--- title: "Models of distributed system" subject: "Distributed System" chapter: 1 key: "semester_7/distributed_system:models-of-ds" source: https://www.bctengineer.com/q/semester_7/distributed_system/models-of-ds site: BCT Engineering --- # Models of distributed system Distributed System · Chapter 1: Introduction - Asked in: Model question - Video: [distributed computing models | Fundamental & Architectural | Lec-07 | Bhanu Priya](https://www.youtube.com/watch?v=VNRmsACNSaY) — Education 4u - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/distributed_system/models-of-ds - Whole chapter: https://www.bctengineer.com/md/semester_7/distributed_system/chapter-1 ## Question Explain the different models of distributed system. ## Short answer The models are physical, architectural, and fundamental. Physical describes hardware and network; architectural describes client-server, peer-to-peer, and multi-tier structures; fundamental covers interaction, failure, and security models common to all distributed systems. ## Answer Models of a distributed system describe its main parts and their relationships. Coulouris classifies them as physical, architectural and fundamental models. #### 1. Physical model Describes the hardware: computers, devices and network. - *Early distributed systems* (1970s-80s): 10-100 nodes on a LAN. - *Internet-scale systems:* many nodes on the Internet, heterogeneous. - *Contemporary systems:* mobile, ubiquitous, cloud and IoT, with a large number of nodes. #### 2. Architectural model Describes the structure, in terms of components and their interconnection. ```text Client-server Peer-to-peer C1 --\ P1 --- P2 C2 ---> Server | \ / | C3 --/ P4 --- P3 ``` - **Client-server:** clients request, servers provide service (web, file server). Variations: multiple servers, proxy servers and caches, mobile code, mobile agents, thin clients. - **Peer-to-peer:** all processes play similar roles and share resources (BitTorrent). - **Multi-tier (layered):** presentation, application logic, data (three-tier web application). - **Cloud / service-oriented** architecture. #### 3. Fundamental model Abstract properties common to all systems. - **Interaction model:** communication delays, clock drift, synchronous vs asynchronous. - **Failure model:** omission, arbitrary (Byzantine) and timing failures. - **Security model:** threats to processes and channels, defended by cryptography and access control. Other classification (Tanenbaum): distributed computing systems (cluster, grid, cloud), distributed information systems (transaction processing, enterprise integration) and pervasive systems. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which three models does Coulouris use to classify distributed system models? A. Physical, architectural and fundamental B. Physical, logical and virtual C. Client, server and peer D. Interaction, failure and security only Answer: A. Coulouris classifies them as physical, architectural and fundamental models. (Key point: Three models) 2. What characterises the peer-to-peer architecture? A. Clients request and one server provides B. All processes play similar roles and share resources, e.g. BitTorrent C. Layers of presentation, logic and data D. A single master controls everything Answer: B. In P2P there is no fixed client/server distinction. (Key point: Peer-to-peer) 3. Which are the parts of the fundamental model? A. Client, server and proxy models B. Cluster, grid and cloud models C. Interaction, failure and security models D. Physical, mobile and cloud models Answer: C. Fundamental models describe abstract properties: interaction, failure, security. (Key point: Fundamental model parts) 4. What does the physical model describe? A. The hardware: computers, devices and the network B. The software layers C. Message formats D. Security threats Answer: A. Physical models describe the underlying hardware composition. (Key point: Physical model) ## Related in Distributed System - [Autonomous vs distributed system](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Aautonomous-vs-distributed) — Distributed System, chapter 1 - [True distributed system; middleware organisation](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Atrue-ds-middleware) — Distributed System, chapter 3 - [Data-centric consistency models](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Adata-centric-consistency) — Distributed System, chapter 7 - [Distributed deadlock and recovery](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Adistributed-deadlock-note) — Distributed System, chapter 8, asked 3× - [Distributed objects and communication](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Adistributed-objects-communication) — Distributed System, chapter 2, asked 2× - [Nested vs distributed transaction; 2PC](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Anested-vs-distributed-2pc) — Distributed System, chapter 8, asked 2× ## Related in other subjects - [Distributed system in big data example](https://www.bctengineer.com/question.md?key=semester_8%2Fbig_data_technologies%3Adistributed-system-example) — Big Data Technologies, chapter 1 - [Short note: Distributed system implementation](https://www.bctengineer.com/question.md?key=semester_6%2Fobject_oriented_analysis_and_design%3Ashort-note-distributed-implementation-issues) — Object Oriented Analysis and Design, chapter 4 - [Distributed system and Hadoop](https://www.bctengineer.com/question.md?key=semester_8%2Finformation_system%3Adistributed-system-hadoop-voluminous-data) — Information System, chapter 8 - [VHDL dataflow/behavioural models; JK flip-flop](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Avhdl-dataflow-behavioural-jk) — Embedded System, chapter 9