Distributed System PDF

DISTRIBUTED SYSTEM Distributed Systems Characterization,goal andclient- server model 1 Instructor:Hailemichael A. OUTLINE 1. What is a Distributed System 2. Common Characteristics 3.organization and goals of...

DISTRIBUTED SYSTEM Distributed Systems Characterization,goal andclient- server model 1 Instructor:Hailemichael A. OUTLINE 1. What is a Distributed System 2. Common Characteristics 3.organization and goals of distributed systems 4. hardware and software concept 5.client-server model 6.SUMMARY 2 Instructor:Hailemichael A. 1. WHAT IS A DISTRIBUTED SYSTEM? Definition: A distributed system is one in which components located at networked computers communicate and coordinate their actions only by passing messages. 3 Instructor:Hailemichael A. 1.1 CENTRALIZED SYSTEM CHARACTERISTICS  One component with non-autonomous parts  Component shared by users all the time  All resources accessible  Software runs in a single process  Single point of control  Single point of failure 4 Instructor:Hailemichael A. CHARACTESTICS OF DISTRIBUTED SYSTEM  Multiple autonomous components  Components are not shared by all users  Resources may not be accessible  Software runs in concurrent processes on different processors  Multiple points of control  Multiple points of failure 5 Instructor:Hailemichael A. 3. COMMON CHARACTERISTICS  What are we trying to achieve when we construct a distributed system?  Certain common characteristics can be used to assess distributed systems  Scalability  Transparency  Fault Tolerance  Concurrency  Heterogeneity 6 Instructor:Hailemichael A. 3.1SCALABILITY  VAbility to grow and manage increased load by adding more resources.  Can be horizontal (adding more machines) or vertical (adding resources to existing machines). 7 Instructor:Hailemichael A. 3.2 TRANSPARENCY  Access Transparency: Users should not be aware of the location of resources.  Location Transparency: Resources can be accessed without knowing their physical location.  Migration Transparency: Resources can move without affecting the operations. 8 Instructor:Hailemichael A. 3.4 FAULT TOLERANCE  Ability to continue operating in the event of a failure of one or more components.  Redundancy and replication are often used to achieve this.  Fault tolerance is achieved by  recovery  redundancy 9 Instructor:Hailemichael A. 3.6 CONCURRENCY  Components in distributed systems are executed in concurrent processes.  Components access and update shared resources (e.g. variables, databases, device drivers).  Integrity of the system may be violated if concurrent updates are not coordinated.  Lost updates  Inconsistent analysis 10 Instructor:Hailemichael A. HETEROGENEITY  Supports a variety of hardware, operating systems, and networks.  Allows for the integration of diverse components. 11 Instructor:Hailemichael A. 4.4 SYSTEM ARCHITECTURES  Client-Server  Peer-to-Peer 12 Instructor:Hailemichael A. 4.4.1 CLIENTS INVOKE INDIVIDUAL SERVERS Client invocation invocation Server result result Server Client Key: Process: Computer: 13 Instructor:Hailemichael A. 4.4.2 PEER-TO-PEER SYSTEMS Peer 2 Peer 1 Application Application Sharable Peer 3 objects Application Peer 4 Application Peers 5.... N 14 Instructor:Hailemichael A. 1.3 ORGANIZATION OF DISTRIBUTED SYSTEMS COMPONENTS:  Nodes: Individual computers or devices in the network.  Middleware: Software that provides common services and capabilities to applications outside of what's offered by the operating system.  Communication Protocols: Define the rules for data exchange between nodes. 15 Instructor:Hailemichael A. ARCHITECTURAL MODELS  Client-Server Architecture: A server provides resources or services, and clients request them.  Peer-to-Peer Architecture: All nodes act as both clients and servers.  Multi-tier Architecture: Divides the application into layers, improving scalability and manageability. 16 Instructor:Hailemichael A. 1.4 GOALS OF DISTRIBUTED SYSTEMS  Resource Sharing: Enable users to access and share resources efficiently.  Openness: Systems should be designed with open standards to allow for easy integration and expansion.  Reliability: Ensure that the system can recover from failures.  Performance: Provide high throughput and low latency in resource access.  Security: Protect data and resources from unauthorized access and threats. 17 Instructor:Hailemichael A. 1.5 HARDWARE AND SOFTWARE CONCEPTS  Hardware:  Diverse hardware components including servers, workstations, and mobile devices.  Network infrastructure like routers, switches, and communication links.  Software:  Distributed operating systems (e.g., Google Kubernetes). 18  Applications designed for distributed environments (e.g., cloud computing services). Instructor:Hailemichael 1.6 THE CLIENT-SERVER MODEL  Overview:  A foundational architecture for distributed systems.  Clients request services, and servers provide them.  Components:  Client: Initiates requests for services.  Server: Listens for requests, processes them, and sends responses. 19 Instructor:Hailemichael A. 5. SUMMARY  Definitions of distributed systems and comparisons to centralized systems.  The characteristics of distributed systems.  The eight forms of transparency.  The basic design issues. 20 Instructor:Hailemichael A.