📌
What is a Computer Network?

Computer Network

🧠
Types of Networks

Type Full Form Range Example
LAN Local Area Network Up to a few kilometers Offices, Schools
MAN Metropolitan Area Network Covers a city Cable TV network in a city
WAN Wide Area Network Covers countries Internet
PAN Personal Area Network Few meters Bluetooth, USB cable
Types of Networks Types of Networks Types of Networks Types of Networks Types of Networks

🌐
Network Topologies

What is Topology?

Topology = Arrangement of different elements (devices, nodes) in a network.

🔸 1. Bus Topology

  • All devices connected to one main cable
  • 📉 Cheap but if cable fails, network goes down
Example: Imagine one electricity wire shared by all bulbs—cut the wire, everything goes off.
Bus Topology

🔸 2. Star Topology

  • All devices connected to a central device (hub/switch)
  • 📈 Easy to manage; one failure doesn't crash the whole network
  • 🔗 Central device is the hub
Star Topology

🔸 3. Ring Topology

  • Each device connected to two others, forming a circle
  • 🔁 Data moves in one direction (unidirectional) or both (bidirectional)
  • 📉 If one device fails, it can disrupt the entire network
Ring Topology

🔸 4. Mesh Topology

  • Every device connected to every other device
  • 💪 High redundancy; expensive and complex
Example: Everyone in a group chat directly messages everyone else.
Mesh Topology

🔸 5. Hybrid Topology

  • Mix of two or more topologies (e.g., Star + Bus)
  • Flexible and widely used in large networks
Hybrid Topology

🔁
Transmission Modes

What is Transmission Mode?

Transmission Mode = Direction in which data flows.

Mode Direction Example
Simplex One-way TV Broadcast
Half Duplex Both ways, one at a time Walkie-Talkie
Full Duplex Both ways at the same time Phone Call
Transmission Modes

📶
Bandwidth vs Throughput vs Latency

Term Meaning (in computer network) Real-World Example
Bandwidth The maximum amount of data that can be transferred over a network in a given time. It defines the **capacity** of the network connection (measured in Mbps or Gbps). You have a 100 Mbps internet plan — this is your bandwidth.
Throughput The **actual** amount of data transferred successfully per second. Why it's less than bandwidth? – Because of congestion, errors, server speed, etc. Though your plan is 100 Mbps, you are only getting 80 Mbps — that's the throughput.
Latency The time it takes for a data packet to travel from source to destination and back (measured in milliseconds). When you play an online game and experience lag — that's caused by high latency.
Bandwidth vs Throughput vs Latency

📚
OSI Model vs TCP/IP Model

What are Reference Models?

Both are reference models used to understand how data travels over a network.

OSI vs TCP/IP Model
  • OSI is a theoretical model
  • TCP/IP is practical and used in real networks
  • HTTP, FTP, DNS work on the Application layer
  • IP (Internet Protocol) works on the Internet layer