COMPUTER NETWORK – WIRELESS PSI / TECHNICAL OPERATOR NOTES
1️⃣ Basics of Computer Networks
What is a Computer Network?
A computer network is a collection of devices connected together to share data, resources, and services.
📌 Exam Connect
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Question type: Definition / MCQ
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Key word: Data sharing
Types of Networks
| Type | Full Form | Coverage |
|---|---|---|
| LAN | Local Area Network | Office, building |
| MAN | Metropolitan Area Network | City |
| WAN | Wide Area Network | Country / Internet |
📌 Exam Tip
👉 Internet = WAN
2️⃣ Network Topologies
Types:
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Bus
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Star ⭐ (most common)
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Ring
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Mesh
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Tree
Star Topology
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All devices connected to central switch
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Easy troubleshooting
📌 Exam Connect
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Most used topology → Star
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Failure of central device → network down
3️⃣ OSI Model (VERY IMPORTANT) ⭐⭐⭐⭐⭐
OSI – 7 Layers (Bottom to Top)
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Physical
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Data Link
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Network
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Transport
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Session
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Presentation
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Application
📌 Mnemonic (Exam Friendly)
Please Do Not Throw Sausage Pizza Away
Layer-wise Exam Focus
| Layer | Key Function | Example |
|---|---|---|
| Physical | Bits, cables | UTP, Fiber |
| Data Link | MAC, frames | Switch |
| Network | IP routing | Router |
| Transport | Port, reliability | TCP / UDP |
| Application | User interface | HTTP, FTP |
📌 Exam Favorite
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Router works at → Layer 3
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Switch works at → Layer 2
4️⃣ TCP vs UDP ⭐⭐⭐
| TCP | UDP |
|---|---|
| Reliable | Fast |
| Connection-oriented | Connectionless |
| Error checking | No guarantee |
📌 Exam Connect
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Voice / Video → UDP
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Email / File transfer → TCP
5️⃣ IP Addressing
IPv4
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32-bit address
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Example:
192.168.1.1
IPv6
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128-bit
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No broadcast
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Uses Unicast, Multicast, Anycast
📌 Exam Connect
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IPv6 does NOT support → Broadcast
Private IP Ranges
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10.0.0.0 – 10.255.255.255
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172.16.0.0 – 172.31.255.255
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192.168.0.0 – 192.168.255.255
📌 MCQ Favorite
6️⃣ Network Devices
| Device | Function |
|---|---|
| Hub | Broadcasts data |
| Switch | MAC-based forwarding |
| Router | IP routing |
| Modem | Digital ↔ Analog |
| Access Point | Wireless connectivity |
📌 Wireless PSI Focus
👉 Access Point connects wireless users
7️⃣ Wireless Networking (VERY IMPORTANT) 📶
What is Wireless Network?
Uses radio waves instead of cables.
Wi-Fi Standards
| Standard | Speed |
|---|---|
| 802.11b | 11 Mbps |
| 802.11g | 54 Mbps |
| 802.11n | 300 Mbps |
| 802.11ac | High speed |
📌 Exam Connect
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Wi-Fi standard starts with → 802.11
Wireless Security
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WEP ❌ (Weak)
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WPA
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WPA2 ✅ (Secure)
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WPA3 (Latest)
📌 Exam Favorite
👉 Most secure (common) → WPA2
8️⃣ Ports & Protocols ⭐⭐⭐⭐⭐
| Protocol | Port | Use |
|---|---|---|
| HTTP | 80 | Web |
| HTTPS | 443 | Secure web |
| FTP | 21 | File transfer |
| SMTP | 25 | Sending mail |
| POP3 | 110 | Receiving mail |
| DNS | 53 | Name resolution |
| SSH | 22 | Secure login |
📌 Guaranteed MCQs
9️⃣ Important Network Protocols
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DNS – Domain name to IP
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DHCP – Auto IP assignment
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ICMP – Ping
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ARP – IP to MAC mapping
📌 Exam Connect
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Ping uses → ICMP
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DHCP provides → IP automatically
🔟 Network Security Basics
Firewall
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Filters traffic
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Based on rules (Allow / Deny)
ACL
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Access Control List
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If rule not matched → Packet dropped
📌 Wireless PSI Relevance
👉 Security + monitoring questions common
1️⃣1️⃣ Bandwidth vs Latency
| Term | Meaning |
|---|---|
| Bandwidth | Data capacity |
| Latency | Delay |
📌 Exam Trick
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High bandwidth ≠ low latency
1️⃣2️⃣ Troubleshooting Tools
| Tool | Purpose |
|---|---|
| Ping | Connectivity |
| Tracert | Path |
| ipconfig | IP info |
| nslookup | DNS check |
📌 Technical Operator Focus
