Network Diagram

📘 Network Diagram (OOAD / System Design View)

---

🔹 1. Definition

A Network Diagram is a graphical representation that shows how different computers, devices, and systems are connected and communicate with each other in a network.

👉 Simple idea: It shows “who is connected to whom and how data flows between them.”

---

🔹 2. Purpose of Network Diagram ⭐

• Show system communication structure
• Understand data flow between devices
• Plan system architecture
• Help in network design and troubleshooting
• Useful in distributed systems

---

🔹 3. Key Components

---

🔸 3.1 Nodes (Devices)

Represents physical devices:

• Computer
• Server
• Router
• Printer
• Mobile device

---

🔸 3.2 Links (Connections)

Represents communication paths:

• Wired connection (LAN, cable)
• Wireless connection (Wi-Fi)

---

🔸 3.3 Data Flow

• Shows direction of communication
• Can be one-way or two-way

---

🔹 4. Types of Network Diagrams ⭐

---

🔸 4.1 Logical Network Diagram

• Shows how data flows
• Focus on communication structure
• Ignores physical hardware details

👉 Example:

• Client → Server → Database

---

🔸 4.2 Physical Network Diagram

• Shows actual hardware setup
• Includes servers, routers, cables

---

🔹 5. Basic Network Diagram Example

[Client PC] → [Web Server] → [Database Server]

👉 Flow:

• Client sends request
• Server processes request
• Database stores/retrieves data

---

🔹 6. Real-Life Example (Online Shopping System)

User Mobile → Internet → App Server → Database Server

---

🔹 7. Network Topologies (Common Structures)

---

🔸 7.1 Star Topology ⭐

• All devices connect to a central hub

     PC
      |
PC — Hub — PC
      |
     PC

---

🔸 7.2 Bus Topology

• All devices share one communication line

---

🔸 7.3 Ring Topology

• Devices connected in a circular loop

---

🔸 7.4 Mesh Topology

• Every device connected to every other device

---

🔹 8. Difference: Network Diagram vs Deployment Diagram ⭐

Feature	Network Diagram	Deployment Diagram
Focus	Communication flow	Software deployment
Level	Logical/physical network	System architecture
Shows	Devices + connections	Nodes + software artifacts
Use	Networking	Software systems

---

🔹 9. Advantages of Network Diagrams

• Easy to understand system communication
• Helps in network planning
• Useful for troubleshooting
• Improves system design clarity
• Supports distributed system design

---

🔹 10. Important Rules / Guidelines

• Clearly label all nodes and connections
• Avoid cluttered diagrams
• Show correct data flow direction
• Separate logical and physical views
• Keep diagram simple and readable

---

🔹 11. Where Network Diagrams are Used

• Internet systems
• Banking systems
• Cloud applications
• Distributed databases
• Client-server applications

---

🔹 12. Likely Exam Questions

1. Define network diagram.
2. What is the purpose of a network diagram?
3. Explain logical vs physical network diagram.
4. Draw a simple network diagram for online system.
5. What are nodes and links?
6. Explain star topology.
7. Difference between network and deployment diagram.
8. Where are network diagrams used?
9. Explain mesh topology.
10. Advantages of network diagrams.

---

🔹 13. Quick Revision Summary 🧠

• Network Diagram = Communication between systems/devices

• Shows:

  • Nodes (devices)
  • Links (connections)
  • Data flow

Types:

• Logical (data flow)
• Physical (hardware setup)

👉 Trick to Remember: "N = Nodes + Networks + Navigation of data"

---