared resources

15. Control the cost of the physical resources
Scalability
Control the cost of the physical resources
Control the performance loss
Prevent software resource running out
Avoid performance bottlenecks
Another perspective
Size scalable
Geographical scalable
Administration scalable

16. Other SLA requirements
Failure handling
Detecting failures
Masking failures
Tolerating failures
Recovering failures
Redundancy
Availability
availability = available time / (available time + down time)
Other SLA requirements

17. A shared resources is invoked by different clients
Concurrency
A shared resources is invoked by different clients
Time, clocks, events and process states
Logical time and physical time
Transactions and synchronization
Mutex and locks
Deadlocks

18. Transparency
Access transparency: enables local and remote resources to be accessed using identical operations. Location transparency: enables resources to be accessed without knowledge of their physical or network location (for example, which building or IP address). Concurrency transparency: enables several processes to operate concurrently using shared resources without interference between them. Replication transparency: enables multiple instances of resources to be used to increase reliability and performance without knowledge of the replicas by users or application programmers. Failure transparency: enables the concealment of faults, allowing users and application programs to complete their tasks despite the failure of hardware or software components. Mobility transparency: allows the movement of resources and clients within a system without affecting the operation of users or programs. Performance transparency: allows the system to be reconfigured to improve performance as loads vary. Scaling transparency: allows the system and applications to expand in scale without change to the system structure or the application algorithms.

19. Adaptability and robustness Scalability
QoS
Latency
Performance loss
Reliability
Security
Adaptability and robustness
Scalability

20. Case Study: The World Wide Web
Web servers
Browsers
Internet
File system of
standards
faq.html

21. Case Study: Mobile eHealth system
Challenges:
What infrastructure is needed?
How can we monitor the data in a robust way?
How to transmit data to the external storage?
How to provide security and privacy?

22. Summary
Distributed system is an operating system that manages multiple computer through networks.
It serves as a middleware that provides interface for multiple applications across multiple machines