MODULE 1

Question 1

Discuss in detail about distributed system models.

Answer 1

Distributed System Models
Distributed system models help in designing, analyzing, and understanding the
behavior of distributed systems. They are categorized into Physical,
Architectural, and Fundamental models

1. Physical Model
   Represents the hardware layout of the system.
   * Nodes: Devices (servers, PCs) that process and communicate.
   * Links: Communication channels (wired/wireless) like point-to-point or
   broadcast.
   * Middleware: Software that enables communication, fault tolerance,
   synchronization.
   * Network Topology: Structure of node connections (bus, star, ring, mesh).
   * Protocols: TCP, UDP, MQTT used for secure and efficient data exchange.
2. Architectural Model
   Defines the system’s organization and interaction patterns.
   * Client-Server Model: Centralized server responds to client requests (e.g.,
   web services).
   * Peer-to-Peer (P2P): All nodes are equal and share services (e.g.,
   BitTorrent).
   * Layered Model: Organized into layers for modular design and abstraction.
   * Microservices Model: Small, independent services performing specific
   functions, enhancing scalability
3. Fundamental Model
   Covers key concepts and formal behaviors.
   * Interaction Model:
   o Message Passing: Synchronous/asynchronous communication.
   o Publish/Subscribe: Topics-based messaging.
   * Failure Model:
   o Types: Crash, omission, timing, Byzantine failures.
   o Handling: Replication, fault detection, recovery methods.
   * Security Model:
   o Authentication: Passwords, keys, multi-factor verification.
   o Encryption: Protects data confidentiality.
   o Data Integrity: Hashing and digital signatures to prevent tampering.

Question 2

Explain the basic Cluster Architecture with a neat diagram.

Answer 2

Cluster computing is a technique where multiple interconnected computers
(nodes) work together as a single system to execute tasks, process data, or run
applications. It provides users with a transparent system that appears as one
virtual machine.
Features of Cluster Computing
1. Transparency: Users see a single virtual system instead of multiple nodes.
2. Reliability: Failure of one node doesn’t affect the entire system.
3. Scalability: Nodes can be added or removed easily.
4. Performance: Parallel task execution improves overall speed.
5. Load Balancing: Tasks are distributed across nodes to prevent overload.
Cluster Computing Architecture
1. Node (Computer)
o Each node has its own processor, memory, and OS.
o Nodes are connected via a high-speed network.
2. Head Node (Master Node)
o Manages the cluster operations.
o Distributes tasks to other nodes (slave nodes).
o Collects results and monitors performance.
3. Slave Nodes (Worker Nodes)
o Execute the assigned tasks.
o Report back to the head node.
o Can perform computations in parallel.
4. Cluster Middleware
o Software that handles job scheduling, communication, and
resource management.
o Examples: MPI (Message Passing Interface), OpenMPI, etc.
5. Interconnect Network
o Ensures high-speed data transfer between nodes.
o Uses Ethernet, Infiniband, or other low-latency networks.
6. Storage System
o Shared or distributed storage system (like NFS or parallel file
systems).
o All nodes may access the same data

Question 3

Write short notes on Peer-to-Peer network families.

Answer 3

Definition
* P2P architecture is a distributed model where each node (peer) acts as
both client and server, sharing resources without a central authority

2. Characteristics
   * Decentralization: No central server; peers communicate directly.
   * Scalability: Easily grows to support more users.
   * Fault Tolerance: Network survives even if some nodes fail.
   * Resource Sharing: Peers contribute bandwidth, storage, and data.
   * Autonomy: Each peer manages its own data and functions.
3. Types of P2P Networks
   * Pure P2P: Fully decentralized (e.g., BitTorrent).
   * Hybrid P2P: Uses central servers or super peers (e.g., Skype).
   * Overlay P2P: Virtual network over physical internet (e.g., Chord).
   * Structured P2P: Organized topology with routing rules (e.g., Pastry).
   * Unstructured P2P: Random topology, no fixed structure (e.g., Gnutella).
4. Components
   * Peer Nodes: Active devices in the network.
   * Overlay Network: Virtual layer connecting peers.
   * Indexing Mechanisms: Help locate shared resources.
   * Bootstrapping Mechanisms: Enable new peers to join the network.
5. Bootstrapping in P2P
   * Helps new peers discover others and connect.
   * Can use centralized servers, peer exchange, or DHTs
   .
6. Data Management
   * Storage: Distributed across peers.
   * Retrieval: Uses search algorithms.
   * Replication: Increases availability.
   * Consistency: Ensures all replicas are up to date
   .
7. Routing Algorithms
   * Flooding: Sends to all neighbors — high traffic.
   * Random Walk: Selects random paths — less overhead.
   * DHTs: Efficient lookups via hash tables (e.g., Kademlia).
   * Small-World Routing: Uses short paths and local/global links.
8. Advantages
   * No central point of failure
   * Efficient resource utilization
   * Cost-effective
   * High availability due to replication
9. Challenges
   * Difficult to scale with efficiency
   * Security risks from malicious nodes
   * Inconsistent content quality
   * Complex consistency and data managemen

Question 4

Discuss system attacks and threats to cyberspace resulting in 4 types of
losses.

Answer 4

1. Common System Attacks:
2. Malware Attacks:
   o Includes viruses, worms, ransomware, spyware, and Trojans.
   o Designed to steal, encrypt, or delete data or disrupt operations.
3. Phishing:
   o Deceptive messages to trick users into giving up sensitive info like
   passwords or credit card numbers.
4. Denial of Service (DoS/DDoS):
   o Overloads networks or servers, making them unavailable to users.
5. Man-in-the-Middle (MitM):
   o Attackers intercept communication between two parties to steal or
   alter data.
6. SQL Injection:
   o Injects malicious SQL queries into input fields to access or
   manipulate databases.
   o
   Four Types of Losses Due to Cyber Attacks
7. Financial Loss
   * (i) Cyber attacks like ransomware or online fraud can lead to direct theft of
   money or demand for large payments.
   * (ii) Organizations incur heavy costs for legal penalties, data recovery, and
   strengthening future security.
8. Data Loss
   * (i) Attacks such as malware, hacking, or unauthorized access can result in
   loss or theft of sensitive data.
   * (ii) Loss of intellectual property, customer information, or confidential
   business records affects compliance and trust.
9. Reputational Loss
   * (i) A successful cyber attack damages an organization’s public image and
   brand value.
   * (ii) Customers may lose confidence, leading to a decline in user base and
   revenue.
10. Operational Loss
    * (i) Cyber threats like Denial of Service (DoS) can bring down servers,
    disrupting business operations.
    * (ii) Delays in service delivery and system downtime reduce productivity
    and efficiency