(SEM V) THEORY EXAMINATION 2023-24 DISTRIBUTED SYSTEM

Course: B.Tech (Semester V)

Subject Code: KDS052

Subject: Distributed System

Maximum Marks: 100

Time: 3 Hours

Format:

Section A: 10 short questions × 2 marks = 20 marks

Section B: Any 3 questions × 10 marks = 30 marks

Section C (Q3–Q7): Each with two alternatives, attempt any 1 part per question × 10 marks = 50 marks

SECTION A – Very Short Answer Questions (2 × 10 = 20 Marks)

a. Briefly explain key characteristics of a distributed system.
b. Provide two real-world examples of distributed systems.
c. Differentiate between resource deadlocks and communication deadlocks.
d. Describe the concept of centralized deadlock detection.
e. Describe two common system models used in distributed systems.
f. Define the Byzantine Agreement Problem.
g. Define backward recovery and forward recovery.
h. Contrast two types of commit protocols used in distributed systems.
i. Define nested transactions.
j. Define timestamp ordering in the context of concurrency control.

SECTION B – Descriptive Questions (Attempt any 3 × 10 = 30 Marks)

a. Differentiate between centralized, decentralized, and distributed architectural models with examples, advantages, and disadvantages.
b. Explain the conditions that must be satisfied by a distributed mutual exclusion algorithm as per the Mutual Exclusion Theorem.
c. Discuss the role of fault tolerance in consensus algorithms and how they handle failures.
d. Explain the challenges in voting protocols for large-scale systems and how they handle delays and node failures.
e. Define flat and nested distributed transactions and discuss their differences from non-distributed transactions along with challenges.

SECTION C – Long / Application-Based Questions (Each 10 Marks)

Q3. Time and Synchronization

a. Discuss challenges due to absence of a global clock and its impact on synchronization.
b. Explain termination detection, its techniques, and its importance for system stability.

Q4. Deadlocks

a. Differentiate between resource and communication deadlocks with examples.
b. Explain path pushing and edge chasing algorithms for distributed deadlock detection — how they identify and resolve deadlocks.

Q5. Shared Memory and Commit Protocols

a. Explain distributed shared memory (DSM) — its concept and an algorithm for implementation.
b. Discuss challenges of atomic commit in distributed databases and how Two-Phase Commit (2PC) addresses them.

Q6. Voting and Recovery

a. Define dynamic voting protocols — explain how they adapt to node additions/failures and their advantages.
b. Discuss the importance of transaction recovery — mechanisms ensuring atomicity and durability after failures.

Q7. Commit and Communication

a. Compare Two-Phase Commit (2PC) and Three-Phase Commit (3PC) protocols — key differences and suitable scenarios.
b. Explain the role of group communication in replicated systems, emphasizing coordination and consistency among nodes.