Distributed systems are a collection of independent computers that appear to the users of the system as a single coherent system. This module will introduce you to the fundamental concepts of distributed systems, their characteristics, and the basic principles that govern their operation.

A distributed system is a network of autonomous computers that communicate with each other in order to achieve a common goal. These systems are designed to share resources, data, and computation across multiple nodes.

Distributed systems exhibit several key characteristics:

• Scalability: Ability to handle growth in workload by adding resources.
• Fault Tolerance: Ability to continue operating despite failures of some components.
• Concurrency: Multiple processes can run simultaneously.
• Transparency: Hides the complexity of the system from the user.

Distributed systems can be categorized based on their architecture and purpose:

• Client-Server Systems: Clients request services and servers provide them.
• Peer-to-Peer Systems: All nodes have equal roles and responsibilities.
• Distributed Databases: Databases spread across multiple locations.
• Cloud Computing: Provides scalable and elastic resources over the internet.

• Nodes: Individual computers in the system.
• Network: The communication medium connecting the nodes.
• Middleware: Software that provides common services and capabilities to applications outside of what's offered by the operating system.

In a client-server model, clients send requests to a server, which processes the requests and sends back the responses. This model is commonly used in web applications.

In a peer-to-peer model, each node can act as both a client and a server. This model is used in file-sharing networks like BitTorrent.

Given the following scenarios, identify the type of distributed system:

1. A web application where users access a central server to retrieve information.
2. A file-sharing network where users can download files from each other.
3. A cloud service that provides scalable storage and computing resources.

Solution:

1. Client-Server System
2. Peer-to-Peer System
3. Cloud Computing

Draw a simple diagram of a distributed system with three clients and one server. Label the components.

Solution:

• Mistake: Assuming all nodes in a distributed system are always available. Tip: Design your system to handle node failures gracefully.

• Mistake: Ignoring network latency and bandwidth limitations. Tip: Optimize communication between nodes to minimize latency and bandwidth usage.

In this section, we covered the basic concepts of distributed systems, including their definition, characteristics, types, and components. Understanding these fundamentals is crucial as we delve deeper into more complex topics in distributed architectures. In the next module, we will explore the different models of distributed systems and how they influence system design and performance.