COMPUTER NETWORK

 

📘 COMPUTER NETWORK (UP LT GRADE)

Topics:

  1. OSI Model

  2. TCP/IP Model

  3. Network Protocols

  4. Network Devices

  5. Network Topologies

🔷 1. OSI MODEL (Most Important ⭐⭐⭐⭐⭐)




📌 What is OSI Model?

OSI (Open Systems Interconnection) is a 7-layer reference model used to understand how data travels from one computer to another.

📖 Developed by: ISO
📖 Type: Conceptual / Theoretical model

🔢 OSI 7 Layers (Bottom → Top)

NoLayerMain WorkExam Keyword
1PhysicalBits, cablesTransmission
2Data LinkFrames, MACError detection
3NetworkPackets, IPRouting
4TransportSegmentsReliable delivery
5SessionSession controlLogin
6PresentationEncryptionFormat
7ApplicationUser servicesEmail, Web

🧠 Memory Trick (Very Important)

👉 “Please Do Not Throw Sausage Pizza Away”

  • P – Physical

  • D – Data Link

  • N – Network

  • T – Transport

  • S – Session

  • P – Presentation

  • A – Application

🎯 MCQ Facts (Repeat Daily)

  • ❓ Which layer does routing? → Network

  • ❓ Encryption/Compression? → Presentation

  • ❓ End-to-end delivery? → Transport

  • ❓ MAC address works at? → Data Link

  • ❓ User interacts with? → Application

🔷 2. TCP/IP MODEL (Practical Model ⭐⭐⭐⭐)




📌 What is TCP/IP?

TCP/IP (Transmission Control Protocol / Internet Protocol) is the actual model used on the Internet.

📖 Developed by: DARPA
📖 Layers: 4

🔢 TCP/IP Layers

TCP/IP LayerWorks Like OSI
ApplicationOSI 7,6,5
TransportOSI 4
InternetOSI 3
Network AccessOSI 2,1

⚔️ OSI vs TCP/IP (Direct MCQ)

OSITCP/IP
7 Layers4 Layers
TheoreticalPractical
ISO ModelDARPA Model
Not used directlyUsed on Internet

🎯 MCQ Hit Lines

  • Internet runs on → TCP/IP

  • OSI is → Reference model

  • TCP/IP is → Protocol suite

🔷 3. NETWORK PROTOCOLS (Very Scoring ⭐⭐⭐⭐⭐)





📌 What is Protocol?

A protocol is a set of rules for communication between devices.

🔑 Important Protocols (Remember This Table)

ProtocolUse
HTTPWeb pages
HTTPSSecure web
FTPFile transfer
SMTPSending email
POP3Receiving email
IMAPOnline email
TCPReliable
UDPFast, no guarantee
IPAddressing

🔥 TCP vs UDP (Guaranteed Question)

TCPUDP
ReliableNot reliable
SlowFast
Connection-orientedConnectionless
Used in Email, WebUsed in Video, Games

🔷 4. NETWORK DEVICES (Direct MCQs ⭐⭐⭐⭐)





📌 Network Device

A device used to connect computers in a network.

🔌 Important Devices

DeviceWorkLayer
HubBroadcastPhysical
SwitchMAC basedData Link
RouterIP routingNetwork
ModemDigital ↔ AnalogPhysical
RepeaterSignal boostPhysical
BridgeSegment networkData Link

🎯 One-Line MCQs

  • ❓ Smart device? → Switch

  • ❓ Internet device? → Router

  • ❓ Old device? → Hub

🔷 5. NETWORK TOPOLOGIES (Diagram Based ⭐⭐⭐⭐)





📌 What is Topology?

Topology = Physical or logical arrangement of computers.

🔺 Types of Topology

TopologyKey Point
BusOne cable
StarCentral hub
RingCircular
MeshFully connected
TreeHierarchical

⚡ Advantages & MCQ Facts

TopologyBest FeatureProblem
BusCheapCable fault
StarEasy to manageHub failure
RingNo collisionOne break stops
MeshReliableExpensive

🧠 FINAL 10-DAY REVISION STRATEGY (Last Chance)

🔁 Daily (2 Hours)

  • 30 min → OSI + TCP/IP tables

  • 30 min → Protocols

  • 30 min → Devices

  • 30 min → MCQs practice

📝 Last 3 Days

  • Only tables + differences + one-liners

  • Revise mnemonics

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