Courses/Distributed Systems

Distributed Systems

CS3.401

Prof. Kishore Kothapalli•Monsoon 2025-26•4 credits

Revision Notes/Unit 1 — Introduction, Challenges & CAP Theorem

Unit 1 — Introduction, Challenges & CAP Theorem

What is a distributed system, why is it useful, and what makes it hard? Tanenbaum's definition; required features (concurrency, independent failures, no global clock, no shared memory); the unique challenges (unreliable communication, lack of global knowledge, no synchronisation); CAP theorem (Brewer) and the C-vs-A trade-off under unavoidable partitions; the Two-Generals problem.

Foundations — Definition, Motivation, Challenges, CAP

10 min

A distributed system is a collection of independent computers that *appears* to its users as a single coherent computer. Every interesting property of the field — fault tolerance, scalability, consistency — flows from the gap between that appearance and the reality of independent components that fail independently, communicate over unreliable networks, and share no clock or memory. The CAP theorem is the headline trade-off: under network partitions you must sacrifice either consistency or availability.