introduction to distributed system
TRANSCRIPT
Definition of a Distributed System
• A distributed system is:
A collection of independent computers that appears to its users as a single coherent system.
• User Programmer User Application Program
Isha Padhy, Department of CSE
Definition of a Distributed System
A distributed system organized as middleware. The middleware layer extends over multiple machines, and offers each application the same interface.
Isha Padhy, Department of CSE
2.2 Examples of distributed systems
Isha Padhy, Department of CSE
GOALS
• Making Resources accessible• Distribution Transparency• Openness• Scalability• Fault Tolerance• Concurrency• Security
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Making Resources Available• Positivity:
Allow user to access remote resources in controlled and efficient way.- Save high cost- Connecting users and resources whether existing or virtually- Easy availability of products.
• Negativity: IntrusionSecurity Encrypted Passwords
Tracking communications
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Distributed Transparency
2. Degree of Transparency
1. Type of Transparency
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Openness
- Easy to add new components or replace existing ones- Portability of applications - Component should provide optimal policy for a user
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Scalability
• Adapted to change in components• Two types - Vertical- Horizontal• Measured in 3 ways- w.r.t. size- Geographically- Administrative
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Scalibilty Problems• W.r.t. size: - services are centralized• Geographically:- Communication in LAN, WAN• Administrative: - Conflict in policies- DS has to protect against malicious attacks from
new domain- New domain has to protect itself against DS.
Isha Padhy, Department of CSE
Scaling Techniques• Hiding Communication latencies
• Distribution: split the components• Replication: helps to balance the loadIsha Padhy, Department of CSE
Fault Tolerance
• 3 kinds of problems (fault, errors, failures)• Types of faults(Transient, Intermittent,
permanent)• Fault Tolerance• Steps of fault tolerance- Fault detection- Fault diagnosis- Assessment- Recovery- Redundancy
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Security
• 3 components- Confidentiality: keeping secret.- Integrity: protection against alteration.- Availability: protection against interference.• Identification of the user• Security challenges- Denial of service attack- Security of mobile code
Isha Padhy, Department of CSE
Trends in DS
• Distributed computing systems: used for high performance computing task.
- Cluster computing: Underlying components are simple and similar.
- Cloud computing: Relies on sharing of resources
- Grid computing: Run an application on different machines.
Isha Padhy, Department of CSE
• Distributed Information systems(EPI): - Transaction Processing system: captures, enters,
stores, retrieves the relevant details of business events and generates information required.
- Enterprise application integration: moderning and co-ordinating applications.
• Distributed pervasive systems: Embedding microprocessors in everyday objects.
Isha Padhy, Department of CSE