Distributed Systems End term Exam Review 2025

What is a distributed system? - Correct Ans-A collection of independent computers that appears to its users as one single coherent system What are the design goals of Distr Syst - Correct Ans-- Availability - Transparency - Openness - Security & Privacy - Scalability & performance Difference between Supercomputer & Distr Computers - Correct Ans-supercomputer has one singular OS, if it goes down the whole computer goes down. Distr computers are collection of many computers with each their own OS, one goes down the whole system is not compromised Describe Openness in D.S - Correct Ans-A set of rules that describe syntax and semantics - Interface Definition Language - Interoperability/portability Describe Security in D.S - Correct Ans-Only authorized users should be able to access data - Access control - Data integrity - Data/service availability Describe Scalability in D.S - Correct Ans-A system should be scalable with respect to size, geography and management What are the challenges with Geographical scalability? - Correct Ans-- Synchronous communication - Unreliable networks - centralized components - Multiple admin domains What are some scalability techniques? - Correct Ans-- Hiding communication latencies (async comms, reducing data transmition) - Distribution - Caching and replication - Load balancing What are the types of Distributed Systems? - Correct Ans-HPC Systems - Cluster computing, Grid computing - FOCUS on throughput Distributed Info Systems - Transaction processing systems, P-2-P Systems - FOCUS on info distribution Distributed Pervasive Systems: - Mobile networks, Sensor networks Cluster Computing vs Grid Computing - Correct Ans-Cluster Computing: - Homogeneity amongst nodes - Master-Slave architecture - Similar OS Grid Computing: - Heterogenous machines - 4 layers: 1. Fabric Layer: Interface to local resources 2. Connectivity LayerL connection handling and security 3. Resource layer: managing single resources 4. Collective layer: Simultaneous management of multiple resources 5. Appl layer Properties of Transactions - Correct Ans-ACID A - Atomic C - Consistent I - Isolated D: Durable Transaction Processing Architectures (TP Monitors) - Correct Ans-- Client sends request to TP monitor - TP monitor sends request to every server - TP monitor receives reply from every server - If at least one fails, whole transaction fails and reply is sent to client What are the different architectures in D.S - Correct Ans-- Components and connectors - Layered Architecture - Object Oriented Architecture - Data centered architectures - Event-based Architectures Layered Architectures - Correct Ans-- the OSI reference model - the TCP/IP model Object Based Architecture - Correct Ans-Similar to OOP Shared Data Architecture - Correct Ans-social media apps Event Based Architecture - Correct Ans-Components communicate by using events that can carry data. Types of System Architectures - Correct Ans-- Centralized Architectures - Decentralized Architectures - Hybrid Architectures Centralized Architectures - Correct Ans-- Client - Server model Decentralized Architectures - Correct Ans-P-2-P (Napster, BitTorrent) Drawbacks of multi-processing - Correct Ans-- Process creation (process control block) is costly. Must create address space & allocate OS resources - Inter Process Communication is costly. Needs kernel interrupt, context switching What is Context Switching? - Correct Ans-When the OS removes a process from CPU to put a new process on there. (Costly) What are threads? - Correct Ans-A Sequential execution stream within a process that is much faster to perform context switching on at the expense of limited resources. How are threads used in D.S - Correct Ans-HTML Browser, Multithreaded servers (dispatcher & worker) Describe a MultiThreaded server - Correct Ans-Client sends a request to a server, server gets the request and deploys a "worker" node to deal with the request on a separate thread Design issues in Servers? - Correct Ans-- Organization: Concurrent vs Iterative - Binding: Fixed endpoint vs Binding using Daemon vs using super server - Stateless vs Stateful server Stateless vs Stateful Servers - Correct Ans-Stateless: Does not contain info about client Stateful: Contains information about client Intermediaries of Stateless vs Stateful? - Correct Ans-Softstate: maintains state for a specific amount of time SessionState: maintains state for the duration of the session What is code migration and the benefits? - Correct Ans-Code migration is moving code from one machine to another. Benefits: - Load distribution - Reducing communication costs - Exploit parallelism - Dynamic configuration What are the three segments of a program? - Correct Ans-- Code segment - Resource segment - Execution segment Weak vs strong mobility? - Correct Ans-Weak: Moves only the code segment Strong: Moves code, resource and execution segment What are the three types of binding? - Correct Ans-Binding by identifier (Strongest) : Process uses URI for binding to a resource Binding by value: std libraries Binding by type (Weakest) What are the different types of resources? - Correct Ans-- Unattached resources: Can be easily moved - Fastened resources: Possible to move but costly - Fixed resources: Cannot be moved What are the types of communications in D.S - Correct Ans-- Persistent communication (provides data storage)