Jawaharlal Nehru Technological University Hyderabad B.Tech III ADVANCED OPERATING SYSTEMS Previous Question Paper (September - 2021 - R18)

A distributed operating system manages a collection of independent computers that appear to the user as a single coherent system. Key issues include:

• Transparency: Hiding the distributed nature of the system from the user, including access, location, migration, and replication transparency.
• Scalability: Ensuring the system performance does not degrade as the number of users or resources increases, often requiring decentralized algorithms.
• Reliability and Fault Tolerance: The system must continue to operate even if individual nodes fail, requiring mechanisms for error detection, recovery, and redundancy.
• Concurrency: Managing multiple processes executing simultaneously across different nodes while maintaining data consistency.
• Heterogeneity: Handling differences in hardware, operating systems, and network protocols across the distributed nodes.
• Security: Protecting data and resources from unauthorized access in an environment where communication occurs over open networks.
• Resource Management: Efficiently scheduling tasks and allocating resources across nodes to maximize utilization and minimize latency.

Communication primitives are the fundamental mechanisms used for data exchange between processes in a distributed system. The primary primitives are:

• Message Passing: The core mechanism where processes communicate by sending and receiving messages. It typically involves send(destination, message) and receive(source, message) primitives. These can be blocking (synchronous), where the sender waits for the receiver to accept, or non-blocking (asynchronous), where the sender continues immediately.
• Remote Procedure Call (RPC): A high-level abstraction that allows a process to execute a procedure in a different address space as if it were a local function call. It hides the underlying message-passing details through stubs.
• Remote Method Invocation (RMI): Similar to RPC but specifically designed for object-oriented systems, allowing an object in one process to invoke methods on an object residing in another process.
• Group Communication: Primitives designed for multicasting messages to a group of processes, often requiring atomic broadcast to ensure all members receive the message in the same order.